p2infohouse.org · 2018-06-13 · WATER AND WASTEWATER MANAGEMENT In Food Processing Plants - An Educational Program The objective of this program is to increase the knowledge of

WATER AND WASTEWATER MANAGEMENT In Food Processing Plants - An

Educational Program The objective of this program is

to increase the knowledge of food scientists, food processors, engineers, scientists, waste management specialists and other practitioners in the concepts and principles needed to properly control water use and product waste in food processing facilities. The materials are designed for individuals con- cerned with management of food plants, with pretreatment of food processing wastewaters, with treatment of food processing wastewaters and with the utilization or disposal of food plant residuals. The modules in this program incorporate knowledge from food science and technology, food processing, sanitary and environmental engineering, agronomy, soil science, agricultural engineering, economics and law.

The program consists of some 15 modules. Introductory material is presented in the Core Manual to introduce the program. Technical specifics are provided in 7 technical spinoffs. The application of water and waste management in specific food plants is related in 7 commodity Spinoff Manuals.

CORE MANUAL CHAPTERS

TECHNICAL SPINOFFS

COMMODITIES I SPINOFFS

I WATER AND WASTEWATER , MANAGEMENT

Published by THE NORTH CAROLINA AGRiCULTURAL EXTENSION SERViCE

North Carolina State University at Raleigh, North Carolina Agricultural and Technical State University at Greensboro, and the U. S. Department of Agricuiture, Cooperating. State University Station, Raleigh, N. C.. T. C. Biaiock, Director. Distributed in furtherance of the Acts of Congress of May 8 and June 30. 1914. The North Carolina Agricultural Extension Service offers its programs to ail eligible persons regardless of race, color, or national origin, and is an equal opportunity employer.

SPINOFF ON

W A S T E W A T E R T R E A T M E N T O F F O O D P R O C E S S I N G E F F L U E N T S

ROY E. CARAWAN

JAMES V. CHAMBERS ROBERT R. ZALL

PROJECT SUPERVISOR

ROGER H WI LKOWSKE

EXTENSION SPECIAL REPORT No. AM-18~ JANUARY, 1979

PREPARED BY: EXTENSION SPECIALISTS AT:

CORNELL UNIVERSITY PURDUE UN I VERS I TY

NORTH CAROL I NA STATE UN IVERS I TY

WITH THE SUPPORT OF THE

Sc I ENCE AND EDUCATION ADM I N I ST RAT I ON-EXTENS I ON

USDA - WASHINGTON, D. C.

WASTEWATER TREATMENT SPNOFF/PREFACE

PREFACE

Purpose: The main purpose o f t h i s WASTEWATER TREATMENT OF FOOD

PROCESSING EFFLUENTS SPINOFF i s t o f u r n i s h knowledge about

t h e var ious types o f waste t reatment systems and t h e f a c t o r s

a f f e c t i n g t h e i r performance. Th is document i s intended as a guide, i n t h a t i t attempts t o p rov ide broad coverage, bu t

cannot be t o t a l l y comprehensive on a l l top ics . Instead, i t

g ives general i n f o r m a t i o n on a wide scale, and then d i r e c t s

t h e reader t o a d d i t i o n a l s p e c i f i c data and b i b l i o g r a p h i c

i nformat ion.

By present ing t h e fundamentals o f wastewater t rea tment

systems, t h e s o l u t i o n , a p p l i c a t i o n and opera t i on o f waste

t rea tment systems w i l l be f a m i l i a r t o t h e ex tens ion spec ia l -

i s t . Thus, t h i s guide can be a t o o l t o he lp ex tens ion

s p e c i a l i s t s and food processors a l l e v i a t e present misunder-

standings and avo id f u t u r e problems i n wastewater d isposa l .

I n add i t i on , t h i s guide can a i d i n b r i n g i n g toge the r repre-

sen ta t i ves f rom t h e food i n d u s t r y and r e g u l a t o r y agencies t o

coo rd ina te t h e i r mutual i n t e r e s t i n reducing water po l l u -

t i o n .

Audience : This guide should be va luab le not o n l y t o ex tens ion

s p e c i a l i s t s f o r which i t was prepared, bu t a l s o f o r food

processors and r e g u l a t o r y o f f i c i a l s charged w i t h t h e review

and approval o f wastewater discharge from food p lan ts not

o n l y t o sur face waters but a l so t o municipal wastewater

t rea tment systems.

Scope: The sub jec t o f t h i s guide i s t h e management and c o n t r o l o f

water use and waste discharge i n food processing, w i t h

emphasis on necessary l e g a l , san i ta ry , environmental and

energy fac to rs . Th is s p e c i f i c document emphasizes

wastewater t r e a t men t concept s .

i

WASTEWATER TREATMENT SPNOFF/PREFACE

I n p repar ing t h i s guide, the committee has attempted t o

ma in ta in a u n i f o r m i t y o f recommendations and suggestions,

desp i te t h e d i s p a r i t y o f requirements throughout the

country.

depends on many d i f f e r e n t f a c t o r s such as l oad ing ra te ,

temperature and n u t r i e n t supply so t h a t un i fo rm recom-

mendations f o r t h e e n t i r e Un i ted Sta tes are not poss ib le i n

t h i s b r i e f review.

A wastewater t reatment system's performance

L i m i t a t i o n s : This document i s intended as a guide and i s not intended t o

be an engineer ing manual f o r t h e design o f wastewater

t rea tment systems. I n f a c t , t he document encourages t h e use

o f speci a1 i s t s i n se l e c t i ng design and recommendi ng

opera t iona l p rac t ices . Regulat ions f o r s p e c i f i c s i t e s and

p l a n t s may make c e r t a i n waste systems descr ibed he re in

unava i l ab le because o f performance l i m i t a t i o n s .

D isc la imer : The mention o f manufacturers, t rade names o r commercial

products i s f o r i l l u s t r a t i o n purposes and does not imply

t h e i r recommendation o r t h e i r endorsement fo r use by the

A g r i c u l t u r a l Extens ion Service.

Learn ing Ob jec t ives :

1. Apprec ia t ion o f t h e concepts o f wastewater t reatment.

2. Recogni t ion o f t h e s i g n i f i c a n t f a c t o r s d i f f e r e n t i a t i n g b i o l o g i c a l and physical-chemical t reatment systems.

3. Awareness o f cons idera t ions impor tant i n t h e s e l e c t i o n and design o f wastewater t reatment systems.

4 . R e a l i z a t i o n o f t h e complex i ty o f wastewater t reatment systems.

5. Educat ion i n opera t ing parameters impor tant f o r proper opera t ion o f s p e c i f i c waste t reatment systems.

6. Reve la t ion of t h e importance o f the opera t ion and management of a food p l a n t on i t s wastewaters and t h e subsequent performance o f i t s waste t reatment system.

ii

WASTEWATER TREATMENT SPNOFF/SUMMARY

SUMMARY

Wastewater t reatment concepts are reviewed and explained f o r both

b i o l o g i c a l and physical-chemical treatment. The d i f f e r e n c e s between t h e

two systems are contrasted. While t h e b i o l o g i c a l system i s noted f o r

b e t t e r removal of d i sso l ved so l i ds , t h e physical-chemical system i s

exp la ined as o f t e n more approp r ia te f o r t he removal o f suspended so l i ds .

and t h e key aspects o f each p r i n c i p l e a re reviewed. The forms and

c o n f i g u r a t i o n s o f waste t reatment systems are i l l u s t r a t e d . Fac tors

a f f e c t i n g t h e optimum performance o f waste systems are elucidated.

i d e n t i f i e d .

The p r i n c i p l e s app l i ed i n t h e t reatment o f wastewater a re i d e n t i f i e d

Impor tan t f a c t o r s i n t h e s e l e c t i o n o f waste t reatment systems are

The complex i n t e r r e l a t i o n s h i p of these f a c t o r s i s explained.

i i i

WW TRMT SPNOFF/

TABLE OF CONTENTS

CHAPTER PAGE NO.

PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . i

SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . v i

LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . v i i

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . 1

2. THE PRINCIPLE OF PHYSICAL-CHEMICAL WASTE TREATMENT A. I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . 2

B. Summary . . . . . . . . . . . . . . . . . . . . . . . 2

C. Removal Based On Phys ica l P r o p e r t i e s . . . . . . . . . . Screening . . . . . . . . . . . . . . . . . . . . . . F l o t a t i o n . . . . . . . . . . . . . . . . . . . . . . Sedimentation/Density . . . . . . . . . . . . . . .

D. Removal Based On Chemical P r o p e r t i e s . . . . . . . . . - F1 occul a t i o n . . . . . . . . . . . . . . . . . . . . - I o n Exchange . . . . . . . . . . . . . . . . . . . . - Adsorpt ion . . . . . . . . . . . . . . . . . . . . .

E. B i b l iography . . . . . . . . . . . . . . . . . . . . . 6

3. THE PRINCIPLE OF BIOLOGICAL WASTE TREATMENT A. I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . 7

B. Summary . . . . . . . . . . . . . . . . . . . . . . . 7

C. Terminology Of Wastewater . . . . . . . . . . . . . . 8 . I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . 8

- Water Sampling, I t s Ana lys is and I n t e r p r e t a t i o n . . 13 . Treatment And Pre-Treatment Systems . . . . . . . . 9

-Summary . . . . . . . . . . . . . . . . . . . . . . 20

D. The B i o l o g i c a l Processes . . . . . . . . . . . . . . . 20 - The Growth Environment . . . . . . . . . . . . . . . 20 - The Na tu ra l B i ogeochemi c a l Cycl es . . . . . . . . . 25 - Aerobic Metabolism . . . . . . . . . . . . . . . . . 28 - Anaerobic Metabolism . . . . . . . . . . . . . . . . 38

E. B ib l i og raphy . . . . . . . . . . . . . . . . . . . . . 41

i v

WW TRMT SPNOFF/

TABLE OF CONTENTS

CHAPTER

4 . SELECTING A WASTE TREATMENT SYSTEM A . I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . B . Summary . . . . . . . . . . . . . . . . . . . . . . . C . The Se lec t i on Process . . . . . . . . . . . . . . . . . Wastewater Charac ter iza t ion . . . . . . . . . . . . . Selec t ing The Process(es) . . . . . . . . . . . . .

5 . PHYSICAL-CHEMICAL WASTE TREATMENT SYSTEMS A . I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . B . Summary . . . . . . . . . . . . . . . . . . . . . . . C . The Systems . . . . . . . . . . . . . . . . . . . . . . Physical Types . . . . . . . . . . . . . . . . . . . . Physiochemical . Dewatering . . . . . . . . . . . . . Chemical Types . . . . . . . . . . . . . . . . . . .

D . Bib l iography . . . . . . . . . . . . . . . . . . . . . 5 . BIOLOGICAL WASTE TREATMENT SYSTEMS

A . I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . B . Summary . . . . . . . . . . . . . . . . . . . . . . . C . The Systems . . . . . . . . . . . . . . . . . . . . .

- A e r o b i c T y p e s . . . . . . . . . . . . . . . . . . . . Aerobic/Anaerobic . Land App l i ca t i ons

. Sludge Disposal . . . . . . . . . . . . . . . . . . . . . . . . .

. Anaerobic Types . . . . . . . . . . . . . . . . . . D . S i t e Se lec t i on and Management . . . . . . . . . . . . . S o i l s . . . . . . . . . . . . . . . . . . . . . . . . Waste Composition . . . . . . . . . . . . . . . . . . Crops . . . . . . . . . . . . . . . . . . . . . . .

E . Operat ional C h a r a c t e r i s t i c s . . . . . . . . . . . . . F . Bib l iography . . . . . . . . . . . . . . . . . . . . .

PAGE NO . 44

44

46 46 46

53

53

54 54 75 80

98

100

101

101 101 125 147 156

164 164 165 168

170

175

V

WW TRMT SPNOFF/

LIST OF TABLES

TABLE

IV-1

v-1

v -2

v-3

v-4

v-5

V-6

v-7

V -8

v -9

PAGE NO.

Alum Dosage f o r Phosphorus Removal . . . . . . . . . . 87

S t a b i l i z e d Sludge Composition . . . . . . . . . . . . . 126

N i t rogen Removal by Coastal Bemudagrsss I r r i g a t e d w i t h Swine Lagoon Waste (NC) . . . . . . . . 141

Anaerobic D i g e s t e r Operat ional C h a r a c t e r i s t i c s . . . . 156

Chemical Composition o f Sewage S1 udge and Amount o f Elements Added t o S o i l A t an A p p l i c a t i o n Rate o f 25 Dry Tons/Acre . . . . . . . . . . . . . . . . . . 159

Average Annual Corn Y i e l d s Obtained With Sludge A p p l i c a t i o n . . . . . . . . . . . . . . . . . . . . . . 163

Y i e l d o f Coastal Bermudagrass F e r t i l i z e d With NPK and Sewage Sludge . . . . . . . . . . . . . . . . . . . 163

To ta l A p p l i c a t i o n I n Dry Tons o f Sewage Sludges Based On t h e Zinc Equivalance Formula [Dry Tons = Cat ions Exchange Capaci ty x 32,600 + ( I n + 2Cu + 4Ni - 300)]. . 167

Land A p p l i c a t i o n o f Wastewater and Sludge . . . . . . . 169

In fo rma t iona l Needs and P o t e n t i a l I n f o r m a t i o n Sources Concerning Land A p p l i c a t i o n . . . . . . . . . . . . . . 174

v i

WW TRMT SPNOFF/

LIST OF FIGURES

PAGE NO. FIGURE

11-1

11-2

A s i m p l i f i e d Scheme o f t h e N i t rogen Cycle . . . . . . 26

The Interdependence o f t h e N i t rogen and and Carbon Cycles . . . . . . . . . . . . . . . . . . 27

The N i t rogen Cycle i n Cropped Land A f t e r Crop Removal . . . . . . . . . . . . . . . . . . . . . . . 11-3

29

Mechanism o f M i c r o b i a l S t a b i l i z a t i o n o f an

A S i m p l i f i e d Scheme f o r t h e Anaerobic Decomposition

Organic Waste . . . . . . . . . . . . . . . . . . . . o f Organic Wastes . . . . . . . . . . . . . . . . . .

11-4 30

11-5 39

47 111-1

111-2

Determining t h e Need f o r Waste Treatment . . . . . . . S e l e c t i n g a Physicochemical Waste Treatment Process . . . . . . . . . . . . . . . . . . . . . . . 48

49

50

50

111-3

111-4

111-5

111-6

S e l e c t i n g a B i o l o g i c a l Waste Treatment Process . . . Suspended S o l i d s Removal Opt ions . . . . . . . . . . . Sludge Disposal /Handl ing Opt ions . . . . . . . . . . . Meeting E f f l u e n t Discharge L i m i t a t i o n s (The Opt i ons ) . . . . . . . . . . . . . . . . . . . . 51

55

57

58

59

63

66

IV-1

I v-2

IV-3

IV-4

IV-5

IV-6

IV-7a

Bar Screen . . . . . . . . . . . . . . . . . . . . . . C i r c u l a r Center-Feed V i b r a t o r y Screen . . . . . . . . Rotary Drum Screen . . . . . . . . . . . . . . . . . . Tangent ia l Screen . . . . . . . . . . . . . . . . . . C1 a r i f i e r . . . . . . . . . . . . . . . . . . . . . . Sol i d Bowl Cen t r i f uge . . . . . . . . . . . . . . . . Disso lved A i r F l o t a t i o n U n i t : Mechanisms o f Operat ion . . . . . . . . . . . . . . . . . . . . . 68

IV-7b Mechanisms f o r Attachemnt o f Gas Bubbles t o S o l i d s o r O i l . . . . . . . . . . . . . . . . . . . . 68

69 IV-8a

IV-8b

Granular Media F i l t r a t i o n . . . . . . . . . . . . . . Granular Media F i l t e r Operates on a C o n t r o l l e d Cycle . . . . . . . . . . . . . . . . . . . 69

73 IV-9 Membrane F i l t r a t i o n . . . . . . . . . . . . . . . . . v i i

FIGURE

WW TRMT SPNOFF/

LIST OF FIGURES

PAGE NO . IV-10 Vacuum F i l t e r U n i t . . . . . . . . . . . . . . . . . . I V - 1 1 P r i m a r y Treatment P l a n t Using Vacuum F i l t r a t i o n

IV-12 F loc Formation With t h e Aid o f Chemical Agents . . . . IV-13 I o n Exchange Process . . . . . . . . . . . . . . . . .

B i o l o g i c a l System . . . . . . . . . . . . . . . . . . V-2 Ac t i va ted Sludge P l a n t Diagram . . . . . . . . . . . . V-3 V a r i a t i o n s o f t h e Act ivated-Sludge Process . . . . . . V-4 T r a d i t i o n a l Ox ida t i on D i t ches . . . . . . . . . . . . V-5 T r i c k l i n g F i l t e r P l a n t . . . . . . . . . . . . . . . . V-6 Waste S t a b i l i z a t i o n By B i o l o g i c a l D i s c F i l t r a t i o n

t o Dewater Sludge . . . . . . . . . . . . . . . . . .

V-1 Growth and Subs t ra te U t i l i z a t i o n I n a

V-7 F a c u l t a t i v e S t a b i l i z a t i o n Lagoon . . . . . . . . . . . V-8 Aera t ion Lagoon System . . . . . . . . . . . . . . . . V-9 Conceptual Land A p p l i c a t i o n o f Wastewater

E f f l u e n t s . . . . . . . . . . . . . . . . . . . . . . V-10 Methods o f Land A p p l i c a t i o n . . . . . . . . . . . . . V-11 S o i l Types Versus L i q u i d Loading Rates f o r

D i f f e r e n t Land A p p l i c a t i o n Approaches . . . . . . . . V-12 Const ruc t ion o f An Anaerobic Lagoon . . . . . . . . . V-13 Anaerobic Contact Process Scheme . . . . . . . . . . . V-14 Anaerobic F i l t e r Process . . . . . . . . . . . . . . . V-15 Schematic Diagram o f an Ac t i va ted Sludge Sewage

Treatment P lan t . I n c l u d i n g a T e n t a t i v e T e r t i a r y Treatment Process . . . . . . . . . . . . . . . . . .

77

79

81

93

104

106

110

111

115

118

121

123

127

129

137

149

151

153

157

v i i i

1 WW TRMT SPNOFF/INTRO

INTRODUCTION

Wastewater, when cha rac te r i zed i n general terms, c o n t a i n p o l l u t a n t s i n

I n order t o p u r i f y t h e wastewater, b a s i c a l l y two p r i n c i p l e s t h e form o f suspended and d i sso l ved s o l i d s . These s o l i d s may be i n e r t o r

biodegradable.

a re employed t o remove t h e p o l l u t a n t s f rom t h e water, namely - b i o l o g i c a l

and phys i ca l - chemical.

removing biodegradable d i sso l ved so l i d s whereas, t h e suspended so l ids a re bes t removed by phys i ca l - chemical means.

The purpose of t h i s S p i n o f f w i l l be t o acquaint you w i t h t h e

b i o l o g i c a l and phys i ca l - chemical p r i n c i p l e s t h a t a re a p p l i e d i n t h e

t reatment o f wastewater. p r i n c i p l e s , i t i s hoped t h a t you w i l l have a b e t t e r i n s i g h t about t h e

waste t reatment systems which use these concepts.

a r e d i c t a t e d by such f a c t o r s as t h e nature o f t h e waste, d ischarge volume

t o be t rea ted , economics, land a v a i l a b i l i t y and energy sources. Once t h e

system i s se lec ted then t h e mechanics are engineered i n t o t h e waste

t reatment system. a i r c o n t r o l systems. However, operator c o n t r o l o f t h e h y d r a u l i c f l o w r a t e s and pa t te rns f o r raw i n f l u e n t , t h e t r e a t e d e f f l u e n t , and ( f o r

a c t i v a t e d sludge systems) t h e sludge r e t u r n and sludge wast ing a r e a l s o i nc luded i n t h e waste t reatment system design. Optimal ope ra t i on

performance o f t h e waste t reatment system depends on t h e marr iage o f a l l of t h e above fac to rs .

f i v e sect ions, each d e a l i n g w i t h a s p e c i f i c aspect.

d iscuss t h e f o l l o w i n g t o p i c s :

The b i o l o g i c a l process i s most e f f e c t i v e i n

By g a i n i n g a b e t t e r understanding o f these

Waste t reatment systems take on many forms and c o n f i g u r a t i o n s which

The p r i n c i p l e mechanics engineered a re h y d r a u l i c and

The wastewater t reatment concepts t o be discussed w i l l be d i v i d e d i n t o

The f i v e sec t i ons

I.

11.

111. I V .

The P r i n c i p l e o f Phys ica l - Chemical Waste Treatment

The P r i n c i p l e o f B i o l o g i c a l Waste Treatment

S e l e c t i n g A Waste Treatment System

Physica l - Chemical Waste Treatment Systems V. B i o l o g i c a l Waste Treatment Systems

2 W W TRMT SPNOFF/PRINCIPLE OF PHYS-CHEM

Sec t ion I

The P r i n c i p l e o f Phys ica l -Chemi c a l Waste Treatment

A. I n t r o d u c t i o n

and chemical techniques commonly used t o remove p o l l u t a n t s f rom

wastewater.

chemical p r o p e r t i e s o f t h e p o l l u t a n t which permi ts i t s removal f rom t h e wastewater stream.

phys ica l and chemical techniques w i l l a i d t h e extens ion s p e c i a l i s t i n

b e t t e r understanding how t h e waste t reatment process func t i ons i n s p e c i f i c

opera t ions (i.e. pr imary t reatment, t e r t i a r y t reatment)

The purpose o f t h i s s e c t i o n i s t o acquaint you w i t h var ious phys ica l

These techniques take advantage o f s p e c i f i c phys ica l and/or

Fami 1 i a r i t y w i t h t h e appl i ed p r i n c i p l es o f these

B. Summary

t e r t i a r y t reatment o f wastewater. However, these techniques can a l s o be used as a secondary t reatment, depending on t h e na ture o f t h e wastewater

t o be t r e a t e d and t h e design o f t h e waste t reatment f a c i l i t y . purpose o f c l a r i t y , primary, secondary and t e r t i a r y t reatment s imply

r e f l e c t t h e sequent ia l s teps i n a waste t reatment process scheme.

t rea tment s teps a re commonly associated wi th munic ipa l waste t reatment

systems and t h e terminology has been c a r r i e d over i n t o o the r waste

t reatment operat ions. Pr imary t reatment genera l l y i nvo l ves t h e phys ica l

removal o f p o l l u t a n t s by means o f s e t t l i n g bas ins o r c o l l e c t i o n screens. Th is t reatment i s t h e f i r s t s tep toward removing p o l l u t a n t s from t h e

wastewater.

which e s s e n t i a l l y prov ides f o r some form o f adjustment (i.e. pH, p a r t i a l

removal o f p o l l u t a n t s , coo l i ng ) t o t h e wastewater stream t o make i t

amenable t o b i o l o g i c a l ass im i la t i on .

b i o l o g i c a l a s s i m i l a t i o n process, can a l s o use physical-chemical techniques

t o remove p o l l u t a n t s not removed by t h e pr imary step. The most f r e q u e n t l y

used p r a c t i c e s employ f l o c c u l a t i n g agents ( i .e. p o l y e l e c t r o l y t e polymers),

a c t i v a t e d carbon, s e t t l i n g and a i r f l o t a t i o n as means f o r secondary removal o f p o l l u t a n t s .

Physical-chemical techniques are genera l l y used i n t h e pr imary and

For t h e

These

Pr imary t reatment should no t be confused w i t h pret reatment

Secondary t reatment, whi 1 e more commonly associated w i t h t h e

3 WW TRMT SPNOFF/PRINCIPLE OF PHYS-CHEM

T e r t i a r y t reatment i s requ i red o f a t r e a t e d wastewater e f f l u e n t when

c e r t a i n composi t ional parameters present may adverse ly e f f e c t t h e ecosystem

o f t h e r e c e i v i n g stream. Such parameters would be pathogenic agents,

ammonia, heavy metals, and phosphates.

parameters t o acceptabl e l e v e l s , chemical f l occul ants, a c t i v a t e d carbon o r

i o n exchange processes may be used.

hazards due t o t h e presence o f d isease producing b a c t e r i a and v i rus ,

d i s i n f e c t i o n processes such as c h l o r i n a t i o n , ozonat ion o r u l t r a v i o l e t

i r r a d i a t i o n might be u t i 1 i zed.

To remove o r reduce these

For min imiz ing p o t e n t i a l p u b l i c h e a l t h

C. Removal Based on Phys ica l P roper t i es

1. Screening: The screening process depends on t h e phys ica l

exc lus ion o f p o l l u t a n t s as a f u n c t i o n o f p a r t i c l e size.

process may be i n the form o f bar racks, mesh screens and f i l t e r s

(sand and membrane). Major a p p l i c a t i o n s o f t he screening process

a re i n pret reatment , pr imary and t e r t i a r y waste t reatment steps.

Th is

2.

Pretreatment and pr imary t reatment a i d i n reducing clogged sewers

and p ipe l i nes .

waste load on t h e waste t reatment system. Screening i n t h e form

o f sand and membrane f i l t e r s i s used as a t e r t i a r y t reatment t o

reduce t h e discharge o f suspended s o l i d s t o t h e t r i b u t a r y stream.

F l o t a t i o n :

pret reatment , pr imary o r secondary t reatment process.

technology i s b a s i c a l l y app l ied t o p o l l u t a n t s t h a t f l o a t under

Also, any organic p a r t i c l e s removed reduce t h e

The f l o t a t i o n technique may be employed i n t h e

Th is

qu iescent cond i t ions . P o l l u t a n t s most amenable t o removal by

f l o t a t i o n are c o l l o i d a l suspended f a t s , o i l s and greases. With

t h e a i d o f chemical a d d i t i v e s (i.e. organic polymers), f a t s , o i l s

and greases may be adsorbed and removed by a i r f l o t a t i o n . Th is

process depends on the entrapment o f a i r bubbles w i t h i n t h e

p a r t i c l e aggregate which add t o the buoyancy o f the p a r t i c l e .

Wi th the added buoyancy, t he p a r t i c l e f l o a t s t o the sur face o f t h e

vessel and i s removed mechanical ly.

p o l l u t a n t p a r t i c l e s having a dens i t y g rea ter than 1, serves as a

c r i t i c a l opera t ing parameter f o r most b i o l o g i c a l l y o r i en ted waste

t rea tment systems. I n these systems, t h e a c t i v e biomass p a r t i c l e

3. Sedimentat ion/Densi ty: Sedimentation, based on removal of

4 WW TRMT SPNOFF/PRINCIPLE OF PHYS-CHEM

i s removed from t h e t r e a t e d wastewater by t h e c l a r i f i c a t i o n

process. Th is c l a r i f i c a t i o n s tep may take p lace i n a c l a r i f i e r

u n i t , designed t o a l l o w s e t t l i n g , c o l l e c t i o n and removal o f t h e

accumulated biomass p a r t i c l e s ; o r i n a so c a l l e d " p o l i s h i n g pond".

The " p o l i s h i n g pond", i n c o n t r a s t t o t h e c l a r i f i e r es tab l i shes a

quiescent s t a t e t h a t permi ts t h e dense p a r t i c l e s t o accumulate and be s to red f o r a p e r i o d o f t ime. When t h e p o l l u t a n t p a r t i c l e s do

n o t s e t t l e , then opera t i ona l problems w i t h i n t h e waste t rea tment system develop which cause a l o s s o f impor tan t s o l i d s from t h e

system and t h e q u a l i t y o f t h e f i n a l discharged e f f l u e n t i s adversely e f fec ted .

Sedimentation may be used as a pretreatment, pr imary o r as

p a r t o f t h e secondary t reatment step. General ly, when used f o r

p re t rea tment and pr imary t reatment steps, d i r t and heavy d e b r i s

a r e removed which reduces system maintenance a c t i v i t i e s and costs.

The use o f sedimentat ion i n t h e secondary t reatment process i s p r i m a r i l y as a c l a r i f i c a t i o n s tep which has been discussed

prev ious ly .

D. Removal Based on Chemical P r o p e r t i e s

1. F loccu la t i on : Chemical f l o c c u l a t i o n i s used t o achieve two

impor tan t ob jec t i ves , namely - 1 ) t h e removal o f suspended p a r t i c l e s f rom t h e wastewater; and 2) t o reduce t h e phosphorus and

i r o n conten t i n t h e discharged e f f l u e n t . chemical agents ( 1 ime, metal f l o c c u l a n t s , o rgan ic polymers) t h a t

chemica l l y i n t e r a c t w i t h t h e p o l l u t a n t p a r t i c l e o r i o n i c specie i n t h e wastewater. Through t h i s i n t e r a c t i o n , t h e p a r t i c l e o r i o n i c

spec ie (i.e. phosphate, i r o n ) i s chemica l l y bonded t o t h e denser

chemical f l o c c u l a n t and i s now amenable t o c l a r i f i c a t i o n processes.

When lime, metal f l o c c u l a n t s and organ ic polymers are used i n

var ious combinations, so l i d s removed from a waste t rea tment system

can be more e f f e c t i v e l y dewatered r e s u l t i n g i n a volume r e d u c t i o n

o f t h e wasted sludge. Th is has an economic impact on t h e sludge

d isposa l a c t i v i t y ( i .e. h a u l i n g cos ts ) .

Advantage i s taken o f

5 W W TRMT SPNOFF/PRINCIPLE OF PHYS-CHEM

2. Adsorpt ion: Reinoval o f o rgan ic p o l l u t a n t s by adsorp t ion i s

impor tan t when t h e i n t e r a c t i o n i s dependant on a hydrophobic

chemical bonding w i t h the adsorbing p a r t i c l e (i.e. o rgan ic

polymers, a c t i v a t e d carbon). Because t h e adsorbent has been

se lec ted based upon i t s c o m p a t i b i l i t y w i t h the t reatment system

used, i t may be removed from t h e wastewater stream by e i t h e r

f 1 o t a t i o n o r c l a r i f i c a t i o n / s e t t l i ng.

3. I o n Exchange: The i o n exchange process i s s p e c i f i c a l l y designed

f o r t h e removal o f se lec ted anions (i.e. C l - ) and ca t i ons (i.e.

NH4+, Ca++, heavy metals) f rom water.

removal i s d i c t a t e d by the i o n i c charge o f t he res in . Most i o n

exchange r e s i n s used are n e g a t i v e l y charged and capture t h e

c a t i o n i c species such as NH4+ and t h e d i v a l e n t l y charged heavy

metals f rom t h e water stream. A f t e r a c e r t a i n bed volume o f water

has passed over t h e r e s i n , it loses i t s capac i t y t o remove t h e

unwanted ions. To regenerate t h e res in , u s u a l l y a b r i n e s o l u t i o n

o f sodium c h l o r i d e i s used t o recharge t h e i o n exchange system. A

t y p i c a l i o n exchange r e a c t i o n i s as fo l l ows :

The s e l e c t i v e i o n i c specie

B

I e g e n e r a t e

where Rc' i s t h e a n i o n i c a l l y charged res in .

t o us ing i o n exchange techniques f o r wastewater i s t h e u t i l i t y o f

t h e r e s i n , c l i n o p t i l o l i t e ( z e o l i t e ) f o r t h e removal of amnonia as a

t e r t i a r y t reatment step.

O f importance

6

WW TRMT SPNOFF/PRINCIPLE OF PHYS-CHEM

E . B i b l i ography

Removed Based on Phys ica l P roper t i es

Hamner, Mark J., 1975. Wastewater Technology" pub l i shed by Wiley & Sons, Inc., New York,

Chapter 11.

"Wastewater Processing" i n "Water and

Removal Based on Chemical P r o p e r t i e s

Weber, W. J., Jr., C. B. Hopkins, and R. Bloom, Jr., 1970. Physicochemical t rea tment o f wastewater.

Cont ro l Fed. 42:83. Jour. Water Pol 1

7 WW TRMT SPNOFF/PRINCIPLE OF BIOLOGICAL

Sec t ion I 1

The P r i n c i p l e o f B i o l o g i c a l Waste Treatment


be t h e master design o f a l l l i v i n g b i o l o g i c a l systems. As one system a s s i m i l a t e s food, metabol izes i t f o r energy and c e l l synthesis, and cas ts

o f f t h e end-products o f those metabolism processes, t h e r e fo l lows a chain o f events t h a t e v e n t u a l l y t ransforms those end-products i n t o a usable form f o r o the r systems. So i t i s w i t h man and h i s consumption o f a r g i c u l t u r a l d e r i v e d products-human food. He u t i l i z e s these products f o r h i s d i e t a r y

purpose and disposes t h e end-products i n t o t h e environment f o r re-use.

o f t h e processes t h a t man has learned t o become dependent upon f o r waste-

water p u r i f i c a t i o n i s t h a t o f t h e b i o l o g i c a l waste a s s i m i l a t i o n process. I t w i l l be t h e purpose o f t h i s s e c t i o n t o acquaint t h e extens ion

s p e c i a l i s t w i t h t h e bas i c p r i n c i p l e s o f b i o l o g i c a l waste treatment. To be

discussed w i l l be those f a c t o r s which d i r e c t l y i n f l u e n c e t h e waste assimi-

l a t i o n c h a r a c t e r i s t i c s o f t h e b i o l o g i c a l system. S p e c i f i c a l l y , t h e

i n f l u e n c e o f t h e growth environment, t h e n a t u r a l biogeochemical cycles, and

aerobic and anaerobic me tab i l i sm w i l l be reviewed. Through t h e presenta-

t i o n o f these top i cs , i t i s hoped t h e extens ion s p e c i a l i s t w i l l have a

work ing knowledge about t h e bas ic p r i n c i p l e s o f b i o l o g i c a l waste t reatment

processes.

Throughout nature t h e conservat ion o f m a t e r i a l and energy appear t o

One

B. Summary

a b i l i t y o f microorganisms t o use organic waste m a t e r i a l s as food t o

support t h e i r growth requirements - s p e c i f i c a l l y , t h e d e r i v a t i o n o f c e l l u l a r energy and t h e synthes is o f e s s e n t i a l c e l l ma te r ia l .

a c t i v i t y i s d i c t a t e d by va r ious f a c t o r s found i n t h e aqua t i c environment,

namely - t h e q u a n t i t y and t ype o f waste ma te r ia l , a v a i l a b i l i t y of oxygen,

temperature, pH, t h e presence o r absence o f t o x i c substances and sun l i gh t .

These f a c t o r s i n a v a r i e t y o f combinations can i n f l u e n c e t h e growth

response and waste assimi 1 a t i on behavior o f t h e aqua t i c m i c r o f l ora.

hav ing on t h e croplands i s t h e displacement o f e s s e n t i a l carbonaceous

The p r i n c i p l e o f b i o l og i c a l waste t reatment concepts focuses upon t h e

T h i s growth

A p o t e n t i a l impact t h a t food p roduc t i on and processing p r a c t i c e s a re

8

W W TRMT SPNOFF/PKINCIPLE OF BIOLOGICAL

p l a n t ma te r ia l f rom the s o i l .

n u t r i e n t balance w i t h a v a i l a b l e n i t rogen compounds i n t h e s o i l can promote

n i t r i f i c a t i o n and d e n i t r i f i c a t i o n processes by t h e ecosystem r e s u l t i n g i n

l o s s o f n i t rogen t o the atmosphere. atmosphere then requ i res a g rea te r expendi ture o f c e l l u l a r chemical energy

der ived from t h e a1 ready depl eated carbonaceous p l an t mater i a1 . p o i n t s up the importance o f t h e a p p l i c a t i o n t o a g r i c u l t u r a l croplands of

food process wastewaters and sludge from waste t reatment systems. these prac t ices , t h i s carbonaceous ma te r ia l i s re tu rned t o t h e s o i l and t h e

na tu ra l biogeochemical cyc les are benef i ted. Whether organic ma t te r i s degraded i n t h e s o i l o r i n t h e aquat ic

environment, two bas ic metabol ic processes are involved.

a re aerobic and anaerobic metabolism. I n t h e process o f generat ing

c e l l u l a r energy, t h e b i o l o g i c a l c e l l depends on ox ida t i ve - reduc t i on chemical reac t i ons t o take p lace r e s u l t i n g i n some form o f r e s p i r a t i o n .

key product o f t h e o x i d a t i v e reac t i ons i s t he hydrogen e l e c t r o n which i s t r a n s f e r r e d t o acceptors.

p r i m a r i l y oxygen which u l t i m a t e l y forms water.

(as under m ic roaeroph i l i c cond i t i ons ) , organic compounds such as py ruv i c

a c i d o r acetaldehyde may serve as hydrogen acceptors. omi t ted f rom t h e c e l l u l a r growth environment then carbon and s u l f u r become

t h e hydrogen acceptors. These f i n a l hydrogen acceptors serve as t h e

r e s p i r a t o r y f u n c t i o n f o r t h e c e l l .

Once c e l l u l a r energy has been generated t o ma in ta in e s s e n t i a l func-

t i o n s o f t h e c e l l , then t h e a d d i t i o n a l chemical energy i s used f o r t h e

syn thes is o f new c e l l components t h a t eventualy become p a r t o f newly formed c e l l s .

wastes, t h e aquat ic m i c r o f l o r a i s able t o support t h e i r growth needs and a t

t h e same t ime remove p o l l u t a n t s from t h e wastewater stream, conver t i ng

these wastes i n t o a form t h a t makes t h e i r removal more economical ly f e a s i - b l e and t h i s type o f water p u r i f i c a t i o n technology more p r a c t i c a l .

Th is carbonaceous ma te r ia l , when not i n

Recapture o f t h e n i t rogen from t h e

Thi s

Through

These processes

A

I n aerobic metabolism, t h e hydrogen acceptor i s

As oxygen becomes l i m i t i n g

When oxygen i s

Thus, through t h e degradat ion and a s s i m i l a t i o n o f food process ing

C. Terminology o f Wastewater

I nt roduc t i on

As one becomes invo lved i n wastewater sub jec t mat ter , f a m i l i a r i t y w i t h

commonly used terminology he1 ps i n t h e understanding and communication o f


t h i s technology. I n t h i s sect ion, se lected terminology s h a l l be presented

as i t r e l a t e s t o the systemat ic removal o f p o l l u t a n t s from wastewater,

sample a c q u i s i t i o n and analys is .

Treatment and Pre-Treatment Systems

e i t h e r a physical-chemical means o r b i o l o g i c a l l y . Physical-chemical

processes depend on s p e c i f i c phys ica l p r o p e r t i e s o r chemical i n t e r a c t i o n s

t h a t a l l ow f o r t h e removal o f t h e p o l l u t a n t f rom t h e wastewater stream.

f a c i l i t a t e removal, t he "captured" p o l l u t a n t p a r t i c l e i s f i l t e r e d , s e t t l e d

o r f l o a t e d out w i t h the a i d o f s p e c i a l l y designed systems. Much o f t he

te rmino logy associated w i t h physical-chemical processes are those used i n t h e f i e l d s o f phys ics and chemistry. Therefore, it i s assumed t h e user o f

t h i s manual has some background i n these sciences and no f u r t h e r d iscuss ion

o f terminology i n t h i s area w i l l be pursued.

I n con t ras t , t h e b i o l o g i c a l t reatment o f wastewater i s more

compl icated and the understanding o f t h e f r e q u e n t l y used terminology

re1 a t i ve t o t h i s techno1 ogy becomes essent i a1 . addresses i t s e l f t o t h e environmental c o n d i t i o n o f t h e system, t h e

r e l a t i o n s h i p o f t he p o l l u t a n t / n u t r i e n t t o the b i o l o g i c a l ecosystem

concent ra t ion , de ten t i on o f the wastewater i n t h e system, sol i d s compaction

a f t e r s e t t l i n g and s o l i d s r e t u r n and removal r a t e s f rom the system.

i n f l u e n c e on t h e behaviora l c h a r a c t e r i s t i c s o f t he conta ined b i o l o g i c a l

systems. Factors which d i r e c t l y a f f e c t t h e v i a b i l i t y o f t he b i o l o g i c a l

ecosystem are: 1) food (expressed as - - BOD, COD o r - TOC);

3 ) pH; r e f l e c t s the l e v e l o f o x i d a t i o n o r reduct ion. d i sso l ved oxygen (D.O.) i n t h e aqueous environment w i l l i n f l u e n c e t h i s

f a c t o r ) ; 5 ) a v a i l a b i l i t y o f water; 6 ) d isso lved s o l i d s concentrat ion; and

7 ) presence o r absence o f t o x i c substances.

s o l i d s and t h e presence or absence o f t o x i c substances (i.e. s a n i t i z e r s ,

heavy metals, minera l o i l ) can be a t t r i b u t e d t o t h e wastewater stream. I f

any o f these f a c t o r s become excessive and would have an adverse e f f e c t on

t h e b i o l o g i c a l ecosystem o f t h e sludge then some form o f pret reatment o f

Treatment systems are designed t o remove p o l l u t a n t s f rom wastewater by

To

Much o f the terminology

The cond i t i ons which e x i s t i n the aquat ic environment have a d i r e c t

2 ) temperature;

and 4 ) redox p o t e n t i a l (expressed as eH o r m i l l i v o l t s ) which

The presence o r absence o f

O f t he f a c t o r s s ta ted above, food, temperature, pH, water, d i sso l ved

10 W W TRMT SPNOFF/PRINCIPLE OF BIOLOGICAL

t h e waste stream must be i n i t i a t e d .

c e n t r a t i o n i s t o o high, t h e f l o w o f t h e wastewater stream cou ld be slowed

down i f t h e pH o f t h e wastewater i s above 10.54 o r below 6.0, t h e waste stream cou ld be neut ra l i zed . Pretreatment s imply means t o p rov ide some

form o f adjustment i n t h e wastewater stream t o make i t amenable t o

b i o l o g i c a l assimi 1 a t ion.

number o f impor tant r e l a t i o n s h i p s must be es tab l i shed i n t h e b i o l o g i c a l

waste t reatment system t o achieve and mon i to r proper system performance

and adequate p o l l u t a n t removal.

parameters are: 1 ) food t o microorganism r a t i o ;

3 ) s ludge r e t e n t i o n t ime/s ludge age;

cont ro l /s ludge re tu rn ; and 6 ) sludge se t t l ing /compact ion proper t ies .

P o l l u t a n t adso rp t i on /ass im i la t i on

i s dependent on t h e b i o l o g i c a l a c t i v i t y o f t h e sludge m i c r o f l o r a and t h e

t ype and amount o f food t h a t i s a v a i l a b l e t o support t h a t m i c r o f l o r a ’ s growth. I n t h e t reatment o f wastewater, t h e m i c r o f l o r a ( a community o f

microorganisms e x i s t i n g toge the r i n a g iven h a b i t a t ) genera l l y i s der ived

from t h e contaminated wastewater and t h e na tura l environment. Through

acc l ima t ion t o t h e wastewater, a popu la t ion o f microorganisms becomes

es tab l i shed and opera t ion o f t h e waste t reatment system evolves.

as the food /po l l u tan t i s i n abundance, t h e m i c r o f l o r a w i l l con t inue t o grow w i thou t r e s t r i c t i o n . However, once t h e n u t r i e n t / p o l l u t a n t becomes

l i m i t e d , t he m i c r o f l o r a w i l l e n t e r i n t o a se r ies o f growth s t a t e s which

i n f l u e n c e i t s behavior i n t h e aquat ic environment (i.e.

s e t t l e ) . It i s b a s i c a l l y t h e r e l a t i o n s h i p between t h e pol lu tant /BOD and

t h e l e v e l o f m i c r o f l o r a concent ra t ion t h a t c o n t r o l s t h e growth s t a t e o f t h e

microorganisms and u l t i m a t e l y i n f l uences t h e s e t t l i n g p r o p e r t i e s and waste

a s s i m i l a t i o n c h a r a c t e r i s t i c s o f t h e sludge f l o c .

i s a composite o f suspended mat te r which cons is t s o f c o l l o i d a l o rgan ic

substances, minera l s a l t s and microorganisms, Often, t h e sludge f l o c

s o l i d s a r e re fe r red t o as t h e biomass and are analyzed as v o l a t i l e

suspended so l i d s (VSS) or suspended so l i d s (SS) ,

so l i ds , t h e food (BOD) t o microorganism (VSS o r S S ) r e l a t i o n s h i p i s estab-

l i shed.

For example, i f t h e food/BOD con-

Once t h e wastewater stream i s amenable t o b i o l o g i c a l ass im i la t i on , a

These r e l a t i o n s h i p s o r ope ra t i ng 2) mixed l i q u o r so l i ds ;

4 ) de ten t i on time; 5 ) s ludge s o l i d s

Food t o Microorganism Ra t io :

As long

a b i l i t y t o

The s ludge / f l oc i n t u r n

As t h e wastewater stream i s brought i n contac t w i t h t h e s ludge f l o c

Des i rab le r a t i o s are d i c t a t e d by t h e system i n use. For var ious

11

WW TRMT SPNOFF/PRINCIPLE OF BIOLOGICAL

a c t i v a t e d sludge systems, t h e r a t i o may vary from 0.05 up t o 1.0 w i t h

r a t i o s o f 0.3 and 0.5 most commonly used. ganism (F/M) r a t i o i s determined by t h e f o l l o w i n g r e l a t i o n s h i p s :

General ly, t h e food t o microor-

F = M

where Q = BOD =

V =

MLSS =

- Q x BOD V x MLSS

r a w wastewater f l o w per day (mgd) BOD s t r e n g t h (mg/l) o f r a w wastewater app l i ed d a i l y

volume o f a e r a t i o n b a s i n (mgd)

mixed l i q u o r suspended s o l i d s i n a e r a t i o n b a s i n (mg/l), a v a i l a b l e d a i l y .

Mixed l i q u o r suspended s o l i d s a r e t h e sludge f l o c s o l i d s which have been

mixed w i t h t h e raw wastewater stream t h a t u l t i m a t e l y r e s u l t i n t h e a s s i m i l a t i o n o r adsorpt ion o f t h e water p o l l u t a n t s .

Other b i o l o g i c a l waste t reatment systems such as lagoons, ponds, r o t a t i n g b i o d i s c s and t r i c k l i n g f i l t e r operat ions do no t use F/M as a

c o n t r o l parameter. Th is i s because t h e sludge f l o c s o l i d s are not c o l l e c -

t e d and then re tu rned t o t h e system as w i t h t h e a c t i v a t e d sludge opera t i ng

modes.

F/M r a t i o cannot be establ ished, thereby negat ing i t s usefulness f o r these

Since sludge s o l i d s cannot be c o n t r o l l e d i n t h e above system, t h e

t ypes o f waste t reatment operations. ( d e t e n t i o n t ime i n system) f o r c o n t r o l o f t h e system.

suspended s o l i d s i n t h e a c t i v a t e d sludge waste t reatment system i s r e f l e c -

t e d i n i t s i n f l u e n c e on p o l l u t a n t removal e f f i c i e n c y and t h e s e t t l i n g performance i n t h e c l a r i f i e r . The mixed l i q u o r suspended s o l i d s concen-

t r a t i o n a f f e c t s t h e p o l l u t a n t a s s i m i l a t i o n r a t e per u n i t t ime and i s d i r e c t l y r e l a t e d t o e s t a b l i s h i n g t h e F/M c o n t r o l parameter. Perhaps t h e

most dramat ic e f f e c t s observed w i t h t h e waste t reatment system i s when t h e

mixed l i q u o r suspended s o l i d s are d i s t u r b e d by sudden surges o f water flow,

sharp increases i n n u t r i e n t s / p o l l u t a n t s o r t h e i n t r o d u c t i o n of t o x i c

substances. Unless t h e system can absorb these sudden changes, t h e mixed

1 i quo r suspended s o l i d s w i l l begin t o demonstrate poor s e t t l i n g p r o p e r t i e s

and e x h i b i t increased volume/unit weight upon s e t t l i n g a f t e r 1 hour. The

l a t t e r r e l a t i o n s h i p i s r e f e r r e d t o as t h e Sludge Volume Index (SVI ) . With

poor s e t t l i n g p r o p e r t i e s and sludge compaction, t h e mixed l i q u o r suspended

s o l i d s can be l o s t from t h e waste t reatment system due t o a "wash over" i n

These systems depend on con tac t t i m e

Mixed L i q u o r Suspended So l i ds : The importance o f t h e mixed l i q u o r

14

W W TRMT SPNOFF/PRINCIPLE OF BIOLOGICAL

based upon se lec ted c h a r a c t e r i s t i c s . These c h a r a c t e r i s t i c s may r e f l e c t an

organ ic p o l l u t a n t cond i t i on , pH, d i sso l ved

s o l i d s , d i sso l ved s o l i d s , c o l i f o r m conten t ,

greases. How t h e q u a n t i t a t e d da ta i s t o be i s t i c s a re t o be analyzed.

Two forms o f o b t a i n i n g samp

a re t h e g r a b and t h e t ime composite sample.

Sampling:

xygen, suspended so l i ds , t o t a l ammonia o r f a t s , o i l s and

used d i c t a t e s what charac ter -

es a re used. These forms

The grab sample i s bes t used

f o r mon i to r i ng day t o day opera t i ona l cond i t i ons o f t h e waste t rea tment system.

and l i t t l e change i s expected over a 24 hour period. Thus, t h e grab sample prov ides a measure o f t h e waste t reatment system's s t a b i l i t y .

ope ra t i ng parameters as mixed 1 i q u o r suspended s o l i d s (MLSS), r e t u r n i n g sludge s o l i d s (RS), SVI, D.O.

t h e grab sample technique. obtained/grabbed a t a s p e c i f i c t ime frame du r ing t h e system's operat ion.

Another use f o r t h e grab sample technique i s t o v e r i f y acc iden ta l

occurrences t h a t may have an adverse e f f e c t on t h e performance o f t h e

waste t reatment process.

p o l l u t a n t o r volume o f water t o t h e wastewater stream) loads o f caus t ic ,

acid, o i l , s a n i t i z e r s o r o rgan ic so l ven ts t h a t have been re leased t o t h e

waste stream w i t h o u t con t ro l . Also, t h e grab sample can a s s i s t t h e system

opera tor t o " t r o u b l e shoot" problem areas i n t h e waste t rea tment process.

The t ime composite sample i s use fu l f o r n ion i to r ing t h e wastewater

stream (un t rea ted and t r e a t e d ) t o determine user sewer charges, system

performance o r compliance w i t h fede ra l and s t a t e discharge permits. The

t ime composite sample may represent a wastewater stream from 5 minutes up t o 34 hours.

sampl e obtained.

t h e accuracy and rep resen ta t i on o f t h a t sample. l i n g frequency, sample a l i q u o t p r o p o r t i o n a l t o t h e f l o w r a t e o f t h e waste-

water, and wastewater f l o w rate.

c o l l e c t i o n u n i t s a re a v a i l a b l e t o t h e opera tors o f waste t rea tment systems.

Design o f these sampling and c o l l e c t i o n u n i t s i s based upon t h e above t h r e e

fac to rs . S e l e c t i o n of a sampling and c o l l e c t i o n u n i t should be determined

General ly, these opera t i ona l cond i t i ons a re i n a "s teady-s ta te"

Such

and pH a r e monitored on a d a i l y bas i s w i t h

As t h e te rm imp l ies , t h e wastewater sample i s

Examples would be s l u g (a sudden re lease o f a

The 24 hour composite sample i s t h e most common t y p e of

When t ime composite samples a re obtained, t h r e e f a c t o r s e n t e r i n t o

These f a c t o r s a re samp-

A number o f commercial sampling and


by t h e s p e c i f i c a p p l i c a t i o n o f t h e user.

u n i t s used t o o b t a i n more exac t i ng representa t ion .

TOC suspended so l i ds , pH and ammonia.

composite sample technique are t h e raw wastewater and more commonly, t h e

t r e a t e d e f f l u e n t discharged t o a r e c e i v i n g water way. Comparison o f t h e

t r e a t e d e f f l u e n t data w i t h the incoming r a w wastewater revea ls t h e waste

t rea tment process e f f i c i e n c y and can a l e r t opera tor personnel t o changing

process cond i t ions . The r a w wastewater composite s p e c i f i c a l l y can r e f l e c t

a l t e r e d produc t ion a c t i v i t y w i t h i n t h e food processing p l a n t n e c e s s i t a t i n g

changes i n t h e opera t ion o f t h e waste t reatment system.

s ludge systems, t h e opera tor can ad jus t t h e s o l i d s concen t ra t i on o f t h e

MLSS t o ma in ta in t h e optimum F/M r a t i o . A d d i t i o n a l l y , a t t e n t i o n would have

t o be given t o t h e r e t u r n sludge f low and sludge wastage rate. I n t h i s

case, i f t h e r e has been an increase i n the nutrient/BOD l o a d o r water f low,

t h e MLSS must be increased.

s ludge s o l i d s w i l l b u i l d up r e q u i r i n g an inc rease wastage i n t h e amount

( n o t t h e r a t e ) o f sludge, on a d a i l y basis. I n con t ras t , t h e aerobic and

anaerobic lagoon systems would have a r a p i d s o l i d s b u i l d up.

aerob ic lagoon system i s considered, t h e s o l i d s b u i l d up would add t o t h e

oxygen demand and u l t i m a t e l y t h e system would go s e p t i c and obnoxious odors

would develop. To vo id t h i s cond i t i on , p e r i o d i c removal o f t h e sludge

s o l i d s would be necessary. The anaerobic lagoon, i n cont ras t , would

r e q u i r e l onger de ten t i on t i m e f o r complete decomposit ion o f t h e organic

s o l i d s . I f t h e anaerobic lagoon cannot p rov ide t h e added d e t e n t i o n t i m e

t h e n e i t h e r an a d d i t i o n a l anaerobic lagoon w i l l need t o be b u i l t o r some

means o f removing t h e excess sludge from t h e anaerobic lagoon w i l l be

necessary.

Occasional ly, samples w i l l r e q u i r e t r a n s p o r t a t i o n t o an a n a l y t i c a l

l abo ra to ry . Should t h i s be t h e case, t h e sample must be maintained a t 4°C o r below but no t frozen. 0.0. mesurement should not he taken on t rans -

p o r t e d samples, o n l y on f r e s h ones.

p r o t e c t i n g t h e sample from d e s t r u c t i o n w h i l e en route, o r undergoing change

which would d i s t o r t t h e a n a l y t i c a l data. Proper sample i d e n t i f i c a t i o n i s a1 so important.

Cost w i l l be h ighe r f o r those

Ana lys i s f r e q u e n t l y performed on t ime composite samples are BOD, COD, Waste streams monitored by t h e t ime

For a c t i v a t e d

As the increased load i s maintained, more

As t h e

Common sense should be used i n

16


I n t e r p r e t a t i o n o f A n a l y t i c a l Data: As t h e i n t e r p r e t a t i o n o f t h e

a n a l y t i c a l da ta obtained on wastewater samples i s discussed, i t w i l l be

assumed t h e samples analyzed a re accura te and representa t ive .

Wastewater c h a r a c t e r i z a t i o n and waste t reatment system performance

a re bes t assessed by ana lyz ing 24 hour composite samples.

examined are p o l l u t a n t l oad ing (BOD, COD, TOC, suspended s o l i d s , d i sso l ved

s o l i d s ) , pH, temperature, D.O. and, i n some cases, f a t s , o i l s and greases.

These parameters a r e r e l a t e d t o t h e m i c r o b i a l growth f a c t o r s p r e v i o u s l y

discussed.

p o l l u t a n t removal e f f i c i e n c y performance o f t h e system can be determined.

Parameters

I n comparing t h e i n f l u e n t da ta w i t h t h e e f f l u e n t data, t h e

To ta l S o l i d (TS) D i s s i l v e d S o l i d s (DS) Suspended s o l i d s ( S S )

I 550°C - 1 h r

V o l a t i l e F i xed/As h Suspended Sol i d s (VSS) Sol i d s

O f importance i s t h e VSS and SS s ince these q u a n t i t a t e d values a re e m p i r i c a l l y i n t e r p r e t e d as represent ing t h e biomass o r v i a b l e p o r t i o n o f

t h e sludge.

c a l c u l a t e t h e F/M r a t i o , t h e value der ived can be e f fec ted .

parameter w i l l y i e l d a s l i g h t l y lower F/M r a t i o . l i q u o r can range from 2000 t o 9500 mg/l i n t h e a c t i v a t e d sludge system.

However, because s o l i d s a re no t recovered and re tu rned i n t h e aerated and

anaerobic lagoon systems, t h e SS value has l i t t l e use f o r c o n t r o l purpose

b u t can i n d i c a t e a t what l e v e l t h e lagoon system should rece ive a t t e n t i o n

f o r removing excess sludge so l i ds . SS i s a l so impor tan t when assayed i n

t h e r a w wastewater and t h e discharged water stream. t h e SS a re suspended p a r t i c l e s which may be complexes o f o rgan ic and

i n o r g a n i c ma te r ia l . p r o p e r l y c o n t r o l l e d i n t h e waste t reatment system. I n cont ras t , t h e SS i n

t h e f i n a l water discharge c o n t a i n o rgan ic ma t te r t h a t c o n t r i b u t e s t o oxygen

demand i n t h e r e c e i v i n g water way.

es tab l i shed i n most discharge permi ts f o r t h i s parameter. SS i n t h e f i n a l e f f l u e n t w i l l a l s o i n d i c a t e t o t h e system's opera tor t h a t t h e MLSS a re no t

s e t t l i n g p roper l y i n t h e c l a r i f i e r and a t t e n t i o n t o t h e system i s needed.

Depending on which parameter (i.e. VSS o r SS) i s used t o The SS

SS values i n t h e mixed

I n t h e r a w wastewater,

These p a r t i c l e s c o n t r i b u t e t o t h e MLSS and must be

Therefore, t h e r e i s a l i m i t a t i o n


The DS analysis i s of value when the wastewater stream contains mostly soluble BOD/pollutants (i .e. corn syrup) or a h igh s a l t (i.e. brine) content. special assistance w i t h other additives and the DS value aids i n determining the correct quantity for addition. used parameter in the management of a waste treatment system.

pH: Another wastewater characterist ic of importance i s i t s pH. This parameter i s important because i t influences the biological aci tvi ty of the bacteria, yeast and fungi. Ranges between 6.0 t o 9.0 f avor the bacteria and most other biological systems. However, as the pH value decreases t o 4.5, the bacteria cease to function and the f u n g i and yeast to le ra te this condition. Further decrease of the pH t o 3.8 will inhibit the growth of the yeast and only the f u n g i continue to function. In contrast , pH values above 10.5 affect the electrostat ic interaction of the microbe's cell wall w i t h the charged food molecule in the aquatic environment. In th i s s i tuat ion, the microbe's cell wall and the food molecule demonstrate predominantly a negative charge which results i n repulsion.

of the MLSS's pH can indicate the type of biological ac i t iv i ty taking place. Normal pH's f a l l between 7.3 t o 7.6 f o r most well operating waste treatment systems. As the pH of the MLSS decreases, biological act ivi ty i s probably nitrogen deficient and considerable carbohydrates and f a t s are being metabolized for cell synthesis and chemical energy derivation. When the pH has a tendancy t o go above 7.6, nitrogen i n the form of amino acids i s being deaminated and the carbon skeleton of the amino acids is being used for energy synthesis. Possibly, the wastewater i s deficient i n carbohydrates.

being discharged t o a municipal sewer or t o be i n compliance w i t h the federal or s t a t e discharge permit. Most l imits on pH f a l l between 6.0 and 9.0.

I n these cases, the waste treatment system may require

DS i s not a frequently

I n a well operating biological waste treatment system, a measurement

pH i s a parameter which must be determined on the wastewater stream

Ammonia: I n the previous pH section, deamination was mentioned a s i t pertained to increasing the pH of the MLSS. A major reason for the increase in pH i s due to the release of ammonia t o the aquatic environment by the deamination process. In contrast, many f u n g i , algae and yeast use ammonia as a nitrogen source for amino acid and protein synthesis.


Recause o f t h i s , a common p r a c t i c e used t o overcome n i t rogen d e f i c i e n t

cond i t i ons i n t h e waste t reatment process i s t o add ammonia con ta in ing

compounds t o the wastewater stream. As long as the ammonia i s captured by

t h e sludge biomass and c e l l growth takes place, l i t t l e i f any ammonia w i l l

escape i n the d ischarg ing water. However, i f the ammonia i s not captured

by the MLSS, then t h i s compound w i l l appear i n the t r e a t e d wastewater and

be discharged t o a r e c e i v i n g water way. Discharge o f ammonia t o the

r e c e i v i n g water way can r e s u l t i n an acce le ra t i on o f t he eu t roph ica t i on

process and r a p i d d e t e r i o r a t i o n o f t he ecosystem present i n the stream,

r i v e r o r lake. For t h i s reason, an ammonia (as NH3) l e v e l l i m i t a t i o n

i s inc luded i n some discharge permits.

Fats , Oils and Greases: For t h e most par t , f a t s , o i l s and greases

(FOG) der ived from animal and vegetable sources are biodegradable.

However, i n some munic ipa l sewer use ordinances, t he re are r e s t r i c t i o n s

p laced on the amount of FOG a l lowed t o en ter t h a t respec t i ve mun ic ipa l ' s

waste t reatment system. P a r t o f the problem focuses upon t h e mun ic ipa l ' s

pumping s t a t i o n s and the added maintenance cos ts t h a t t he FOG i n t h e

wastewater stream causes. Some sewer use ordinances l i m i t the FOG t o 100

m g / l and i s s p e c i f i c a l l y enforced toward food processing p lan ts who use the

sewer system.

dec la red on a s t a t e discharge permi t and compliance i s mandated. I n the

above cases where FOG reduc t i on i s needed, some form o f spec ia l waste

t reatment i s employed. The f r e q u e n t l y used technique i s complexing t h e FOG

w i t h an organic polymer and f l o a t i n g the Polymer-FOG complex out w i t h a i r

bubbles ( i .e . c e l l f l o t a t i o n ) . High q u a n t i t i e s o f FOG ( i .e . 300 mg / l ) i n

t h e wastewater can adversely a f f e c t the t r a n s f e r o f a i r i n t o the MLSS by

b l o c k i n g oxygen capture o f the biomass or lower ing sur face tens ion which

a l lows the a i r t o escape r a p i d l y from the wastewater.

Grab Sample Analyses: Four grab sample analyses which have importance

t o the opera t ion o f a waste t reatment system are temperature, d isso lved

oxygen (D.O.), S V I and the co l i f o rm content. The c o l i f o r m content ana lys is

i s requ i red p r i m a r i l y t o meet the l i m i t s set i n a federa l o r s t a t e

d ischarge permit . Th is ana lys i s i s used as an i n d i c a t o r o f f eca l p o l l u t i o n

and the poss ib le escape o f d isease producing b a c t e r i a from the waste

t reatment system. To comply w i t h the permi t , some waste t reatment

FOG'S can a l so be o f importance when a l i m i t a t i o n i s


system opera tors may d i s i n f e c t t h e f i n a l d ischarge stream w i t h ch lo r i ne ,

ozone o r s i m i l a r d i s i n f e c t a n t s .

s to rage t ime i s minimized and b a c t e r i a l growth reduced.

A grab sample prov ides t h e bes t data s ince

Temperature - Th is parameter has s i g n i f i c a n c e when the temperature

o f t h e wastewater o r t r e a t e d water stream cou ld a l t e r t h e

temperature o f a r i v e r , lake, pond o r stream thus, adverse ly

e f f e c t i n g t h e es tab l i shed ecosystem present. Temperature can

a l s o have a d i r e c t i n f l u e n c e on t h e r a t e o f b i o l o g i c a l a c t i v i t y

o f t h e waste t reatment system and the s o l u b i l i t y o f oxygen i n

t h e water. These f a c t o r s w i l l be discussed b r i e f l y i n t h e

f o l l o w i n g sect ion. Obviously i f temperature i s t o be

determined, i t must be taken a t t he t ime t h e sample has been

obtained.

1 )

2 ) - D.O. - Measurement of t h i s parameter i s important i n the

i n f l u e n t , MLSS and e f f l u e n t . B e t t e r BOD removal appears

assoc ia ted w i t h a v a i l a b l e D.O. i n t he i n f l u e n t p r i o r t o e n t r y

i n t o t h e waste t reatment process. Leve ls o f 1 t o 3 mg/l D.O.

appear des i rab le . I n the waste t reatment process, t h e MLSS

should be maintained a t D.O. l e v e l s between 1.0 t o 3.0 mg/l

f o r optimum waste t reatment due t o fede ra l and s t a t e requ i re -

ments i n t h e discharge permit . D.O. uptake i s d i r e c t l y

e f f e c t e d by t h e b i o l o g i c a l a c t i v i t y o f t he biomass, amount o f a v a i l a b l e nutr ient/BOD and temperature. Temperature

i n f l u e n c e s the m i c r o b i a l growth and a s s i m i l a t i o n r a t e bu t a l so

a f f e c t s the d i f f u s i v i t y and s o l u b i l i t y o f oxygen. The h ighe r

t h e temperature, t h e f a s t e r t h e growth and a s s i m i l a t i o n ra te ,

t h e g rea te r t h e oxygen uptake by t h e sludge m i c r o f l o r a w i l l

be. Concurrent ly, t h e s o l u b i l i t y p roper t y o f oxygen becomes

lower. Because o f t h i s increased oxygen uptake and s o l u b i l i t y

p roper ty , t h e D.O. de te rm ina t ion must be taken immediately

a f t e r t h e sample has been taken.

t h e MLSS bu t a l so i n d i c a t e s t h e d e n s i t y o f t he sludge, a f t e r

one hour o f s e t t l i n g . To determine t h e SVI value, one l i t e r

o f MLSS ( w e l l mixed) i s placed i n an Imho f f cone and t h e

volume o f t h e sludge b lanket ( t h e c l e a r water/s ludge s o l i d s

3 ) - S V I - Th is parameter i s use fu l i n mon i to r i ng t h e s e t t l i n g r a t e o f

20


i n t e r f a c e ) i s observed and recorded a t 30, 45 and 60 minutes.

I n a d d i t i o n , a t o t a l suspended s o l i d s i s determined repre-

s e n t i n g t h e one l i t e r volume.

i n t o t h e s e t t l e d volume, a f t e r one hour (as m i l l i l i t e r ) , t h e

S V I va lue can be c a l c u l a t e d and expressed as ml/g o f MLSS.

Values i n the range o f 250 o r below suggest acceptable sludge

and l i t t l e l o s s o f s o l i d s c o n t r o l w i l l be encountered i n t h e

c l a r i f i e r . However, the h ighe r t h e S V I va lue t h e more l i k e l y

s ludge suspended s o l i d s w i l l be l o s t from the c l a r i f i e r and the

discharged water w i l l be out o f compliance.

By d i v i d i n g t h e MLSS ( i n grams)

S umma ry :

organized and presented gives the reader a b e t t e r understanding o f t h e

te rmino logy f r e q u e n t l y used w i t h wastewater processes. A1 so, an under-

s tand ing o f t h e use o f commonly monitored parameters i n the wastewater

f i e l d should have been achieved. B i o l o g i c a l waste t reatment o f food/

p rocess ing wastewater depend on e s t a b l i s h i n g t h e c o r r e c t and optimum growth

environment f o r those oryanisnis who are t o ass i rn i la te t h a t waste.

t o c o r r e c t performance o f any b i o l o g i c a l waste t reatment system i s t o

m a i n t a i n t h e v i a b i l i t y o f the microorganisms present i n the aquat ic

environment. The v i a b i l i t y o f these organisms d i c t a t e s the n u t r i e n t

a s s i m i l a t i o n character, t h e a b i l i t y o f t h e m i c r o b i a l c e l l s t o form f l o c s

and t h e s ludge 's s e t t l i n g property. A l l o f these f a c t o r s i n f l uence t h e

u l t i m a t e p o l l u t a n t removal e f f i c i e n c y o f t he waste t reatment system. A l l

terminology, wastewater parameter c h a r a c t e r i s t i c s and system mon i to r i ng parameters t h a t have been presented i n t h i s sec t i on are essen t ia l t o t h e

assessment and c o n t r o l o f t h e b i o l o g i c a l waste t reatment process and t h e

q u a l i t y o f water being discharged.

parameters w i l l g r e a t l y a s s i s t a s p e c i a l i s t i n addressing those a c t i v i t i e s

r e l a t e d t o waste t reatment processes f o r food processing waste streams.

It i s hoped t h a t t he general manner i n which t h i s s e c t i o n has been

The key

F a m i l i a r i t y w i t h these terms and

4

D. The B i o l o g i c a l Processes

1. The Growth Environment: Waste t reatment systems which are

dependent upon t h e microbe f o r a s s i m i l a t i o n o f p o l l u t a n t s f rom t h e

waste stream must ma in ta in the best poss ib le growth environment t o

op t im ize t h a t a s s i m i l a t i o n process. The p r i n c i p l e behind t h e use

21


o f b i o l o g i c a l waste t reatment processes i s t h e u t i l i z a t i o n of t h e

n u t r i e n t value o f t h e p o l l u t a n t f o r t h e d e r i v a t i o n o f c e l l energy and syn thes is o f new c e l l mater ia l . Several f a c t o r s i n t h e aquat ic

environment can have a d i r e c t i n f l u e n c e on t h e metabol ic behavior o f t h e microbe c u l t u r e r e s u l t i n g i n e i t h e r a b e n e f i c i a l (growth) o r

de t r imen ta l (death) outcome. Those f a c t o r s which have a d i r e c t

e f f e c t on t h e m ic rob ia l c e l l are: 1) n u t r i e n t type and

a v a i l a b i l i t y , 2 ) absence o r presence o f oxygen i n t h e water, 3 ) temperature, 4 ) pH, 5) presence o f t o x i c substances, and 6 ) l i g h t

a v a i l a b i l i t y i n t h e v i s i b l e wavelength range. Once t h e d e s i r a b l e

phys ica l and chemical environment i s estab l ished, then t h e a b i l i t y

of t h e system t o t r e a t t h e food processing waste becomes dependent upon t h e metabol ic c a p a b i l i t i e s o f t h e water 's m i c r o f l o r a t o

breakdown and a s s i m i l a t e t h e organ ic c o n s t i t u e n t s t h a t a re present.

a. Nu t r i en ts : Essen t ia l t o t h e growth response o f t h e b i o l o g i c a l

waste t reatment process i s t h e n u t r i e n t q u a l i t y and q u a n t i t y

of t h e wastewater. However, i n p rac t i ce , t h e n u t r i e n t q u a n t i t y i s on l y e m p i r i c a l l y measured as t h e b i o l o g i c a l oxygen

demand (BOD), chemical oxygen demand (COD), o r t h e t o t a l o rgan ic carbon (TOC).

n i t r o g e n and phosphate. These analyses a re used t o a s c e r t a i n

t h e amount and t ype o f n u t r i e n t present i n t h e wastewater f o r

t h e purpose o f improving t h e n u t r i e n t q u a l i t y . Th is n u t r i e n t

q u a l i t y i s based on optimum waste a s s i m i l a t i o n by t h e

m i c r o b i a l c e l l when t h e chemical balance o f carbon t o n i t r o g e n t o phosphorus i s 100:6:1, respec t i ve l y .

be more accu ra te l y de f ined as poss ib l y con ta in ing assor ted

combinat ions o f so lub le sugars, starches, dextrans, ce l l u lose , p ro te ins , i no rgan ic i ons and s a l t s , v i tamins, f a t s , o i l s ,

greases, emu1 s i f i e r s , detergents and complexes thereo f . Those

substances present i n t h e wastewater p rov ide t h e sources f o r

d e r i v i n g t h e microbe 's c e l l u l a r energy through i t s o x i d a t i v e

and r e s p i r a t o r y processes and t h e b u i l d i n g b locks f o r

syn thes i z ing c e l l u l a r s t r u c t u r e s (i.e. enzymes, c e l l wa l l ,

Q u a l i t a t i v e measurements a re ammonia,

I n food process ing wastewaters, t h e n u t r i e n t q u a l i t y can


cytoplasm). O f importance a re t h e carbohydrates and f a t s f o r

genera t ing c e l l u l a r energy, ammonia and p r o t e i n f o r syn thes is o f nuc lear m a t e r i a l and c o n s t i t u t i v e enzymes, and phosphorus

which i s needed i n t h e fo rma t ion o f energy t r a n s f e r compounds ( i .e. adenosine d i - and t r iphosphate) .

The q u a l i t y o f t h e n u t r i e n t s a v a i l a b l e i n t h e wastewater

can a l s o d i c t a t e t h e composi t ional makeup o f t h e m i c r o f l o r a i n

t h e waste a s s i m i l a t i o n environment.

a t t r i b u t e d t o t h e acc l ima t ion c a p a b i l i t i e s o f t h e microorgan-

isms present and t h e i r a b i l i t y t o compete, a s s i m i l a t e and use

t h e a v a i l a b l e n u t r i e n t s f o r t h e i r growth needs. I n many cases,

t h e food processing wastewater w i l l c o n t a i n a n u t r i e n t imbalance and r e q u i r e some form o f adjustment (i.e. a d d i t i o n

of a n i t r o g e n source). Also, c e r t a i n wastewaters f rom food

processing opera t ions w i l l promote a t ype o f growth response

t h a t r e s u l t s i n poor performance o f t h e waste t reatment system

(i.e. f i l amentous b a c t e r i a and f u n g i ) .

microorganism present i n t h e waste a s s i m i l a t i o n process

g r e a t l y i n f l uences t h e m i c r o f l o r a l popu la t i on types, t h e

r e s p i r a t o r y mechani sins t h a t w i 11 be f u n c t i o n a l , and how

subs t ra tes ass im i la ted w i l l be metabol ized w i t h s p e c i f i c end products be ing generated. Three types o f b i o l o g i c a l waste

t rea tment processes are used, namely- 1 ) aerobic, 2 )

m ic roaeroph i l i c / f a c u l t a t i v e and 3 ) anaerobic. Perhaps t h e most

e x t e n s i v e l y used process i s t h e aerobic t ype which depends upon

t h e presence o f oxygen a t t h e 0.8 mg/l up t o 4 mg/l l e v e l as

d i sso l ved oxygen. Th is oxygen concen t ra t i on range w i l l support

predominant ly o x i d a t i v e inetabol i c a c t i v i t y and t h e m i c r o f l o r a

w i l l be oxygen dependent f o r t h e i r r e s p i r a t o r y func t ions . End

products o f aerobic metabolism processes a re C02, water and

r e s i d u a l amounts o f ammonia. As t h e d i sso l ved oxygen l e v e l i n

t h e acquat ic environment decreases below 0.5 mg/l , t h e

m i c r o a e r o p h i l i c o r f a c u l a t i v e t ype m i c r o f l o r a (namely a c i d

producers) i s favored. Under f a c u l t a t i v e growth cond i t ions ,

l i t t l e dependency i s p laced on oxygen f o r t h e r e s p i r a t o r y

Th is phenomenon can be

b. Oxygen conten t : The a v a i l a b i l i t y o f oxygen t o t h e


func t ion . Instead, in te rmed ia te metabol ic products ( i .e.

p y r u v i c acid, acetaldehyde) a re used i n the r e s p i r a t o r y

process. Also, n i t rogen and s u l f u r may be used by these

microorganism as an a l t e r n a t e t o oxygen f o r r e s p i r a t i o n . End

products o f mic roaeroph i l i c r e s p i r a t o r y processes are l a c t i c

ac id , a lcohol , ketones and aldehydes. The anaerobic c o n d i t i o n

descr ibes the waste a s s i m i l a t i o n cond i t i ons where t h e metabol ic

and r e s p i r a t o r y processes proceed i n the absence o f oxygen.

Under the anaerobic growth cond i t ion , the microorganisms use

carbon and s u l f u r as the hydrogen acceptors i n the o x i d a t i v e

ca tabo l ism o f ass im i la ted n u t r i e n t s . Also, the anaerobic

microbes w i l l e x i s t i n harmony (commensalism) w i t h the

f a c u l t a t i v e microorganisms, b e n e f i t i n g from the organic acids,

a lcoho ls , ketones and aldehydes produced by the l a t t e r .

P r i m a r y end products o f anaerobic r e s p i r a t i o n are methane,

hydrogen s u l f i d e and CO2 gases.

c a t a l y t i c a c t i v i t y o f t he i nna te enzyme systems present i n t h e

m i c r o f l o r a populat ion. S p e c i f i c a l l y , temperature a f f e c t s the

r a t e o r speed o f t he c a t a l y t i c a c t i v i t y ; whereas, pH in f l uences

t h e s to i ch iomet ry o f t he enzyme a c t i v i t y . F u r t h e r i t i s

repo r ted t h a t low temperatures (i.e. 40 C i n con t ras t t o

200 C) do not e f f e c t t h e growth r a t e o f t he m ic rob ia l

popu la t i on d i r e c t l y but an i n f l uence i s exer ted on the biomass

f l o c p a r t i c l e s ize. Usual ly , a t low growth temperatures (i.e.

40 C ) , t h e f l o c s i ze i s p in -po in t which causes poor

s e t t l i n g i n t h e c l a r i f i c a t i o n step. With respect t o pH,

cond i t i ons between 6 and 8 w i l l p rov ide an adequate growth

environment. However, pH values below 6 beg in t o f a v o r yeast

and fung i growth w h i l e pH values below 3.8 f a v o r t h e fung i

only. Also, pH values i n the wastewater above 10.5 w i l l

decrease the suspended s o l i d aggregat ion process and n u t r i e n t

c a p t u r i n g a c t i v i t y o f t he m ic ro f l o ra .

d. Tox ic Substances: These substances are p o l l u t a n t s t h a t do not

b e n e f i t t he waste a s s i m i l a t i o n process, b i o l o g i c a l l y . Tox ic

substances would be those ma te r ia l s which could adverse ly

c. Temperature and pH: These growth f a c t o r s i n f l uence the


e f f e c t t h e b i o l o g i c a l waste t reatment process o r cou ld be

c a r r i e d over i n t o the food chain, and u l t i m a t e l y be consumed by

man. However, f o r our purposes here, t o x i c substances w i l l be

discussed as they r e l a t e t o the b i o l o g i c a l system's growth

environment.

Tox ic substances such as heavy metals (a rsen ic , copper,

mercury) , c h l o r i n e , and i o d i n e have t h e i r de t r imenta l i n f l u e n c e

on s p e c i f i c c e l l components (cytochrome system, enzyme) which

cause c e r t a i n c e l l f unc t i ons ( r e s p i r a t i o n , subs t ra te t r a n s p o r t , nuc lea r ma te r ia l rep1 i c a t i o n ) t o cease. When a t o x i c c o n d i t i o n

develops, cons iderab le b i o l o g i c a l a c t i v i t y and waste

a s s i m i l a t i o n i s l o s t . There are many organic and ino rgan ic

substances t h a t can adversely e f f e c t m i c r o b i a l a c t i v i t y . The

t o x i c i t y o f these m a t e r i a l s can be in f luenced by such f a c t o r s

as temperature, s a l t concent ra t ion , pH and contac t t ime. For

example, a m ic rob ia l c e l l membrane serves t o p r o t e c t t he c e l l ' s

cytoplasm from be ing a f f e c t e d by a t o x i c agent. But suppose

t h a t agent were i on i zed by a s h i f t i n t he environment's pH, then t h e t o x i c substance, i n t h e i on i zed form, could penet ra te

t h e membrane and cause some d i so rde r t o develop. Poss ib ly , t he

d i s o r d e r could be severe enough t o cause death t o t h e c e l l .

L i g h t : The photosynthesis process i s important t o many

b i o l o g i c a l systems f o r t he d e r i v a t i o n of c e l l energy. Also, a

major b e n e f i t from photosynthesis i s t he generat ion o f oxygen

which i s released t o the atmosphere or aquat ic environment as

t h e case may be. As l i g h t i s r e l a t e d t o the b i o l o g i c a l system

and t h e waste t reatment process, one cannot ignore i t s

importance t o the growth environment o f algae. Algae are very

impor tan t t o the opera t ion o f f a c u l t a t i v e lagoon systems.

However, algae can a l s o be found as a nuisance growth i n

p o l i s h i n g ponds and c l a r i f i e r s . I n t h e f a c u l t a t i v e lagoon

system, algae provides the oxygen t o the aquat ic environment which supports the growth o f the mic roaeroph i l i c biomass

present. The avai 1 ab i 1 i ty o f sun1 i ght d r i v e s the

photosynthesis process and thus, a ids t h e growth a c t i v i t y o f

25


t h e algae and generates the l i f e suppport ing oxygen.

growth i n a p o l i s h i n g pond o r c l a r i f i e r i s considered, a

problem develops which d i r e c t l y a f f e c t s the q u a l i t y o f t he

t r e a t e d wastewater. A lga l growth, i f not removed from a

discharged t r e a t e d waste stream, can c o n t r i b u t e t o an apparent

inc rease i n BOD and suspended s o l i d s load which then reaches

t h e t r i b u t a r y stream. Th is problem occurs genera l l y between

A p r i l through October o f each year.

As a l g a l

2. The Na tu ra l Biogeochemical Cycles: The na tu ra l biogeochemical

c y c l e s become important t o waste t reatment systems when s t a b i l i z e d

sludge s o l i d s are disposed o f upon a g r i c u l t u r e land.

s ludge places n u t r i e n t s back i n t o t h e s o i l which are the a v a i l a b l e

f o r p l a n t l i f e (crops). A key t o the biogeochemical cyc les i s the

a v a i l a b i l i t y o f organic carbon and n i t r o g e n (as ammonia o r i n an

organ ic form), i n proper balance, f o r use by t h e s o i l ecosystem.

t h e n a t u r a l ecosystem. I n t h i s f igure , t he i n t e r r e l a t i o n s h i p s o f

n i t r o g e n can be seen between p l a n t , animal, so i 1 and atmosphere.

The r o l e o f t he microorganism i s t o decompose p r o t e i n t o ammonia

which can be r e a d i l y f i x e d by the p l a n t o r t o n i t r i f y ammonia t o

n i t r i t e (N02) and n i t r a t e (NO3).

used as a n i t r o g e n source by the p lan t . Microbes a l so can f i x

n i t r o g e n from t h e atmosphere and conver t i t i n t o a form t h a t t he

p l a n t can u t i l i z e .

carbon cycles. Photosynthesis, p l a n t growth and decay p l a y key

r o l e s i n t h e interdependence o f these cycles.

n i t r o g e n and carbon sources remain i n the same l o c a t i o n , t h e

c y c l i c processes w i l l proceed e f f i c i e n t l y and t h e chances o f

l o s i n g n i t r o g e n from the s o i l are minimal.

n a t u r a l ecosystem, n i t r o g e n and carbonaceous p l a n t m a t e r i a l s w i l l ma in ta in balance o f t h e " i n t e r n a l " n i t r o g e n and carbon cyc les

which w i l l preserve t h e na tu ra l biogeochemical processes.

Un fo r tuna te l y , t h e natura 1 b i ogeoc hemi c a 1 processes are

th rea tened by i n t e n s i v e c rop produc t ion and food processing.

must r e a l i z e t h a t these a c t i v i t i e s promote a displacement o f

Here, t he

F i g u r e 11-1 presents t h e basic n i t r o g e n c y c l e as it e x i s t s i n

The n i t r a t e can then be

F i g u r e 11-2 shows t h e interdependence o f t he n i t r o g e n and

As long as the

Under t h i s type o f

One

\ a t tiio spher i c

26

W W THMT SPNOFF/PKINCIPLE OF BIOLOGICAL

N I T H O G E N ATMOSP t i ER I C -- /

b i o l og i ca 1 /

\ p r c c i p i t a t i o n

i n d u s tri a 1 \ f i x a t i o n / f i x a t i o n

\ / /

A N I N A L ! \ - N p l a n t up take I

m i c r o b i a l decornposi t i o n

1 \ v

n i Cri f i c a t i o n

i f i c -

F i g u r e 11-1. A s i t i t p l i f i e d scheme o f t h e n i t r o g e n cyc le.


Figure 11-2. The interdependence o f t he nitrogen and carbon cycles.

28


3 .

cons iderab le carbonaceous 1) an t i na te r ia l froin t h e land. I f t h i s

carbonaceous p l a n t ma te r ia l i s not a v a i l a b l e f o r d e r i v i n g c e l l u l a r

energy and i s out o f balance w i t h the a v a i l a b l e i no rgan ic o r

o rgan ic n i t rogen, then the n i t rogen i n the s o i l w i l l accumulate

and be transformed i n t o n i t r a t e through n i t r i f i c a t i o n . N i t r a t e i s

a h i g h l y mob i le i o n and can leach through the s o i l u l t i m a t e l y

reach ing water sources. Another f a t e t h a t n i t r a t e might encounter

i s d e n i t r i f i c a t i o n t o a n i t r o g e n gas which r e s u l t s i n loss o f

n i t r o g e n froin the s o i l and escape i n t o the atmosphere. General ly,

d e n i t r i f i c a t i o n takes p lace under anaerobic cond i t i ons where

organ ic carbon is being metabolized. Th is n i t r o g e n l o s s c rea tes

an i n e f f i c i e n c y o f n i t r o g e n conserva t ion and u l t i m a t e l y more

chemical energy w i l l be requ i red t o recapture the n i t r o g e n gas and

f i x i t i n t o a form the p l a n t can use. F igu re 11-3 demonstrates

t h e n i t r o g e n c y c l e a f t e r a crop has been harvested frorii the land.

Aerobic Metabolism: Most b i o l o g i c a l waste t reatment systems i n

ope ra t i on today depend on aerobic metabolism t o a s s i m i l a t e and

s t a b i l i z e ( o x i d i z e ) wastewater p o l l u t a n t s . These systems inc lude

a c t i v a t e d sludge, contac t surfaces, ponds, lagoons and aerob ic

d iges ters . One should be aware t h a t several l e v e l s o f h i o l o g i c a l

processes are i nvo l ved i n the a s s i m i l a t i o n o f n u t r i e n t s ,

d e r i vat i on o f energy , and synt ties i z i ng o f c e l l t i l a r components.

F i g u r e 11-4 presents a f l o w cha r t o f t he d i f f e r e n t metabo l ic

a c t i v i t i e s r e l a t e d t o the m i c r o b i a l s t a b i l i z a t i o n o f organic

wastes (16). The waste uptake begins when t h e m i c r o f l o r a becomes

a t tached t o o r a t t r a c t s the degradable organic ma te r ia l . I n t h e

presence o f oxygen, the m i c r o f l o r a i s able t o d e r i v e energy from

t h e f r e s h l y acquired n u t r i e n t s w h i l e producing carbon d i o x i d e and

water as end products o f r e s p i r a t i o n . U t i l i z i n g the newly

generated energy, t h e m i c r o b i a l c e l l synthesizes p r o t e i n and o the r

impor tan t c e l l u l a r components which way e i t h e r be used by the c e l l

o r d i r e c t e d toward new c e l l for ination. Concurrent w i t h the

s y n t h e s i z i n g process i s the dy ing and a u t o l y s i s o f t h e o lde r c e l l

r e s u l t i n g i n the re lease o f i n e r t organic i na te r ia l and some

degradable organic ma te r ia l . The l a t t e r phase o f the c e l l ' s l i f e

i s r e f e r r e d t o as " the endogenous phase". These metabol ic pro-

- WW TRMT SPNOFF/PRINCIPLE OF BIOLOGICAL 29

CROP RESIDUE

Decomposi tion]*-b

II"obilization1 .1 -1

SOIL ORGANIC N -?.r--A-.

4

I & Leachin

F i g u r e 11-3. The n i t r o g e n c y c l e i n cropped l a n d a f t e r c r o p removal.


v, r: ln

W r

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I: 1

I I I I I I I I I #

9

1 I

I I

I I

I I

A

N 0

W

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cesses, i n

catabol ism

ww

phy s i o l og i c a 1 t e m s

and end-products of

31 TRMT SPNOFF/PRINCIPLE OF BIOLOGICAL

are membrane t ranspor t ; carbohydrate

metabolism; o x i d a t i v e phosphoryla-

t ion; r e s p i r a t i o n (exogenous and endogenous) ; c a t a b o l i t e re-

pression; and t h e syn thes i z ing processes r e q u i r i n g t h e a s s i m i l a t i o n

of n i t r o g e n compounds (i.e. amino ac ids) and p r o t e i n synthesis.

The c e l l u l a r membrane i s fundamental l y impermeable t o most

me tabo l i t es and n u t r i e n t s . Passage o f subs t ra te across the mem-

brane i s c a r r i e d out by s p e c i f i c t r a n s p o r t systems f o r carbohy-

d r a t e s and amino acids. These t r a n s p o r t systems are associated

w i t h a source o f metabol ic energy and have t h e c a p a b i l i t y o f

c o l l e c t i n g s u b s t a n t i a l concentrat ions o f subst rates w i t h i n t h e

endoplasm o f the c e l l (1, 4).

c o n t r a s t t o t h e carbohydrate t r a n s p o r t processes, are c o n s t i t u t i v e

i n nature r a t h e r than induc ib le . The amino a c i d t r a n s p o r t systems

demonstrate much lower k i n e t i c e q u i l i b r i u m s and appear t o possess

broader s p e c i f i c i t i e s .

i so leuc ine , and v a l i n e are t ranspor ted by a s i n g l e system. I n

c o n t r a s t t o sugars, amino a c i d t r a n s p o r t i s o f t e n r a p i d enough

( re1 a t i ve t o met abol i sm) t o e x h i b i t act i ve concent r a t i o n even

d u r i n g normal metabolism; bu t t h e k i n e t i c s are s impler t o study i f p r o t e i n synthes is i s blocked. One important f a c t o r concerning t h e

broad s p e c i f i c i t y o f amino ac ids t r a n s p o r t systems i s t h e f a c t t h a t

amino ac ids common t o t h a t t r a n s p o r t must compete f o r mediat ion

across t h e c e l l membrane (5).

Carbohydrate Catabolism. Carbohydrate catabol ism invo lves

t h e conversion o f 6-carbon sugars t o glucose which are u l t i m a t e l y

converted t o pyruvate v i a f o u r poss ib le pathways:

1. Embden-Meyerhof-Parnas (EMP) pathway

2. 3. Entner-Doudoroff (ED) pathway

4. Phosphoketolase pathway

Amino Acid Transport. The amino a c i d t r a n s p o r t systems, i n

Thus, t h e a l i p h a t i c amino ac ids leuc ine,

Warburg-Dickens o r hexose monophosphate (HMP) pathway

The reader i s r e f e r r e d t o D o e l l e ' s comprehensive t reatment on

b a c t e r i a l metabolism f o r an in-depth d iscuss ion o f these pathways

(6). atoms, s i n g l e atoms, o r e l e c t r o n s from combination w i t h one

E s s e n t i a l l y , metabolism invo lves the t r a n s f e r o f groups o f

32 W W TKMT SPNOFF/PKINCIPLE OF BIOLOGICAL

cesses, i n phys io l o g i c d l terms are wiribrane t ranspor t ; carbohydrate

catabol ism and end-products o f nietabol ism; o x i d a t i v e phosphoryla-

t i o n ; r e s p i r a t i o n (pxogenous and endogenous); c a t a b o l i t e re-

press ion; and t h e syn thes iz ing processes r e q u i r i n g t h e a s s i m i l a t i o n

o f n i t r o g e n compounds ( i .e. amino ac ids) and p r o t e i n synthesis.

The c e l l u l a r niernbrdne i s fundamental l y impermeable t o i m s t

metabo l i tes and n u t r i e n t s . Passage o f subs t ra te across t h e mem-

brane i s c a r r i e d out by s p e c i f i c t r d n s p o r t systems f o r carbohy-

d r a t e s and amino acids. These t r a n s p o r t systems are associated

w i t h a source o f metabol i c energy and have t h e c a p a b i l i t y of

c o l l e c t i n g s u b s t a n t i a l concentrdt ions o f s i rbstrates w i t h i n t h e

endoplasm o f the c e l l (1 , 4 ) . Amino Ac id Transport . The amino a c i d t r a n s p o r t systems, i n

c o n t r a s t t o t h e carbohydrate t ranspor t processes, are c o n s t i t u t i v e

i n nature r a t h e r thdn induc ib le . The amino a c i d t r a n s p o r t systems

demonstrate much lower k i n c t i c e q u i l ibr iun is and appear t o possess

broader s p e c i f i c i t i e s . Thus, the a1 i p h a t i c dinino ac ids leuc ine,

i s o l e u c i n e , and v a l i n e are t,ransported by a s i n g l e system. I n

c o n t r a s t t o sugars, amino a c i d t r a n s i i o r t i s o f t e n r a p i d enough

( r e l a t i v e t o irietabolisiir) t o e x h i b i t a c t i v e concent ra t ion even

d u r i n g normal inetabolisrri; bu t the k i n e t i c s are s imp ler t o study i f

p r o t e i n synthes is i s blocked. One impor tant f a c t o r concerning t h e

broad s p e c i f i c i t y o f amino ac ids t r d n s p o r t systems i s the f a c t t h a t

amino ac ids coininon t o t h a t t r a n s p o r t must compete f o r mediat ion

across t h e c e l l membrane ( 5 ) .

Carbohydrate Catabolism. Carbohydrate ca tabo l ism invo lves

t h e conversion o f 6-carbon suydrs t o qlt icose which w e i r l t i m a t e l y

conver ted t o pyruvate v i d f o u r i ’oss ib le pathways:

1 . Embden-P!eyerhof-!)drri(is (EMP) pathway

2.

3. Entner-Dourtoroff ( E l ) ) pattiway

4. Phosphoketol asc pathway

Warburg-Dickens 01% hexose monophosphate (HMP) pathway

The reader i s r e f e r r e d t o Doe1 l e ’ s coiripreiiensive t redt inent on

b a c t e r i a l rnetabolisrn f o r dn in-depth d iscuss ion o f these pathways

( 6 ) . Essent ia l l y , met.abo1 ism i i i v o l ves the t r a n s f e r o f groups of

a t o m , s i n g l e atoms, o r e l e c t r o n s froin COmbindtiOn w i t h one

33 WW TRMT SPNOFF/PRINCIPLE OF B I O L O G I C A L

d e f

Catabol i t e repress

ned as those catabo

i n t h e c e l l and repress

on o f carbohydrate metabolism has been

i t e s formed from glucose which accumulate

t h e fo rmat ion o f enzymes whose a c t i v i t y

would augment t h e already l a r g e i n t r a c e l l u l a r pool o f these

compounds (1) . The l a r g e s t group o f enzymes observed t o be

s e n s i t i v e t o c a t a b o l i t e repress ion are those requ i red t o i n t roduce

a subs t ra te i n t o one o f t h e main pathways o f energy metabolism.

Inc luded are t h e enzymes which b r i n g carbohydrates i n t o t h e

Embden-Meyerhof pathway, t h e hexose monophosphate shunt, o r t h e

Entner-Doudoroff pathway.

Gray, e t a l . ( 9 ) examined the i n f l u e n c e o f glucose on t h e

enzymes associated wi th t h e t r i c a r b o x y l i c a c i d c y c l e ( T C A ) o f a

K12 s t r a i n o f - - E. c o l i .

markedly repressed t h e fo rmat ion o f t he TCA c y c l e enzymes when t h e

c e l l s were grown on casein hydrolysate. However, t he repress ion

was p a r t i a l l y counteracted by t h e growth o f t h e c e l l s on a

s y n t h e t i c mineral s a l t s medium w i t h glucose, i n which t h e TCA

c y c l e must be used f o r s y n t h e t i c purposes. They observed t h a t

when glutamate had t o be synthesized, t he enzymes lead ing t o i t s

f o rma t ion increased i n a c t i v i t y even though glucose was present.

However, t h e o the r enzymes o f t he TCA c y c l e were not depressed

p r o p o r t i o n a l l y du r ing t h i s synthesis.

i s an i nve rse r e l a t i o n s h i p between growth r a t e and c a t a b o l i t e

repression. One circumstance where catabol i t e repress ion o f t h e

TCA c y c l e would no t i n f l u e n c e growth r a t e would be i f t h e

carbohydrate metabol i c pathway p r e v i o u s l y mentioned cou ld f u r n i s h

c e l l u l a r energy (ATP) i n s u f f i c i e n t quan t i t y .

l a c t o s e t ranspor t . They found t h a t t he metabol ic products o f

ga lac tose suppressed f u r t h e r u t i 1 i zat i o n o f galactose and thereby

suppressed t r a n s p o r t o f lactose. Other c a t a b o l i t e repress ion

s t u d i e s have i n d i c a t e d t h a t pyruvate metabolism can be repressed by

glucose and c o n t r o l l e d by the i n t r o d u c t i o n and removal o f reduced

diphosphopyr id ine nuc leo t i de (DPNH). The i n t r o d u c t i o n o f

DPNH s t imu la ted glucose repress ion and removal o f DPNH derepressed

t h e i n f l u e n c e o f glucose.

These workers observed t h a t glucose

It was observed t h a t t h e r e

Beggs and Rogers (2 ) i n v e s t i g a t e d catabol i t e repress ion f o r

34

WW TRMT SPNOFF/PKINCIPLE OF BIOLOGICAL

C a t a b o l i t e repress ion i s a l so associated w i t h r a p i d l y growing

c e l l s and r e f l e c t s the energy s t a t e o f t h e c e l l (14).

yeas t have shown c a t a b o l i t e repress ion o f glucose on cytochromes and several o f t he enzymes t h a t have r e s p i r a t o r y func t ions .

P o l a k i s e t a l . (17) repo r ted t h a t yeast grown on glucose developed

fewer mitochondr ia per c e l l and a l so poor l y developed c r i s t a e

w i t h i n t h e mitochondr ia. Based on o the r observat ions, they

suggested t h a t oxygen i s not a t r u e inducer o f r e s p i r a t o r y

adap ta t i on and mi tochondr ia format ion, bu t t h a t r a t h e r ae rob ios i s

p rov ides a p a r t i a l re lease from t h e c a t a b o l i t e repress ion produced

by glucose.

observa t ion f o r s ta rved c e l l s i n an a c t i v a t e d sludge (7) . Rapid

a s s i m i l a t i o n has been a t t r i b u t e d t o t h e conversion o f subs t ra te

i n t o energy s to res which are l a t e r used f o r b i o s y n t h e t i c purposes.

The process i n v o l ves resp i r a t i o n , o x i da t i ve phosphoryl a t i on, and

t h e b iosyn thes i s o f p r o t e i n s and the nuc le i c acids. The

r e l a t i o n s h i p o f t he percentage o f t h e o r e t i c a l oxygen demand

exe r ted a t subs t ra te removal t o i n i t i a l s o l i d s can be exp la ined

p a r t i a l l y on the bas is o f t he o b l i g a t o r y coup l i ng between

phosphoryl a t i o n and oxygen uptake, under the c o n t r o l o f

r e s p i r a t i o n .

syn thes is i s predominant ly carbohydrate, which i s channel led i n t o

t h e fo rma t ion o f glycogen and serves as an ove r f l ow o u t l e t f o r

excess ATP. It i s considered t h a t t he energy requirement f o r such

syn thes is would be cons iderab ly lower than t h a t f o r balanced

syn thes is and growth. Busch (3a) observed t h a t maximal m ic rob ia l

growth ( " s o l i d s p roduc t ion" ) occurred i n sewage (supplemented w i t h

glucose) a f t e r a l l o f t he sugar was u t i l i z e d .

Resp i ra t i on . The products o f o x i d a t i v e a s s i m i l a t i o n o f

subs t ra te i n mixed popu la t ions are c e l l s , carbon d iox ide , and

water. The c e l l w i l l be budget ing bo th subs t ra te carbon and

e l e c t r o n s i n t o two types o f r e s p i r a t i o n , namely, ex te rna l and

endogenous. Considerable confusion i n te rmino logy i s associated

w i t h t h e concept o f r e s p i r a t i o n . For the purpose o f c l a r i t y ,

S tud ies w i t h

The r a p i d a s s i m i l a t i o n o f organic subs t ra te has been a common

Experimental evidence has shown t h a t t h e i n i t i a l product o f

35


r e s p i r a t i on s h a l l be de f i ned as "any r e a c t i o n t h a t y i e l d s energy

t o t h e c e l l (13)" . Ex terna l r e s p i r a t i o n i nvo l ves t h e removal o f

hydrogen atoms and e lec t rons from subs t ra te o r metabol ic

in te rmed ia tes which are brought i n t o combinat ion w i t h oxygen. Endogenous r e s p i r a t i o n encompasses t h e removal o f hydrogen atoms

and e lec t rons from a subs t ra te in te rmed ia te which are t rans fe r red

t o organic compounds t h a t ac t as hydrogen acceptors.

Resp i ra t i on serves severa l funct ions: 1) t o coord ina te energy requirements f o r c e l l u l a r maintenance and growth, 2) t o

c o n t r o l c a t a b o l i t e repression, and 3 ) t o r e g u l a t e subs t ra te ass im i la t i on . Ex terna l r e s p i r a t i o n i s commonly associated w i t h

t h e t r i c a r b o x y l i c a c i d c y c l e (TCA) and t h e e l e c t r o n t r a n s p o r t

system. I n cont ras t , endogenous r e s p i r a t i o n i s a f f i l i a t e d wi th t h e l a c t a t e and a lcoho l dehydrogenase enzymes which use pyruvate

and acetaldehyde, respec t i ve l y , as hydrogen acceptors.

Apparent ly, t h e accumulation o f DPNH s t imu la tes t h e c a t a b o l i t e

repress ion o f glucose, whereas, a dep le t i on of DPNH depresses t h e

i n f l u e n c e o f g lucose (14). a l s o r e f l e c t s t h e energy s ta tus o f t h e c e l l and i s assoc iated wi th r a p i d l y growing c e l l s . Therefore, t h e removal o f t he reduced DPN becomes a f u n c t i o n o f t h e ex terna l o r endogenous r e s p i r a t i o n

processes. Dur ing c a t a b o l i t e repression, Gray e t a l . ( 9 ) repor ted t h a t t h e TCA c y c l e enzymes and ex te rna l r e s p i r a t i o n (oxygen

uptake) were suppressed.

requirements a re taken over by the endogenous r e s p i r a t i o n process.

Only subs t ra te phosphoryl a t i o n occurs f o r energy produc t ion by t h i s process.

t h e b iosyn thes is processes, t h e c a t a b o l i t e repress ion i n f l u e n c e o f glucose i s removed and t h e ex terna l r e s p i r a t i o n process i s

resumed.

Winz ler (22) demonstrated t h a t a t low oxygen tens ion, t h e

r e s p i r a t i o n r a t e i s l i m i t e d .

unsa tu ra t i on o f t h e enzyme sur faces (yeas t ) r a t h e r than due t o

slow d i f f u s i o n o f oxygen i n t o t h e protoplasm.

oxygen concent ra t ion where n e i t h e r d i f f u s i o n nor unsa tu ra t i on i s a f a c t o r i t i s presumed t h a t t h e r a t e a t which reduced subs t ra te can

Th is s t a t e o f c a t a b o l i t e repress ion

Thus, t h e c e l l u l a r energy syn thes iz ing

However, once t h e c e l l begins growing and requ i res

This was found t o be due t o

Above t h e c r i t i c a l


be supp l ied sets t h e pace o f r e s p i r a t i o n .

a l . (10) o f c e l l s recover ing from an anaerobic environment

presented evidence o f t he i n f l u e n c e o f reduced subs t ra te on

r e s p i r a t i o n . L i t t l e i n f o r m a t i o n i s a v a i l a b l e about t h e i n f l u e n c e

o f h igh n u t r i e n t concen t ra t i on on the peak o f oxygen demand o f an

a c t i v e l y growing m i c r o b i a l c u l t u r e . However, i t has been observed

t h a t t h e h ighes t oxygen uptake occurs when the c u l t u r e reaches t h e

phase o f d e c l i n i n g growth and c e l l concen t ra t i on i s highest.

Thus, mathemat ica l l y expressed:

Rate o f oxygen demand = c e l l concen t ra t i on . oxygen r e s p i r a t i o n

Fac to rs t h a t have been repor ted t o a f f e c t oxygen demand r a t e are:

1.

Studies by Johnson e t

r a t e on molar bas is

Concentrat ion o f sugar o r some o the r n u t r i e n t which a f f e c t s the

c e l l y i e l d

2. C e l l y i e l d which i s a f f e c t e d by t o x i c end-products o r l oss o f

vo l a t i 1 e in te rmed ia tes 3. A v a i l a b i l i t y and c h a r a c t e r i s t i c s o f n i t r o g e n sources, minera l

s a l t s , and accessory growth fac to rs ; and

4. Rate o f oxygen mass t r a n s f e r and supply

O x i d a t i v e Phosphorylat ion. L o g i c a l l y , t he r a t e o f oxygen

uptake has been c o r r e l a t e d w i t h c e l l product ion. Thus, a mo lecu la r

o f

and i n

oxygen o r i t s a l t e r n a t i v e i s i nvo l ved i n both the

energy v i a t he coupled redox-pa i rs l ead ing t o ATP

i n t e r a c t i o n s i n v o l v i n g the i n i t i a l a t tack on h igh

subs t ra tes such as f a t t y ac ids which were used i n

The dependency on oxygen tens ion o f the yeast ce l

d e r i va t i on

genera t ion

y reduced

b i osynt hes

has been

S .

demonstrated by Gray e t a l . t o i n f l u e n c e enzymes o f t he TCA cyc le ,

such as the succ ina te oxidase system, and enzymes associated w i t h

g l y c o l y s i s and thereby t h e produc t ion o f ATP (9 ) . With ATP as the

energy c d r r i e r , McCarty (12) suggested t h a t the energy u t i l i z e d f o r

c e l l syn thes is i s composed o f t h e ATP energy used t o r a i s e the c e l l

carbon source t o some in te rmed ia te l e v e l and o f t h a t ATP energy used f o r t h e conversion o f t he metabo l ic i n te rmed ia te i n t o c e l l u l a r

m a t e r i a l ( i .e. amino ac ids i n t o p r o t e i n s ) . The key i n te rmed ia te

f o r both energy generat ion and b iosyn thes i s has been demonstrated

t o be pyruvate (12). I n c a l c u l a t i n g the e f f i c i e n c i e s o f t r a n s f e r


o f subs t ra te energy t o ATP energy for aerobic, he te ro t roph ic

microorganism c e l l growth, McCarty (12) observed t h a t c e l l growth

was lower than t h e accountable oxygen uptake. He a t t r i b u t e d the

d i f f e r e n c e o f t he energy losses t o the d i v e r s i o n o f ATP t o

product i o n o f re1 a t i v e l y undegradable e x t r a c e l l u l a r ma te r ia l .

f u r t h e r de f ined these energy losses as being due t o t h e

accumulat ion o f polymeric products e i t h e r i n s torage form o r as

unused mate r ia l , a c t i v a t i o n o f the shunt mechanism (by-passing

energy-y ie ld reac t i ons ) and d i s s i p a t i o n o f heat v i a the "ATPase

mechani sml'.

He

ATP generat ion i s p r i m a r i l y l i n k e d t o the r e s p i r a t o r y chain

and i s o b l i g a t o r i l y assoc iated w i t h the membrane s t r u c t u r e s o f t h e

c e l l . The dehydrogenase enzymes appear t o be t i g h t l y coupled w i t h

t h e e l e c t r o n c a r r i e r s o f r e s p i r a t i o n , and most o f these enzymes

a re associated w i t h the membrane f r a c t i o n . ATP i s formed from the

f r e e energy re leased a t c e r t a i n s i t e s i n the e l e c t r o n t ranspor t

chain. The f r e e energy i s preserved i n the form o f energy-r ich

in termediates. A sequence o f r e v e r s i b l e chemical t ransformat ions,

which inc lude both nonphosphoryl a ted and phosphorylated i n t e r -

mediates, l i n k t h e redox reac t i ons o f the r e s p i r a t o r y cha in t o the

fo rmat ion o f ATP. The bas ic r e a c t i o n under ly ing the fo rmat ion o f

m e t a b o l i c a l l y usable energy i s the t r a n s f e r o f a p a i r of e lec t rons

f rom a donor t o an acceptor.

de r i ved from t h a t p o r t i o n o f n u t r i e n t s t h a t can be degraded t o

pyruvate, fat ty acids, and amino ac ids and channel led i n t o the TCA

cycle. A f t e r conversion t o acetyl-coA o r t o another member o f t he

cyc le , t h e c a t a b o l i t e s are subjected t o i n t ramo lecu la r

m o d i f i c a t i o n s which a l l ow the sequent ia l wi thdrawal o f e l e c t r o n

pa i r s .

o f r e s p i r a t o r y enzymes ( t h e cytochromes) t o oxygen r e s u l t i n g i n the

fo rma t ion o f water.

succ inate, and cytochrome c i s 3,2, and 1 moles per one mole o f

oxygen consumed, respec t i ve l y .

cytochrome b becomes one o f the f i r s t invo lved i n t h i s process.

Th is cytochrome i s common among a l l l i v i n g c e l l s and i s c l o s e l y

The pr imary hydrogen donors are

These e l e c t r o n p a i r s are t ranspor ted by means o f t he chain

The ATP y i e l d f o r t he ox ida t i on o f DPNH,

O f t he cytochromes invo lved i n the r e s p i r a t i o n process,

38


assoc ia ted w i t h the dehydrogenase systems (19). White and Smith

(21 ) repo r ted t h a t Hemophi 1 us p a r a i nf 1 uenzae, i n t h e presence o f

glucose demonstrated l a c t a t e r e s p i r a t i o n which was l i n k e d t o the

cytochrome system. They a1 so showed t h a t o the r sugar subs t ra tes

(i.e. g luconate and glucuronate) d i d not l i n k w i t h the cytochrome

system, p r i m a r i l y because o f t h e h igh o x i d a t i v e s t a t e s o f t h e

sugars. Boyer (3 ) has discussed experimental evidence which

supports the c lose re1 a t i o n s h i p between t h e dehydrogenase enzymes

and cytochrome b, and t h e reader i s r e f e r r e d t o t h a t i n fo rma t ion

source f o r an in-depth t reatment o f t h i s subject .

metabolism t o a s s i m i l a t e wastes.

tank - leach f i e l d process, t h e anaerobic lagoon and t h e anaerobic

d iges tor . Anaerobic metabolism, i n con t ras t t o aerobic metabolism

uses o the r o x i d a t i o n - r e d u c t i o n metabo l ic pathways t o generate

c e l l u l a r energy and t o syn thes ize new c e l l u l a r ma te r ia l .

11-5 presents a s i m p l i f i e d scheme f o r t h e anaerobic decomposit ion

o f organic wastes. O f importance i s the r o l e the m i c r o a e r o p h i l i c

" a c i d producing" b a c t e r i a p lay i n p r o v i d i n g subs t ra te in te rmed ia tes

(i.e. o rgan ic ac ids) f o r t he anaerobic m i c r o f l o r a ( p r i m a r i l y

%ethane produci ngl' bac te r ia ) . Der i v a t i o n o f c e l l u l a r energy under

anaerobic metabol ism requ i res 14 t imes more subs t ra te when compared

t o t h e aerob ic metabolisrn process. Most o f t he a n a e r o b i c a l l y metabol i z e d energy i s s to red i n t h e end product o f r e s p i r a t i o n ,

methane, which represents approximately 93% o f t he energy released

d u r i n g aerob ic o x i d a t i o n o f glucose. Thus, t he produc t ion o f t h e

anaerobic biomass w i l l be l ess per amount o f subs t ra te ass im i la ted

when compared t o t h e same q u a n t i t y ass im i la ted by t h e aerobic type

processes. Because o f t h i s , t h e anaerobic d i g e s t e r system i s

e x t e n s i v e l y used u n i v e r s a l l y t o reduce the volume o f sludge s o l i d s

produced by t h e a c t i v a t e d sludge system. Also, most methane

producing b a c t e r i a p r e f e r a growth temperature around 500 C

(1000 F), thus, t he methane gas produced from the anaerobic

d i g e s t i o n process i s used as a heat source t o op t im ize the growth

c o n d i t i o n s o f t he anaerobic m ic ro f l o ra .

4. Anaerobic Metabol ism: Bas ica l l y th ree systems use anaerobic

These systems are t h e s e p t i c

F i g u r e

. 39


INSOLUBLE ORGANIC MATERIAL

SOLUBLE ORGANIC MATERIAL

"A c i d Prod uc i n g " Bac te r ia

BACTERIAL +

CELLS

BACTERIAL CELLS + CH4+ C02

F igu re 11-5. A S i m p l i f i e d scheme f o r t h e Anaerobic Decomposition o f Organic Wastes

4 0


One o t h e r process which takes p lace d u r i n q anaerobic

metabolism i s t h e d e n i t r i f i c a t i o n o f n i t r a t e . Th is a l lows n i t r o g e n t o be transformed from t h e i o n i c s t a t e t o a gas.

n i t r o g e n gas becomes l o s t t o t h e atmosphere and i s u l t i m a t e l y

recyc led v i a n i t r o g e n f i x a t i o n .

b a c t e r i a use t h e molecular oxygen i n t h e n i t r a t e f o r a s p e c i f i c

o x i d a t i v e r e s p i r a t o r y process.

The

E s s e n t i a l l y , t h e anaerobic

41

WW TRMT SPNOFF/PRINCIPLE OF BIOLOGICAL

E . B i b l i ography

McCarty, P. L. 1970. B i o l o g i c a l t reatment o f food processing wastes.

The Growth Environment

In. Proc. 1 s t Nat. Symp. on Food Proc. Wastes, Port land, Oregon, A p r i l 6-8.

McGraw-Hill Company, New York. McKinney, R. E. 1962. Microbio logy f o r s a n i t a r y engineers.

The Natura l Biogeochemical Cycles

Nriagu, 3. 0. 1977. "Environmental Biogeochemistry" I n "Proceedings o f t h e Second I n t e r n a t i o n a l Symposium on Environmental

Biogeochemistry", Ann Arbor Science Publ ishers, Inc., Ann Arbor,

Michigan, Vol. 1.

Biogeochemical Cycles", J. M i l k Food Technol. Vol. 39(4):297-300. Robinson, J. B. 1976. " I n t e g r a t i n g Food Product ion i n t o Nature 's

Aerobic Metabol ism

1. Anderson, R. L. and Wood, W. A. (1969) Carbohydrate Metabolism i n

M i croorgani sms i n "Annual Review o f M i c r o b i ol ogy" ed by

C l i f t o n , C. E. R a f f e l , S., and S ta r r , M. P. Reviews, Inc. Palo Al to , C a l i f . Vol. 23:539-578.

2. Beggs, W. H. and Rogers, P. (1966). J. B a c t e r i o l . 91:1869.

3 . Boyer, P. D. (1969). Ox ida t i ve phosphorylat ion i n " B i o l o g i c a l

Publ. Annual

Oxidations," publ. by In te rsc ience Publrs., New York, 193-231.

3a. Busch, A. W. (1966). Water Resour. Res. 2:59. 4. Cohen, G. N. and Monod, 3. (1957). B a c t e r i a l premeases. Bact.

Rev. 21:169. 5. Davis, B. D., Dulbecco, R., Eisen, H. N., Ginsberg, H. S. and

Wood, W. B., Jr. (1969). Membrane Transport i n "Microbiology", Publ. Harper and Ron, New York, p. 160-167.

6. Doe1 le , H. W. (1969). Chemosynthesis-Pathways o f Carbohydrate

Breakdown i n "Bac te r ia l Metabol ism", publ Academic Press,

New York, chap. 4, p. 129-198.

42


7. Eckenfelder, W. W., Jr., and

B i o l o g i c a l Oxidat ion,"

I n d u s t r i a l Wastes, Vol.

McCabe, B. J., Reinhold

8. Fox, C. J., Kennedy, E. P.

9. Gray, C. T., Wimpenny, J. W.

54~891-99.

Weston, R. F. (1956), " K i n e t i c s o f

n B i o l o g i c a l Treatment o f Sewage and

I, ed. by Eckenfelder, W. W., Jr., and

P u b l i s h i n g Corp., New York.

1965) Proc. Na t l . Acad. Sci.

T. and Mossman, M. R . (1966).

Regu la t i on o f Metabolism i n F a c u l t a t i v e Bac ter ia . Biophys Acta, 117:33-41.

(1939) The f l a s h o f luminescence f o l l o w i n g anaerob ios is o f

luminous bac ter ia . Enzymologia 7:195-224.

Fed. 38:85-101.

Biochem.

10. Johnson, F. H., Van Schonwenburg, K. L., and Van Der Burg, A.

11. Kornolr i t , K. and Gaudy, A. F., Jr. (1966) J. Wat. P o l l . Cont.

12. McCarty, P. L. (1965) Thennodynamics o f b i o l o g i c a l syn thes is and

growth. I n Advances i n Water P o l l u t i o n Research, Vol. 11,

J. K. Baars, Ed. (Proc. 2nd I n t . Conf., Tokyo, Aug. 1964).

13. Oginsky, E. L., and Umbreit, W. W. (1959) Dehydrogenation and

R e s p i r a t i o n i n "An I n t r o d u c t i o n t o B a c t e r i a l Physiology."

Publ. by W. H. Freeman and Co., San Francisco, p. 210-234. 14. Okinaka, R. T. and Dobrogosz, W. 3. (1967). 3. B a c t e r i o l .

93:1644.

15. Paigen, K. and Wil l iams, B. (1970) C a t a b o l i t e Repression and

Other Cont ro l Mechanisms i n Carboyhdrate U t i l i z a t i o n i n "Advances i n M ic rob ia l Physiology".

Wi lk inson Publ. Academic Press, London. p. 252-324. 16. Palmer, W. G. Cannery Waste Treatment by a High S o l i d s Ac t i va ted

Sludge Process, p. 229 Proceedings (1970) 1 s t Na t l . Symp. on

Food Proc. Wastes, Port land, Oregon, A p r i l 6-8 FWOA

p u b l i c a t i o n D-2305.

Yeast Enzymes Dur ing Aerobic Growth on D i f f e r e n t Carbon

Sources. Biochem. J. 9-:369.

Ed. by Rose and

17. Po lak is , E. S . , B a r t l e y , W. and Meek, G. A. (1964). Changes i n

43


18. S i d d i g i , R. H. Englebrecht, R . S., and Speece, R. E. (1967). The

r o l e o f enzymes i n t h e contac t s t a b i l i z a t i o n process. Wat. P o l l . Cont. Fed., 38:(3)369.

" B i o l o g i c a l Oxidations," Publ. In te rsc ience, New York,

J.

19. Smith, L. (1968). The Resp i ra to ry Chain System o f B a c t e r i a i n

p. 56-113.

20. Thimann, K. V. (1966) Cond i t ions o f Cu l tu re : Oxygen and

Ox ida t ions i n "The L i f e o f Bacteria," 2nd E d i t i o n publ. The

Macmil lan Co. New York, Chap. 5, p. 194-256.

21. White, 0. C., and Smith, L. (1964). J. B i o l . Chem. 239-2956.

22. Winzler, R. J. (1941) The r e s p i r a t i o n o f baker 's yeas t a t low

oxygen tension. J. C e l l u l a r Comp. Physiolo. 17:263-276.

Add i t i ona l Reference

Chambers, James V. 1972. " E f f e c t o f Selected Fac tors on t h e

Ph.D. D i s s e r t a t i o n , The Ohio S t a t e U n i v e r s i t y . R e s p i r a t i o n and Performance o f a Model Dairy Ac t i va ted Sludge System".

D. ANAEROBIC METABOLISM

Andrews, J. F., Cole, R. D., and Pearson, E. A. 1964. K i n e t i c s and

c h a r a c t e r i s t i c s o f mu l t i - s tage methane fermentat ion. Engineer ing Research Laboratory Report No. 64-1 1, U n i v e r s i t y o f

C a l i f o r n i a , Berkely, C a l i f o r n i a .

W i l l i a m , E. P. and J. F. Andrews. 1969. M u l t i s t a g e B i o l o g i c a l

Processes f o r Waste Treatment, Journa l WPCF Vol . 41 (1 ) :99.

San i ta ry

44 W W TRMT SPNOFF/SELECTING A TRMT SYSTEM

Sect ion I 1 1

Se lec t i ng a Waste Treatment System

A . I n t r o d u c t i o n

The wastewater t reatment system may take several d i f f e r e n t forms

which are d i c t a t e d by such f a c t o r s as the nature o f the waste, wastewater

volume t o be t rea ted , economics, land a v a i l a b i l i t y , geographic l o c a t i o n

and energy sources. Other cons idera t ions are t h e degree o f t reatment

r e q u i r e d and whether the wastewater i s t o he discharged i n t o a munic ipa l

waste t reatment system o r d i r e c t l y t o a t r i b u t a r y stream.

The purpose o f t h i s sec t i on i s t o f a m i l i a r i z e the extens ion s p e c i a l i s t

While t h e ac tua l w i t h t h e mechanics o f s e l e c t i n g a waste t reatment system.

s e l e c t i o n process w i l l evo lve main ly from inpu t con t r i bu ted by the food

processor, c o n s u l t i n g environmental engineer and the regu la to ry agency, t he

ex tens ion s p e c i a l i s t may have some c o n t r i b u t i o n s t o make ( i .e., i n p l a n t

waste c o n t r o l , water reuse, s o l i d s d i sposa l ) which cou ld a s s i s t the food

processor i n ob ta in ing the best and most economical system. How the

ex tens ion s p e c i a l i s t con t r i bu tes t o t h i s s e l e c t i o n process w i l l be

determined by h i s /he r comnitment t o a s s i s t i n g the food processor t o comply

w i t h the environmental laws and regu la t ions . This ass is tance can be

s i g n i f i c a n t l y increased by the extens ion s p e c i a l i s t s ' s f a m i l i a r i t y w i t h

elements o f t he s e l e c t i o n process f o r waste t reatment systems and how each

u n i t process func t ions . These process func t i ons w i l l be covered i n

Sect ions I V and V o f t h i s u n i t .

B. Summary

I n t h e s e l e c t i o n o f a waste t reatment system, i t should f i r s t he

determined t o what l e v e l a wastewater must be t rea ted , i f a t a l l . I n t h i s

determinat ion, f o u r sequent ia l steps are taken t o p roper l y evaluate the

waste t reatment needs. The four assessment steps invo lve : 1 ) character-

i z i n g t h e wastewater, 2 ) e v a l u a t i n g the degree o f t reatment needed, 3) s e l e c t i n g the system which best app l ies t o the t reatment requ i red and 4 ) develop ing uni t -process design c r i t e r i a .

To cha rac te r i ze the wastewater, the food processor must acqui re the

se rv i ces o f a c o n s u l t i n g environmental engineer w i t h a p ro fess iona l engi-

neer ing l i c e n s e f o r t he s t a t e i n which the system i s t o be b u i l t . I n the

45 WW TRMT SPNOFF/SELECTING A TRMT SYSTEM

c h a r a c t e r i z a t i o n o f t h e food p l a n t wastewater, t he engineer w i l l document

t h e water f l o w which inc ludes hour ly , d a i l y , weekly and monthly h y d r a u l i c

p r o f i l e s . A1 1 wastewater sources are i d e n t i f i e d (i.e. product ion, process-

ing, t r u c k washing, stormwater i n f i l t r a t i o n ) and accounted. The wastewater

w i l l be analyzed f o r composit ion, pH and s t reng th (i.e. BOD, suspended

s o l i d s ) .

survey and t h e i r ana lys i s be performed by competent chemists.

c o l l e c t e d , i t must now be assessed f o r t he degree o f t reatment t h a t w i l l

be r e q u i r e d t o meet the l e g a l needs of t h e food processor. For example,

if t h e processor i s t o discharge t o a municipal waste t reatment system,

t h e n cons ide ra t i on must be d i r e c t e d t o the es tab l i shed l i m i t a t i o n s as

s t a t e d i n t h e l o c a l sewer use ordinance. On t h e o the r hand, i f the

processor i s t o discharge the wastewater t o a t r i b u t a r y stream, then

c e r t a i n discharge l i m i t a t i o n s w i l l be d i c t a t e d by the NPDES Permit Un i t s ,

and the stream's c l a s s i f i c a t i o n , determined by use, water f l o w and i t s

a b i l i l t y t o absorb p o l l u t a n t s (based on t h e oxygen sag curve o f t he

stream).

wastewaters which are t o be discharged from t h e processing p lan t , t h e t h i r d

s t e p i n t h e waste t reatment system s e l e c t i o n can be i n i t i a t e d . A t t h i s

p o i n t i n t h e dec i s ion making process, i n p u t from the food processor, t he

c o n s u l t i n g engineer, r e g u l a t o r y agency and t h e extension s p e c i a l i s t can be

made which w i l l d i c t a t e t h e s e l e c t i o n o f t he most app rop r ia te and

economical system. Based on previous survey informat ion, u n i t processes

can be i d e n t i f i e d t h a t w i l l p rov ide t h e requ i red waste removal (i.e.,

p r imary s e t t l i n g vs. a i r f l o t a t i o n ) and the combination o f these se lec ted

u n i t processes w i l l c o n s t i t u t e the waste t reatment system.

To prove out t he se lec ted waste t reatment system, i t i s essen t ia l

t h a t bench sca le and p i l o t p l a n t opera t ions be set up. opera t ions , design c r i t e r i a can be developed f o r f i n a l i z i n g the sca le up

f o r ac tua l c o n s t r u c t i o n o f t h e se lec ted waste t reatment system.

those systems, design c r i t e r i a such as ae ra t i on requirements, c l a r i f i e r

s i z i n g , d e t e n t i o n capaci ty, so l i d s c o n t r o l and f l o w through pa t te rns are

es tab l i shed. A f t e r t h e design c r i t e r i a are es tab l i shed, c o n s t r u c t i o n o f

t h e waste t reatment f a c i l i t i e s can begin a f t e r r e g u l a t o r y approval o f t h e

system design has been obtained.

It i s impera t ive t h a t rep resen ta t i ve samples are obtained i n t h e

Once t h e survey data fo r t h e food processing wastewater has been

A f t e r t h e food processor knows what the l e g a l l i m i t a t i o n s are f o r

From these

U t i 1 i z i n g

4 I;

W W TKMT SPNOFF/SELECTINC A TKMT SYSTEM

C. The S e l e c t i o n Process

The wastewater t reatment systerri may tdke scvera l d i f f e r e n t forms which

a r e d i c t a t e d by such f a c t o r s as t h e na tu re o f t h e waste, wastewater volume

t o be t rea ted , economics, l a n d a v a i l a b i l i t y , geographic l o c a t i o n and energy

sources. Other cons idera t ions a re t h e deyrtbe o f t reatment requ i red and whether t h e wastewater i s t o be discharged i n t o a munic ipa l waste t reatment

system o r t o a t r i b u t a r y stream.

I n t h e s e l e c t i o n o f a waste t reatment system, i t should f i r s t be

determined t o what l e v e l a wastewater must be t rea ted , i f a t a l l . I n t h i s

de terminat ion t h e f o u r sequent ia l steps mentioned p r e v i o u s l y a re taken t o

p r o p e r l y eva lua te t h e waste t reatment needs.

111-6) a r e presented i n t h e sequent ia l steps necessary f o r s e l e c t i n g a

waste treatrnent system.

The f i g u r e s (111-1 through

Wastewater Charac ter iza t ion :

F i g u r e 111-1 addresses t h e quest ions as t o whether a waste t reatment

process i s needed and, i f so, t h d t a c h a r a c t e r i z a t i o n o f t h e food process-

i n g wastewater i s required. To chdrac ter ize t h e Wastewater, t h e food processor must acqu i re t h e se rv i ces o f a c o n s u l t i n g environmental engi necr

who holds a p ro fess iona l engineer ing l i c e n s e w i t h i n t h e s ta te , when t h e system i s t o be b u i l t . It i s impera t i ve t h a t r e p r e s e n t a t i v e samples a r e

obta ined i n t h e survey and t h e i r a n a l y s i s be preformed by competent

c hemi s t s . S e l e c t i n g t h e Process(es):

wastewater which a r e t o be discharged from t h e processing p l a n t , t h e t h i r d

s t e p i n t h e waste t reatment system s e l e c t i o n can be i n i t i a t e d .

111-2 and 111-3 present f a c t o r s impor tant i n s e l e c t i n g physiochernical and

b i o l o g i c a l processes, respec t i ve l y . As these f i g u r e s a re used, i t i s

assumed t h a t : 1.

2. t h e d a i l y wastewater f l o w r a t e s have been p r o f i l e d ; and

3.

Once t h e food processor knows t h a t t h e l e g a l l i m i t a t i o n s a re f o r t h e

F igures

t h e wastewater tids been character ized;

t h e s p e c i f i c waste t reatment goals have been de f i ned - a ) d ischarge t o munic ipa l sewer system and iiiust meet sewer use

1 i m i t a t i o n s .


The Selection Process

1. Is treatment of plant wastewater needed:

A

*Is wastewater t o be Is pretreat- ~-

discharged to municipal Yes + No ment required of I

waste treatment system? #

I, > No further "Characterization of

"Spin off" Manual, Sec. * Wastewater 'I Refer to

(based on commodity) 6

Select ion Required

4

1

Treatment of wastewater is needed!

I

Step 2

Figure 111-1. Determining the need for waste treatment.


Is l a n d rcnt l i l y a v a i l a b l e ? d I

1

I H t . l c 1 - t o S c c t i o n V Par t s C l c 2 )

Proccc.d t o s t e p 115

F i g u r e 111-5. Sludge I ~ i s p o s a l / H a n d l i n g O p t i o n s

1s t h e S ludge H a ~ l away f o r \'olumc E s t r c m c l y ?: 0 4 Land a p p l i c n t i o n C o s t l y to Hnndle? -

& b

O p t i o i ~ s b a s e d

Acr o h i c n c! Igcstcr A n a e r o b i c t l igcss t c'r


h

Is E f f l u e n t meet ing e s t a b l i s h e d l i m i t a t i o n s ? - Yes

I No f u r t h e r a c t i v i t y Required

Is Suspended So 1 i d s b e i n g d i scha rged over t h e l i m i t ?

1 Need t o improve by

Refer t o S e c t i o n V P a r t Clc2)

I - P o l i s h i n g Pond o r

S e c t i o n IV f i l t r a t i o n sys tem

I Is F e c a l Col i form l i m i t

I n i t i a t e d i s i n f e c t i o n t r e a t m e n t

Is BOD b e i n g d i scha rged ove r t h e l i m i t

Waste t r e a t m e n t sys tem performance needs improvement

I Refe r t o S e c t i o n 11, P a r t C 1

Refer t o S e c t i o n IV U P a r t C3d

of d i s c h a r g e w i t h c h l o r i n e

Figure 111-6. Meeting e f f l u e n t discharge l i m i t a t i o n s ( t h e options).

52 W W TKMT SPNOFF/SELECTING A TRMT SYSTEM

b ) discharge t o t r i b u t a r y streams and NPDES permit l i m i t a t i o n s

must be met.

c ) d ischarge t o land w i t h no f l o w going t o a sewer system o r t r i b u t a r y stream.

A t t h i s p o i n t i n the dec i s ion making process, i n p u t from the food

processor, t he consu l t i ng engineer, r e g u l a t o r y agency and the extension

s p e c i a l i s t can be made which w i l l a i d i n s e l e c t i n g t h e most appropr ia te and

economical waste t reatment system. Rased on previous survey i n fo rma t ion , u n i t processes can be i d e n t i f i e d t h a t w i l l p rov ide the requ i red waste

removal means ( i .e. pr imary s e t t l i n g vs. a i r f l o a t i o n ) and t h e combination

o f these se lec ted u n i t processes w i l l c o n s t i t u t e the waste t reatment

system. I n a d d i t i o n t o s e l e c t i n g the p r i n c i p a l waste t reatment process, a

means f o r removing, hand1 i n g and d ispos ing t h e suspended so l i d s must be

determined. F igures 111-4 and 111-5 present the options. I f the e f f l u e n t

t o be discharged does not meet the ordinance o r permit l i m i t a t i o n s then

a d d i t i o n a l op t ions iriust be considered. These op t ions are presented i n

F igu re 111-6.

53 WW TRMT SPNOFF/PHYS-CHEM TRMT SYSTEMS

Sec t ion I V Physica l - Chemical Waste Treatment Systems

A . I n t r o d u c t i o n

The purpose o f t h i s sec t i on i s t o acquaint you w i t h var ious phys ica l

and chemical systems commonly used t o remove p o l l u t a n t s from wastewater.

These systems are designed t o take advantage o f spec i f i c phys ica l and/or

chemical p roper t i es o f t he p o l l u t a n t which permi ts i t s removal f rom the

wastewater stream. I n con t ras t t o the b i o l o g i c a l type waste t reatment

systems ( t o be discussed i n Sec t ion V ) , the phys ica l - chemical waste

t rea tment systems u t i l i z e p o l l u t a n t s ize, dens i t y and sur face chemist ry

( i .e. i on i c ; van der Waal fo rces) r a t h e r than f l o c adsorpt ion, subs t ra te

breakdown and c e l l a s s i m i l a t i o n f o r removal from the acquat ic environment.

Each'system discussed i n t h i s sec t i on o f f e r s an op t i on t o the u l t i m a t e

system design f o r achiev ing the des i red l e v e l o f waste treatment.

B. Summary

E s s e n t i a l l y , phys ica l p roper t i es used i n the removal o f p o l l u t a n t s

f rom wastewater are p a r t i c l e exc lus ion, buoyancy and densi ty , whereas such

chemical p roper t i es as che la t ion , adsorpt ion, e l e c t r o s t a t i c i n t e r a c t i o n and

o x i d a t i o n reac t i ons are used.

The a p p l i c a t i o n o f p a r t i c l e exc lus ion i s used i n such u n i t opera t ions

as bar screens, r o t a t i n g screens, media f i l t e r s and membrane f i l t r a t i o n .

Buoyancy o f t h e p o l l u t a n t p a r t i c l e i s used f o r i t s removal i n pr imary

s e t t l i n g basins and a i r f l o t a t i o n processes whi le , i n cont ras t , t h e dens i t y

o f t h e suspended s o l i d s i s used f o r i t s e l i m i n a t i o n f rom the aquat ic

environment v i a such u n i t operat ions as c l a r i f i e r s and cent r i fuges .

agents such as l ime, metal c h e l a t i n g agents and organic polymers. A chemical phenomenon, adsorpt ion i s used t o remove p r i m a r i l y t o x i c and o i l

based mater ia ls . Th is i s accomplished through the use o f a c t i v a t e d carbon

granules which have exce l l en t adsorp t ion proper t ies . E l e c t r o s t a t i c i n t e r -

ac t rons a r e employed i n i o n exchange processes where se lec ted i o n i c species

( i .e . The "hear t " o f t h e

i o n exchange i s the r e s i n bed which may be e i t h e r p o s i t i v e l y o r nega t i ve l y

Che la t ion o f the p o l l u t a n t i s achieved by the use o f f l o c c u l a t i n g

heavy meta ls) are removed from the waste stream.

54

W W TRMT SI’NOFF/PHY S-CHEM TRMT SYSTEMS

charged. Pe r iod i c recharg ing o f the i o n exchange u n i t i s requ i red t o

main ta in s e l e c t i v e i o n i c species removal.

I n con t ras t t o a l l o f the u n i t operat ions p rev ious l y mentioned, the

o x i d a t i o n reac t i on o f the d i s i n f e c t a n t does not remove p o l l u t a n t s from the

waste stream but reduces the p o t e n t i a l o f d ischarg ing i n f e c t i o u s agents t o

a t r i b u t a r y stream. B a s i c a l l y , t h ree ox ida t i on processes are commercial ly

used i n d i s i n f e c t i n g wastewater. These processes are c h l o r i n a t i o n , ozone

and u l t r a v i o l e t l i g h t .

wastewater and the degree o f t reatment t h a t w i l l be requ i red t o meet l ega l

l i m i t s . Each phys ica l and chemical process has i t s own inherent problems

(i.e. sludge handl ing, t reatment and d isposa l ) which must be considered i n

t h e o v e r a l l assessment o f des ign ing o r upgrading a waste t reatment system

f o r food processing wastewaters.

Use o f the above technologies depend on t h e c h a r a c t e r i s t i c s o f t he

C. The Systems

1. Physica l Types

a. Screening: Screening is one o f the i n i t i a l pretreatment steps

i n waste t reatment. When the wastewater en ters a t reatment

p l a n t i t may con ta in l a r g e p a r t i c l e s t h a t p o t e n t i a l l y could

c l o g sewers o r cause o ther t reatment problems. To remove

these l a r g e objects , wastewater en te r ing the waste t reatment

f a c i l i t y i s passed through some type o f screen.

types o f screens may be used f o r t h i s process step.

comnonly used i s t he bar screen. Bar screens cons is t o f

p a r a l l e l bars t h a t are placed a t an angle (F igure IV-1).

t h e wastewater f lows through the p a r a l l e l bars, the l a r g e

p a r t i c l e s are re ta ined on the bars, and removed by raking.

t h e wastewater i n the food processing indus t ry . The most

comnon screen s izes are 20-40 mesh.

mesh) can a l so be used t o remove considerable amounts o f

suspended s o l i d s from the waste stream.

one i s the v i b r a t i n g o r o s c i l l a t i n g screen. There are two

types o f o s c i l l a t i n g screens:

D i f f e r e n t

Most

As

Four types o f screens are comnonly employed f o r t r e a t i n g

F ine screens (200 t o 400

The most comnonly used

1) t h e c i r c u l a r center fed

55 W W TRMT SPNOFF/PHYS-CHEM TRMT SYSTEMS

(a) Screen Cleaning Mechanism

(b) BAR SCREEN I N USE

F i g . - - 1 BAR SCREEN


screen, i n which s o l i d s may be discharged i n a s p i r a l toward

t h e center o r per iphery (F igu re IV-2) ; and 2) t he rec tangu lar

end-fed screen i n which s o l i d s are discharged along the screen

toward t h e lower end.

The r o t a r y drum screen (F igure IV-3) i s t he next commonly

used screen i n which the hyd rau l i c f l o w i s f rom the i n s i d e o f

t h e drum toward the outside, o r v ice versa. I n a screen w i t h

t h e inward f low, s o l i d s are re ta ined on the i n s i d e o f the

screen and removed by wash troughs o r augers. The s o l i d s are

r e t a i n e d on the ou ter sur face o f t he r o t a t i n g drum screen i n

which t h e d i r e c t i o n a l f l o w moves from the ou ts ide toward the

center , and are removed by a scraper.

The t h i r d type o f screening device i s the tangen t ia l

screen (F igure IV-4) , i n which water i s fed from the top

through a parabo l ic screen, but the s o l i d s are re ta ined on the

sur face o f the screen and discharged from i t s lower end.

Another type o f screening system i s the r o t a t i n g drum

c e n t r i f u g a l screens which are o f very f i n e mesh (up t o 400) and

a re used when h igh s o l i d s capture i s requi red. I n these u n i t s ,

t h e wastewater i s sprayed under pressure onto the i n s i d e o f the

r o t a t i n g drum, passing through the screen. So l i ds are re ta ined

on the i n t e r i o r p o r t i o n o f the drum and are h igh i n mois ture

content.

Se lec t i on o f a screen f o r t r e a t i n g the wastewater w i l l

depend upon a number o f fac to rs .

i n i t i a1 cost ; opera t ing and maintenance costs; space requi red;

h y d r a u l i c capac i ty ; percent o f s o l i d s captured; and volume o f

removed s o l i d s t o be disposed.

Advantages o f Screening: 1. Screening i s an inexpensive method f o r removing l a r g e

2.

These f a c t o r s would be:

p a r t i c l e s f rom wastewater.

Screens r e q u i r e very l i t t l e space and can be e a s i l y

i n s t a l l e d a t an e x i s t i n g p lant .

s e t t l e a b l e and f l o a t a b l e so l ids .

3. Screens o r d i n a r i l y achieve a h igh removal r a t e o f

57

WW TRMT SPNOFF/PHYS-CHEM TRMT SYSTEMS

Figure IV-2. Circular center-feed vibratory screen.

i I

I i i

( ' I )

SW31SAS 1 W U W3H3-S AHd/J JON CIS I W U M M 8s

Gravity feod

Solf cleaning.

steel scrtmn for continuous dewatori

W W TRMT SPNOFF/PHYS-CHEM TRMT 59 SYSTEMS

F i g . - - 4 TANGENTIAL SCREEN

60

W W TRMT SPNOFF/PHY S-CHEM TRMT SYSTEMS

4 . Propor t i ona l amounts o f BOD a r e removed w i t h the

5. Removal o f l a r g e p a r t i c l e s reduces c logg ing o f pipes,

suspended so l ids.

p r o t e c t s pumping equipment and he1 ps reduce BOD 1 oad i ng.

Suspended so l i d s co l 1 ec ted v i a screeni ng can be

removed and disposed o f a t a land f i 11 o r by

i n c i n e r a t i o n . Other op t ions i nc lude the p a r t i c l e

r e d u c t i o n o f t he suspended s o l i d s which are l e f t i n t he

wastewater and removed du r ing the c l a r i f i c a t i o n stage.

b. G r i t Chambers: P a r t i c l e m a t e r i a l s t h a t s e t t l e out are

r e f e r r e d t o as g r i t , which i nc lude sand, g rave l , and

o t h e r heavy m a t e r i a l s such as seeds and c o f f e e grounds.

These heavy p a r t i c l e s are c o l l e c t e d i n the g r i t chamber

which i s designed so t h a t t he v e l o c i t y o f the hyd rau l i c

f l o w i s slowed down t o about one f o o t per second, o r

slower, thus a l l o w i n g the heavy p a r t i c u l a t e mat te r t o

s e t t 1 e.

There are several types o f g r i t chambers employed t o

remove g r i t . The e a r l i e s t form of the g r i t chamber used

i s a l ong narrow trough. The v e l o c i t y o f f l o w i s

c o n t r o l l e d by p l a c i n g a p r o p o r t i o n a l we i r a t t h e

d ischarge end a l l o w i n g t h e g r i t t o s e t t l e . The s e t t l e d

g r i t cou ld be removed manually o r mechanical ly.

A more r e c e n t l y developed g r i t chamber design i s the

channel-shaped s e t t l i n g tank equipped w i t h an ae ra t i on

u n i t and a hopper bottom capable o f removing f i n e

p a r t i c l e s up t o 0.2" diameters, w i t h a minimum o f

o rgan ic suspended p a r t i c l es bei ng removed. Th is type

chamber i s r e l a t i v e l y s m a l l w i t h a de ten t i on t ime o f

about 1 minute. The organic mat te r passing through t h i s

g r i t chamber i s maintained i n suspension by d i f f u s e d

a e r a t i o n w h i l e the g r i t p a r t i c l e s s e t t l e out.

t h e s e t t l e a b l e ma te r ia l , a cyclone separator o r g r i t

Should t h e r e be a h i g h amount o f organic content i n

61


washer may be used. These u n i t s wash and dewater the

g r i t s l u r r y , r e t u r n i ng the resuspended p a r t i c l e s t o t h e

ove r f l ow and u l t i m a t e l y t o the wastewater stream. To

improve t h e g r i t s e t t l e a b i l i t y , p reaera t i on o f raw wastes

p r i o r t o pr imary s e t t l i n g i s p r a c t i c a l . The r a w waste i s

h e l d i n a p reaera t i on bas in f o r 15 t o 20 minutes which

inc rease the d i sso l ved oxygen and scrubs out en t ra ined gases

thus improving p a r t i c l e s e t t l e a b i l i t y .

Advantages o f G r i t Chambers:

1. G r i t removal i s very important e a r l y i n t h e

t rea tment process. If the g r i t i s not removed i t can

q u i c k l y cause maintenance problems f o r pumps and

o t h e r process equipment . 2 . G r i t removal reduces the inc idence o f clogged pipes

and a l s o reduces the accumulation o f sludge i n t h e

h o l d i n g tanks and digesters.

amenable t o waste removal v i a b i o l o g i c a l processes,

3. G r i t i s most ly i no rgan ic and there fore i s not

c. Sedimentation: The sedimentat ion process i s used

p r i m a r i l y i n the waste t reatment system t o remove

s e t t l e a b l e o rgan ic and ino rgan ic s o l i d s suspended i n the

i n f l u e n t . Th is removal i s achieved i n two ways, namely - c l a r i f i e r s and c e n t r i f u g a t i o n .

1. C l a r i f i e r s : The removal o f s o l i d s i n a c l a r i f i e r i s

accomplished by g r a v i t y o r by skimming as i n t h e case

o f f l o a t a b l e s .

t ank i n which wastewater moves very s lowly, thus

a l l o w i n g t h e s e t t l e a b l e s o l i d s an oppor tun i t y t o s ink

t o the bottom o f t h e tank.

c l a r i f i e r tank can be e i t h e r rec tangu la r o r c i r c u l a r .

However, t h e tank should be a t l e a s t 10 f e e t i n depth

t o a l l o w f o r uneven f l o w d i s t r i b u t i o n , f l o w surges,

and the sludge b lanket t o form.

a t t h i s stage o f t h e t reatment are r e f e r r e d t o as

pr imary c l a r i f i e r s . A pr imary c l a r i f i e r i s a

s e t t l i n g tank t h a t rece ives r a w waste p r i o r t o

A c l a r i f i e r i s b a s i c a l l y a s e t t l i n g

The con f igu ra t i on o f t h e

The c l a r i f i e r s used

62 WW TKMT SPNOFF/PHYS-CHEM TRMT SYSTEMS

b i o l o g i c a l treatment. There a r e a s e r i e s o f p o r t s

near the surface along one cnd o f the tank, through

which t h e wastewater i s passed. A b a f f l e i n the tank

d i s s i p a t e s the i n f l u e n t v e l o c i t y , d i r e c t i n g the f l o w

downward (F igure I V - 5 ) . Water i s al lowed t o move a t a

very slow r a t e and i s discharged over m u l t i p l e

e f f l u e n t weirs. While i n t h e s e t t l i n g phase, the

h y d r a u l i c f l o w should be moving much slower i n

c o n t r a s t t o the wastewater v e l o c i t y noted f o r t he

g r i t chambers. Enough t ime should be provided f o r

t h e suspended s o l i d s t o s e t t l e t o the bottom o f the

tank. Usua l l y an hour o r two i s enough t ime i n the

pr imary c l a r i f i e r . Th i s s e t t l i n g t ime i s r e f e r r e d t o

as t h e de ten t i on time. The s e t t l e d s o l i d s a t the

bottom o f t he tank i s known as sludge and the

f l o a t i n g l a y e r a t the sur face i s r e f e r r e d t o as scum.

The s e t t l i n g tanks have d i f f e r e n t mechanisms f o r

c o l l e c t i n g sludge and scum depending upon t h e

c l a r i f i e r ' s con f igu ra t i on . Wooden planks, usual l y

known as f l i g h t s , are used i n rec tangu la r tanks t o

c o l l e c t sludge and scum. These planks or f l i g h t s are

a t tached t o a con t inuous ly looped chain. The f l i g h t s

f o l l o w a loop p a t t e r n t h a t a l t e r n a t e between t h e

su r face and bottom o f t h e c l a r i f i e r tank. These

f l i g h t s t r a v e l a long the surface o f t h e wastewater

and c o l l e c t t he scum. The c o l l e c t e d scum i s depos i ted i n t o a scum t rough which i s a c y l i n d r i c a l

tube having a s l i t opening along the top. Then the

f l i g h t s submerse below the sur face and scrape along t h e

bottom o f t he c l a r i f i e r tank c o l l e c t i n g the s e t t l e d sludge.

The bottom sludge i s then pushed i n t o a sludge hopper where

i t i s re ta ined u n t i l removed. The sludge and scum must be

removed p e r i o d i c a l l y from the hoppers and troughed, and

disposed o f , seperately.

Scum Box \

Surface Skimmer

Ef f

Hopper Move Solids to Hopper

rif ier

F i g . IV - 5 CLARIFIER - -< (n

I 0 I m 3


I n c i r c u l a r tanks, scrapers at tached t o a r o t a t i n g a r m

t u r n s low ly around the bottom o f the tank, pushing t h e

s e t t l e d sludge toward t h e center i n t o the sludge o r trough.

On t h e surface, a skimmer at tached t o a r o t a t i n g arm,

pushes the scum i n t o a scum box t h a t d ra ins t o an ou ts ide

receptac le . C i r c u l a r tanks have fewer moving p a r t s i n

c o n t r a s t t o the "chain - and - sprocket " scraper mechanisms

t h a t are associated w i t h the rec tangu la r tanks. Thus,

c i r c u l a r tanks are general l y p re fe r red t o rec tangu la r tanks

because o f lower i n s t a l l a t i o n and maintenance costs.

Chemicals, such as alum, l i m e o r polymers, may

be added t o t h e c l a r i f i e r as an a i d i n improving

suspended p a r t i c l e s e t t l i n g . Th is s e t t l i n g i s

accompl i shed by aggregat i ng the small e r suspended

s o l i d p a r t i c l e s i n t o l a r g e r , more dense p a r t i c l e s .

by chemical means i s use fu l f o r wastewater streams

which have a cons is ten t composition. However, due t o

t h e wide v a r i a t i o n s encountered i n many food

processing waste e f f l u e n t s , t he use o f chemical

f l o c c u l e n t s becomes expensive and d i f f i c u l t t o

c o n t r o l . However, f l o w e q u a l i z a t i o n steps can reduce

t h e d i f f i c u l t y i n use o f and improve t h e e f fec t i veness o f

t h e chemical f l o c c u l e n t s .

Advantages For Use o f The C l a r i f i e r :

1. Aids i n the removal o f 40 t o 60% o f t he suspended

2 . Provides a p a r t i a l t h i c k e n i n g o f the suspended

3. Approximately 30% o f t h e i n i t i a l BOD i n t h e

i n f l u e n t i s removed, thus lessen ing the organic

l oad ing on the waste t redtment system.

The p r a c t i c e o f aggregat i ng suspended p a r t i c l es

s o l i d s f rom the wastewater stream.

s o l i d s f o r more e f f i c i e n t hand1 ing.

2. Cent r i fuges : Cent r i fuges genera l l y are used t o

f u r t h e r concentrate sludge o r t o remove res idua l

suspended s o l i d s from a t r e a t e d wastewater p r i o r t o d ischarge t o a tri h u t a r y stream. S1 udge compact i o n

65

WW TRMT SPNOFF/PHY S-CHEM TRMT SYSTEMS

and suspended s o l i d s removal are g r e a t l y in f luenced by the

na ture o f the suspended p a r t i c l e s and the dens i t y and type

o f m i c r o f l o r a present i n the biomass. Thus, day t o day

v a r i a t i o n i n performance may be experienced w i t h any o f t he

c e n t r i f u g e systems.

The under ly ing p r i n c i p l e o f the process i s t o

separate t h e s o l i d s f rom the water by c e n t r i f u g a l force.

The c e n t r i f u g e genera l l y used i n dewater ing wastewater

sludge i s t he h o r i z o n t a l s o l i d bowl type. These u n i t s can

dewater o r separate out the s o l i d mass from most f l u i d

streams producing a sludge cake hav ing from 15 t o 25 percent sol i d s du r ing normal opera t ing cond i t ions .

Cent r i fuges may a lso be used f o r t h i cken ing sludge so l ids .

One example o f a c e n t r i f u g a t i o n process used i s the

convent ional so l i d bowl c e n t r i f u g e (F igure I V - 6 ) which

cons is t s o f an ou te r bowl t h a t r o t a t e s a t h igh speed and an

i n t e r i o r screw conveyer t h a t a lso ro ta tes . The sludge i s

pumped from the center feed tube i n t o t h e r o t a t i n g bowl.

The sludge s o l i d s are he ld against the bowl wa l l by the c e n t r i f u g a l force. The heavier s o l i d s s ink t o the bottom

of the bowl and the l i g h t e r ma te r ia l s remain c o l l e c t e d a t

t h e top.

conveyer v i a a d ischarge nozzle t o one end o f the bowl

w h i l e t h e c l a r i f i e r l i q u i d a t t h e t o p i s discharged a t t he

opposi te end. Other c e n t r i f u g a t i o n processes are avai 1 ab1 e

bu t w i l l not be discussed.

The ob jec t i ves o f c e n t r i f u g a t i o n are t o ob ta in a

So l i ds s e t t l e d i n the bowl are discharged t o a

concentrated cake, a c l e a r l i q u i d and a reasonable

c e n t r i f u g e process rate. These ob jec t i ves depend

upon v a r i ab1 es such as co l 1 e c t i on vol ume, compos i t i on

o f t he sludge s o l i d s , bowl speed and conveyor speed.

ope ra t i on o f c e n t r i f u g e s used i n waste t reatment systems are c o s t l y and t h e i r use must be adequately

j u s t i f i e d (i.e., as the on ly means f o r remaining i n

compliance w i t h a permi t o r meeting a d ischarge

It should be emphasized t h a t maintenance and

b

66

W W TRMT SPNOFF/PHYS-CHEM TRMT SYSTEMS

F igu re IV-6. Sol i d Bowl Cent r i f uge

67


1 i m i t a t i o n ) .

desludging c e n t r i f u g e s i s 3500 gph, w i t h

approximately 5-6% concentrated sol i d s per volume

discharged.

Present capac i t y f o r most

d. F l o t a t i o n : Suspended s o l i d s removal may be achieved by

another induced means, namely - a i r f l o t a t i o n (F igure I V - 7 ) . A i r f l o t a t i o n i s normal ly a t reatment process t h a t removes

suspended s o l i d s i n t h e form o f a f l o a t i n g sludge. A i r f l o t a t i o n i nvo l ves t h e atmospheric p r e s s u r i z i n g o f t h e

wastewater stream and t h e i n j e c t i o n o f a i r i n t o t h e stream. Then as t h i s m ix tu re i s re leased i n t o an open tank, t h e a i r

re leases from t h e bu lk f l u i d as small bubbles. The removal o f suspended s o l i d s depends upon t h e attachment o f f i n e a i r

bubbles t o each suspended s o l i d p a r t i c l e . bubbles improve t h e buoyancy o f t h e suspended p a r t i c l e causing

i t t o f l o a t t o t h e surface. The en t ra ined a i r escapes and t h e

f l o a t i n g s o l i d s are then c o l l e c t e d from t h e water su r face by

mechanical means.

The at tached a i r

A i r f l o t a t i o n has an advantage over g r a v i t y

sedimentat ion when used f o r t h e removal o f o i l s , f i n e

p a r t i c u l a t e matter, and f a t which are not as r e a d i l y

amenable t o sedimentation. The a i r f l o t a t i o n process i s p a r t i c u l a r l y usefu l i n t h e t reatment o f p o u l t r y and meat

packing wastewater. Th is process has a l so been used i n c lean ing foundry wastewaters which are then reused. A i r

f l o t a t i o n has a lower c a p i t a l cos t as compared t o

sedimentat ion but a h ighe r ope ra t i on cost.

r e d u c t i o n o f suspended solids f rom t h e wastewater stream which

a r e not removed by o the r processes used i n t h e waste t reatment

system. F i l t r a t i o n i nco rpo ra tes t h e use o f a f i l t e r i n g

medium/media t h a t ent raps t h e suspended sol i d s / c o l l o i d s as they

pass through t h e f i l t e r matr ix .

based on f i v e parameters. These parameters are: 1) t ype o f f i l t r a t i o n media; 2) f l o w ra te ; 3 ) f l o w d i r e c t i o n ; 4) t ype of

head provided; and 5 ) c lean ing method.

e. F i l t r a t i o n : F i l t r a t i o n processes (F igu re IV-8) a i d i n t h e

F i l t e r systems are c l a s s i f i e d

F

68 WW TRMT SPNOFF/PHY S-CHEM TRMT SYSTEMS

Surface skimming mechanism

/

F igu re IV-7a. Dissolved a i r f l o t a t i o n u n i t : mechanisms o f operat ion.

' .QQ &I O Q Q b ' Preclpitrtion 0 Collision

c. Adrorptlm 1 '

F i gu re IV-7b. Mechanisms f o r attachment o f gas bubbles t o s o l i d s o r o i l .

\

/ ----- --

luenljul I

r

7 0

bIW TKMT SPNOFF/PHYS-CHEM TRMT SYSTEMS

Cur ren t ly , t he most w ide ly dcceptud f i l t e r type used

f n r t r e a t i n g wastewater a re the downflow f i l t e r s which

u t i l i z e a dual o r t r i -med ia m a t r i x . However, t he sand

f i l t r a t i o n system prov ided the p re l im ina ry concept on

which t h e dual and t r i -med ia systems are now constructed.

Three func t i ons are served by t h e f i l t e r bed, namely

- s t r a i n i n g , f l o c c u l a t i o n and sedimentation. To achieve

these func t i ons i n a f i l t e r bed, t h e media should be coarse enough t o r e t a i n l a r g e q u a n t i t i e s o f f l o c y e t

should be s u f f i c i e n t l y f i n e t o prevent t h e passage o f suspended so l i ds . The f i l t e r media should have an

adequate depth t o a l l ow f o r a r e l a t i v e l y prolonged opera t ion o f the system.

e f f e c t i v e c lean ing du r ing t h e backwash.

a concrete box w i t h a sand f i l t e r bed supported by a graded gravel l a y e r con ta in ing underdrains. Wastewater

i s al lowed t o pass downward through the f i l t e r bed by a

combinat ion of water pressure f rom above and s u c t i o n from

t h e bottom. S ing le medium f i l t e r s such as sand, tend t o " b l i n d o f f " a t t h e surface, thus reducing t h e opera t ion

t ime o f t h e f i l t e r and r e q u i r i n g more f requent

backwashing.

importance f o r t h e successful opera t ion o f these type

f i l t e r s .

sur face s l ime and caking.

The media should permi t

. 1 ) Sand F i l t e r : A t y p i c a l sand f i l t e r cons i s t s of

Adequate backwashing i s o f pr imary

There must be adequate p r o v i s i o n t o break up

Sand f i l t e r s , which represent t h e o r i g i n a l t ype of

system used du r ing t h e h i s t o r i c a l development o f waste t reatment systems, a re c l a s s i f i e d as a s i n g l e medium.

The e a r l y sand f i l t e r design demonstrated f i l t r a t i o n

r a t e s o f 0.05 t o 0.13 gpm/ft2 and was termed "slow

sand f i 1 t r a t ion". However, f u r t h e r ir,iprovements have been made on t h e cons t ruc t i on o f the f i l t r a t i o n design

r e s u l t i n g i n t h e development o f the dual and t r i -med ia

f i l t e r systems.


2) Dual and Tri-media F i l t e r s : Downflow f i l t e r

systems w i t h dual o r t r i -med ia can achieve f i l t r a t i o n

r a t e s o f 2.5 t o 5 gpm/ft2.

cons tan t g radat ion o f pore s i z e i n t h e f i l t e r f rom coarse on t h e sur face t o f i n e on t h e bottom. The g rada t ion i n - pore s i z e a l lows f i l t r a t i o n and s torage o f s o l i d s

throughout t h e depth o f t h e bed u n l i k e a single-medium

bed i n which f i l t r a t i o n takes p lace on t h e top. Mixed media us ing coal and sand i s an example o f a

dual-media. A f t e r backwashing, l a r g e f l o c p a r t i c l e s a re adsorbed and t rapped w i t h i n t h e coal l aye r , w h i l e f i n e r

m a t e r i a l i s h e l d i n t h e sand f i l t e r , p reven t ing premature

su r face plugging.

t h e r e i s no d i s c r e t e i n t e r f a c e between t h e t h r e e medium

mate r ia l s , thus e l i m i n a t i n g s t r a t i f i c a t i o n and c r e a t i n g a

un i form, decreased gradat ion i n pore space w i t h an

i nc reas ing f i l t e r depth.

polymers o r alum are added t o s t rengthen f l o c fo rma t ion

and improve s o l i d s removal.

A new type o f sand f i l t e r system has been r e c e n t l y

repo r ted by t h e New York Col lege o f Engineer ing, (Newark, New

Jersey) known as t h e "MBF-moving bed f i l t e r " . The f i l t r a t i o n

concept i s based upon t h e sand be ing d r i v e n through a p ipe i n

one d i r e c t i o n , w h i l e s imul taneously t h e wastewater stream

passes counter c u r r e n t through the same pipe. The i m p u r i t i e s removed are d r i v e n along the p ipe i n t h e d i r e c t i o n o f t he

f i l t e r medi,um movement and are removed a t t h e f i l t e r medium

channel e x i t . The llmoving bed f i l t e r " system operates

cont inuous ly and does no t r e q u i r e backwashing.

i s cons tan t l y be ing removed automat i c a l l y from t h e system,

c leaned and re tu rned t o t h e system f o r f u r t h e r use.

3) Ac t i va ted Carbon/Charcoal F i l t e r s : Ac t i va ted

carbon/charcoal f i l t e r s , i n con t ras t t o t h e s ing le , dual

and t r i -med ia f i l t r a t i o n systems are not employed

p r i m a r i l y t o reduce suspended s o l i d s i n t h e waste

Mixed media prov ides a

A t r i -med ia f i l t e r may c o n s i s t of a

. coal , sand, and gravel . A f t e r backwashing t h e media,

F i l t r a t i o n a ids such as

F i l t e r ma te r ia l


i n f l u e n t . Instead, t h i s f i l t e r system i s used t o remove

r e f r a c t o r y organic compounds from the water t h a t are

respons ib le f o r t a s t e and odor ( tann ins , l i g n i n s , and e the rs ) . The act i vated carbon/charcoal f i 1 t e r requ i res

t h e i n f l u e n t t o be low i n BOD, COD and suspended so l i ds .

Otherwise anaerobic cond i t i ons w i l l develop w i t h hydrogen

s u l f i d e be ing re1 eased t o t h e envi ronment . Advantages and Disadvantages o f Conventional F i l t r a t i o n

Systems :

1. S ing le medium f i l t e r s remove up t o 70 percent o f t he

i n f l u e n t s o l i d s w i t h "b ind ing" o f the f i l t r a t i o n

m a t r i x f r e q u e n t l y occurr ing. Frequent backwashing

and maintenance i s requ i red t o ma in ta in an e f f i c i e n t

system.

and b e t t e r removal e f f i c i e n c i e s .

2. Dual o r t r i -med ia p rov ide longer per iods o f opera t ion

3. F i l t r a t i o n systems should not be used when the

i n f l u e n t suspended s o l i d s exceeds 100 mg/l o r

i n c o m p a t i b i l i t y o f suspended p a r t i c l e s i z e

d i s t r i bu t ion.

4. Should t h e backwash volume exceed 10 percent of t he

h y d r a u l i c l oad ing e n t e r i n g t h e waste t reatment

system, t h e use o f t he f i l t r a t i o n process becomes

uneconomical.

5. Ac t i va ted carbon/charcoal f i l t e r m a t r i x have l i m i t e d

a p p l i c a t i o n and r e q u i r e r e l a t i v e l y low BOD, COD and

suspended so l i d s l oad ing cond i t i ons . These f i l t e r s are

p a r t i c u l a r i l y e f f e c t i v e i n t h e removal o f r e f r a c t o r y

organics.

4 ) Membrane F i l t r a t i o n : The process which employs the

use o f porous membranes t o separate so lu tes f rom an aqueous

s o l u t i o n i s termed as membrane f i l t r a t i o n . There are two such

processes commercial ly a v a i l a b l e which are:

(F igu re IV-9) and 2) reverse osmosis. Both processes are

s i m i l a r i n p r i n c i p l e and can be thought o f as f i l t e r s which

operate a t t he molecular l e v e l r a t h e r then a t t he macroscopic

1 eve1 .

1 ) u l t r a f i l t r a t i o n

7 1 WW TRMT SPNOFF/PHYS-CHEM TRMT SYSTEMS

t

2 ) Dual and Tri-media F i l t e r s : Downflow f i l t e r

systems w i t h dual o r t r i - m e d i a can achieve f i l t r a t i o n r a t e s o f 2.5 t o 5 gpm/ft2.

constant g rada t ion o f pore s i z e i n t h e f i l t e r from coarse on t h e sur face t o f i n e on t h e bottom.

pore s i z e a l lows f i l t r a t i o n and storage o f s o l i d s

throughout t h e depth o f t h e bed u n l i k e a single-medium

bed i n which f i l t r a t i o n takes p lace on t h e top. Mixed media us ing coal and sand i s an example of a

dual-media. A f t e r backwashing, l a r g e f l o c p a r t i c l e s are

adsorbed and trapped w i t h i n t h e coal l aye r , w h i l e f i n e r

m a t e r i a l i s h e l d i n t h e sand f i l t e r , p reven t ing premature

su r face plugging.

coal , sand, and gravel . t h e r e i s no d i s c r e t e i n t e r f a c e between t h e t h r e e medium

m a t e r i a l s , t hus e l i m i n a t i n g s t r a t i f i c a t i o n and c r e a t i n g a

uniform, decreased g rada t ion i n pore space w i t h an

i n c r e a s i n g f i l t e r depth.

polymers o r alum a re added t o s t rengthen f l o c fo rma t ion

Mixed media prov ides a

The g rada t ion i n

A t r i - m e d i a f i l t e r may c o n s i s t o f a

A f t e r backwashing t h e media,

F i l t r a t i o n a i d s such as

and improve so l i d s removal.

A new t ype o f sand f i l t e r system has been r e c e n t l y

n e e r i ng, (Newark , New

t e r " . The f i l t r a t i o n

repo r ted by t h e New York Col lege o f Eng

Jersey) known as t h e "MBF-moving bed fi concept i s based upon t h e sand be ing d r

one d i r e c t i o n , w h i l e s imul taneously t h e

passes counter c u r r e n t through t h e same

ven through a p ipe i n

wastewater stream

pipe. The i m p u r i t i e s

removed are d r i v e n along t h e p ipe i n t h e d i r e c t i o n o f t h e

f i l t e r medium movement and a re removed a t t h e f i l t e r medium channel e x i t .

cont inuously and does no t r e q u i r e backwashing.

i s cons tan t l y being removed a u t o m a t i c a l l y from t h e system,

c leaned and re tu rned t o t h e system f o r f u r t h e r use.

3 ) Ac t i va ted Carbon/Charcoal F i 1 t e r s : A c t i v a t e d

carbon/charcoal f i l t e r s , i n c o n t r a s t t o t h e s ing le , dual

and t r i -med ia f i l t r a t i o n systems a re not employed

p r i m a r i l y t o reduce suspended s o l i d s i n t h e waste

The "moving bed f i l t e r " system operates

F i l t e r m a t e r i a l

i f

I 72


i n f l u e n t . Instead, t h i s f i l t e r system i s used t o remove

r e f r a c t o r y organic compounds from the water t h a t are

respons ib le f o r t a s t e and odor ( tann ins , 1 i gni ns , and e t hers) . The act i vated carbon/charcoal f i 1 t e r requ i res

t h e i n f l u e n t t o be low i n BOD, COD and suspended so l ids .

Otherwise anaerobic cond i t i ons w i l l develop w i t h hydrogen

s u l f i d e being re leased t o the environment.

Advantages and Disadvantages o f Convent ional F i l t r a t i o n

Systems:

1 .

2.

3.

4.

5 .

4 )

S ing le medium f i l t e r s remove up t o 70 percent o f the

i n f l u e n t sol i d s w i t h "b ind ing" o f the f i l t r a t i o n

m a t r i x f r equen t l y occu r r i ng.

and maintenance i s requ i red t o ma in ta in an e f f i c i e n t

system.

Dual o r t r i -med ia p rov ide longer per iods o f opera t ion

and b e t t e r removal e f f i c i e n c i e s .

F i l t r a t i o n systems should not be used when the

i n f l u e n t suspended so l i d s exceeds 100 mg/l o r

i ncompat i b i 1 i t y o f suspended p a r t i c l e s i ze

d i s t r i but ion.

Should the backwash volume exceed 10 percent o f the

hydraul i c load ing e n t e r i n g the waste t reatment

system, the use o f the f i l t r a t i o n process becomes

uneconomical.

Ac t i va ted carbon/charcoal f i l t e r m a t r i x have l i m i t e d

a p p l i c a t i o n and r e q u i r e r e l a t i v e l y low BOD, COD and

suspended s o l i d s load ing cond i t ions .

p a r t i c u l a r i l y e f f e c t i v e i n the removal o f r e f r a c t o r y

organics.

Membrane F i l t r a t i o n :

Frequent backwashi ng

These f i l t e r s are

The process which employs the

use o f porous membranes t o separate so lu tes f rom an aqueous

s o l u t i o n i s termed as membrane f i l t r a t i o n . There are two such

processes commercial ly a v a i l a b l e which are:

(F igure IV -9 ) and 2) reverse osmosis. Both processes are

s i m i l a r i n p r i n c i p l e and can be thought o f as f i l t e r s which operate a t the molecular l e v e l r a t h e r then a t the macroscopic

1 eve1 .

1 ) u l t r a f i l t r a t i o n


Q Macrosol Ute (rejected by membrane)

Microsol Ute

+ Sol vent

F i g . - - 9 Membrane F i l t r a t i o n


I

U l t r a f i l t r a t i o n employs rneinbranes w i t h pore s izes o f 25 t o

100 A 0 i n diameter, thus a l l ow ing water molecules and most

i no rgan ic so lu tes t o f l o w through the nlembrane, wh i l e organic

m a t e r i a l s and suspended s o l i d s are re ta ined by the f i l t e r

medium. Reverse osmosis membranes d i f f e r on ly by the smal le r

pore s izes which range between 5 t o 25 AO, and movement

across the membrane i s f a c i l i t a t e d by a pressure induced

osmosis r a t h e r than d i r e c t f l u i d flow. Reverse osmosis i s

sometimes r e f e r r e d t o as "super f i l t r a t i o n " o r "hyper

f i l t r a t i o n " . A bas ic reverse osmosis u n i t cons i s t s o f

pret reatment o f t he i n f l u e n t , pumps t o p rov ide the opera t i ng

pressure, tanks and apertures fo r c lean ing and f l ush ing , and a

d isposa l system f o r t he waste b r i n e i n a d d i t i o n t o the

retainment. Pretreatment may r e q u i r e the use o f f i l t r a t i o n or

carbon adsorpt ion t o remove res idua l suspended sol i d s which can

otherwise f o u l t he membranes.

Development o f a membrane f i 1 t r a t i o n u n i t by Dorr-01 i ver , Inc. incorpora tes the reverse osmosis - u l t r a f i l t r a t i o n - membrane concept. Dorr-01 i ver c la ims t h i s system w i 11 rep1 ace

many steps now used i n the waste t reatment process. The system

i s repor ted t o e l im ina te a l l suspended so l i ds , bac te r ia , and

v i ruses from an e f f l u e n t . E f f l u e n t BOD ranges from 5 t o 10

m i l l i g r a m s per l i t e r , can be achieved, according t o

Dor r -O l iver , by the use o f t h e i r reverse osmosis - u l t r a f i l t r a t i o n system.

system w i l l be needed t o support D o r r - O l i v e r ' s c la ims.

osmosis process. The most successfu l membranes employed

t o date f o r d e s a l i n a t i o n are based on c e l l u l o s e acetate

and ho l l ow f i b e r s of nylon. Serv iceable l i f e of the

membrane i s o f great importance t o the economics o f t h i s

process. Clogging o f the membrane i s f r e q u e n t l y encountered

and the membrane replacement cost i s p resen t l y high.

I n theory the reverse osmosis process i s capable o f

removing more than 90% o f inorgan ic ions and most organic

Fu r the r opera t ing exper ience w i t h t h i s

D i f f e r e n t types of membranes are used i n the reverse

75


matter. The reverse osmosis process is p r i n c i p a l l y used

i n t h e t reatment o f b rack i sh water and rec lamat ion o f sea

water. Experience w i t h wastewater a p p l i c a t i o n has

r e s u l t e d i n severe problems re1 a t i v e t o membrane f o u l i ng.

2. Physiochemical - Dewater ing

Dur ing each phase o f t h e waste t reatment process, as

water i m p u r i t i e s are removed, new s o l i d s cont inue t o

accumulate which c o n s t i t u t e t h e sludge, General ly, sludge i s 4 t o 6% s o l i d s and t h e r e s t i s water, As such, sludge i s very watery i n consistency and d i f f i c u l t t o handle d u r i n g

d isposal operat ions.

impor tant i n t h e waste t reatment scheme as a means o f improvi ng sludge hand1 i ng and disposal .

hydrophi 1 i c c h a r a c t e r i s t i c s f o r t h e sludge mass.

p r a c t i c e s i n v o l v e t h e a d d i t i o n o f l ime, f e r r i c c h l o r i d e o r

alum (aluminum s u l f a t e ) t o f a c i l i t a t e an i n s o l u b l e

p r e c i p i t a t e t h a t can be c o l l e c t e d and concentrated. Organic polymers, w i t h and w i thou t t h e above chemical add i t i ons , are

a l s o used as dewatering agents.

groups o f t h e organic polymer molecule i n t e r a c t w i t h t h e

h y d r o p h i l i c p o r t i o n o f t h e c o l l o d i a l p a r t i c l e . As

polymer/chemical a d d i t i o n s are increased, t h e h y d r o p h i l i c

na tu re o f t h e c o l l o i d i a l m a t e r i a l s e v e n t u a l l y becomes a l te red , t hus

reducing t h e water b ind ing p roper t y o f t h e c o l l o i d i a l MSS and t h e

Therefore, a dewatering process becomes

The dewatering process depends on t h e a l t e r a t i o n o f t h e Common

E s s e n t i a l l y , t h e r e a c t i v e

re lease o f water f o r removal.

Dewatering, which i s t h e re lease o f

a s o l i d mass, may be accomplished by any

processes; 1) d r y i n g beds; 2) vacuum f

f i l t r a t i o n ; and 4) c e n t r i f u g a t i o n . a. D ry ing Beds: Sand beds were h i s t o r i

entrapped water f rom

o f t h e f o l l o w i n g

l t e r s ; 3) pressure

a l l y t h e f i r s t method o f

sludge dewatering. bottoms and t i l e drains.

these beds t o a depth o f up t o 18 inches. f o r t h e sludge t o dewater and d r y may range from several weeks

They c o n s i s t o f shal low ponds w i t h sand The d igested sludge i s pumped t o

The t ime requ i red

76


t o several months depending upon sludge composi t ion, c l i m a t i c

and sand pe rco la t i on cond i t ions .

B a s i c a l l y dewater ing a c t i o n on sand beds i s by g r a v i t y

dra inage and by evaporat ion s imultaneously.

f r e e l y a v a i l a b l e water d ra ins o f f wi th a concurrent s e t t l i n g o f

t h e sludge so l i ds . Channels i n the sludge mass u s u a l l y form t o

f a c i l i t a t e the movement o f water f rom the sludge t o the sand

and u l t i m a t e l y the d r a i n t i l e .

p r i n c i p a l e f f e c t t he rea f te r . A f t e r repeated sludge

a p p l i c a t i o n , a sludge cake i s formed which can be removed by a mechanical scraper device.

d r y i n g beds i s o f t e n l i m i t e d .

b. Vacuum F i l t e r s : The most f requen t l y used method o f dewater ing

sludge i s the vacuum f i l t e r (F igure IV-10).

been used fo r over f i f t y years i n concent ra t ing s l udge so l ids .

The vacuum f i l t e r i s s imply a round drum covered w i t h a f i n e

interwoven c l o t h / p l a s t i c media on which a vacuum i s pu l led. As

vacuum i s created i n s i d e the r o t a t i n g drum, f ree water i s drawn

f rom the sludge mass u l t i m a t e l y l eav ing a dewatered sludge cake

on t h e media surface.

chemica l l y t r e a t e d sludge l i q u i d i n t o a ho ld ing vessel.

vessel i s loca ted a t the base o f t he f i l t e r un i t .

l e v e l i s maintained h igh enough t o submerge approximat ley 30 percent o f the r o t a t i n g drum's diameter. Vacuum, a t a 10 t o 20

inches o f mercury range, i s app l ied t o the f i l t e r drum and a ids

i n the adsorpt ion o f t he sludge t o the f i l t e r i n g medium.

t h e f i l t e r drum ro ta tes , t he adsorbed sludge forms a cake which

becomes exposed t o the ambient a i r . On cont inued r o t a t i o n i n

t h e a i r , t he sludge cake cont inues t o d r y w i t h an u l t i m a t e

c rack ing ev ident i n the d r i e d sludge. F i n a l l y , the dewatered

sludge cake i s discharged t o a c o l l e c t i o n t rough from which the

. d r i e d sludge s o l i d s are removed and disposed. General ly, t h e

d isposal w i l l be t o a l a n d f i l l o r i nc ine ra t i on .

I n i t i a l l y t h e

Evaporat ion becomes the

Due t o the cos t o f land, the use o f

This process has

The vacuum f i l t r a t i o n process cons is t s o f f i r s t pumping a

Th is

The sludge

As


FILTER DRUM-

EQUALIZING BAR

DISCHARGE ROLL

-FILTER CAKE

T H SPRAY PIPES

WASH TROUGH

DISCHARGE BRACKET

F i g . - 1 0 Vacuum F i l t e r U n i t -

7H

W W TKF.1T SI’WOFF/t’\lY S-CHEM TKMl SYSTEMS

10 pounds o f d r y sludge cake per

f i 1 t e r drum area.

While the vacuum f i l t r a t i o n

successful i n the reduc t i on o f s

The optirriuni r a t e o f slridge dewatering by neans o f the

vacuum f i l t r a t i o n process (F igu re IV-11) i s approximately 2 t o

f o o t o f hour f o r each square

process has proven

udge volumes and hau i n g

cos ts , i t i s s t i l l expensive t o e s t a b l i s h and maintain.

I n i t i a l c a p i t a l and opera t i ng and chemical cos ts are

h ighes t among t h e dewater ing processes commercial ly

avai 1 ab1 e.

c. Pressure F i l t r a t i o n : Pressure f i l t r a t i o n d i f f e r s from

vacuum f i l t r a t i o n i n t h a t t h e l i q u i d i s fo rced through

t h e f i l t e r medium by a p o s i t i v e pressure i ns tead o f a

vacuum. The most common pressure f i l t e r i s known as the

f i l t e r press. Th is press method i s used i n t h e chemical

i n d u s t r i e s f o r dewater ing s l u r r i e s . However, t he f i l t e r

press process i s no t amendable t o food waste t reatment

sludges. The f i l t e r press i s a p l a t e and frame type

f i l t e r , sometimes r e f e r r e d t o as a pressure l e a f f i l t e r .

It cons is t s o f p l a t e s covered w i t h some types o f porous

f a b r i c . A number o f these p l a t e s then form a s e r i e s o f

chambers.

Pressure f i l t r a t i o n i n a f i l t e r press i s achieved i n

t h r e e steps which include, p recoat ing the f i l t e r media,

p ressu r i zed s l udge dewater i ng, and discharge o f t h e

s ludge cakes. Sometimes, t h e sludge i s subjected t o

chemical c o n d i t i o n i n g when necessary. Precoat ing o f t he

media i s achieved by feed ing a water suspension o f

diatomaceous e a r t h over t h e porous ma te r ia l which forms a

precoat t o b ind wi th the sludge p a r t i c l e s and t o

f a c i l i t a t e the discharge o f a cake a t t he end o f the

f i l t e r cycle. The sludge i s pumped between t h e p l a t e s

i s fo rced through t h e f i l t e r media l eav ing t h e s o l i d s

. and i s d i s t r i b u t e d throughout t h e chambers. The l i q u i d

i

.--

Plant Effluent

Screens

*2 / Sol ids

Clarif ieq

-7 Treated Flow

Flow Measurement I \

I \

Fi 1 t rate

/

Pump

Sludge : 4% to 15% Total Solids

Filter

f /.\*

? c- d >

Filter Cake : 8% to .G I. ,\- 50% Total Solids ---

Fig. fl - 11 Primary Treatment P lant Using Vacuum F i 1 t r a ti on t o Dewater S1 udge

-

WJ V


behind, between the p la tes , and a h igh pressure c y c l e

conso l ida tes the cakes. When the spaces between the p la tes are

f i l l e d , t h e sludge cake i s discharged from the p l a t e by a

reve rsa l o f the hyd rau l i c f low.

The pressure f i l t r a t i o n system which takes from 1 t o

2 hours f o r t he completion of one cyc le , i s completely

automat ic i n c l u d i n g precoat, f i l t r a t i o n , and discharge.

One o f t he major advantages a t t r i b u t e d t o pressure

f i l t r a t i o n i s the need f o r minimum superv is ion o f the

operat ion, and thus lower ing the opera t ion costs. It

a l s o has the advantages of y i e l d i n g a h igh s o l i d s

concen t ra t i on i n the f i l t e r cake, and a c l e a r f i l t r a t e

w i t h low suspended so l i ds . The disadvantages t h i s

process has are w i t h the removal of s o l i d s a f t e r the

complet ion o f f i l t r a t i o n , l i m i t e d sludge type

a p p l i c a t i o n s , and low opera t i ng capaci ty. Th is process

i s a l so expensive t o i n i t i a t e due t o c a p i t a l expendi tures

requ i red.

3. Chemical Types

a. F l o c c u l a t i n g agents: Frequent ly, waste t reatment

a

opera t ions encounter d i f f i c u l t i e s i n the removal o f

suspended p a r t i c l e s f rom the wastewater stream. Much

o f t h e d i f f i c u l t y l i e s i n the s i z e and dens i t y o f

those p a r t i c l e s . To a i d i n the removal o f these

p a r t i c l e s , f l o c c u l a t i n g agents are used. F l o c c u l a t i n g

agents he lp t o p h y s i c a l l y entrap the suspended p a r t i c l e s

th rough e l e c t r o s t a t i c i n t e r a c t i o n s and adsorp t ion (F igu re

IV-12). The entrapment r e s u l t s i n the fo rmat ion o f l a r g e r s i z e d and denser p a r t i c l e s which become amenable t o

c l a r i f i c a t i o n processes.

i n t h e removal o f organic suspended so l i ds . Suspended

organ ic mat te r common t o most food processing wastewater

streams cons is t s o f c o l l o i d a l p ro te in , starches and o i l s .

P r o t e i n and starches possess negat ive charges on t h e i r

Chemical f l o c c u l a n t s have proven q u i t e e f f e c t i v e


!

Fkrculrttn

. .

Fig. - - 12 Floc Formation w i t h t h e A i d o f C hemi ca 1 Agents


r e s p e c t i v e inolecular s t r u c t u r e s which c o n t r i b u t e t o t h e i r

d i s p e r s i o n i n an aqueous environment. Through t h e a d d i t i o n

of t h e chemical coagulant , t h e net negat ive charges o f

these suspended c o l l o i d a l m a t e r i a l s are s u b s t a n t i a l l y

reduced o r n e u t r a l i z e d render ing them l e s s a t t r a c t e d t o t h e

water medium. Also, a "b r idg ing" e f f e c t takes p lace which

i n i t i a t e s t h e f l o c format ion. O i l s , i n cont ras t , r e q u i r e

an hydrophobic i n t e r a c t i o n and, there fore , are not amenable

t o t h e i n f l u e n c e o f common chemical f l o c c u l a t i n g agents.

F l o c c u l a t i n g agents are u s u a l l y used i n con junc t ion w i t h

some form o f phys ica l t reatment method t o f a c i l i t a t e

removal o f t h e f l o c sludge.

agents, several f a c t o r s must be taken i n t o

cons idera t ion . These are: type o f coagulant t o be

used; i t s dosage ra te ; pH; a l k a l i n i t y ; s e l e c t i o n o f

i o n i c specie f o r i n t e r a c t i o n ; water t u r b i d i t y ;

p a r t i c l e s ize; temperature; and a g i t a t i o n rate. O f

these f a c t o r s , pH, a l k a l i n i t y , p a r t i c l e s i z e

d i s t r i b u t i o n and t h e f l o c c u l a n t b lending method are

o f s i g n i f i c a n c e and must be c o n t r o l l e d i n t h e p l a n t

opera t ion process. F u r t h e r d iscuss ion o f these

f a c t o r s s h a l l f o l l o w as the s p e c i f i c f l o c c u l a n t s are

reviewed.

1. Lime: The f i r s t o f the f l o c c u l a t i n g a i d s t o be

I n s e l e c t i n g and us ing chemical f l o c c u l a t i n g

used was lime. Lime was found t o be inexpensive,

r e a d i l y a v a i l a b l e and p r a c t i c a l t o use. I t s f l o c

fo rming p r o p e r t i e s were e x t e n s i v e l y e x p l o i t e d i n

t h e removal o f suspended so l ids . However, t h e

use o f l i m e had an inherent problem. The problem

was w i t h p i p e l i n e c logg ing due t o a l i m e deposi t .

Much o f t h i s problem was a t t r i b u t e d t o t h e manner

i n which t h e l i m e was added t o t h e wastewater

stream. The s o l u t i o n t o t h i s problem was

development o f a b e t t e r d ispersa l o f t h e l ime t o

83 W W TRMT SPNOFF/PHY S-CHEM TRMT SYSTEMS

t h e wastewater. As t he l ime d i spe rs ion process

was improved, an improvement o f suspended

p a r t i c l e removal e f f i c i e n c i e s were a l so observed.

Another problem i n the excessive use o f l i m e was

a h ighe r accumulation o f sludge. Thus, some form

o f l i m e a d d i t i o n c o n t r o l must be used.

Lime, i n combination w i t h f e r r i c c h l o r i d e

has a l so been used as a f l o c c u l a t i n g agent. I n

c o n t r a s t t o t h e use o f l ime f o r improved

s e t t l i n g , f e r r i c c h l o r i d e and l i m e are used i n

combination t o a id i n t h e dewatering o f t he

s ludge mass. E s s e n t i a l l y , t he sludge i s

chemica l l y cond i t ioned by these agents p r i o r t o

t h e water removal process. I n t h e use o f f e r r i c

c h l o r i d e , one should be aware o f a pH r e d u c t i o n

(below pH 6.0) t h a t must be u l t i m a t e l y d e a l t w i t h

th rough r e c y c l i n g t o the un t rea ted wastewater

stream and t h e r e f o r e must be neut ra l i zed .

Another use f o r l ime i s i n the phosphate

removal process. General ly, t h i s process i s

considered a t e r t i a r y t reatment whereby t h e

phosphate i s removed from a t r e a t e d wastewater

system. Phosphorus i s most e f f e c t i v e l y removed

a t a pH range o f 9.5 t o 11.5. Through the

a d d i t i o n o f l ime, t h e pH o f the wastewater i s

increased and a chemical r e a c t i o n occurs w i t h the

carbonate f r a c t i o n (as r e f l e c t e d by a l k a l i n i t y )

t o form ca lc ium carbonate, a p r e c i p i t a t e . The

ca l c ium ions a l so reac t w i t h t h e orthophosphate

present i n t h e wastewater and w h i l e i n the

presence o f hydroxyl ions a ge la t inous ma te r ia l ,

ca l c ium hydroxyapat i te i s formed. The r e a c t i o n

i s as fo l l ows :

5Ca++ + 4 OH- + 3HP04 Cag(OH)(PO4) + 3HZ0

I f t h e l ime dosage i s s u f f i c i e n t l y high, t h e pH l e v e l

cou ld be r a i s e d enough t o p r e c i p i t a t e t h e fo rmat ion o f

84


2.

magnesium hydroxide. Typ ica l 1 irne dosages range from

150 t o 300 mg/l as CaO. A t these dosage leve ls ,

approximately 80 t o 90 percent o f t h e phosphate i s

removed from a domestic wastewater. Lime dosage r a t e s

should take i n t o cons ide ra t i on t h e a l k a l i n i t y and

phosphorus conten t o f t h e wastewater as w e l l as t h e

amount o f phosphorus removal desired.

Metal f l o c c u l a t i n g agents: I n a d d i t i o n t o t h e use o f l i m e as a f l o c c u l a t i n g agent, t h e r e a r e two o the r

commonly used classes o f f l occu lan ts .

f l o c c u l a n t s a re t h e se lec ted s a l t s o f i r o n and

aluminum. These metal coagulants a re q u i t e e f f e c t i v e

i n t h e removal o f o rgan ic c o l l o i d s and emulsions from wastewater streams.

a r e f e r r i c s u l f a t e , f e r rous s u l f a t e and f e r r i c

ch lo r i de .

a re aluminum s u l f a t e , sodium aluminate, potash alum and

ammonia a1 urn.

I ron coagulants have p r i i na r i l y t h r e e areas o f use,

namely - 1 ) sludge c o n d i t i o n i n g f o r dewatering; 2 )

phosphorus removal; and 3 ) a ids f o r sedimentation. I n

t h e use o f i r o n con ta in ing f l o c c u l a n t s , one must always

be aware o f t h e i n f l u e n c e these agents have i n lower ing

t h e pH o f t h e wastewater. Therefore, i t i s necessary

t o add l ime o r c a u s t i c t o t h e wastewater t o o f f s e t t h e

a c i d nature o f t he i r o n coagulants.

elsewhere i n t h i s sect ion. I n t h e sludge c o n d i t i o n i n g

step, f e r r i c c h l o r i d e and l ime are combined p r i o r t o e x t r a c t i o n o f t he f r e e water.

These

Examples o f t he i r o n s a l t s used

Aluminum s a l t s used as f l o c c u l a t i n g agents

Sludge c o n d i t i o n i n g f o r dewatering i s discussed

When us ing t h e f e r r i c and f e r r o u s s u l f a t e s a l t s as

f l o c c u l a n t s f o r phosphorus and suspended s o l i d s removal, blends a re made w i t h l ime and a se lec ted

polymer. A t y p i c a l dosage might cons i s t o f 40 mg/l o f

t h e i r o n s a l t , 70 mg/l o f l ime and 0.5 mg/l o f t h e

polymer. It i s repor ted t h a t 80 percent o f t h e

- 85


phosphorus and 60 percent o f t h e BOD (as suspended

s o l i d s ) can be removed by t h i s t ype chemical treatment.

Chemical ly, t h e f e r r i c i ons combine w i t h t h e phosphates

t o form FeP04 a t t h e molar r a t i o o f 1 :l. The o t h e r w ide ly used metal coagulant i s t h e

aluminum based sa l t s . These s a l t s a re s i m i l a r t o t h e

i r o n based coagulants i n chemical behavior w i t h respect

t o phosphorus and suspended s o l i d s removal. aluminum type f l o c c u l a n t s a re most e f f e c t i v e i n a pH

range o f 5.5 t o 8.0, depend on a b icarbonate

a l k a l i n i t y , and i s i n f l uenced by t h e q u a n t i t y and

na ture o f t h e c o l l o i d a l i na te r ia l and i o n i c species present i n t h e aqueous environment.

Of t h e aluminum based s a l t s used as a f l o c c u l a t i n g

agent, aluminum s u l f a t e i s perhaps t h e most w ide ly

used. Common names f o r t h i s aluminum s a l t a re alum,

f i l t e r alum and alumina su l fa te .

employed f l o c c u l a t i n g agent, alum i s used i n waste t rea tment a t a dosage range o f 5 t o 50 mg/l. dosage r a t e be ing d i c t a t e d by t h e f a c t o r s s t a t e d

prev ious ly .

7 due t o t h e s o l u b i l i t y behavior o f aluminum hydroxide. Good t u r b i d i t y and organic c o l o r removal a re observed

w i t h i n t h i s range. F l o c p roduc t ion i s a l s o enhanced by t h e presence o f a carbonate a l k a l i n i t y which can be

aided by t h e a d d i t i o n o f e i t h e r sodium b icarbonate o r l ime. Other coagulant a ids used w i t h alum a re

a c t i v a t e d s i l i c a , polymers and clay. These a ids improve a1 um f l occul a t i on by c o n t r o l 1 i ng t h e suspended

s o l i d s s i z e d i s t r i b u t i o n . Dosage rates, sequence o f

a p p l i c a t i o n and t h e b lend ing process a re a l s o c r i t i c a l

t o o p t i m i z i n g alum f l o c c u l a t i o n . When us ing coagulant

aids, chemical r e a c t i o n r a t e s are accelerated, alum

dosage r a t e s are reduced, t h e e f f e c t i v e pH range f o r

f l o c c u l a t i o n i s extended and t h e f l o c i s found t o

The

As a r o u t i n e l y

The

Optimum pH range f o r f l o c c u l a t i o n i s 6 t o

c


s e t t l e more q u i c k l y and i s less suscept ib le t o f l o c

fragment a t i on.

The e f f e c t i v e n e s s o f alum f l o c u l a t i o n f o r

c l a r i f y i n g wastewater a f t e r secondary t reatment has

been shown t o produce a good q u a l i t y e f f l u e n t .

E f f l u e n t s have been demonstrated t o possess good

c l a r i t y , low r e s i d u a l BOD l e v e l s , and reduced

concent ra t ions o f i r o n , manganese and chromium.

Molybdenum, lead, z inc and cadmium are not reduced

s i g n i f i c a n t l y by t h e use o f alum.

coagulants i s i n t h e removal o f phosphorus from the

wastewater stream. This invo lves a t e r t i a r y t reatment

t o reduce phosphorus t o t h e d ischarge l i m i t s d i c t a t e d

by the EPA o r s t a t e water discharge permit . As noted

f o r i r o n coagulants, t h e aluminum ions a l s o combine

w i t h the orthophosphates present i n t h e wastewater.

However, the removal o f polyphosphates and organic

phosphorus compounds appear t o i n v o l v e mechanical

entrapment o r adsorpt ion on t h e f l o c p a r t i c l e s . The

aluminum - phosphate r e a c t i o n occurs as fo l lows:

Perhaps the most extens ive use o f aluminum

A12(S04)3*14.3H20 + 2PO4" 2 A 1 PO4 + 3S04' + 14.3H20.

From t h e above r e a c t i o n formula, i t may be seen t h a t

t h e A 1 t o P r a t i o i s 1. However, t h e weight r a t i o o f

comniercial alum i s 9.7 t o 1 of phosphorus. Table IV-1

l i s t s the r a t i o o f alum dosage t o percent o f

phosphorus removal desi red.

I n t h e use o f alum as a f l o c c u l a t i n g agent, one

must a l s o deal w i t h t h e sludge hand l ing and d isposal

problem which u s u a l l y occurs. Th is i s p a r t i c u l a r l y

t r u e when phosphorus must be removed from the wastewater e f f l u e n t s ince h igher alum dosage r a t e s are

requi red. Much o f the problem focuses on t h e presence

o f h igh mois ture commonly associated w i t h alum type

sludges. This h igh mois ture content r e s u l t s i n t h e

produc t ion o f l a r g e volumes o f sludge which must be

87


Table IV-1. Alum Dosage for Phosphorus Removal

A 1 um dosage/l Des i red Percent

P Removal

13 75

16 85

22 95

1/ mg/l o f alum per 1 mg/l o f phosphorus found i n the

wastewater t o be treated.

88 W W TKMT SPNOFF/PHYS-CHEM TRMT SYSTEMS

dewatered.

a r e d ry ing beds o r mechanicdl f i l t r a t i o n .

f l o c c u l a n t s i s t h e t r a d e o f f o f water p o l l u t a n t s .

While suspended s o l i d s , phosphorus and o t h e r metal i ons

a r e being removed by these f l o c c u l a t i n g agents,

So4' i s being released t o the water stream. How important t h i s i s w i l l have t o be determined on a

case by case basis.

3. Organic polymers: A c lass o f f l o c c u l a t i n g agents which

i s ga in ing acceptance i n t h e t reatment o f wastewater i s

t h e organic polymer. Th is polymer i s genera l l y used i n con junc t i on w i t h l ime and t h e metal coagulants t o speed

up t h e r a t e o f suspended p a r t i c l e coalescence and t o

inc rease t h e f l o c dens i t y thereby f a c i l i t a t i n g a more

r a p i d s e t t l i n g . The organic polymer i s a s y n t h e t i c a l l y manufactured long chain, h igh molecular weight c o l l o i d

which possesses an ion ic , c a t i o n i c and non ion ic e l e c t r o s t a t i c c h a r a c t e r i s t i c s . Thus, t h e organic

polymer o f f e r s considerable f l e x i b i l i t y i n a p p l i c a t i o n due t o t h e v a r i e t y o f polymers a v a i l a b l e commercially.

a re t h e reduc t i on i n t h e use o f l ime and metal t ype

f 1 occul a t i ng agents, improvement o f s l udge dewateri ng

c h a r a c t e r i s t i c s and reduc t i on i n sludge hand l ing

volumes. Also, dosage l e v e l s f o r t h e polymers i s o f

t h e order o f 0.1 t o 1.0 mg/l, cons iderab ly l e s s than

t h e o the r f l o c c u l a t i n g agents.

polymers are used p r i m a r i l y as a f l o c c u l a t i n g a id , they

have been used success fu l l y as a f l o c c u l a n t , e s p e c i a l l y

t h e c a t i o n i c polymers.

As chemical f l o c c u l a n t s are used, two major

o b j e c t i v e s always remain i n t h e f o r e f r o n t , namely - 1 )

t h e removal o f suspended so l i ds ; and 2 ) reduc t i on o f

phosphorus and i r o n concent ra t ions i n t h e discharged

e f f l u e n t . These compounds are r o u t i n e l y used du r ing

Two approaches used t o e x t r a c t t h e water

Another cons ide ra t i on i n t h e use o f e i t h e r metal

The major advantages f o r us ing organic polymers

While t h e organic

89


t h e sludge c l a r i f i c a t i o n s tep o r i n t h e t e r t i a r y waste

t rea tment process. Inherent i n t h e use o f f l o c c u l a t i n g agents i s t h e increased sludge hand l ing and d isposa l

requirement. However, t h e use o f chemical f l o c c u l a t i n g

agents does g i ve t h e system's opera tor f l e x i b i l i t y t o

t h e v a r i a b i l i t y o f p o l l u t a n t and h y d r a u l i c l oad ing cond i t i ons commonly encountered i n most waste t rea tment

operat ions. b. Ac t i va ted carbon: H i s t o r i c a l l y , a c t i v a t e d carbon has been

r o u t i n e l y used as an a d d i t i v e i n f l o c c u l a t i o n , sedimenta-

t i o n and f i l t r a t i o n processes f o r t h e reduc t i on o f

odors and t a s t e s and t h e e l i m i n a t i o n o f c o l o r from wastewater.

remove f i n e l y suspended organ ic p a r t i c l e s from several d i f f e r e n t type i n d u s t r i a l waste streams. Two methods o f

a p p l i c a t i o n have been used f o r a c t i v a t e d carbon, namely - a

f i l t r a t i o n process and d i r e c t a d d i t i o n t o t h e a c t i v a t e d

sludge system. a d d i t i o n s have been experienced, i t s a p p l i c a t i o n s have

gained w ider acceptance by bo th i n d u s t r y and t h e

mun ic ipa l i t ies. A1 so a i d i ng i t s acceptance has been t h e

advent o f an economical ly f e a s i b l e regenera t ion system which provides a means f o r recovery o f "spent" a c t i v a t e d

carbon, thereby reducing t h e cos t i n i t s use.

a r e a t t r i b u t e d t o i t s a b i l i t y t o adsorb organ ic compounds

and t h e p r o v i s i o n o f an attachment s i t e f o r t h e

b iodegradat ion process t o take place. A microscopic examination o f t h e a c t i v a t e d carbon p a r t i c l e revea ls i t t o

be a h i g h l y porous macromolecular sponge i n t o which

dispersed molecules and suspended p a r t i c l e s a re at tached

and absorbed from so lu t ion . Area measurements o f t h e

carbon p a r t i c l e show sur face areas ranging from 500

c d / g t o 1000 c d / g .

a v a i l a b l e on t h e p a r t i c l e , t h e g rea te r t h e adsorp t ive

capac i t y o f t h a t p a r t i c l e .

More recen t l y , t h i s a d d i t i v e has been used t o

As t h e b e n e f i t s o f a c t i v a t e d carbon

The p o l l u t a n t removal c a p a b i l i t i e s o f a c t i v a t e d carbon

The more sur face area

Adsorpt ion has been c o n t r i b u t e d

90


p r i m a r i l y t o Van der Waal fo rces o r d i spe rs ion fo rces

s i m i l a r t o those respons ib le f o r t h e c o n d i t i o n o f nonpolar

l i q u i d s , and t o a l e s s e r degree, p o l a r forces. As l ong as

sur face areas are exposed, t h e carbon p a r t i c l e r e t a i n s i t s p o l l u t a n t removing c a p a b i l i t y . However, a f t e r t h e capac i t y

of t he p a r t i c l e f o r adsorp t ion i s exhausted, i t then can be regenerated by an i n c i n e r a t i o n process.

The regenerat i o n process used t o recover "spent" carbon u t i l i z e s heat a t a h igh temperature w h i l e

ma in ta in ing oxygen a t a low l e v e l t o minimize combustion. The adsorbed organics a re d r i v e n o f f as gases and water

through the hea t ing process and t h e a c t i v e sur face areas o f

t h e carbon p a r t i c l e s a re renewed f o r a d d i t i o n a l use. Th is

regenera t ion and recovery system o f f e r s an economic advantage f o r t h e use o f a c t i v a t e d carbon i n t h e t reatment

of wastewater. General ly, 2 t o 10% o f t h e o r i g i n a l carbon

i s l o s t du r ing i t s r e c y c l i n g and t h e r e f o r e requ i res some

rep1 en i shment.

A p p l i c a t i o n s

E s s e n t i a l l y , t h e r e a re two methods o f a p p l i c a t i o n used

f o r a c t i v a t e d carbon. These methods a re carbon f i l t e r beds

and as a combination w i t h f l o c c u l e n t s and c l a r i f i c a t i o n

aids.

As carbon f i l t e r beds are employed, t h e wastewater

passes through t h e carbon m a t r i x w i t h a contac t t ime

rang ing from 30 t o 60 minutes.

vary from 2 t o 8 gpm/ft2 o f f i l t r a t i o n area. two t ype f i l t r a t i o n beds used.

2 ) moving t ype carbon f i l t r a t i o n beds.

i n municipal and i n d u s t r i a l waste t reatment f a c i l i t i e s

where t h e carbon exhaust ion r a t e s are l e s s than 1000 l b o f

carbon per n i i l l i o n ga l l ons o f wastewater processed. con t ras t , moving carbon f i l t r a t i o n beds are t h e system o f

cho ice where organic loadings and carbon exhaust ion r a t e s a re above 1000 l b per m i l l i o n ga l lons processed and t h e

Hydrau l i c f l o w r a t e s w i l l

These a re

There a re

1 ) t h e f i x e d and F ixed beds are used

I n

91


suspended s o l i d s content o f t he wastewater i s low. The

moving bed system a l s o possesses an advantage over t h e

f i x e d bed process through i t s min imiz ing o f p rogress ive

c logg ing and t h e r e s u l t a n t l oss o f h y d r a u l i c head pressure.

The moving bed concept a l so lends i t s e l f t o automation

whereby t h e "spent" carbon p a r t i c l e s can be removed from

t h e f i l t r a t i o n bed, dewatered, regenerated by passage

th rough a r o t a r y k i l n a t 1600-18OOOF and re tu rned t o

t h e f i l t r a t i o n bed f o r reuse.

S e l e c t i o n based on t h e s p e c i f i c use o f t h e a c t i v a t e d

carbon i s o f importance. Two types o f carbon are

commercial ly ava i l ab le , namely: powdered and granular. As t h e s e l e c t i o n process takes place, one must consider t h e

phys i ca l c h a r a c t e r i s t i c s w i t h respect t o g ranu lar size,

sur face area and pore size. Other cons idera t ions are

carbon dens i t y and regenera t ion c a p a b i l i t i e s .

fo rm appears t o o f f e r t he best c h a r a c t e r i s t i c s f o r t h e

f i x e d and moving carbon f i l t r a t i o n beds.

appears best f o r use as a c l a r i f i c a t i o n aid. Experience

shows t h e granu lar carbon a l s o t o be eas ie r t o regenerate

than t h e powdered form.

p a r t i c l e , h y d r a u l i c f l o w e q u a l i z a t i o n and pH c o n t r o l are

important. Also, wastewater should be p re t rea ted i f the

suspended s o l i d s exceed 50 mg/l and/or o i l s and greases are

above 10 mg/l s ince t h e e f fec t i veness o f carbon adsorp t ion

t reatment w i l l be g r e a t l y reduced. I n most app l i ca t i ons ,

t h e use o f a c t i v a t e d carbon u s u a l l y f o l l o w s t h e secondary

t rea tment process. When counter cu r ren t f i x e d bed con-

t r a c t o r s are used, a c t i v a t e d carbon w i l l absorb up t o

20-30% o f i t s weight o f mixed organics and reduce these

organ ics i n the discharge by 90%.

has e x i s t e d f o r many years. Early use was found i n the

home and i n d u s t r y f o r t h e removal o f i r o n o r water

s o f t e n i n g purposes (F igu re IV-13a). Over the years, t h ree

bas i c i o n exchange systems have been developed and are i n

The g ranu la r

The powdered form

For optimum adsorp t ion o f t he a c t i v a t e d carbon

c. I o n Exchange: The use o f i o n exchange i n water t reatment


use today. The systems used are: 1 ) t h e Si ro therm process,

2 ) t h e convent ional process and 3) t h e c l i n o p t i l o l i t e

( z e o l i t e ) process/specia l i o n s e l e c t i o n (F igure IV-13b).

o n l y one which appears t o have wastewater a p p l i c a t i o n i s

t h e z e o l i t e o r c l i n o p t i l o l i t e process.

t h i s process i s i n t h e removal o f ammonia from t r e a t e d

wastewater. Therefore, the c l i n o p t i l o 1 i t e process can be

used as a t e r t i a r y t reatment s tep i n t h e system. F i e l d

s t u d i e s show t h a t c l i n o p t i l o l i t e , when used a t t h e 20 t o 50

mesh size, can reduce a waste stream c o n t a i n i n g 20 mg/l o f

ammonia down t o 1 mg/l a t a f l o w r a t e o f approximately 10

r e s i n bed volumes per hour. The ammonia removal c a p a c i t y

appears s t a b l e over a pH range o f 4 t o 8 b u t diminishes

r a p i d l y ou ts ide t h i s range. Usual ly , a f t e r 150 t o 200 bed

volumes o f wastewater have passed through t h e bed, t h e

c l i n o p t i l o l i t e becomes sa tura ted w i t h ammonia and ammonia

begins t o leak through the bed. When thi; occurs, regen-

e r a t i o n o f t h e c l i n o p t i l o l i t e i s needed. To regenerate the

r e s i n , a s a l t b r i n e s o l u t i o n i s used. The ammonia-laden

spent-regenerant represents approximately 2.5 t o 5 percent

o f t h e waste stream through-put before regenerat ion. Th is

spent-regenerant s o l u t i o n can be f u r t h e r t r e a t e d e l e c t r o -

l y t i c a l l y by t h e generat ion o f c h l o r i n e gas from t h e

c h l o r i d e s i n t h e so lu t ion . The c h l o r i n e reac ts w i t h t h e

ammonia conver t ing it t o n i t r o g e n gas which then i s

re leased t o t h e atmosphere.

Specia l i o n exchange res ins, l i k e c l i n o p t i l o l i t e , have

been developed r e c e n t l y t o s e l e c t i v e l y remove s p e c i f i c ions

i n so lu t ions . O f pr imary importance i s t h e a b i l i t y t o

remove t h e mercur ic ion, methyl mercury, lead, s i l v e r , z inc

and copper species. Each species r e q u i r e s a s p e c i f i c a l l y

designed i o n exchange r e s i n t o achieve t h e des i red removal.

One Dutch designed i o n exchange r e s i n (Imac GT-73, Akzo

Chemie) i s repor ted t o remove zinc, copper, lead and

s i l v e r , c o n c u r r e n t l y f rom water t o extremely low

concent ra t ions on t h e f i n a l discharge. Special i o n

O f t h e t h r e e i o n exchange processes a v a i l a b l e , t h e

The a p p l i c a t i o n o f

(a) Sof te l l ing


1. - L L - - L . -

MINERALIZED FEED INLET

c--- WASTE REGENERANTS (Ce Ne SALT$ M(

.b) Demineral i z a t i o n

REGENERANT CAUSTIC

(OH SOURCE)

WASTE REGENERANTS CI SO4 SALTS

F i g . - - 13 Ion Exchange Processes

94

W W TRMT SPNOFF/PliYS-CHEM TRMT SYSTEMS

exchange r e s i n s o f f e r a d d i t i o n a l op t ions i n the wastewater

t rea tment f i e l d but t h e i r use can be r e l a t i v e l y h igh ( i .e.

$.60 net/1000 gal o f wastewater t r e a t e d f o r removal o f

mercury).

d. D i s i n f e c t i o n : The purpose o f d i s i n f e c t i n g any water source

i s t o render i t safe t o the general pub l i c . Thus, t h a t

same o b j e c t i v e i s app l i ed t o the p r a c t i c e o f d i s i n f e c t i o n

o f t he t r e a t e d wastewater stream. That i s , t o p r o t e c t t h e

p u b l i c hea l th from the spread o f disease by c o n t r o l l i n g the

po in t -source discharge. I n general, t he p r a c t i c e o f

d i s i n f e c t i o n i s c a r r i e d ou t where feca l p o l l u t e d wastewater

has been t r e a t e d and i s t o be discharged t o a t r i b u t a r y

stream. However, t h i s p r a c t i c e may be requ i red by the

s t a t e r e g u l a t o r y agency f o r a l l point-source discharges.

I t i s f o r t h i s reason t h a t t he process o f d i s i n f e c t i o n i s

i nc luded i n t h i s sect ion.

The process o f d i s i n f e c t i n g the point-source discharge

may i n v o l v e one o f t h r e e methods. These methods are: 1 )

c h l o r i n a t i o n , 2 ) ozone and 3 ) u l t r a v i o l e t l i g h t .

1 ) C h l o r i n a t i o n - t h i s p r a c t i c e i s w ide l y used bu t i s

o f t e n abused.

( i n t h e form o f a powder, l i q u i d o r gas) t o water which

c rea tes an o x i d i z i n g cond i t ion . The o x i d i z i n g c o n d i t i o n

d i s r u p t s the b a c t e r i a and v i r u s c e l l / p a r t i c l e o rgan iza t i on

causing i n a c t i v i t y and death t o t h e respec t i ve b i o l o g i c a l

systems i n t h e aquat ic environment. I n a d d i t i o n t o the

d i s i n f e c t i n g p roper t y o f c h l o r i n e , it a lso i s use fu l i n the

removal o f i r o n and manganese from water as w e l l as con-

t r o l l i n g odor and s l ime growth i n the flumes and process

u n i t s o f vegetable and f r u i t processing operat ions.

a f f e c t e d by several f a c t o r s . These f a c t o r s are: 1 ) c h l o r -

i n e res idua l , 2 ) con tac t t ime, 3 ) pH, 4 ) temperature and

5 ) res idua l o rgan ic matter. Perhaps the most c r i t i c a l

f a c t o r s are the c h l o r i n e res idua l concent ra t ion and contac t

t ime. Current p r a c t i c e s i n t r e a t i n g point-source

Th is method employs the a d d i t i o n o f c h l o r i n e

E f f e c t i v e d i s i n f e c t i o n by the c h l o r i n a t i n g method i s


discharges i nc lude c h l o r i n e use concent ra t ion l e v e l s o f 8 t o 15 mg/l w i t h a minimum contac t t ime o f 20 t o 30 minutes.

However, should t h e pH of t he water be above 9 o r r e s i d u a l

o rgan ic mat te r be present, c e r t a i n c h l o r i n a t i o n adjustments

become necessary. I n t h e case o f t h e pH, s l i g h t a c i d i f i -

c a t i o n w i l l be requ i red t o lower t h e pH.

values above 9 i s q u i t e uns tab le and no t e f f e c t i v e as a

d i s i n f e c t a n t .

e f fec t i veness , t h e pH should be adjusted t o approximately

7.0. As t h e res idua l organic mat te r i s considered, one

must be aware t h a t organic mat te r and carbon a c t i v e l y

absorb ch lo r i ne .

o rgan ic ma t te r must be s a t i s f i e d be fore any res idua l

c h l o r i n e can be establ ished. A net e f f e c t here i s t he

l ower ing o f t he BOD value f o r t h e discharged water.

S a t i s f y i n g the c h l o r i n e demand fo r s p e c i f i c waste t reatment

systems can be a problem due t o t h e presence o f both

suspended organic s o l i d s and algae. The key i n d i c a t o r t o

adequate c h l o r i n a t i o n i s t he reduc t i on t o o r maintenance o f

t h e c o l i f o r m b a c t e r i a a t t h e discharge permit l i m i t a t i o n .

2 ) Ozone - has been used f o r q u i t e sometime t o t r e a t water supp l i es i n Europe and Canada. However, i t s use i n

wastewater a p p l i c a t i o n s has been l i m i t e d t o p i l o t p l a n t

s tud ies f o r t he purpose o f e s t a b l i s h i n g i t s f e a s i b i l i t y and

r e l i a b i l i t y , process l i m i t a t i o n s and cos t in fo rmat ion .

There are no f u l l sca le p l a n t s i n t h e U.S. us ing ozone

t o d i s i n f e c t wastewaters a t t h i s time. However, it has

been repo r ted t h a t t h e r e are a few new waste t reatment

f a c i l i t i e s i n t h e U.S. t h a t have spec i f i ed ozone f o r t h e

t e r t i a r y d i s i n f e c t i o n stage.

I n c o n t r a s t t o c h l o r i n a t i o n , ozone requ i res t h e

a v a i l a b i l i t y o f e l e c t r i c a l energy. Ozone i s produced

o n - s i t e by the a p p l i c a t i o n o f an e l e c t r i c a l d ischarge

across an atmosphere of oxygen or a i r . A t present, approximately 6 k i l o w a t t hours o f power are requ i red t o

Ch lo r ine a t pH

Therefore, t o improve i t s s t a b i l i t y and

Thus, t h e c h l o r i n e requirements o f t he

0 0

W W TKMT SI’NOFF/PtiY S-Ct iEM TRMT SYSTEMS

generate one pound o f ozone froin pure oxygen; whereas 12

k i l o w a t t s are requ i red t o gpnerate 1 pound o f ozone froin

a i r . For comparison, c h l o r i n e uses 1.3 k i l o w a t t hours o f

e l e c t r i c i t y t o produce one pound o f c h l o r i n e gas. I n one study i t has been repor ted t h a t i t i s d i f f i c u l t

t o d i s i n f e c t secondary e f f l u e n t w i t h ozone and c o n s i s t e n t l y

meet es tab l i shed b a c t e r i o l o g i c a l standards. Therefore,

t e r t i a r y t reatment i s required. F i l t r a t i o n has been shown

t o be an e f f e c t i v e pretreatment s tep t h a t enhances t h e

d i s i n f e c t i o n e f f i c i e n c y o f ozone. Research i s s t i l l needed

t o a s c e r t a i n t h e optimum parameter f o r c o n t r o l 1 i ng ozone

dosage. Present technology u t i l i z e s a constant ozone dosage which r e s u l t s i n excessive ozone consumption and i n

some cases inadequate d i s i n f e c t i o n . Residual o x i d a t i o n products need t o be i n v e s t i g a t e d t o determine i f t o x i c

compounds are formed when t h e r e a c t i o n o f ozone w i t h

organics do not proceed t o complet ion ( C O 2 and H20).

U l t r a v i o l e t (UV I r r a d i a t i o n ) - i s used as a

d i s i n f e c t a n t method f o r demineral ized water systems. It i s

used f o r d i s i n f e c t i n g po tab le water systems i n overseas

h o t e l s , ocean vessels, res taurants and a t r e c r e a t i o n and

vacat ion s i t e s . There are many i n d u s t r i a l and product

water a p p l i c a t i o n s t h a t use UV, such as breweries, pharmaceutical manufacturers, and f i s h hatcher ies.

Al though u l t r a v i o l e t l i g h t has not been w ide ly used t o

d i s i n f e c t wastewater, t h e r e i s l i m i t e d i n f o r m a t i o n t h a t

i n d i c a t e s i t may become a p o t e n t i a l l y d e s i r a b l e

a l t e r n a t i v e .

process was demonstrated a t a 40,000 waste t reatment p l a n t

a t S t . Michaels, MD. I t s r e l i a b i l i t y as a d i s i n f e c t a n t

method was h i g h l y dependant upon e f f l u e n t q u a l i t y (i .e.

c l a r i t y ) . As w i t h the ozone process, t h e f a c i l i t y w i l l u t i l i z e f i l t r a t i o n as a pretreatment stage p r i o r t o UV

d i s i n f e c t i o n .

There are numerous s u p p l i e r s o f UV equipment.

3 )

The f e a s i b i l i t y o f t h e UV d i s i n f e c t i o n

These

equipment manufacturers have made s i g n i f i c a n t design

- 97


improvements w i t h regard t o equipment cons t ruc t ion ,

maintenance, sur face contac t and dosage (UV i n t e n s i t y ) .

The manufacturers i nco rpo ra te a continuous UV mon i to r t o

measure l i g h t transmission, which serves as t h e parameter

f o r mon i to r i ng t h e d i s i n f e c t i o n process.

U l t r a v i o l e t l i g h t i s germic ida l when absorbed by

organ ic molecular compounds essen t ia l t o t h e c e l l ' s

b i o l o g i c a l func t ion ing . The e x c i t a t i o n o f t h e molecu causes a d i s r u p t i o n o f unsaturated bonds t h a t produce

progress ive l e t h a l biochemical change. For most spec t h e b a c t e r i c i d a l e f f e c t i s a f u n c t i o n o f UV l i g h t

t h e

es a

es ,

absorp t ion a t a s p e c i f i c wave leng th range and t h e e f f e c t i s g rea tes t between 2500 and 2600 angstroms.

an e f f e c t i v e germicide, t h e energy dosage must reach t h e

organism.

For UV t o be

Some o f t h e f a c t o r s t h a t a f f e c t t h e pene t ra t i on

of UV energy i n t o t h e water a re t u r b i d i t y , co lo r , and

organ ic compounds.

UV system.

chambers t h a t p r o t e c t aga ins t i r r a d i a t i o n exposure which

can be harmful t o t h e eyes and skin.

Safety i s of utmost importance i n t h e opera t i on o f t h e

The newer designs o f UV equipment have enclosed

A study has shown t h a t a good q u a l i t y e f f l u e n t can be

d i s i n f e c t e d w i t h UV, however, pretreatment o f t h e e f f l u e n t

may be requ i red t o p rov ide adequate c l a r i t y f o r t h e

d i s i n f e c t i o n process. Whenever t h e e f f l u e n t i s h igh i n

s o l i d s o r t u r b i d i t y , t h e use o f UV as a d i s i n f e c t a n t agent

becomes l e s s e f f e c t i v e . Add i t i ona l i n fo rma t ion i s needed

t o e s t a b l i s h t h e minimum pretreatment requirements f o r

o p t i m i z i n g t h e opera t i ona l parameters, such as UV dosage, hyd rau l i cs , con tac t t ime and energy requirements.

98

W W TKMT SPNOFF/PHYS-CHEM TRMT SYSTEMS

D. B i b l i ography General Overview o f Systems

Hamner, Mark J., 1975. "Wastewater Processing" I n "Water and

Wastewater Techno1 ogy" pub1 i shed by W i 1 ey and Sons , Inc. , New

Y ork.

C H ~ M H i l l , 1976.

Lash, L. 0. and Kominek, E. G., 1975. "Primary - Waste - Treatment

"Wastewater Treatment" a v a i l a b l e frorn CH2M

H i l l , Box 428, C o r v a l l i s , Oregon 97330.

Methods", Chemical Engineer ing, Vol. 82 (21-Deskbook Issue) :

49-61.

Sand F i l t e r s

H a r r i s , S. E., Reynolds, J. H., H i l l , D. W., F i l i p , D. S. and

Middlebrooks, E. J. , 1977. Upgrading Waste S t a b i l i z a t i o n Pond E f f l u e n t s " , Jour. Water P o l l .

Cont ro l Fed., 49:83-102.

" I n t e r m i t t e n t San F i l t r a t i o n f o r

Chemical Processes - Overview

Weber, W. J. , Jr. , Hopkins, C. B. , and Bloom R . , Jr. , 1970.

Physiochemical Treatment o f Wastewater. Journ. Water Pol 1. Cont ro l Fed. 42:83.

F l o c c u l a t i n g Agents

Bel lew, E. F., 1978. Comparing P r e c i p i t a t i o n Methods f o r Water

Treatment. Chem. Engineer. Vol. 85, p. 85-91.

Kawamura, Susumu, 1976. Considerat ions on Improving F loccu la t ion . Jour. AWWA, Vol. 70 ( 6 ) : 328-336.

L i n s t e d t , K. D., Bennett, E. R., Fox, R. L. and Heaton, R. D., 1974.

Alum C l a r i f i c a t i o n f o r I inproving Wastewater E f f l u e n t Q u a l i t y .

Water Research (G.B.) 8:753-760.

A c t i v a t e d Carbon

Cohen; J. M., 1977. Trace Metal Removal by Wastewater Treatment.

Technology Trans fer (EPA), January issue.

39 W W TKMT SPNOFF/PHYS-CHEM TKMT SYSTEMS

D r . John, P. B. and Adam, A. D., 1$375. A c t i v a t e d Carbon Improves

Wastewater Treatment. Hydrocarbon Processing, October issue: page

104- 11 1. Engl ish, 3. N. e t al., 1970. Removal o f Orgdnics frorn Wastewater by

A c t i v a t e d Carbon. Water - Chemical Engineer ing Symposium Ser ies

67:147-153.

I o n Exchange Processes

Cadman, T. W. and D e l l i n g e r , R. W., 1974. Techniques f o r

Meta ls f rom Process Wastewater. Chem. Engineer., Vo 79-85.

Calmon, C a l v i n and Gold, H a r r i s , 1976. New D i r e c t i o n i n

Removing

. 80, p.

on Exchange.

Environmental Science and Technology Vol . 10, p. 980-984.

C l i f f o r d , D. A. and Weber, W. J . , 1978. Multicomponent I o n Exchange:

Nitrate-Removal Process w i t h Land-Disposable Regenerant. Indust .

Water Engineer., March issue, p. 18-26.

Gregory, J . and Dhond, R. V., 1972. Wastewater Treatment by I o n

Exchange. Water Research (G.B.), Vol. 6, p. 681-694.

Jorgensen, S.E., L i b o r , O., Graber, K. L. and Barkacs, K., 1974.

Ammonia Reirioval by Use o f C l i n o p t i l o l i t e . Water Research (G.B.)

Vol. 10, p. 213-224.

D i s i n f ect, ant s

B o l l y k y , L. J . and Siegel , B . , 1977. Ozone D i s i n f e c t i o n o f Secondary

E f f l u e n t . Water and Sewage Works, A p r i l issue, p. 90-92.

Dugan, P. R . , 1978. Use and Misuse o f C h l o r i n a t i o n f o r t h e P r o t e c t i o n

o f P u b l i c Water Suppl ies and t h e Treatment o f Wastewater.

News, Vol . 44 (33) : 97-101.

Report i n Wastewater D i s i n f e c t i o n . Technology Trans fer

(News le t te r ) , October issue.

E f f l u e n t D i s i n f e c t i o n Water and Sewage Works, A p r i l issue, p.

ASM

Environmental P r o t e c t i o n Agency, 1977. EPA's Research and Development

Nebel, Car l e t a l . , 1976. Ozone Prov ides A l t e r n a t i v e f o r Secondary

76-78.

Prengle, H. W., e t al., 1975. Ozone/UV Process E f f e c t i v e Wastewater

Treatment Hydrocarbon Processing, October issue: page 82-87.

100

W W TRMT SPNOFF/BIOLOG W TRMT SYSTEMS

Sec t ion V BIOLOGICAL WASTE TREATMENT SYSTEMS


The p r i n c i p l e s o f b i o l o g i c a l waste t reatment have been reviewed i n

Sec t ion 11. B a s i c a l l y , t he b i o l o g i c a l waste t reatment systems prov ide t h e

growth environment f o r microorganisms t o degrade, a s s i m i l a t e and metabo l ize

t h e p o l l u t a n t m a t e r i a l s which serve as the pr imary food source. As t h e

p o l l u t a n t s are removed from the growth environment, they are t ransformed

i n t o c e l l u l a r energy, new c e l l u l a r m a t e r i a l , carbon d iox ide , water and

o t h e r end products o f metabol ism. P o l l u t a n t p a r t i c l e s not r e a d i l y degraded

and ass im i la ted a re c o l l e c t e d through phys ica l attachment t o the water

suspended biomass so l ids. These suspended s o l i d s , when s e t t l e d out, are

r e f e r r e d t o as sludge so l i ds .

When b i o l o g i c a l waste t reatment systems are selected, a number o f

f a c t o r s en te r i n t o t h e s e l e c t i o n process and design. These f a c t o r s are the

na tu re o f t h e waste, d ischarge volume t o be t rea ted , economics, l and

a v a i l a b i l i t y and energy resources. Once t h e system i s selected, inherent

ope ra t i ona l l i m i t a t i o n s must be recognized and the system operated w i t h i n

those l i m i t s . Two p r i n c i p l e l i m i t a t i o n s common t o a l l b i o l o g i c a l waste

t rea tment systems are d a i l y p o l l u t a n t and volume load ings o f t he system.

Both o f these load ing c o n d i t i o n s can a l t e r t he waste a s s i m i l a t i o n

c h a r a c t e r i s t i c s o f t h e system and i n f l u e n c e the q u a l i t y o f t he t r e a t e d

wastewater.

O f t h e systems t o be discussed i n t h i s sect ion, t h e one r e q u i r i n g a

s p e c i f i c l e v e l o f opera tor knowledge and s k i l l i s the a c t i v a t e d sludge

system. While t h e a c t i v a t e d sludge system i s one o f t h e most e f f e c t i v e

systems f o r t h e t reatment o f food processing wastewaters, i t requ i res

constant opera tor a t t e n t i o n and p rec i se opera t ion parameters must be

mai n t a i ned f o r optimum performance.

a re such opera t i ng parameters as food t o microorganism r a t i o s , r e t u r n

s ludge f l o w ra tes , and sludge age.

Cannon t o a1 1 b i o l o g i c a l waste t reatment systems are de f ined de ten t i on

t imes , o x i dat i ve-reduct i on condi t ions t o met speci f i c m i c r o h i a1 r e s p i r a t o r y

func t i ons , food t o microorganism contac t zones and a suspended s o l i d s

s e t t l i n g area fo l l owed by a discharge o u t l e t f e d t u r i n g a we i r o r o u t f a l l .

Unique t o the act i vated s l udge system

101 W W TRMT SPNOFF/BIOLOG W TRMT SYSTEMS

The waste t reatment systems t o be discussed i n t h i s s e c t i o n w i l l be

t y p i c a l designs which are i n coinmon use. Desigri fea tures w i l l be i d e n t i f i e d and system l i m i t a t i o n s defined. Also, general waste t reatment

a p p l i c a t i o n s o f t h e system w i l l be presented.

B. Summary

When opera t ing a b i o l o g i c a l waste t reatment system, one must know t h e

des ign l i m i t a t i o n s o f t h a t system and be f a m i l i a r w i t h i t s c o r r e c t operat ion. Also, as a system i s operated, a knowledge o f t h e cause and

e f f e c t o f t h e raw wastewater stream on t h a t system's performance must be

ascertained. With t h i s knowledge, one can e s t a b l i s h a growth environment

e s s e n t i a l t o waste a s s i m i l a t i o n and removal.

C: The Systems

1. Aerobic types

a. The A c t i v a t e d Sludge Process - By d e f i n i t i o n , t h i s process i s a b i o l o g i c a l waste t reatment a c t i v i t y i n which a m i x t u r e o f

wastewater and a c t i v a t e d sludge i s combined, a g i t a t e d and aerated. The a c t i v a t e d sludge i s a f l o c o f b i o l o g i c a l l y a c t i v e

m a t e r i a l composed o f v i a b l e microorganisms and suspended s o l i d s

which have been developed from def ined a g i t a t e d and aerated

cond i t ions . The mix tu re o f a c t i v a t e d sludge s o l i d s and raw

wastewater i s r e f e r r e d t o as t h e mixed l i q u o r suspended so l ids .

A f t e r a s p e c i f i c d e t e n t i o n t ime under aerat ion, t h e mixed

1 i q u o r suspended s o l i d s en ter a s e t t l i n g b a s i n ( c l a r i f i e r )

where t h e s o l i d s are al lowed t o s e t t l e out and t h e t r e a t e d

wastewater i s discharged from t h e system.

a r e termed "sludge s o l i d s " which are c o l l e c t e d i n t h e c l a r i f i e r

and re tu rned t o t h e head o f t h e a e r a t i o n / a g i t a t i o n zone o f t h e

process.

When t h e a c t i v a t e d sludge process i s c o r r e c t l y operat ing,

i t can e f f e c t i v e l y t r e a t l a r g e q u a n t i t i e s o f wastewater. However, i f t h e sludge s o l i d s are not s e t t l i n g o r t h e waste i s

no t being adequately ass imi la ted ( i .e. f a t s , p r o t e i n s ) , then

t h e waste t reatment performance o f t h i s process decreases

dramat ica l l y and several c o r r e c t i v e steps become necessary f o r

r e t u r n i n g t h e system back t o i t s opt imal performance.

The s e t t l e d s o l i d s

102


C r u c i a l t o the a c t i v a t e d sludge process are the q u a n t i t y

o f suspended s o l i d s i n t h e mixed l i q u o r , type o f m i c r o f l o r a i n

t h e s o l i d s , balance between the a c t i v a t e d sludge s o l i d s and t h e

waste s t reng th (BOD), a v a i l a b i 1 i t y o f a i r per u n i t o f BOD

app l ied , d e t e n t i o n t ime i n the ae ra t i on zone and the c l a r i f i e r ,

and systems design.

impor tan t t o system performance i n two ways, namely - 1)

prov ides the necessary mass a c t i o n e f f e c t of the sludge

m i c r o f l o r a t o c o l l e c t , degrade and remove p o l l u t a n t s f rom t h e

wastewater; and 2 ) s u f f i c i e n t enough cond i t ioned suspended

s o l i d s t o implement the essen t ia l s e t t l i n g step. F u r t h e r

examinat ion o f t h e sludge suspended so l i d s revea ls the presence

o f a m i c r o f l o r a which va r ies w ide ly i n s p e c i f i c m ic rob ia l

species from system t o system. A reason f o r t h i s wide

v a r i a t i o n i n m i c r o f l o r a l types i s due t o t h e ‘ ‘na tura l ”

development o f t he m i c r o b i a l species through i n n o c u l a t i o n by

t h e waste stream, a i r and i n c i d e n t a l s o i l p a r t i c l e s . I n most

cases, a m i c r o f l o r a es tab l i shes i t s e l f t h a t has become

acc l imated t o the wastewater stream and f a c i l i t a t e s the

p o l l u t a n t removal process. However, t he re are s t i l l a

s i g n i f i c a n t number o f waste t reatment processes t h a t do no t

develop t h e d e s i r a b l e sludge m i c r o f l o r a ; and thus, exper ience

c o n s i s t e n t l y poor system performance r e s u l t i n g i n low q u a l i t y

water discharges. Much o f t h e problem focuses on the

m i c r o f l o r a ’ s i n a b i l i t y t o degrade and a s s i m i l a t e s p e c i f i c

p o l l u t a n t s o r f a i l u r e t o form dense f l o c masses which are

impor tan t t o the c l a r i f i c a t i o n step. H i s t o r i c a l l y , t he

presence o f b a c t e r i a l species i n the genera o f B a c i l l u s ,

Enterobacter, Pseudomonas, Zooglea, N i t r o b a c t e r ,

Rhodopseudomonas and Cellulomomas has been found b e n e f i c i a l t o

p r o p e r l y ope ra t i ng a c t i v a t e d sludge processes.

f i l amentous b a c t e r i a belonging t o the genera Sphaero t i l us a re

assoc ia ted w i t h poor s e t t l i n g sludge and “bu l k ing ” cond i t i ons .

The q u a n t i t y o f suspended s o l i d s i n t h e mixed l i q u o r i s

General ly,

I n a d d i t i o n t o the importance o f t he concent ra t ion o f

mixed l i q u o r s o l i d s and t ype m i c r o f l o r a present, t h e balance


between these s o l i d s and the n u t r i e n t (BOD) load ing o f the

wastewater can have a s i g n i f i c a n t e f f e c t on the proper

performance o f t he a c t i v a t e d sludge process. This r e l a t i o n s h i p

i s commonly r e f e r r e d t o as the food t o microorganism (F/M)

r a t i o which i s expressed as pounds o f BOD app l i ed t o the system

pe r day r e l a t i v e t o t h e pounds o f mixed l i q u o r suspended s o l i d s

i n the a e r a t i o n / a g i t a t i o n zone basin.

a c t i v a t e d sludge system design, t h i s r a t i o may range from 0.05

f o r an extended ae ra t i on system t o 0.5 f o r a convent ional

design. F igure V - 1 presents the c l a s s i c a l growth curve f o r

b a c t e r i a and r e l a t e s t h i s growth a c t i v i t y t o n u t r i e n t uptake as

a f u n c t i o n o f time. It i s b a s i c a l l y t h i s p r i n c i p l e on which an

a c t i v a t e d sludge process i s operated w i t h t ime represent ing t h e

de ten t i on pe r iod w i t h i n the a e r a t i o n / a g i t a t i o n zone basin. The

growth stage i s important because the microorganisms i n the

s ludge must be maintained so t h a t e f f i c i e n t removal o f waste

and s e t t l i n g can be achieved.

ma in ta ins the sludge m i c r o f l o r a i n the proper growth stage i s t h e F/M r a t i o . Deten t ion t ime w i t h i n the system i s the

secondary f a c t o r t h a t in f luences the growth phase of the sludge

m i c r o f l o r a wh i l e a t h i r d opera t ing parameter i s temperature

which can acce le ra te o r suppress t h i s growth a c t i v i t y . I n a

c o r r e c t l y operated system, t h i s phasic growth cyc le i s

mainta ined through inechani ca l mani pu l a t i o n o f the water f low,

c o n t r o l 1 i n g the sludge so l i d s concent ra t ion and r a t e o f r e t u r n

t o t h e a e r a t i o n / a g i t a t i o n zone.

A l l a c t i v a t e d sludge processes depend on a mechanical

means f o r supp ly ing a i r /oxygen t o the waste t reatment system.

Th is i s because the BOD app l i ed t o the system would r a p i d l y

dep le te the inherent d isso lved oxygen i n the water and cause

t h e treatment process t o go sept ic .

w i l l p rov ide f o r d e l i v e r y of 1.25 l b s . o f a i r f o r each

a n t i c i p a t e d lb . o f BOD app l i ed t o the system. B i o l o g i c a l

uptake o f oxygen w i l l genera l l y range between 10 t o 30 mg/ l /hour and s u f f i c i e n t oxygen must be suppl ied t o ma in ta in a

d i sso l ved oxygen (D.O.) content i n the mixed l i q u o r suspended

Depending on the

The pr imary parameter t h a t

A good engineered system


1 A ' B C ' 0

I I I

SOLIDS RETENTION TIME

A- LAG GROWTH PHASE 8 - LOGARITHMIC GROWTH C - OECLININC EXPONENTIAL D - ENDOGENOUS RESPIRATION E - POINT O F INFLECTION F - OPERATION PARAMETER FOR

CONVEWTIONAL ACTIVATED SLUDGE SYSTEM

i

Growth and Substrate Utilization in a B i ol og i cal System

FIG. V-1

105


s o l i d s o f 1 t o 3 mg/l. A D.O. content o f l ess than 0.5 mg/l

can l ead t o reduced metabol ic a c t i v i t y by t h e system's

m i c r o f l o r a and poor process performance.

De ten t i on t ime i n t h e a e r a t i o n bas in has already been

discussed as t o i t s importance t o t h e growth c y c l e bu t t h i s

parameter i s a l so important i n t h e c l a r i f i e r . A l l c l a r i f i e r s

a re designed t o s e t t l e t h e mixed l i q u o r suspended s o l i d s based

on t h e depth o f t h e c l a r i f i e r , d a i l y water f l o w t o t h i s u n i t

a v a i l a b l e water sur face area and volume capaci ty.

c r i t e r i a d i c t a t e s t h e de ten t i on t ime as a f u n c t i o n o f water

f low t o t h e c l a r i f i e r . Depending on t h e a c t i v a t e d sludge

process design selected, t he des i red de ten t i on t ime may range f rom 2 t o 4 o r more hours f o r optimum performance o f t h e

c l a r i f i e r . Less t ime r e s u l t s i n low recovery o f sludge s o l i d s

and poor q u a l i t y e f f l u e n t due t o t h e loss o f suspended s o l i d s

f rom t h e system.

System design i s a l so important t o t h e t reatment o f food

processing wastewaters. and c a p a b i l i t y f o r t h e job i t has been engineered t o do.

f o l l o w w i l l be an overview o f t h r e e w ide ly used systems, namely - t h e convent ional , con tac t s t a b i l i z a t i o n and extended

a e r a t i o n / o x i d a t i o n d i t ch .

w i l l be discussed i n terms o f t h e i r bas ic design, ope ra t i ng

parameters, p o t e n t i a l problem areas o f operat ion, general

cons ide ra t i ons f o r adopting, and usual app l i ca t i ons .

The l a t t e r

Each design conta ins c e r t a i n fea tu res

To

As these systems are presented they

b. Ac t i va ted S1 udye Process

1) The Conventional Ac t i va ted Sludge Design - f i g u r e V-2

presents t h e t y p i c a l convent ional a c t i v a t e d sludge

f low-through design. Th is design i s t h e most bas ic o f t h e

a c t i v a t e d sludge processes. Usua l l y t h i s design uses pr imary s e t t l i n g p r i o r t o i n i t i a t i n g t h e a c t i v a t e d sludge

process. A f t e r t h e r e t u r n i n g sludge s o l i d s are combined w i t h t h e raw wastewater, t h e r e s u l t a n t mixed l i q u o r i s

aerated f o r per iods ranging from 4 t o 12 hours. Aera t ion

may be completely mixed o r g r a d i e n t l y app l i ed depending on

,

Mechanical Aerator

From

I I

Primary

/ Eff luent

Clar i f ier

Waste Return Solids Pump

Solids

FIG. V - 2 ACTIVATED SLUDGE PLANT DIAGRAM 0 r 0 0


t h e s t reng th o f t he wastewater. The mixed l i q u o r then

passes i n t o the c l a r i f i e r where the s o l i d s s e t t l e out and

t h e t r e a t e d wastewater i s discharged. Normal r e t e n t i o n

t i m e o f t h e mixed l i q u o r i n t h e c l a r i f i e r i s f rom 2 t o 3 hours. The s e t t l e d sludge i s re tu rned t o t h e ae ra t i on

bas in a t t he r a t e o f 30% o f t he under f low from the

c l a r i f i e r . The remaining 70% o f the s e t t l e d s o l i d s are

removed from t h e system.

f o r t reatment o f l a r g e volumes o f wastewater con ta in ing BOD s t rengths o f l ess than 1000 mg/l. Most common BOD

s t rengths range from 400 t o 800 mg/l. Th is system requ i res

F/M r a t i o s between 0.2 t o 0.5 and can handle d a i l y BOD l oad ings o f 30 t o 40 pounds per 1000 cu. ft. o f ae ra t i on

basin. Aera t ion r a t e i s 1000 cu. ft. o f a i r f o r each 1 pound o f BOD app l i ed t o the system.

Inherent problem areas associated w i t h the conven-

t i o n a l a c t i v a t e d sludge system i s i t s s e n s i t i v i t y t o

h y d r a u l i c and BOD shock loads, t he presence o f t o x i c

ma te r ia l s , and t o v a r i a t i o n s i n the nature, composi t ion and

q u a n t i t y o f the raw waste, Essent ia l t o opt imal system

performance i s es tab l ishment o f the "steady-state ' '

c o n d i t i o n with a minimum amount o f environmental d i s t u r -

bances. H y d r a u l i c a l l y , t he ae ra t i on basin, c l a r i f i e r and

r e t u r n i n g s l udge must be bal anced.

General cons idera t ions f o r adopt ing the convent ional

ope ra t i ng mode are: 1) t ype o f wastewater t o be t rea ted ,

2 ) volume t o be t rea ted , 3 ) a v a i l a b i l i t y o f u t i l i t i e s , 4) l a n d r e s t r i c t i o n s , and 5 ) economics. Th is system i s used

e x t e n s i v e l y f o r t r e a t i n g domestic and domest ic- indust ry

t y p e wastewaters. Because o f the shor t ae ra t i on per iod,

t h e so lub le BOD i n the wastewater must be low and the

suspended BOD r e a d i l y removed by f l o c adsorpt ion.

convent ional waste t reatment system i s not app l i cab le t o

h i g h BOD s t reng th wastes.

The convent ional a c t i v a t e d sludge design i s t a rge ted

The

P

108

W W TKMT S P N O F F / B I O L O G W TRMT SYSTEMS

2 ) Contac t -S tab i l i z a t i o r i - F igu re V - 3 ( b ) presents the usual

ope ra t i ng mode f o r Contac t -S tab i l i za t i on .

scheme, t h e wastewater i s brought i n t o con tac t w i t h t h e

r e t u r n i n g sludge s o l i d s and a e r a t i o n zone f o r on l y a sho r t

p e r i o d (2 t o 4 hours).

removed through adsorp t ion by the sludge f l o c and separated ou t i n t h e c l a r i f i e r . A p o r t i o n o f t h e s e t t l e d sludge i s

wasted w h i l e t h e remainder i s channel led through an aerated s t a b i l i z a t i o n basin. The sludge s o l i d s a re h e l d i n t h e

s t a b i l i z a t i o n bas in f o r a 4 t o 6 hour p e r i o d where t h e

organ ic ma te r ia l adsorbed i s degraded and ass imi la ted . To

complete t h e sludge r e c y c l i n g process, t h e s t a b i l i z e d sludge s o l i d s a re re tu rned t o t h e contac t zone f o r f u r t h e r

n u t r i e n t adsorp t ion and aera t ion .

mixed l i q u o r suspended s o l i d s are maintained a t a 1500 t o

2000 mg/l l e v e l i n t h e Contact zone and a t a 3000 t o 5000

mg/l l e v e l i n t h e S t a b i l i z a t i o n basin. These values are

f o r domestic wastewaters, however, they cdn be 1.5 t o 2

f o l d h ighe r when t r e a t i n g food proessing wastewaters. F/M r a t i o s a re i n t h e 0.2 t o 0.5 range w i t h d a i l y BOD load ings

between 30 t o 60 pounds per 1000 cu. ft. o f a e r a t i o n space.

D isso lved oxygen i s maintained between 1 t o 3 mg/l . Sludge

r e t u r n f l o w r a t e i s 100% o f t h e c l a r i f i e r underflow.

Sludge s o l i d s r e t e n t i o n t ime should no t exceed 20 days.

n o t apply t h i s system t o d a i l y h y d r a u l i c load ings t h a t

exceed 500,000 gal lons.

load ings make t h e Contact S t a b i l i z a t i o n process expensive

t o operate and BOD removal e f f i c i e n c i e s a re i n t h e range o f

85%.

wastewater and food processing wastewaters c o n t a i n i n g

carbohydrates t h a t a re amenable t o t reatment by t h i s

process (i.e. starches). As f o r assessment o f t h e Conventional a c t i v a t e d sludge system, one must consider:

1) t h e economic fac to rs , 2 ) q u a n t i t y o f wastewater t o be

I n t h e process

B a s i c a l l y , t h e p o l l u t a n t s a re

I n opera t ing a C o n t a c t - S t a b i l i z a t i o n process, t h e

When Contact S t a b i l i z a t i o n i s considered, one should

The l a r g e r d a i l y h y d r a u l i c

This system i s commonly used f o r t r e a t i n g domestic

109

WW TRMT SPNOFF/BIOLOG W TRMT SYSTEMS

t r e a t e d d a i l y , 3 ) t ype and s t reng th o f wastewater, 4 ) land

a v a i l a b i l i t y , and 5 ) u t i l i t y support.

3 ) Extended aera t ion /Ox ida t ion D i t c h - I n c o n t r a s t t o t h e

Conventional and Contact S t a b i l i z a t i o n opera t i ng modes, t h e extended a e r a t i o n / o x i d a t i o n d i t c h (F igures V-3(d) and V-4)

p rov ides a l onger a e r a t i o n p e r i o d and u s u a l l y does not

i nco rpo ra te a s e t t l i n g s tep f o r t h e raw wastewater p r i o r t o

e n t e r i n g t h e a e r a t i o n zone. The a e r a t i o n p e r i o d i s f rom 20 t o 30 hours fo l lowed by t h e c l a r i f i c a t i o n process.

s e t t l e d sludge s o l i d s a re re tu rned d i r e c t l y t o t h e a e r a t i o n b a s i n o r c o l l e c t e d i n a sludge r e a e r a t i o n tank and then

rechanneled t o t h e a e r a t i o n basin. R e c i r c u l a t i o n o f t h e

r e t u r n i n g sludge i s a t 100% o f t h e c l a r i f i e r underflow.

T h i s ope ra t i ng mode i s designed f o r lower d a i l y BOD

1 oadi ngs and t h e o r e t i c a l ly, t h e s l udge s o l i d s a re degraded

and t o t a l l y ass im i la ted by t h e system.

I n p rac t i ce , t h i s i s not t h e case. Experience w i t h

t h e extended a e r a t i o n mode o f opera t ion shows t h e system

capable o f accumulating mixed l i q u o r suspended s o l i d s up t o

10,000 mg/l be fo re a no t i ceab le change can be seen i n t h e discharged water. s ludge s o l i d s must be wasted on a d a i l y bas i s i n t h e amount

r e q u i r e d t o c o n t r o l des i red sludge age (16 t o 20 days), and

t h e proper F/M r a t i o . These s o l i d s should never go below 3000 mg/l. Usual ly, F/M r a t i o s between 0.05 and 0.2 a r e

used f o r these t ype systems. D a i l y BOD load ings range

between 10 t o 30 pounds per 1000 cu. ft. o f a e r a t i o n space. The d i sso l ved oxygen must be maintained above 1 mg/l and

t h e a e r a t i o n r a t e i s 2000 cu. ft. o f a i r supp l ied f o r each

pound of BOD a p p l i e d per u n i t time.

Operat ion o f t he o x i d a t i o n d i t c h (F igu re V-4) i s

s i m i l a r t o t h e extended a e r a t i o n except f o r i t s charac ter -

i s t i c "race t rack ' ' con f i gu ra t i on and t h e use o f b rush - l i ke

aerators.

t h e mixed l i q u o r suspended s o l i d s a re aerated through

mechanical means and t h e aerobic zone i s not un i fo rm

The

Thus, t o operate t h i s system c o r r e c t l y ,

I n c o n t r a s t t o t h e extended a e r a t i o n process,

,VL $4 C J @,' 110


StCONOAHV C L A H I F i t r(

Figure V-3. Variations o f the activated-sludge process.


- +----.--- Outflow T

F i g u r e V-4. T r a d i t i o n a l o x i d a t i o n d i t c h .

112

W W TKMT SPNOFF/BIOLOG W TRMT SYSTEMS

throughout t h e mixed l i q u o r f l u i d i n t h e race t rack . The

o x i d a t i o n d i t c h can not handle t h e same BOD l o a d i n g l e v e l s

as t h e extended a e r a t i o n process. Loadings between 10 t o

15 pounds o f BOD pe r 1000 cu. ft. tend t o be t h e bes t

l e v e l s f o r optimum system operat ion.

pounds favo r a r a p i d accumulation o f sludge s o l i d s and t h e

opera t i on of t h e c l a r i f i e r requ i res c l o s e r a t t e n t i o n by t h e

p l a n t operator.

expected w i t h excessive BOD load ings beyond t h e system's

designed capac i ty . The o x i d a t i o n d i t c h i s as suscep t ib le t o easy upsets due t o shock l oad ing c o n d i t i o n s (i.e.

h y d r a u l i c ) and changes i n wastewater c h a r a c t e r i s t i c s as a re t h e Conventional, Contact S t a b i l i z a t i o n and Extended

A e r a t i o n processes. Thus, i t i s w e l l t o i nco rpo ra te some

fo rm o f f l o w e q u a l i z a t i o n c o n t r o l i n t o these designs t o

o f f s e t p o t e n t i a l upsets. BOD reinoval e f f i c i e n c i e s between

85 t o 95% can be expected.

The general cons idera t ions f o r adopt ing t h e o x i d a t i o n

d i t c h are t h e same f o r t h e o t h e r a c t i v a t e d sludge systems

p r e v i o u s l y discussed i n t h i s sec t ion . The o x i d a t i o n d i t c h

design, i n general i s l e s s expensive t o cons t ruc t and

opera te than t h e extended a e r a t i o n process.

w i d e l y used i n Europe f o r t r e a t i n g d a i r y wastewaters.

Loadings above 15

Higher s o l i d s wastage r a t e s can be

BOD,

Th is system i s

c. Contact Surfaces

Another form o f b i o l o g i c a l waste t rea tment i s t h e use o f

con tac t sur faces c o n t a i n i n g f i x e d b i o l o g i c a l m a t e r i a l which e x t r a c t s t h e p o l l u t a n t s from t h e wastewater stream. Common

con tac t sur face systems are t h e t r i c k l i n g f i l t e r / a c t i v a t e d b i o - f i l t r a t i o n process and t h e r o t a t i n g b i o l o g i c a l con tac to rs

arrangement.

I n c o n t r a s t t o t h e a c t i v a t e d sludge systems, t h e contac t

su r face t ype u n i t ope ra t i on requ i res l e s s c a p i t a l t o b u i l d and

t h e knowledge and s k i l l o f t he p l a n t opera tor does not have t o

be as h igh f o r t h i s type operat ion.

s y n t h e t i c support inedia and approp r ia te system design, t h e

contac t sur face process i s no longer suscep t ib le t o t h e

With t h e advent o f

113

W W TKMT SPNOFF/BIOLOG W TKMT SYSTEMS

t r a d i t i o n a l hydraul i c and organ ic l o a d i n g problems associated

w i t h t h e e a r l y designed t r i c k l i n g f i l t e r systems.

importance i s t h e e l i m i n a t i o n o f ponding and blockage problems

common t o t h e crushed rock sur face con tac t media. I n add i t i on , t h e contac t sur face process u t i 1 i z e s aerobic, f a c u l t a t i v e and

anaerobic b i o l o g i c a l r e s p i r a t o r y processes i n a commensal-l ike

manner whereby oxygen i s supp l ied i n t h e wastewater and a i r i s

drawn i n t o t h e sur face contac t medium voids v i a a c t i o n o f t h e h y d r a u l i c f low. Thus, t h e need f o r mechanical a e r a t i o n i s

e l i m i n a t e d and system cos ts reduced. B a s i c a l l y , a1 1 contac t

su r face systems work on t h e same p r i n c i p l e - BOD e x t r a c t i o n

from t h e wastewater by a f i x e d b i o l o g i c a l mass composed o f

assor ted m i c r o f l o r a , r o t i f e r s , f l y lavae, sludge worms, and

algae. The g red tes t abundance o f growth occurs i n t h e upper

t h i r d o f t h e contac t sur face medium bed. As t h e f i x e d biomass

accumulates, t h e r e w i l l be some p o i n t i n t ime t h a t some

b i o l o g i c a l s o l i d s w i l l be sloughed o f f froin t h e sur face o f t h e

bed m a t e r i a l and f a l l t o t h e bottom o f t h e bed. The sloughed

b i o l o g i c a l m a t e r i a l i s c o l l e c t e d and channel led t o a f i n a l

c l a r i f i e r where t h e s e t t l e d sludge i s re tu rned t o t h e head o f

t h e system, r e s e t t l e d i n a pr imary c l a r i f i e r and then removed

f rom t h e system.

1)

O f major

The T r i c k l i n g F i l t e r / A c t i v a t e d B i o - f i l t r a t i o n Process:

b i o - f i l t r a t i o n process i s e s s e n t i a l l y d i f f e r e n t i a t e d by t h e

t y p e o f con tac t su r face m a t e r i a l used and f i l t e r bed depth.

The t r i c k l i n g f i l t e r system uses crushed rock as t h e

con tac t su r face medium.

f e e t a re commonly u t i l i z e d . The a c t i v a t e d b i o - f i l t r a t i o n

process uses s y n t h e t i c m a t e r i a l s (i.e. p l a s t i c ) which are

designed t o be un i fo rm i n s i z e and y i e l d maximum con tac t

surface a re per cub ic f e e t o f f i l t r a t i o n bed volume.

bed depths o f 5 t o 7 f e e t a re used, a more common p r a c t i c e

i s t o cons t ruc t a f i l t r a t i o n bed which has a depth up t o 20

fee t . F i l t r a t i o n beds o f t h i s t ype a re r e f e r r e d t o as

" b i o l o g i c a l towers'' o r " a c t i v a t e d b i o l o g i c a l f i l t e r s " .

The t r i c k l i n g f i l t e r system, i n c o n t r a s t t o t h e

F i l t r a t i o n bed depths o f 5 t o 7

While


F igu re V - 5 presents the h y d r a u l i c f low-through f o r a

t y p i c a l h i g h r a t e t r i c k l i n g f i l t e r process. It should be

noted t h a t t h e d i r e c t r e c i r c u l a t i o n by pumping o f the

f i l t e r d ischarge back t o t h e head o t h e system i s combined

w i t h t h e r a w wastewater ( i n f l u e n t ) . An advantage t o doing

t h i s i s t o even ou t t he h y d r a u l i c f ow r a t e and BOD l o a d i n g

t o t h e f i l t e r bed, thus e l i m i n a t i n g blockage o f t h e medium

v o i d spaces.

I n t h e opera t i on o f a t r i c k l i n g f i l t e r p l a n t , one

should be cognizant o f such f a c t o r s as 1) t h e na ture and

s i z e o f t h e contac t sur face m a t e r i a l used as t h e f i l t e r

medium, 2 ) r a t e o f dosage, 3 ) ope ra t i ng temperature and 4 ) p e n e t r a t i o n e f f i c i e n c y o f a i r . The na ture and s i z e of t he

f i l t e r medium in f l uences t h e a v a i l a b l e contace sur face

area, res i s tance t o vo id space blockage dnd ponding. The

r a t e o f dosage a f f e c t s the e f f i c i e n c y o f biomass e x t r a c t i o n

o f t h e organics i n t h e wdstewater odor development and t h e

necessary purg i ng o f the f i l t e r i ng niedi urn t o m i niini ze

blockage o f t h e vo id spaces.

can a l s o have a d i r e c t e f f e c t on t h e performance of t h e t r i c k l i n g f i l t e r operat ion. i n t h e popu la t i on make-up of the biomass b i o t d and BOD .

removal e f f i c i e n c e s . For example, t h e f i l t e r medium w i l l u s u a l l y c o n t a i n more s l ime m a t e r i a l d u r i n g t h e l a t e autumn

t o e a r l y sp r ing i n comparison t o o the r t imes o f t h e year.

Dur ing l a t e spr ing , t h i s accumulated s l ime m a t e r i a l i s

sloughed o f f and removed froin t h e system.

temperatures a l so a l t e r t h e b i o t a popu la t i on dynamics as

w e l l as a s s i m i l a t i o n c a p a b i l i t i e s . Thus, a 5 t o 10%

r e d u c t i o n i n BOD reinoval e f f i c i ences w i 1 1 be observed under

Temperature of t h e wastewater

Th is i n f l u e n c e i s no t i ceab le

Lower

t 00 c o l d weather opera t ing cond i t ions .

co ld , f r e e z i n g o f t he water i n t h e f i l t e r medium vo id

spaces cou ld occur and blockage o f t h e system would be

r e s u l t . Pene t ra t i on e f f i c i e n c y o f t h e a i r i n t o t h e vo

spaces o f t h e medium i s another f a c t o r t h a t can e f f e c t

t r i c k l i n g f i l t e r system. Th is f a c t o r i n f l uences t h e f

I f t h e system gets

t h e

d

t h e

ow

Distributor 1

Filter Media /

Ef f I ue r!

Recycle

v, -0 z 0 7 7 \ W

0 I- O c, =z

Waste Solids

U

2 5-

;;I K

4

WJW -< v,

FIG. V . - 5 TRICKLING FILTER PLANT

116 W W TliMT S P N O F F / B 1 OLOG W TRMT SYSTEMS

o f a i r t o t h e f i l t e r medium and the a v a i l a b i l i t y o f oxygen

f o r r e s p i r a t o r y funct ions. A common problem w i t h t r i c k l i n g

f i l t e r systems i s the development o f obnoxious odors due t o

inadequate a i r v e n t i l a t i o n and h igh BOD loadings. A t best ,

a good operated system (crushed rock as f i l t e r medium - low

r a t e ) w i l l p rov ide a maximum t r a n s f e r r a t e o f about 1 pound

o f oxygen per cubic ya rd o f bed volume per day.

t r i c k l i n g f i l t e r systems have dn oxygen t r a n s f e r r a t e o f

about 3 pounds o f oxygen per cubic y a r d o f f i l t e r bed per

day. Therefore, when d a i l y BOD l o a d i n g i s considered, low

r a t e systems can handle between 5 and 20 lbs/1000 cu.

f t . /day a t an h y d r a u l i c l oad ing o f 2 t o 5 m i l l i o n

gal lons/acre/day.

t o 75 lbs/1000 cu. f t . /day a t h y d r a u l i c load ings ranging

f rom 10 t o 30 m i l l i o n ga l lons lacre lday . Depending on the

r e c i r c u l a t i o n r a t e o f the f i l t e r d ischarge back t o the head

o f t h e system and the l e v e l o f BOD l oad ing being appl ied,

t h e t r i c k l i n g f i l t e r system can remove between 70 and 80%

o f t he BOD app l i ed da i l y .

operated i n a s i m i l a r manner as the t r i c k l i n g f i l t e r

system. However, t he f i l t r a t i o n medium i s f a b r i c a t e d and

may be cons t ruc ted o f po lystyrene, p o l y v i n y l ch lo r i de , o r

redwood s l a t s and r a i l s . I n t h e f a b r i c a t i o n o f these

f i l t r a t i o n media, advantage i s taken i n producing a un i fo rm

medium t h a t has a h igh s p e c i f i c sur face area per u n i t bed

volume (sq. f t . /cu. f t . ) w i t h a h igh percentage o f vo id

volume. This l a t t e r f e a t u r e a l lows a s u f f i c i e n t q u a n t i t y

o f biomass t o form on t h e exposed contac t sur faces w i thou t

p lugg ing a i r passages and o b s t r u c t i n g h y d r a u l i c f l o w

through.

1 i g h t e r weight and capable o f w i ths tdnd ing cons iderab le

weight s t ress , g rea te r f i l t r a t i o n bed depths are poss ib le

w i t h o u t increased cos ts i n c o n s t r u c t i o n design. Thus, t he

evol u t i on o f t h e " b i o l og i c a l tower'' concept. Th i s concept

takes advantage o f f i l t r a t i o n bed depths o f 20 f e e t o r

High r a t e

The h igh r a t e systems may apply from 20

The a c t i v a t e d b i o l o g i c a l f i l t e r / b i o l o g i c a l towers are

Because the f a b r i c a t e d f i l t r a t i o n medium i s

117

WW TKMT SPNOFF/BIOLOG W TRMT SYSTEMS

,

grea ter , and t h e fea tu res of t h e f a b r i c a t e d f i l t e r medium

t o design d t r i c k l i n g f i l t e r system t h a t can handle between

25 and 150 l b . BOD pe r 1000 cu. ft. app l i ed per day w i t h

wastewater f l o w r a t e s up t o 2 gpm/sq. ft. o f con tac t

su r face area.

b i o l o g i c a l tower i s d i c t a t e d by such f a c t o r s as: t ype of f a b r i c a t e d f i l t r a t i o n medium selected; s t rength ,

t r e a t a b i 1 i t y and temperature o f t h e wastewater; where t h e

tower ope ra t i on " f i t s " w i t h i n t h e over a l l t rea tment

scheme; and t h e r a t i o and r e c i r c u l a t i o n p a t t e r n o f t h e

f i l t e r discharge. As f o r t h e t r i c k l i n g f i l t e r system, one

can expect s i m i l a r BOD removal e f f i c i e n c i e s o f between 70 and 80%.

The comprehensive design l oad ing f o r t h e

2 ) R o t a t i n g B i o l o g i c a l Contactors:

The use of r o t a t i n g b i o l o g i c a l con tac tors , o f t e n re-

f e r r e d t o as " b i o l o g i c a l d i sks " i s one o f t h e more recent

innovat ions i n waste t reatment design (F igu re V-6) . This

system operates on t h e same p r i n c i p l e and f l o w scheme as t h e t r i c k l i n g f i l t e r / a c t i v a t e d b i o l o g i c a l f i l t e r opera-

t i o n s . That i s , t h e organ ic waste i s ex t rac ted from t h e

water stream by b i o t a f i l m at tached t o r o t a t i n g contac t

su r face disks. The d i s k s are u s u a l l y 12 f e e t i n diameter

and made of l i g h t weight p l a s t i c .

t h e d i s k i s immersed i n a t rough c o n t a i n i n g t h e wastewater.

The d i sk r o t a t e s s low ly t o a l l o w proper f i l m con tac t w i t h

t h e wastewater. As t h e d i sk ro ta tes , i t b r i n g s an adsorbed

f i l m o f wastewater i n t o t h e a i r where t h e f i l m absorbs t h e

ava i 1 ab1 e oxygen. With t h e renewed supply o f n u t r i e n t , t h e

adsorbed b i o t a f i l m con t inues i t s growth r e s u l t i n g i n t h e

fo rma t ion of new biomass so l i ds . U l t i m a t e l y these s o l i d s

a r e sloughed o f f by t h e shear fo rces o f t h e r o t a t i n g disc. The sloughed s o l i d s f l o w out w i t h t h e t r e a t e d wastewater t o

t h e f i n a l c l a r i f i e r f o r separation. E s s e n t i a l l y a p l u g

f low p a t t e r n i s used f o r wastewater streams t h a t a r e t o be

t r e a t e d by t h e r o t a t i n g b i o l o g i c a l con tac to r process.

General ly, t h e r o t a t i n g b i o l o g i c a l con tac to r d i s k s a r e

Approximately h a l f o f

118 WW TRMT SPNOFF/BIOLOG W TRMT SYSTEMS


staged i n f o u r i n d i v i d u a l sec t ions where each s e c t i o n i s

separated by ba f f l es . The wastewater w i l l pass through

each s e c t i o n i n s e r i e s and t h e r o t a t i n g d i s k s w i l l be

e i t h e r perpend icu la r t o o r p a r a l l e l t o t h e water f low.

s t r a i g h t forward and does no t r e q u i r e a h i g h l e v e l o f

opera tor knowledge and s k i l l .

t h i s system depend on 1) c o r r e c t d e t e n t i o n t ime, 2 ) r o t a t i o n a l v e l o c i t y o f t he d i s k s ' con tac t surfaces, 3 )

arrangement o f d i s k u n i t stages, 4 ) wastewater strength, 5 ) temperature o f wastewater and 6 ) pH o f wastewater. Loadings as h igh as 11 lb . o f BOD/1000 s'q. ft. o f con tac t

su r face area app l i ed d a i l y can demonstrate BOD removal

e f f i c i e n c i e s as h igh as 90%.

s o l i d s discharge i s used.

Advantages t o t h e r o t a t i n g b i o l o g i c a l con tac to r system

a r e i t s ease o f operat ion, t h e low power requirements, and

compactness o f t h e u n i t s ' space needs. I n i t i a l cos t o f t h e

p l a s t i c d i scs and r o t a t i n g u n i t i s h igh bu t ope ra t i ona l

cos ts a re minimal.

b i o l o g i c a l con tac to r u n i t s i s r e l i a b l e i n c o n s i s t a n t BOD

removal and t h e s o l i d s der ived froin t h e u n i t s demonstrate

good s e t t l e a b i l i t y , thus good s o l i d s removal from t h e

system.

Opera t ion o f t he r o t a t i n g d i s k system i s r e l a t i v e l y

Keys t o proper ope ra t i on o f

No r e c i r c u l a t i o n o f t h e d i sk

The performance o f t h e r o t a t i n g

c. Ponds/Lagoons

Probably one o f t h e more w ide ly used waste t rea tment

processes i s t h e pond/lagoon system. Th is system has t h e

advantages o f be ing r e l a t i v e l y maintenance f r e e and can handle

moderate shock loads, hydraul i c a l l y and o rgan ica l l y w i thou t

l o s s o f waste removal performance. The pond/lagoon system i s

commonly found i n r u r a l areas where l and i s a v a i l a b l e and t h e

l o c a l popu la t i on i s low. Frequent ly, communities o f l e s s than 10,000 u t i l i z e some form o f t he pond/lagoon process f o r

t r e a t i ng t h e i r domestic wastewaters.

system i s u t i l i z e d e i t h e r as a f a c u l t a t i v e s t a b i l i z a t i o n pond,

General l y t h e pond/l agoon

120 l 4 d i';FiT SPNOFF/BIOLOG W TRMT SYSTEMS

t e r t i a r y pond o r an dei'dted lagoon.

F i g u r e V-7 presents a schematic o f d f a c u l t a t i v e s t a b i l i -

z a t i o n pond. [ h i s type system depends on a symbiosis

r e l a t i o n s h i p w i t h i n t h e aquat ic ecosystem and on wind d i s -

turbances f o r phys ica l i n c o r p o r a t i o n o f d i s s o l v e d oxygen i n t o

t h e water. The symbiosis r e l a t i o n s h i p u t i l i z e s the metabol ic

i n t e r a c t i o n s between a v a r i e t y o f acc l imated microorganisms

found i n t h e aquat ic environment. These organisms c o l e c t i v e l y

capture, degrade and a s s i m i l a t e t h e organic p o l l u t a n t s i n t h e

wastewater. Three r e s p i r a t o r y f u n c t i o n s are i n v o l v e d n these

metabol ic processes, namely - aerobic, m i c r o a e r o p h i l i c and

dnaerobic.

microorganisms becomes t h e s u b s t r a t e ( i .e. ammonia, C O 2 )

f o r o thers ( i .e. a lgae). Oxygen needed f o r t h e aerobic and

m i c r o a e r o p h i l i c r e s p i r a t o r y f u n c t i o n s i s generated p r i m a r i l y

from t h e a c t i o n o f pnotosynthe t ic algae and, thus, complet ion

o f t h e symbiot ic cycle.

between l a t e s p r i n g and e a r l y f a l l s ince t h e f a c u l t a t i v e

s t a b i l i z a t i o n systerli i s g r e a t l y in f luenced by temperature and

t h e avai 1 ab i 1 i t y o f sun1 i ght essent 1 a1 t o a1 gal photosynthes is processes. It i s a l s o dur ing t h i j p e r i o d o f t h e year t h a t

m i c r o b i a l a c t i v i t y i s a t i t s optimum f o r maximal BOD removal.

t h e depth o f t h e water be no less than 3 f e e t and no more t h a n

6 fee t .

i n t h e n o r t h e r n p a r t o f t h e u . 5 . and as h igh as 50

pounds/acre/day i n t h e south dnd muthwest. Deten t ion t imes

m y vary frorn 6U to 180 days. The pond may be operated i n

s t r i e s o r para1 le1 . 1 , er:e ; J O ~ / yoon on system i s l o c d t e d i n an

a w 1 j where sol 1 s may a1 i r ) ~ pe rco? d t i on and subsequent

contaminat ion o f ground water, the r e t e n t i o n bas in must be

sealed w i t h b e n t o n i t e clay or a p l a s t i c l i n e r on t h e bottom and

s des o f t h e poiid t o rwevent s r e p c i ~ e i n t o t h e s o i 1 .

When t h e f a c u l t a t i v e s t a b i l i z a t i m pond i s used as a

t 3 r t i a r y system, -,he >sa: '31' I C Y ? ' x ~ d m I S above 3 fee t . The

p r i n c i p l e LIS? of t h e ~e~*:E~ii-y r ~ ~ n t ~ 1 5 t o reduce the r e s i d u a l

The by-products o f metabolism from some o f these

The pond's bes t performance occurs

Design o f the f a c u l t a t i v e s t d b i l i z a t i o n pond r e q u i r e s t h a t

Appl i e d BOG i o d d i n g s may range frorn 20 poundslacrelday

\ i 1

121 WW TRM

T SPNOFF/BIOLOG W TRMT SYSTEM

S

c

b

> I

122


suspended s o l i d s and ROD i n t h e wastewater discharged from an

a c t i v a t e d sludge o r b i o l o g i c a l f i l t r a t i o n system. D a i l y BOD l oad ings should no t exceed 12 lbs/acre/day and a 10 t o 18 days

d e t e n t i o n t ime i s required.

r e f e r r e d t o as a p o l i s h i n g pond.

I n c o n t r a s t t o t h e f a c u l t a t i v e s t a b i l i z a t i o n pond, t h e

aera ted lagoon (F igu re V-8) incorpora tes t h e use o f mechanical

a g i t a t i o n and a e r a t i o n t o p rov ide d complete-mixing aerated

aqua t i c environment. The r a w wastewater i s more u n i f o r m l y

a p p l i e d t o the system, thus prevent ing p e r i o d i c

upsets due t o h y d r a u l i c and organ ic shock loads. General ly,

t h e lagoon depth i s between 10 t o 12 f e e t and can handle

between 1 t o 15 l b . BOD/1000 cu. f t . /day. Ae ra t i on

requirements a re t h e same as f o r an a c t i v a t e d sludge system,

t h a t i s d i sso l ved oxygen l e v e l s o f 1 t o 3 mg/l. Approximately

0.2 pounds o f sludge s o l i d s w i l l be produced f o r each pound o f

BOD a p p l i e d t o t h e system. Therefore, a p o l i s h i n g pond should

be used i n con junc t i on w i t h t h e aerated lagoon opera t i on t o

remove t h e suspended s o l i d s and reduce BOD i n t h e f i n a l

e f f l uen t . I n t h e t reatment o f most wastewaters, on l y 7 t o 10 days i s needed, however, f o r s t ronger p o l l u t e d wastewaters, up

t o 30 days o f d e t e n t i o n t ime w i l l be required.

be used as a f i r s t stage o f t reatment f o r municipal wastewater

or as a pretreatment f o r i n d u s t r i a l wastewater.

F o r a l l ponds/lagoons which r e q u i r e t h e a v a i l a b i l i t y o f

d i sso l ved oxygen f o r metabol ic r e s p i r a t o r y f u n c t i o n s and BOD removal, t h e e f f i c i e n c y o f oxygen incorpora ted i n t h e

wastewater and t h e d a i l y o rgan ic l oad ing can i n f l u e n c e t h e performance of these systems. Therefore, i f t o o much organ ic

p o l l u t a n t i s app l i ed a t one t ime, these systems can go s e p t i c

r a t h e r q u i c k l y and obnoxious odors w i l l develop. Also t h e BOD removal e f f i c i e n c y w i l l decrease r a p i d l y thus producing a poor

q u a l i t y e f f l u e n t . These pond systems should be cleaned

p e r i o d i c a l l y t o reduce the p o s s i b i l i t y o f s e p t i c c o n d i t i o n s

developing and p o s s i b l e d e t e r i o r a t i o n o f t h e discharged

wastewater's suspended so l i d s and BOD content.

The t e r t i a r y pond may a l so be

Th is system may

A e r o l o r .

Means of W A g i t a t i o n

and Aera t i o n

WW TRMT I .-

I. -.-.e

123 SPNOFF/BIOLOG W TRMT SYSTEMS

1

-1

I( Multiple entry arid sinqli: i ix i t

1. J

- 4:- - . J

!;I IlltS

’ \ 4, 1 r-- ‘( 1 4 I I

1- I I

~ : l l l l l l l l l ’ I I 1 1 1 ) l l I l I ~ 1 1 1 1 ; l ~ l l l , I 1 1 1 l l l I . I l l 1 1 1 I . I I I ( 1 l l < l l l l ~ l l **y\tl’lll*,

Figure V-8. Ae ra t i on Lagoon System.


d. Aerobic ,d iges te r f o r sludge s o l i d s - a by-product o f a l l

a c t i v a t e d sludge and contac t sur face t ype waste t reatment

processes i s a m a t e r i a l r e f e r r e d t o as llsludge". While most o f

t h i s m a t e r i a l i s used t o c o n t r o l t h e proper opera t ion o f t he

waste t reatment system, a p o r t i o n o f t h e sludge must be wasted

f rom t h e system and disposed. However, be fore d isposa l i s

p o s s i b l e t h e wasted sludge must be s t a b i l i z e d . Th is

s t a b i 1 i z a t i o n process usual l y takes place i n a s l udge d i g e s t e r

which may operate under aerob ic o r anaerobic cond i t ions . The

anaerobic d i g e s t e r w i l l be discussed i n t h e l a t t e r p o r t i o n o f

t h i s u n i t .

Sludge d i g e s t e r s which operate under aerobic cond i t i ons

use an i s o l a t e d h o l d i n g bas in f o r t h e wasted sludge. Th is

s ludge i s he ld under a e r a t i o n / a g i t a t i o n cond i t i ons from 10 t o

20 days. The d a i l y s o l i d s l oad ing i s around 0.1 t o 0.2 pounds

o f v o l a t i l e so l ids /cu . ft. o f bas in volume. Approximately 1.5

t o 2.0 pounds o f oxygen i s requ i red t o degrade and s t a b i l i z e

one pound o f v o l a t i l e so l i ds . I f the opera tor wishes t o f i l t e r

t h e sludge a f t e r aerob ic d iges t i on , t h i s should be done w i t h i n

t h e f i r s t 4 t o 6 days. Also, t he sludge s o l i d s w i l l tend t o

compact and re lease bound water f o r easy removal w i t h i n t h i s

same t i m e frame. Sludge s o l i d concent ra t ions should no t exceed

5000 mg/l s ince h ighe r s o l i d l e v e l s w i l l increase the

f i l t r a t i o n t ime and lower the dewatering property. Expected

o rgan ic so l i d s reduc t i on can run as h igh as 40% o f t h e o r i g i n a l

s ludge so l i d s l e v e l .

S o l i d s reduc t i on i s made poss ib le by s u s t a i n i n g the aerob ic

degradat i on, ass i m i 1 a t i on and u t i 1 i za t i on processes o f t h e s l udge

m i c r o f l o r a . Eventua l l y , a l l r es idua l food m a t e r i a l s are dep le ted

f rom t h e aquat ic environment which then fo rces the m i c r o f l o r a t o

use up i t s own energy reserves and t o cann iba l i ze on themselves.

Dur ing aerob ic d iges t i on , t he m i c r o f l o r a l oxygen uptake l e v e l s o f f

t o l e s s than 10 mg/ l /hour a f t e r t h e 4 t h day o f t reatment and

v i a b i l i t y o f t h e s ludge m i c r o f l o r a decreases a f t e r t h e 6 t h day o f

t h e d i g e s t i o n process. Th is tends t o c o r r e l a t e w i t h the dewater ing

and f i l t e r a b i l i t y p r o p e r t i e s o f t h e sludge. By t h e 10 th t o 20 th


day of aerobic d iges t i on , t h e sludge becomes s t a b i l i z e d which i s

impor tan t t o odor c o n t r o l du r ing d isposa l and reducing t h e

b i o l o g i c a l oxygen demand o f the res idua l organic ma te r ia l s .

1) sludge age (days) o f t he s o l i d s ; 2 ) h y d r a u l i c de ten t i on t ime

(days); 3 ) temperature o f operat ion; and 4 ) number o f u n i t s

Fac to rs found t o i n f l u e n c e the aerobic d i g e s t i o n process are

ava i 1 ab1 e ( c a p a c i t y ) . These parameters have

percent reduc t i on o f t he b i odegradabl e vol a t

t h e sludge (Refer t o Rich, 1977 f o r f u r t h e r

When reduc t i on and s t a b i l i z a t i o n o f t h e

d i g e s t i o n process has been achieved, t he f o l

be expected as shown i n Table V-1 .

a d i r e c t e f f e c t on t h e

1 e suspended so l i d s i n

n fo rmat ion) .

sludge v i a t h e aerobic

owi ng composi t i on can

2. Aerobic/Anaerobic - Land A p p l i c a t i o n s

a. The Concept - Land treatment o r l and appl i c a t i o n i s t he

t rea tment o f wastewater by us ing p l a n t cover, s o i l surface,

s o i l p r o f i l e , and geo log ic m a t e r i a l s t o remove c e r t a i n

wastewater p o l l u t a n t s . F igu re V-9 i s a conceptual drawing o f

t h e r e l a t i o n s h i p o f l and a p p l i c a t i o n t o t h e e n t i r e water cycle,

f rom the water supply t o the t reatment and disposal o f t h e used

water. Once app l i ed t o t h e land, a p o r t i o n o f t he water i s l o s t

t o evapora t ion and t r a n s p i r a t i o n , and t h e remainder r e t u r n s t o

t h e ground water o r sur face water. Many p o l l u t a n t s are removed

by t h e s o i l and p l a n t s as the wastewater moves through t h e

vege ta t i on and s o i 1 p r o f i 1 e.

wastewater t reatment i s t he poss ib le harmful e f f e c t s o f t he

p o l l u t a n t s on t h e vegetat ion, s o i l , and sur face and

groundwaters. To avo id adverse environmental impacts, many

f a c t o r s such as s o i l and c rop c h a r a c t e r i s t i c s and wastewater

makeup must be considered i n designing a land a p p l i c a t i o n

system. Consequently, a l and a p p l i c a t i o n method o f t r e a t i n g

food processing wastewater i s s p e c i f i c a l l y designed f o r a

se lec ted s i t e .

a t another l oca t i on .

The main concern about us ing land a p p l i c a t i o n f o r

The design f o r one s i t e cannot normal ly be used

126


Table V-1. S t a b i l i z e d Sludge Composit ion

Component Range Median Mean

Organic C, % 27-37 29.5 31.7

To ta l N, % 0.05-7.6 4.8 4.9

NH4-N, mg/l 30-11,300 400 950

NO3-N, mg/l 7- 830 180 300

T o t a l P, % 1.1 -5.5 2.7 2.9

To ta l S, % 0.6 -1.1 0.8 0.8

S a l t s K, % 0.08-1.10 0.38

Na, % 0.03-3.07 0.77

Ca, % 0.6 -13.5 3.0

Mg, % 0.03-1 . l o 0.41

Ba, % 0.01-0.03 0.02 Fe, % 0.1 -4.0 1.0

A l , % 0.1 -2.3 0.4

0.46

1.11

3.3 0.52

0.02 1.1

0.7


T R E A T M E N T i& S T O U A G t

t V N O H A T ION

I t4 I t 1G A T € D F 01: E ST

IMPEflMLABLE I A Y E H

GROUND W A l E I4 HECHAt4GL


Four processes have been used success fu l l y f o r land-based

t rea tment o f wastewater e f f l u e n t s . These f o u r processes are

o v e r l and f low, i r r i g a t i o n , h igh - ra te i r r i g a t i o n , and

i n f i l t r a t i o n - p e r c o l a t i o n . Except f o r over land f low, a l l

processes have been used success fu l l y i n t h i s count ry f o r t h e

t reatment o f munic ipa l wastewater. I n o the r count r ies , t he

over land f l o w process has been used success fu l l y f o r domestic

wastewater t reatment. A l l f o u r processes have been used f o r

successfu l t reatment o f i n d u s t r i a l wastewater, both i n t h i s

coun t ry and e l sewhere.

The ob jec t i ves and o the r c h a r a c t e r i s t i c s , as we l l as how

t h e app l i ed water i s dispersed, are d i s t i n c t l y d i f f e r e n t among

t h e four processes. The q u a l i t y o f the water a f t e r t reatment

a l s o va r ies among the processes and i s a f u n c t i o n o f s o i l

c h a r a c t e r i s t i c s , crop type, system management, and e s p e c i a l l y

l o a d i n g ra te . Loading r a t e s and land area requirements over lap

f o r t he d i f f e r e n t processes.

geology, topography, l and a v a i l a b i l i t y , and r e t u r n f l o w q u a l i t y

requirements w i l l determine which o f t he f o u r processes would

u s u a l l y be most s u i t a b l e f o r a p a r t i c u l a r region. The

f o l l o w i n g d e s c r i p t i o n s o f these processes i n d i c a t e under what

general cond i t i ons the processes would be f e a s i b l e f o r food

process ing wastewater t reatment.

i r r i g a t i o n , i n f i 1 t r a t ion-perco la t ion , and ove r l and f low. Each

method, shown schemat ica l l y i n F igure V-10, can produce

renovated water o f d i f f e r e n t q u a l i t y , can be adapted t o

d i f f e r e n t s i t e cond i t ions , and can s a t i s f y d i f f e r e n t o v e r a l l

ob jec t i ves .

Fac to rs such as wastewater qual i t y , c l imate , soi 1,

The th ree bas ic methods o f land a p p l i c a t i o n are

b. I r r i g a t i o n

The predominant land a p p l i c a t i o n method i n use today,

i nvo l ves the a p p l i c a t i o n o f e f f l u e n t t o t h e land f o r t reatment

and fo r meeting the growth needs o f p lan ts . The app l i ed

e f f l u e n t i s t r e a t e d by phys ica l , chemical, and b i o l o g i c a l means

as i t seeps i n t o t h e s o i l . E f f l u e n t can be app l i ed t o crops o r

129 W W TRMT SPNOFF/B IOLOG W TRMT SYSTEMS

I V A I ' O I l l A N ~ l ' l l ~ A l ION

EVAI'ORA r l O N

I P F ~ C O L A T I O N THROUGH UNSATURATED ZONE JiJ 1

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k -& -?.

130


vege ta t i on ( i n c l u d i n g fo res t land) e i t h e r by s p r i n k l i n g o r by

su r face techniques, f o r purposes such as: - Avoidance o f sur face discharge o f n u t r i e n t s

- Economic r e t u r n from use o f water and n u t r i e n t s t o produce

- Water conserva t ion by exchange when lawns, parks, g o l f

- Prese rva t i on and enlargement o f g reenbe l ts and open space

maximize c rop product ion. E f f l u e n t t rea tment and d isposa l a re

secondary bene f i t s .

i n t h e r a i n f a l l - s h o r t western p a r t o f t h e U n i t e d S ta tes where

i r r i g a t i o n i s r e q u i r e d f o r optimum crop product ion. I n areas

where t h e r e i s s u f f i c i e n t r a i n f a l l t o grow crops, t h e

i r r i g a t i o n t rea tment process would o n l y be used f o r

supplemental water ing o r du r ing sporadic d r y per iods and thus

probab ly would no t be considered a v i ab le wastewater t rea tment

a1 t e r n a t ive.

marketable crops

courses are i r r i g a t e d

The o b j e c t i v e o f t h e i r r i g a t i o n process i s p r i m a r i l y t o

The i r r i g a t i o n process i s a s u i t a b l e t rea tment a l t e r n a t i v e

V i r t u a l l y a l l p l a n t n u t r i e n t s a re found i n municipal

secondary e f f l u e n t . Thus, i r r i g a t i n g w i t h wastewater r a t h e r

than o t h e r water cou ld have a g rea te r a g r i c u l t u r a l value. I n

some cases, t h e i r r i g a t i o n process may more a p p r o p r i a t e l y be

c l a s s i f i e d as a wastewater reuse a l t e r n a t i v e as w e l l as a

t rea tment process.

The i r r i g a t i o n process has t h e h ighes t p o t e n t i a l o f t h e

f o u r l a n d a p p l i c a t i o n systems f o r removal o f most wastewater

p o l l u t a n t s .

process i nvo l ves t h e l a r g e s t l and area and widest d i spe rsa l o f

p o l l u t a n t s . As a r e s u l t , adverse impacts on t h e s o i l and

vege ta t i on a re minimized. However, because o f t h e h igh

percentage o f water l o s t t o evapot ransp i ra t ion , t h e

concen t ra t i on o f t o t a l d i sso l ved i o n i c s o l i d s (sal ts-TDIS) i n

p e r c o l a t e t o t h e groundwater may be undesirable. Where water f o r i r r i g a t i o n i s valuable, crops can be

i r r i g a t e d a t consumptive use r a t e s (1 t o 3 in./wk. depending on

Because o f i t s lower l oad ing ra tes , t h e i r r i g a t i o n


t h e crop), and t h e economic r e t u r n from t h e s a l e o f t h e crop

can be balanced aga ins t t h e increased cos t o f t h e l and and

d i s t r i b u t i o n system. On t h e o t h e r hand, where water f o r

i r r i g a t i o n i s o f l i t t l e value, h y d r a u l i c load ings can be

maximized (p rov ided t h a t renovated water q u a l i t y c r i t e r i a a re

met), thereby m in im iz ing system costs.

h i g h - r a t e i r r i g a t i o n (2.5 t o 4 in./wk) a re u s u a l l y

w a t e r - t o l e r a n t grasses w i t h lower p o t e n t i a l f o r economic r e t u r n b u t w i t h h i g h n u t r i e n t uptakes.

When requirements f o r sur face d ischarge a re very s t r i n g e n t

w i t h regard t o n i t rogen, phosphorus, and BOD, i r r i g a t i o n can

meet t h e o b j e c t i v e s by avo id ing a su r face discharge, provided

t h a t groundwater c r i t e r i a can be met. I f t h e renovated water

qual i ty must meet Environmental P r o t e c t i o n Agency d r i n k i ng

water standards, reduc t i on i n n i t r o g e n below t h e 10 mg/l

standard f o r n i t r a t e n i t r o g e n i s o f t e n t h e l i m i t i n g c r i t e r i o n .

I n a r i d regions, however, increases i n c h l o r i d e s and t o t a l

d i sso l ved s a l t s i n t h e groundwater may be l i m i t i n g .

Crops grown under

c. H igh- ra te I r r i g a t i o n

U n l i k e t h e i r r i g a t i o n process descr ibed above, h igh - ra te

i r r i g a t i o n i s p r i m a r i l y a method o f e f f l u e n t t rea tment and has

t h e s i d e a g r i c u l t u r a l b e n e f i t o f producing h i g h - y i e l d crops.

H igher l oad ing r a t e s are used than w i t h t h e i r r i g a t i o n process,

and much o f t h e water perco la tes below t h e r o o t zone. For t h e

bes t n u t r i e n t removal, crops t h a t can remove n u t r i e n t s t o very

low concent ra t ions should be grown. Much o f t h e n i t r o g e n no t

removed by t h e c rop w i l l be leached t o groundwater because o f

t h e h i g h wastewater app l i ca t i ons . It i s necessary t o s e l e c t a c r o p t h a t w i l l respond t o t h e d i l u t e n u t r i e n t s i n wastewater;

otherwise, chemical f e r t i l i z e r may have t o be added t o produce

t h e des i red c rop growth.

H igh - ra te i r r i g a t i o n i s a f e a s i b l e t rea tment method i n

almost a l l c l imates. Usua l ly , a reg ion w i l l have some area

where l and i s a v a i l a b l e and where t h e s o i l , geo log i ca l , and

topograph ica l c o n d i t i o n s are s u i t a b l e f o r h i g h - r a t e i r r i g a t i o n .

The h i g h - r a t e i r r i g a t i o n process has t h e second h ighes t


p o t e n t i a l f o r removal o f wastewater p o l l u t a n t s . Because i t s

l oad ing r a t e s are considerably h igher than f o r t h e i r r i g a t i o n

process, i n a g iven area h igh - ra te i r r i g a t i o n requ i res l e s s

land, bu t t h e p o l l u t a n t load on t h e land i s more concentrated.

Thus, t h e p o t e n t i a l impact on s o i l and vegeta t ion i s g rea te r

t han f o r t h e i r r i g a t i o n process.

d. I n f i 1 t r a t ion-Percol a t i o n

I n i n f i 1 t r a t i on-percol a t i on systems, e f f 1 uent i s appl i ed

Treatment occurs as t h e water passes through t h e

t o t h e s o i l a t h ighe r r a t e s by spreading i n bas ins o r by

s p r i n k l i n g .

s o i l mat r i x . System ob jec t i ves can inc lude:

- Groundwater recharge

- Natura l t reatment fo l lowed by pumped withdrawal o r

- Natura l t reatment wi th renovated water moving v e r t i c a l l y

underdra ins f o r recovery

and l a t e r a l l y i n t h e s o i l and recharg ing a surface

watercourse

I n f i l t r a t i o n - p e r c o l a t i o n t r e a t s t h e wastewater w i t h i n a

minimum land area and under some cond i t i ons has t h e added

b e n e f i t o f recharg ing t h e groundwater.

a t h igh r a t e s f o r several days t o weeks and then i s removed

d u r i n g a r e s t pe r iod so t h e s o i l p r o f i l e can dry. The r e s t

p e r i o d res to res t h e s o i l ' s i n f i l t r a t i o n and t reatment capaci ty .

A crop may be grown t o he lp ma in ta in i n f i l t r a t i o n ra tes , but

harves t u s u a l l y would not be an ob jec t i ve .

I n f i l t r a t i o n - p e r c o l a t i o n can be used f o r wastewater

Wastewater i s app l i ed

ves h igh

t r a t i o n

t rea tment i n most c l imates. Because t h i s process i nvo

loadings, s o i l and geologic cond i t i ons w i t h r a p i d i n f i and pe rmeab i l i t y a re necessary. I n areas where these

c o n d i t i o n s are not found, the i n f i l t r a t i o n - p e r c o l a t i o n

can q u i c k l y be d iscarded from f u r t h e r cons idera t ion .

process

The i n f i 1 t r a t i on-percol a t i on process has t h e 1 owest

p o t e n t i a l f o r removal o f p o l l u t a n t s where t h e app l i ed water

moves through t h e so i l -geo log i c p r o f i l e .

and crops t o remove n u t r i e n t s a t h igh a p p l i c a t i o n r a t e s i s

l i m i t e d . Therefore, t h i s process may not be a f e a s i b l e

The capac i t y o f s o i l

133

W W TKMT SPNOFF/BLOLOG W TRMT SYSTEMS

t rea tment inethod where t h e r e are s t r i c t l i m i t a t i o n s on

d ischarge of n u t r i e n t s i n t o groundwater. I n f i l t r a t i o n -

p e r c o l a t i o n has been success fu l l y used i n combination w i t h

w e l l s o r o the r drainage t o p rov ide a good q u a l i t y water f o r

i r r i g a t i o n o r i n d u s t r i a l purposes.

Where groundwater qual i ty i s be i ng degraded by sa l i n i t y

i n t r u s i o n , groundwater recharge can reverse the h y d r a u l i c

g r a d i e n t and p r o t e c t t h e e x i s t i n g groundwater. groundwater q u a l i t y i s not compat ib le w i t h expected renovated

q u a l i t y , o r where e x i s t i n g water r i g h t s c o n t r o l t h e discharge

l o c a t i o n , a r e t u r n o f renovated water t o sur face water can be

designed, us ing pumped withdrawal, underdrains, o r n a t u r a l

Where e x i s t i n g

Phoenix, Arizona, f o r example, t h e n a t i v e ground-

i s poor, and t h e renovated water i s t o be w i th - ng , w i t h d i scharge i n t o an i rri gat i on canal.

drainage. A t

water qual i ty

drawn by pump

e. Overland Flow

Over1 and 1 ow i s essent i a1 l y a b i o l og i c a l t rea tment process

i n which wastewater i s app l i ed over t h e upper reaches o f sloped

t e r r a c e s and al lowed t o f l o w across t h e vegetated sur face t o

r u n o f f c o l l e c t i o n di tches. Renovation i s accomplished by

phys ica l , chemical, and b i o l o g i c a l means as t h e wastewater

f l o w s i n a t h i n sheet down t h e r e l a t i v e l y impervious slope.

With t h e over land f l o w process, t h e wastewater i s f i l t e r e d

and o x i d i z e d as i t passes over t h e s o i l sur face and through t h e

grass cover. The land sur face should have a un i fo rm s lope of 2 t o 8 percent so t h a t sur face r u n o f f w i l l move downslope and

u n i f o r m l y spread over t h e s o i l surface. A cover crop, u s u a l l y

grass, should be grown t o p r o t e c t t h e s o i l from e ros ion and t o

maximize t h e wastewater t reatment by p r o v i d i n g sur face area f o r

b i o l og i ca 1 t rea trnent .

i s slow and/or t h e groundwater t a b l e i s h igh so t h e water

cannot move i n t o t h e s o i l p r o f i l e . The s o i l su r face i s

c a r e f u l l y shaped t o produce t h e necessary un i fo rm f l o w o f water over t h e s o i l surface. Thus, i n areas w i t h sandy s o i l , adverse

topography, o r very shal low s o i l s , over land f l o w would be

The over land f l o w process i s used where s o i l pe rmeab i l i t y


eliminated froin further considerations as a treatment alternative.

Because the applied water does not move t h r o u g h the soil prof i le , the overland flow process does not have the benefit o f the large buffering capacity and time lag of the soil profile. This land application system i s dependent on biological processes t o t r ea t the wastewater. Like a l l biological systems, overland flow i s subject t o temperature e f fec ts and shock loads. With i t s sensi t ivi ty t o temperatures below freezing, the overland flow process may not be a feasible treatment alternative in areas with cold climates unless the wastewater can be stored for application during warm weather. To be stored, the wastewater would have t o be biologically stabi 1 i zed.

Because i t provides only limited removal of phosphorus and heavy metals, overland flow without chemical aids as a f inal treatment process may not be suitable i f an ultra-high level of treatment i s required. Certain chemical additions such as lime o r alum may improve the removal of phosphorous and heavy metals.

where discharge of a n i t r i f ied effluent low in BOD i s acceptable o r as an advanced wastewater treatment process. l a t t e r objective will allow higher rates of applications ( 5 in./wk. o r more), depending on the degree of advanced wastewater treatment required. Where a surface discharge i s prohibited, runoff can be recycled o r applied t o the land in i r r igat ion or infiltration-percolation systems.

Overland flow can be used as a secondary treatment process

The

f . Land Application Factors

1) Soil Characteristics - Depending u p o n the application ra te and method, vegetative cover, and soil type, slopes as high as 15 percent can be tolerated f o r the land application of wastewater. As the slope of the land increases, the runoff potential increases, and t h i s generates a res t r ic t ion for the use of land application. Topographic maps, available

135


f rom USGS i n 15-degree quadrants, o r a e r i a l photographs a r e

i d e a l resources f o r i d e n t i f y i n g p o t e n t i a l l and a p p l i c a t i o n

s i t e s .

The s o i l mant le

p a r t i c l e size. Vary

c l a y form a l l s o i l s .

General l y deep,

can be descr ibed on t h e bas i s o f s o i l

ng combinations o f sand, s i l t , and

we l l -d ra ined loamy s o i l s c o n t a i n equal

p ropor t i ons o f t h e sand, s i l t , and c l a y f r a c t i o n s and are i d e a l f o r l and app l i ca t i on . S o i l extremes, l i k e sand o r

c lay , a re l e s s acceptable. Coarse sandy s o i l , f o r example, i s w e l l drained, bu t t h e wastewater passes through t h e s o i l

a t such r a p i d r a t e s t h a t t h e renova t i ve capac i t y o f t h e

s o i l i s low. S o i l i s a c r i t i c a l f a c t o r i n t h e s e l e c t i o n o f

a land a p p l i c a t i o n s i t e . Each o f t h e s o i l p r o f i l e

c h a r a c t e r i s t i c s ac ts i n concert t o determine t h e degree o f

wastewater t reatment p o t e n t i a l l y poss ib le i n t h e s o i l . T h i s i s c r u c i a l because once wastewater penet ra tes through

t h e s o i l t o groundwater, l i t t l e a d d i t i o n a l renova t ion w i l l

occur.

A v a r i e t y o f s o i l p r o p e r t i e s and s i t e c h a r a c t e r i s t i c s

a r e used t o eva lua te a p o t e n t i a l l and a p p l i c a t i o n s i t e .

Several o f these c h a r a c t e r i s i t i c s a re discussed below:

I n f i l t r a t i o n Rate. Th is i s a measure o f t h e r a t e a t which

water en te rs t h e s o i l sur face hor izon. I n f i l t r a t i o n r a t e

i s i n f l uenced by several f a c t o r s i nc lud ing :

1. sur face seal ing,

2. 3. sur face s o i l t ex tu re ,

4. s o i l sur face temperature, and

5.

s lope and c o n f i g u r a t i o n o f land,

t ype and growth stage o f vege ta t i ve cover.

Water Ho ld ing Capacity. Th i s i s a measure o f s o i l water

a v a i l a b l e t o p lan ts . P lan ts genera l l y u t i l i z e water from

t h e upper l a y e r s o f t h e s o i l .

es t imates a re a v a i l a b l e f o r most s o i l t ypes from t h e S o i l

Conservat ion Service.

Water-holding capac i t y

136


Permeab i l i t y . Th i s r e f e r s t o a b i l i t y o f t h e s o i l t o a l l o w

water t o move through i t when sa tu ra ted and a c t i v a t e d by h y d r o s t a t i c pressure. Pe rmeab i l i t y r a t e s a re es t imated

f rom f i e l d da ta such as po ros i t y , s t r u c t u r e , and tex tu re .

Each o f these parameters i n f l uences t h e s o i l p e r m e a b i l i t y

o r downward movement o f water through t h e s o i l .

Permeabi 1 i ty i s commonly expressed as i nches/hour; however,

i n t h e f u t u r e t h i s w i l l change t o cm/hr.

f o r s o i l types and l i q u i d l oad ing ra tes , thereo f .

Runoff. Rate o f water movement o f f o f an a p p l i c a t i o n s i t e

i s runo f f . Th i s f a c t o r i s i n f l uenced by slope,

c o n f i g u r a t i o n , permeab i l i t y , i n f i l t r a t i o n ra te , water con ten t o f t h e s o i l , and vege ta t i ve cover.

Depth t o Bedrock.

s u i t a b i l i t y o f a s i t e f o r l and a p p l i c a t i o n .

f e e t o f s o i l i s d e s i r a b l e f o r l and a p p l i c a t i o n s i t e s .

Depth t o Water Table.

p o l l u t i o n i s a pr imary cons ide ra t i on i n any l and

a p p l i c a t i o n operat ion, t h e depth t o t h e water t a b l e i s a

c r u c i a l f a c t o r i n s e l e c t i n g a s i t e . Minimum depths depend

upon severa l s o i l f a c t o r s discussed here.

Slope and Conf igura t ion .

f rom t h e h o r i z o n t a l and i s expressed i n degrees w h i l e

c o n f i g u r a t i o n i s an expression o f concav i t y o r convex i t y o f

t h e s o i l surface.

S o i l Drainage Class. S o i l s may be cha rac te r i zed by

drainage class.

water removed f o l 1 owi ng r a i n f a l 1 .

See F igu re V-11

Th is s o i l parameter i s used t o r a t e t h e

A t l e a s t f i v e

Since p reven t ion o f groundwater

Slope i s a measure o f d e v i a t i o n

Th is i s an expression f o r t h e r a t e o f

The accepted s o i 1

d r a i nage c lasses are:

Very poo r l y d ra ined - water remains

s o i l sur face and i s very wet

2. Poor ly d ra ined - s o i l sa tu ra ted f o r

3. Somewhat poo r l y d ra ined - s o i l rema

1.

y e a r

a r t i f i c i a1 1 y d r a i ned

i n pools on

most o f

ns wet

t h e

f not


1

2

4

6

8

10

za

4c

0C

8(

lo( SAND CLAY SlLl SANDY LOAMY

LOAM L O A M L O A M SAND CLAY


4. Moderately w e l l d ra ined - s o i l remains wet f o r

5. Well d ra ined - s o i l i s wet, water removed r e a d i l y ,

6. Somewhat excess ive ly w e l l d ra ined - r a p i d movement

7. Excess ive ly w e l l d ra ined - very r a p i d movement o f

Some poor l y d ra ined and w e t t e r s o i l s can be modif ied

much o f growing season

n o t r a p i d l y

of water away from s i t e

wa te r

t o improve them f o r l and a p p l i c a t i o n w h i l e t h e excess i ve l y we l l -d ra ined s o i l s may remove water t o o f a s t f o r e f f e c t i v e

n u t r i e n t removal, unless a p p l i c a t i o n r a t e s a re reduced.

Texture. S o i l i s composed o f p a r t i c l e s o f var ious s i z e s

such as sand, s i l t , and clay; and based upon t h e r e l a t i v e

p r o p o r t i o n o f these i n a s o i l , t h e t e x t u r e c lass i s

determined.

Organics and M i c r o b i a l Populat ion. Organic ma t te r i n t h e

s o i l i s c h a r a c t e r i s t i c a l l y s t a b l e and g e n e r a l l y more

concent ra ted i n t h e uppermost l a y e r o f s o i l t han i n t h e

subsurface layers. Organic ma t te r improves s o i l s t r u c t u r e

and enhances i n f i l t r a t i o n rates. The m i c r o b i a l popu la t i on

i n t h e s o i l a c t u a l l y decomposes waste m a t e r i a l and prov ides

e s s e n t i a l n u t r i e n t s f o r hea l thy p l a n t growth. These

microbes a re an essen t ia l element i n t h e s o i l system.

Type o f Clay M ine ra l s and Sesquioxides.

sesquioxides are chemica l l y a c t i v e compounds t h a t i n f l u e n c e

t h e c a t i o n exchdnge capac i t y o f t h e s o i l .

Ca t ion Exchange Capaci ty (CEC). A ne t negat ive e l e c t r i c a l

charge i s associated w i t h s o i l p a r t i c l e s and permi ts them

t o h o l d p o s i t i v e l y charged p a r t i c l e s ( ca t i ons ) .

charge o r i g i n a t e s i n t h e c l a y and organ ic ma t te r and

pe rm i t s t h e s o i l t o adsorb e s s e n t i a l p l a n t n u t r i e n t s l i k e

ammonium, calcium, potassium, and magnesium.

2) Loading Fac tors - There a re several l o a d i n g f a c t o r s

t h a t must be considered i n t h e design and successful

o p e r a t i o n o f a land a p p l i c a t i o n system.

Both c lays and

Th is

These f a c t o r s are:

139 W W TRMT SPNOFF/RIOLOG W TRMT SYSTEMS

n u t r i e n t loading, s a l t loading, h y d r a u l i c load ing , organic

load ing , and s p e c i f i c t o x i c elements. I n the past, many

designers claimed t h a t land a p p l i c a t i o n systems were

l i m i t e d o n l y by h y d r a u l i c l oad ing ra tes . Today, t h e r e i s

evidence t h a t any one o r a combination o f these l o a d i n g

f a c t o r s may l i m i t and c o n t r o l t he design and opera t i on o f a

system.

N u t r i e n t Loading

P l a n t n u t r i e n t s are the chemical compounds t h a t a

p l a n t r e q u i r e s i n o rder t o grow. The n u t r i e n t l oad r e f e r s

t o t h e ac tua l concen t ra t i on o f these chemicals i n

wastewater. Removing these n u t r i e n t s i s the p r i n c i p a l j o b

of t h e vege ta t i ve cover. P lan ts vary i n t h e i r requirement

f o r s p e c i f i c n u t r i e n t s . Corn, f o r example, requ i res about

4-5 k i lograms o f n i t r o g e n per hec tare (ha) p e r day du r ing

t h e growing season w h i l e a stand o f Coastal bermuda grass

may r e q u i r e as much as 8 kglhalday.

Ni t rogen. One o f the elements found i n p r o t e i n i s

n i t rogen , and a l l l i v i n g t h i n g s are made from pro te ins .

N i t rogen, then, i s essen t ia l f o r p l a n t growth.

U n i v e r s i t y ' s I n s t i t u t e f o r Research on Land and Water

Resources w i t h wastewater i n d i c a t e s t h a t a h i g h percentage

o f n i t r o g e n i s removed from wastewater by the a g r i c u l t u r a l

crops. I n some extreme cases, t he n i t r o g e n concen t ra t i on

recovered from the c rop a c t u a l l y exceeded the amount o f

n i t r o g e n present i n the wastewater.

some crops a c t u a l l y drew upon the n i t r o g e n reserves b u i l t

up i n t h e s o i l by previous a p p l i c a t i o n s o f n i t r o g e n and

from decomposing organ ic matter. The n i t r o g e n removed from

wastewater and recovered i n t h e g r a i n o f corn p l a n t s o f t e n

exceeded 65 percent o f t he n i t r o g e n appl ied. The s i l a g e o f

c o r n p l a n t s u t i l i z e d from 105 t o 200 percent o f t h e

n i t r o g e n i n i t i a l l y present i n t h e so i l /was tewater system.

These f i g u r e s i n d i c a t e t h a t t he s i l a g e o f p l a n t s u t i l i z e

n u t r i e n t s a l ready a v a i l a b l e i n the s o i l .

Wastewater research conducted a t Pennsylvania S ta te

Th is ' ind ica tes t h a t

140


Research i n d i c a t e s t h a t a p l o t o f Coastal hermuda

grass may remove as much as 70 percent o f the n u t r i e n t

appl ied. As t h e amount o f n i t rogen app l i ed increases,

however, t h e removal e f f i c i e n c y decreases. See Table V-2. The n i t r a t e form o f n i t rogen i s most c r i t i c a l f o r land

a p p l i c a t i o n because o f several f a c t o r s : (1) n i t r a t e s are

h i g h l y so lub le i n water, ( 2 ) once d isso lved, t he n i t r a t e i s

h i g h l y mobi le and very s tab le, ( 3 ) h igh concen t ra t i on o f

n i t r a t e i n groundwater poses hea l th hazards, and ( 4 ) n i t r a t e s have been imp l i ca ted i n the e u t r o p h i c a t i o n o f

1 akes , rese rvo i r s , and es tuar ies .

I no rgan ic forms o f n i t r o g e n are removed from

wastewater through uptake by p lan ts . I f these p l a n t s are

n o t harvested and removed from the s i t e , then n i t r o g e n w i l l t e n d t o b u i l d up a t t he a p p l i c a t i o n s i t e . The n i t r o g e n

a p p l i e d i n wastewater should not exceed the vege ta t i ve

cove r ' s n i t rogen uptake r a t e by more than 50 percent.

N i t rogen removal i s the j ob o f p lan ts , and n i t r o g e n r i c h

wastewaters should be app l i ed on ly t o a growing crop. Both

t h e dec i s ion t o apply and the a p p l i c a t i o n o f wastewater

w i t h n i t rogen concent ra t ions h igher than 10 mg/l t o

unproduc t ive lands should be made c a r e f u l l y .

s tandard i s the proposed USEPA/USPHS d r i n k i n g water

standard.

This 10 mg/l

N i t rogen uptake ra tes range from a low o f about 100

kg/ha f o r f o r e s t crops t o highs of 800 kg/ha f o r Coastal

bermuda grass overseeded w i t h w i n t e r rye. These n i t r o g e n

requirements are essen t ia l f o r determin ing pe rm iss ib le

n i t r o g e n load ing r a t e s f o r a s p e c i f i c l and a p p l i c a t i o n

s i t e .

Phosphates. Phosphorus, l i k e n i t rogen, i s a major

c o n s t i t u e n t o f wastewater, i s a p l a n t n u t r i e n t , and i s present i n wastewater i n several d i f f e r e n t forms. Since

many wastes c o n t a i n cons iderab ly more o f a c rop ' s phosphate

than n i t rogen requirement, wastewater a p p l i c a t i o n based

e n t i r e l y upon n i t r o g e n loads may exceed crops need w i t h

14 1 W W TRMT SPNOFF/B IOLOG W TRMT SYSTEMS

Table V-2. N i t rogen Removal by Coastal Bermuda Grass I r r i g a t e d

N i t rogen App l ied N i t rogen Removed Percent

w i t h Swine Lagoon Waste (NC)

Kg/Ha/yr (1 b /ac /y r ) Kg/Ha/yr (1 b /ac /y r ) E f f i c i en cy

348 (310)

692 (620) 1383 ( 1 240)

70

57 32

SOURCE: Courtesy o f D r . L. D. King.

142


respec t t o phosphorus.

o f phosphates i n most wastewater; another source i s

biodegradable o rgan ic matter.

Wastewater conta ins bo th o rgan ic and ino rgan ic

phosphorus. The organic phosphorus i s adsorbed onto s o i 1

p a r t i c l e s , s low ly converted t o i no rgan ic phosphorus and u t i l i z e d by p l a n t s o r cornplexed i n t h e s o i l mat r i x . Much

of t h e phosphorus app l i ed t o t h e s o i l i s a c t u a l l y adsorbed

t o p a r t i c l e s i n t h e s o i l ; however, when t h e adso rp t i on

capac i t y o f t h e s o i l i s exceeded, phosphorus movement can r e s u l t .

Detergents a re t h e pr imary source

S a l t Loading

which a l and a p p l i c a t i o n s i t e may accept.

p a r t i c u l a r l y important i n i n d u s t r i a l operat ions. However,

some so lub le s a l t s a re present i n food process wastewater.

These compounds do not accumulate i n t h e s o i l s of t h e

Southeast because annual p r e c i p i t a t i o n exceeds

evapo t ransp i ra t i on and s a l t s w i l l be leached from t h e s o i l .

may occur. Th i s f a c t o r t hen becomes a c r i t i c a l l o a d i n g

c r i t e r i a and l i m i t s t h e q u a n t i t y o f wastewater a p p l i c a b l e

t o t h e s o i l . Excess s a l t may a c t u a l l y i n j u r e a g r i c u l t u r a l

crops.

Pe rm iss ib le sodium concent ra t ions a re c a l c u l a t e d w i t h

sodium adsorp t i on r a t i o s (SAR). Th is SAR i s t h e r a t i o o f

t h e exchangeable sodium t o some o f t h e o t h e r m e t a l l i c

elements (Mg++ and Ca++) p resent i n wastewater.

T h i s i s an impor tan t cons ide ra t i on i n t h e l a n d a p p l i c a t i o n

f o r h igh concen t ra t i on o f Na may c r e a t e problems by

d e s t r o y i n g t h e s o i l s t r u c t u r e and thereby reduc ing t h e

wa te r i n f i l t r a t i o n ra te . Typ ica l mun ic ipa l wastewater may

have an SAR o f approximately f o u r u n i t s .

c r i t i c a l a t t h e 10-12 u n i t l e v e l , f o r a t t h i s value sodium

may a c t u a l l y a l t e r s o i l s t r u c t u r e and u l t i m a t e l y reduce

s o i l p e r m e a b i l i t y and i n f i l t r a t i o n ra tes .

S a l t l o a d i n g r e f e r s t o t h e q u a n t i t y o f so lub le s a l t s

Th is f a c t o r i s

I n some i n d u s t r i a l wastewater, excessive s a l t loads

The SAR becomes

143 W W TKMT SPNOFF/BIOLOG W TRMT SYSTEMS

Excessive s a l t loads have c rea ted some problems w i t h

l a n d a p p l i c a t i o n systems i n v e s t i g a t e d i n t h e past.

s a l t l oad ing f a c t o r i s o f t e n t h e most ignored o f t h e

c r i t i c a l wastewater c h a r a c t e r i s t i c s . Once s a l t damage t o

s o i l ocurs, i t i s a slow and ted ious procedure t o even

p a r t i a l l y r e s t o r e t h e s o i l t o i t s o r i g i n a l cond i t ion .

Hydraul i c Loadi ng

a p p l i e d d u r i n g any g iven p e r i o d o f time.

a p p l i c a t i o n r a t e s are genera l l y expressed i n inches o f

wastewater pe r u n i t t ime, such as two inches pe r week ( 2 in/wk) o r f i v e cent imeters pe r week ( 5 cm/wk).

t r a n s l a t e s t o about 54,400 ga l /ac re t o 140,000 l i t e r s o f

wastewater on one hec tare o f land. The ac tua l r a t e may

vary cons iderab ly du r ing t h e year, s ince i n t h e summer and

e a r l y f a l l evapo t ransp i ra t i on i s h igh and g r e a t e r

q u a n t i t i e s o f water may be added t o t h e l and w i t h o u t

c r e a t i n g a r u n o f f hazard.

t h e average r a i n f a l l exceeds t h e evapo t ransp i ra t i on ra te ;

consequently, cons iderab ly l e s s wastewater may be appl i e d

t o t h e land. The h y d r a u l i c l oad ing r a t e f o r any s i t e i s

s p e c i f i c .

knowledge o f t he f i e l d capac i t y o f t he s o i l .

water content o f t h e s o i l a f t e r i t has been thorough ly

wet ted o r sa tu ra ted and then t h e excess water drained.

T h i s i s u s u a l l y expressed as a percent o f water remaining

i n t h e s o i l a f t e r drainage o f excess water. There i s

cons iderab le t ime requ i red f o r s o i l s t o d r a i n t o t h e i r

f i e l d capac i ty . Times i n t h e 2-3 day range a re no t

uncommon f o r medium t e x t u r e d s o i l s such as sandy loams.

The volume o f water l o s t between s a t u r a t i o n and f i e l d

c a p a c i t y represents t h e q u a n t i t y o f water t h a t may be

a p p l i e d t o a land a p p l i c a t i o n s i t e .

o f water l o s t and t h e t ime requ i red t o reach f i e l d

capac i ty , t h e h y d r a u l i c l oad ing r a t e o f most s o i l s can be

The

The h y d r a u l i c l oad i s s imply t h e amount o f wastewater

Today,

Th is

Dur ing t h e remainder o f t h e year

C a l c u l a t i n g t h e pe rm iss ib le h y d r a u l i c load r e q u i r e s

Th is i s t h e

By knowing t h e amount


estimated. Typica l Piedmont s o i l may on ly accept 2.5 cm

p e r week w h i l e b e t t e r Coastal P l a i n s o i l s may accept 3.75 t o 5 cm/wk as a l i m i t i n g r a t e f o r t h e h y d r a u l i c load.

Organic Loading

i n t h e form o f l a r g e suspended s o l i d s , d i sso l ved

carbonaceous compounds, o r both. Th is organic ma t te r i s

degraded i n t h e s o i l by microbes. There must be an

adequate supply o f oxygen i n t h e s o i l f o r aerobic microbes

t o e f f e c t i v e l y decompose t h e organic matter. I t i s

e s s e n t i a l t h a t t h e s o i l d r a i n adequately, f o r under

water logged c o n d i t i o n s oxygen d i f f u s i o n may be severe ly

r e s t r i c t e d .

t h e oxygen t o d i f f u s e and f o r t h e m i c r o b i a l degradat ion t o

occur. Hence, t h e i r r i g a t i o n frequency i s q u i t e important.

Organic over loading can occur i f t h e above load ing f a c t o r s

a r e not adequately addressed.

surface, may generate a b i o l o g i c a l s l ime on t h e s o i l

surface. Th is i s composed p r i m a r i l y o f anaerobic bac te r ia .

Once establ ished, t h i s s l ime precludes t h e d i f f u s i o n o f

oxygen i n t o t h e s o i l and anaerobic c o n d i t i o n s w i l l develop

under t h e s o i l surface. Under such c o n d i t i o n s a t i l l a g e

o p e r a t i o n must be considered.

zone i s most impor tant s ince a g r i c u l t u r a l crops may show

adverse e f f e c t s from inadequate oxygen a t concentrat ions o f

l e s s than 10 percent i n t h e s o i l atmosphere.

p a r t i c u l a r s o i l , several f a c t o r s must be known, and a l l a re

r e l a t e d t o oxygen.

normal a g r i c u l t u r a l s o i l has been determined t o be between

4 and 6 kg oxygen/ha/hr.

t h e p l a n t r o o t t i p f o r r e s p i r a t i o n , and t h e o t h e r h a l f i s

used by t h e s o i l microorganisms. The second impor tant

f a c t o r i s t h e r a t e o f oxygen d i f f u s i o n i n t o t h e s o i l .

Organic ma t te r i s found i n a l l wastewater. It may be

A second requirement i s s u f f i c i e n t t ime f o r

Suspended s o l i d s , i f improper ly app l i ed t o t h e l a n d

Aera t i on o f t h e p l a n t r o o t

To determine t h e pe rm iss ib le organic load o f a

The r a t e o f oxygen consumption i n a

About one-hal f o f t h i s i s used by

Th is

145


depends on a number o f s o i l f ac to rs , b u t p r i m a r i l y t h e

a i r - f i l l e d p o r o s i t y of t h e s o i l . f a c t o r , oxygen d i f f u s i o n r a t e may v a r y considerably. The

t o t a l oxygen demand (TOD) o f t h e s o i l i s perhaps t h e most

c r i t i c a l f a c t o r i n de termin ing t h e organ ic load. Knowledge

o f t h e oxygen d i f f u s i o n r a t e i n t o t h e s o i l and bo th t h e

oxygen demand o f t h e s o i l and t h e wastewater must be

considered t o a r r i v e a t an acceptable o rgan ic l oad ing rate.

Typ ica l Southeastern Piedmont and Coastal P1 a i n s o i 1 s may

accept o rgan ic loads c o n t a i n i n g from 1000 t o 2000 kglhajwk,

r e s p e c t i v e l y , o f t o t a1 oxygen demand.

Depending on t h e p o r o s i t y

Heavy Metal Loads and Other Tox ic Substances

sludge may be t o x i c t o a v a r i e t y o f l i v i n g organisms.

Cadmium, lead, copper, z inc, chromium, and n i c k e l a re t h e

m e t a l l i c i o n s o f most concern t o p u b l i c h e a l t h o f f i c i a l s ,

and gu ide l i nes f o r pe rm iss ib le l e v e l s o f these heavy

m e t a l l i c i ons are developed i n t h e water q u a l i t y sect ion.

A t o x i c waste product has a r a t h e r broad d e f i n i t i o n ;

genera l l y , t o x i c waste products w i l l cause death, disease,

behavor ia l abnormal i ty, cancer, gene t i c mutation, or p h y s i o l o g i c a l ma l func t i on o f an organism upon exposure o r

a s s i i n i l a t i o n o f t h e product i n t o t h a t organism. The heavy

metals a re not t h e on ly t o x i c m a t e r i a l s o f i n t e r e s t ; many

s y n t h e t i c compounds are a l s o c l a s s i f i e d as tox i c .

D i c h l o r o - d i p h e n y l t r i c h l orethane (DDT) and P o l y c h l o r i n a t e d

b ipheny ls (PCB) and o t h e r o rgan ic chemicals and p e s t i c i d e s

a r e r e c e i v i n g much i n t e r e s t as t o x i c substances i n water.

The pr imary concern w i t h u t i l i z i n g t h e s o i l t o dispose

t o heavy metals and o t h e r t o x i c substances i s t h a t these

compounds a re s t a b l e and o f t e n r e s i s t weather ing and

decomposition.

p l a n t leaves o r i n t h e s o i l .

uptake o f these substances from t h e s o i l , bu t t h e i r

accumulat ion on p l a n t leaves through i r r i g a t i o n may permi t

them t o e n t e r var ious food chains. The paramount quest ions

Excessive l e v e l s o f heavy metals i n wastewater o r

These compounds may then accumul a t e on

P lan ts genera l l y r e s i s t t h e


fac ing c i t i e s o r i n d u s t r i e s contemplat ing l a n d spreading

wastes c o n t a i n i n g heavy metals o r t o x i c substances are:

How many acres o f l and are requ i red t o dispose o f t h i s

waste? and What i s t h e a n t i c i p a t e d " l i f e expectancy" o f t h e

s i t e g iven t h e accumulation o f heavy metals o r o t h e r t o x i c

substances? M u n i c i p a l i t i e s should r e q u i r e r e d u c t i o n i n t h e

concen t ra t i on o f problem metals a t t h e source through

i n s t a l l a t i o n o f pretreatment systems. ques t ions depend upon several parameters:

Answers t o these

1. t h e c a t i o n exchange capac i t y (CEC) o f t h e s o i l , 2. 3.

4. t h e n i t r o g e n load, and

5. t h e proposed s i t e management.

t h e cover crop t o be grown,

t h e heavy me ta l - tox i c substance load,

Depending upon t h e c h a r a c t e r i s t i c s o f t h e waste, any one of

t h e heavy metals may l i m i t t h e annual a p p l i c a t i o n q u a n t i t y

and t h e l i f e expectancy o f t h e s i t e i n quest ion.

example, a waste sample i s h igh i n m e t a l l i c z inc, t hen t h e

z i n c concen t ra t i on may l i m i t t h e q u a n t i t y o f waste which

may be app l i ed t o t h e land.

substances are a major problem i n t h e d isposa l o f

wastewater. Recently, t h e USDA-EPA j o i n t l y proposed a s e t

o f gu ide l i nes f o r t h e a p p l i c a t i o n o f these and o t h e r heavy

m e t a l - t o x i c substances t o both a g r i c u l t u r a l and f o r e s t

land. A d d i t i o n a l i n f o r m a t i o n i s a v a i l a b l e i n t h e USDA

A g r i c u l t u r a l Waste Manual, USDA, 1975.

o t h e r t o x i c substances i s d i r e c t l y r e l a t e d t o t h e c a t i o n

exchange capac i t y (CEC) , pH, o rgan ic matter, and hydrous

i r o n and manganous oxide conten t o f t h e s o i l .

t h e sum t o t a l o f exchangeable ca t ions , such as aluminum

(Al+++), potassium (K+), calc ium (Ca++),

magnesium (Mg++) , sodium (Na+) , copper (Cu+),

and z i n c (Zn++) t h a t a s o i l can adsorb.

When app ly ing sludge t o land, spec ia l a t t e n t i o n must

be pa id t o pH o f t h e s o i l o f t h e s i t e . I f t h e s o i l i s

If, f o r

These metals and t o x i c

The s o i l ' s a b i l i t y t o a s s i m i l a t e heavy metals and

Th is CEC i s

147


accumulat ion o f c e r t a i n metals i n t h e

matter, hydrous i r o n and manganous ox

c o n d i t i o n s are a l l important i n reduc

o f t o x i c metals f o r p l a n t uptake.

S o i l o rgan ic ma t te r i s impor tan t

a l lowed t o become a c i d i c (pH 6.5), t h e s o l u b i l i t y o f heavy

metals increases, and t h i s cou ld r e s u l t i n excessive

Organic

d i z i ng a b i l i t y

vegetat ion.

des, and ox ng t h e avai

i n removing heavy

Th is o rgan ic m a t t e r metals f rom wastewater and sludge.

forms an organo-meta l l i c compound c a l l e d a chelate.

Sesqui o x i des (a1 umi num, i ron , and manganous oxides) r e a c t

w i t h heavy metals t o form i n s o l u b l e compounds and a r e a l s o

impor tan t i n t h e removal o f heavy metals f rom wastewater o r

sludge.

3. Anaerobic types

I n c o n t r a s t t o t h e aerobic waste t reatment system types, t h e

anaerobic process o f f e r s some d e f i n i t e advantages t o t h e system

user. These advantages are: 1) t h e e l i m i n a t i o n o f t h e c a p i t a l and

opera t i ona l cos t f a c t o r s associated w i t h t h e mechanical means o f

aera t ion ; 2 ) l e s s s o l i d s a re accumulated i n t h e sludge under these

c o n d i t i o n s per u n i t o f BOD u t i l i z e d ; and 3) a cons iderab le amount

o f energy i s conserved from t h e raw wastewater p o l l u t a n t s i n t h e

form o f methane gas, a major end product o f anaerobic metabolism.

Nevertheless, t h e anaerobic process has no t been t o o w ide ly adopted, except f o r sludge s o l i d s reduc t i on and s t a b i l i z a t i o n .

Major reasons f o r re luc tance t o adopt t h e anaerobic process have

been: 1) u n s a t i s f a c t o r y BOD removal e f f i c i e n c i e s , 2 ) poor e f f l u e n t

q u a l i t y , 3 ) l ack o f c o n t r o l f o r t h e obnoxious odors (i.e. HzS), and 4 ) s e n s i t i v i t y o f t h e process t o excessive organ ic and

h y d r a u l i c l oad ing and t o t h e presence o f t o x i c mater ia ls .

The concept o f t h e anaerobic process f o r a s s i m i l a t i n g waste i s

discussed i n Sec t i on I 1 C4 o f t h i s u n i t . Essen t ia l t o t h i s process

i s t h e commensalism r e l a t i o n s h i p between t h e m i c r o a e r o p h i l i c

"organic a c i d producing" b a c t e r i a and t h e anaerobic ''methane producing" mic ro f lo ra .

scheme whereby t h e ' 'organic ac id producing" b a c t e r i a i n i t i a l l y

degrade t h e a v a i l a b l e p ro te ins , carbohydrates and f a t s i n t h e waste

Th is requ i res a two s tep a s s i m i l a t i o n

148


stream. As i n fe r red , a major end product r e s u l t i n g from t h i s

degradat ion, a s s i m i l a t i o n and metabol ic a c t i v i t y i s t h e format ion

o f organic ac ids ( i .e. ace t ic , propion ic , b u t y r i c and v a l e r i c ) .

Wai t ing t o u t i l i z e these organic ac ids a re t h e "methane producing"

bac ter ia .

t h e r a t e l i m i t i n g s tep o f t he anaerobic waste a s s i m i l a t i o n process.

Therefore, care must be excer ised not t o a l l o w t h e anaerobic growth

environment t o go a c i d nor t o permi t t h e b iocarbonate a l k a l i n i t y i n

t h e medium t o be depleted. Both cond i t i ons w i l l i n h i b i t t h e growth

o f t h e methane - forming b a c t e r i a and s t a b i l i t y o f t he anaerobic

process w i l l d e t e r i o r a t e r a p i d l y .

Successful opera t ion o f t h e anaerobic process depends upon:

1) a balanced d a i l y organic and hyd rau l i c loading; 2 ) an adequate

b icarbonate a l k a l i n i t y (miniinurn o f 2500 mg/l as NaHC03) t o

permi t maintenance o f a pH range between 6.8 and 7.2; 3 ) c o r r e c t

res idence time; 4) temperature s t a b i l i t y o f t h e growth medium; and

adequate sur face cover t o e s t a b l i s h the anaerobic environment.

A t t h e present t ime the re are th ree anaerobic waste t reatment

processes ava i lab le . These processes are 1 ) t h e lagoon system, 2 )

t h e contac t process, and 3 ) t h e f i l t r a t i o n concept. ope ra t i ona l designs w i l l be discussed i n terms o f t h e i r

f low-through schemes and opera t ing features.

It should be noted here t h a t i t i s t h i s phase t h a t i s

These

a. The anaerobic lagoon: F igure V-12 presents t h e general

f ea tu res o f an anaerobic lagoon.

u s u a l l y cons t ruc ted w i t h a minimal depth o f 15 f e e t and water

sur face area. The reduced sur face area a l lows f o r t h e

development o f a cover which i s der ived from t h e f a t i n t h e

wastewater. Th is cover a l s o func t i ons as a thermal i n s u l a t o r

and prevents the escape o f ob jec t i onab le odors t o the

atmosphere. When a cover does not develop, then i t may become

necessary t o p lace an a r t i f i c a l cover over t h e lagoon. Also,

t h e banks o f t he bas in a re r e l a t i v e l y steep i n c o n t r a s t t o t h e

aerated lagoon. To assure a 75% BOD removal, a n u t r i e n t

l oad ing o f 20 lbs./1000 cu.ft . /day should be maintained.

Deten t ion t ime may v a r y from 4 t o 21 days w i t h 9 t o 14 days the

most commonly used r e t e n t i o n per iods.

The r e t a i n i n g bas in i s

This system can be


crease cover floatinq on wdte

Supernatant with about 0.1 percent volattle sollds

Figure V-12. Const ruc t ion o f an Anaerobic Lagoon.

150


f u n c t i o n a l a t 250 C b u t h igher teniperatures f a v o r t h e

b i o l o g i c a l a c t i v i t y o f t h e system. Th is system i s most

amenable t o wastewaters f r e e o f t o x i c m a t e r i a l s and c o n t a i n i n g

h i g h organic s t rengths, p a r t i c u l a r l y i n f a t and p r o t e i n . Since

approx imate ly 25% o f t h e BOD s t i l l remains i n t h e wastewater,

t h e r e i s u s u a l l y an aerobic waste t reatment s tep t h a t f o l l o w s

t h e anaerobic lagoon. A f t e r adequate BOD r e d u c t i o n under

aerob ic t reatment , t h e t r e a t e d wastewater en ters a p o l i s h i n g o r

f a c u l t a t i v e s t a b i l i z a t i o n pond where t h e suspended s o l i d s are

p e r m i t t e d t o s e t t l e and t h e r e s i d u a l organic mat te r t o

s t a b i l i z e p r i o r t o d ischarge t o t h e r e c e i v i n g stream.

b. The anaerobic contac t Process: T h i s process i s best f o r

t r e a t i n g wastewaters c o n t a i n i n g h i g h organic s o l i d s

concentrat ions. The contac t procc?ss i s no t amenable t o

wastewater s o l i d s composed o f l e s s than 0.1% s o l i d s l e v e l . The

anaerobic contac t process i s schemat ica l l y shown i n F i g u r e

V-13. It i s d e s i r a b l e t h a t the food process wastewater pass

through a f l o w e q u a l i z a t i o n s tep s ince t h i s process i s

s e n s i t i v e t o surges i n h y d r a u l i c l o a d i n g and t o x i c substances.

Sequent ia l t o f l o w e q u a l i z a t i o n i s t h e need t o r a i s e o r

m a i n t a i n t h e wastewater temperature a t 32-350 C v i a some

form o f heat t r a n s f e r u n i t . The wastewater i s then brought i n

contac t w i t h r e c y c l i n g s ludge s o l i d s t o b r i n g t h e mixed l i q u o r

suspended s o l i d s t o between 9000 and 12000 mg/l as i t enters

t h e d i g e s t i o n chamber. A 90% BOD and suspended s o l i d s

r e d u c t i o n o f t h e o r i g i n a l i n f l u e n t waste i s achieved through a

d e t e n t i o n t i m e o f 12 t o 13 hours i n t h e d iges ter . Usual BOD l oad ings o f about 0.15 l b s / c u / f t . d iges ter /day i s a common

p r a c t i c e f o r t h i s process. Methane gas generated from t h e

anaerobic d i g e s t i o n process can be recovered and used t o

m a i n t a i n t h e heat t r a n s f e r u n i t o r be u t i l i z e d f o r o t h e r heat

genera t ing equipment ( i .e. burners) . However, e x t r i c a t i o n of

t h e methane gas from t h e sludge s o l i d s can prove t o be a

problem and does r e q u i r e some form o f shear s t r e s s o r vacuum

pressure t o re lease t h e gas f o r recovery. Therefore as t h e

d i g e s t e d sludge leaves t h e d i g e s t e r i t should pass through a

Cavtured Methane Gas

XSAERO BIC COSTACT

DIGESTER AT 32OC

FLOW

EQUAL IZ.4TION Raw Xastewater - I I

CLARIFIER E f f l u e n t

S t a b i l i z a t i o n Pond

F i g ? ? r e \.'-13. 4 n a c r o b i i Con tac t Prdcess ScheLne

Wasted S o l i d s

F i n a l D i

152


d e g a s i f i c a t i o n s tep p r i o r t o e n t e r i n g t h e c l a r i f i c a t i o n phase.

Once s e t t l i n g takes p lace t h e s o l i d s a re re tu rned t o t h e

d i g e s t e r v i a t h e r e c y c l i n g r o u t e p r e v i o u s l y mentioned. The

t r e a t e d water i s then channel led t o an o x i d a t i o n pond where t h e

r e s i d u a l o rgan ic m a t e r i a l i s s t a b i l i z e d and suspended s o l i d s

s e t t l e d ou t preceding discharge t o a t r i b u t a r y stream.

c. The anaerobic f i l t e r : Experience w i t h t h i s system i s ma in ly

w i t h p o t a t o wastewaters.

t r i c k l i n g f i l t e r process, t h e anaerobic f i l t e r operates i n a reverse f l o w through pa t te rn . That i s , t h e wastewater en te rs

a t t h e bottom o f t h e f i l t e r medium and passes i n an upward

f low. The f i l t e r medium i s composed o f l imestone, i n rock

form.

scheme. Important t o t h i s process i s t h e fo rma t ion o f t h e

m i c r o f l o r a and t h e d i s c r e t e p a r t i c l e s which do no t become

a t tached t o t h e f i l t e r medium bu t are suspended i n t h e

i n t e r s t i t i a l spaces between t h e rocks. The system operates a t

temperatures around 25OC w i t h so l i d s r e t e n t i o n tir i les

exceeding 200 days.

anaerobic f i l t r a t i o n u n i t ranges from 4.5 hours a t a 63% C O D removal e f f i c i e n c y up t o 97% reriioval w i t h 18 hours re ten t i on .

The h y d r a u l i c f l o w r a t e i s c r i t i c a l t o t h e proper ope ra t i on o f

t h i s t y p e process whereby the f l o w r a t e o f t h e r a w wastes i s

combined w i t h a p o r t i o n o f t h e t r e a t e d wastewater t o c o n t r o l

t h e h y d r a u l i c l o a d i n g t o t h e f i l t r a t i o n u n i t .

ope ra t i ona l f a c t o r i s t he COD l o a d i n g c a p a c i t y o f t h i s process.

The anaerobic f i l t r a t i o n system possesses lower n u t r i e n t

l o a d i n g capac i t y i n con t ras t t o t h e anaerobic lagoon system.

The f i l t r a t i o n process can handle up t o .07 l b o f BOD/cu.ft.

o f bed vo id volume.

I n c o n t r a s t t o t h e convent ional

F igu re V-14 presents t h e anaerobic f i l t e r process

Hydrau l i c d e t e n t i o n t ime w i t h i n t h e

Another

d. Anaerobic d i g e s t e r : The anaerobic d i g e s t i o n o f sludge s o l i d s

de r i ved f rom aerob ic a c t i v a t e d sludge systems i s perhaps t h e

most common use o f t h i s type o f metabo l ic process. Advantage

i s taken o f t h e anaerobic process t o reduce t h e sludge s o l i d s

volume and t o s t a b i l i z e it f o r disposal . Successful ope ra t i on

o f t h i s process i s dependent on t h e same parameters as f o r any

Iu al c- ..

aJ c 13

\

k 0


k 'u &J

0 k al ol C --c


anaerobic o r i e n t e d system. That i s - a balanced d a i l y organic

and hyd rau l i c loading, a proper l e v e l o f a l k a l i n i t y (expressed

as bicarbonate, HCO3') t o permi t maintenance o f t h e

c r i t i c a l pH range (6.8 t o 7.2), temperature s t a b i l i t y and

adequate so l i d s residence time.

Anaerobic d i g e s t i o n may u t i l i z e one o f two a v a i l a b l e

process schemes. These schemes are the s ing le -s tage process

and t h e h igh ra te , dual stage system. The s ing le -s tage process

incorpora tes the func t i ons o f sludge s o l i d s reduct ion,

t h i c k e n i n g and storage. A f t e r t he d i g e s t i o n and t h i c k e n i n g

process, t h e s t a b i l i z e d sludge s o l i d s are drawn o f f and removed

f rom t h e system.

s ludge i s re tu rned t o the f r o n t o f t he a c t i v a t e d sludge system

s ince t h i s water i s r e l a t i v e l y h igh i n o x i d i z a b l e organic

ma t te r and requ i res f u r t h e r t reatment. The dual phase system

d i v i d e s the func t i ons o f the anaerobic d i g e s t e r i n t o two

stages, namely - a h igh - ra te u n i t where the b i o l o g i c a l a c t i v i t y

takes p lace and a secondary u n i t where t h e d igested sludge

s o l i d s a re th ickened and stored. The thickened, s t a b i l i z e d

s ludge s o l i d s are removed from the system f o r d isposal and the

c l a r i f i e d water i s re tu rned t o the a c t i v a t e d sludge system.

Basic ope ra t i ng c h a r a c t e r i s t i c s o f the anaerobic d i g e s t e r

a re are d e t a i l e d i n Table V-3. Under normal opera t ing

cond i t i ons , one w i l l observe a constant concent ra t ion o f

v o l a t i l e organic ac ids a t a steady l oad ing r a t e and opera t i ng

temperature. As t h e organic l oad ing i s increased o r decreased,

t h e gas produc t ion w i l l vary p ropor t i ona l . I f the organic

l o a d i n g acce le ra tes the b i o l o g i c a l a c t i v i t y t oo much, ac id

devel opment w i 1 1 exceed the ass i m i 1 a t i on capac i t y of the

"methane producing" b a c t e r i a and suppress t h e i r metabol i c

a c t i v i t y by i nc reas ing the a c i d i t y o f t he growth environment.

Also, one may observe a s h i f t i n t h e C02 and methane gas

composi t ion i n the d i g e s t e r headspace.

poss ib le , it i s des i rab le t o measure the C02 conten t f rom

t h e head gases o f t h e d i g e s t e r t o moni tor s h i f t i n g metabo l ic

a c t i v i t y due t o changes i n organic load ing o r t he presence

The supernatant der ived from the s t a b i l i z e d

Therefore, whenever


Table V-3. Anaerobic D i g e s t e r Operat ional C h a r a c t e r i s t i c s

1) V o l a t i l e s o l i d s l oad ing

( a ) S i ng l e-stage 0.03-0.10 l b . VS/cu.ft./day

( b ) Dual phase 0.1-0.4 l b . VS/cu.ft./day

( a ) S i ng l e-stage 20 t o 60 days*

(b ) Dual phase 10 t o 15 days*

*dependent o f a v a i l a b i l i t y o f heat and temperature o f

ope ra t i on

2 ) S o l i d s Re ten t ion Time

3 ) Temperature ("C) 30 t o 80

4 ) PH 6.8 t o 7.2 5 ) A l k a l i n i t y as NaHC03 miniinum o f 2500 mg/l

6 ) G a s Composition

( a ) methane 50 t o 69%

( b ) carbon d i o x i d e 30 t o 502

( c ) hydrogen s u l f i d e t r a c e

Expected V o l a t i l e so l i d s reduc t i on (5) ( a ) S ing le -s tage 50 t o 60

( b ) Dual phase Approx. 50

7 )


of t o x i c substances ( i .e. heavy metals) . Increases i n the

CO2 conten t i n d i c a t e t h a t an uns tab le anaerobic d i g e s t e r

c o n d i t i o n i s developing. A good opera t i ng d i g e s t e r depends on

adequate so l i d s mix ing and the temperature o f ope ra t i on

e s t a b l i s h e d a t 32 t o 35OC.

4. Sludge Disposal

Under t h e Resource Conservation and Recovery Act o f 1976 (RCRA), Congress formal l y dec la red sewage sludge a l lsoi 1 waste" and imposed

a f u l l a r r a y o f new environmental r e s p o n s i b i l i t i e s on i t s d isposa l .

RCRA de f i nes t h e term " s o l i d waste" i n a r a t h e r broad meaning which

i nc ludes s l udges de r i ved from re fuse , garbage and o the r discards.

"Sludge" i s f u r t h e r de f i ned t o mean "any s o l i d , semiso l id o r l i q u i d

waste generated from a municipal , commercial o r i n d u s t r i a l

wastewater t reatment p l a n t ; water supply t reatment, o r a i r

p o l l u t i o n c o n t r o l f a c i l i t y , o r any o the r such waste having s i m i l a r

c h a r a c t e r i s t i c s o r e f f e c t s " . Congress f u r t h e r decreed t h a t

mun ic ipa l and most i n d u s t r i a l sludge source would have t o end t h e i r

"open dumpi ng'l i n t o t h e envi ronment.

RCRA p r o v i s i o n t h a t i s designated t o p r o t e c t t h e food-chain crops

f rom i n d i s c r i m i n a t e a p p l i c a t i o n o f wastes t o a g r i c u l t u r a l land.

However, EPA recognizes the value o f sludge land a p p l i c a t i o n

p r a c t i c e s and i s developing c r i t e r i a t o encourage conservat ion,

recovery o r u t i l i z a t i o n o f waste mater ia ls . A p p l i c a t i o n o f sludge

and o the r wastes t o t h e land may p rov ide s i g n i f i c a n t b e n e f i t s

through a d d i t i o n o f o rgan ic mat te r , n i t rogen, phosphorus and o the r

e s s e n t i a l elements t o t h e s o i l . But, c r i t e r i a must a l so be

developed t o prevent p o t e n t i a l harmful t h r e a t s t o t h e fu tu re l and

p r o d u c t i v i t y and t h e human food chain.

As sewage sludge i s considered, i t may be der ived from t h r e e

s t e p s i n t h e waste t reatment process as presented i n F igu re V-15.

These steps are .......... the anaerobic d i g e s t i o n o f s e t t l e a b l e

s?udge s o l i d s (d iges ted sludge), t h e aerobic d i g e s t i o n o f p a r t i a l l y

c l a r i f i e d sewage ( a c t i v a t e d sludge), and the t e r t i a r y t reatment of

secondary e f f 1 uent ( t e r t i a r y sl udge) e

O f spec ia l importance t o the d isposa l o f sewage sludge i s t he

Digested and a c t i v a t e d

3 ; E f T E G G m I

E E -I W x -I

v, TI z 0 -fl -n FIGURE v - 1 5 . SCHEMATIC DIAGRRM OF AN ACTIVATED SLUWE SEWAGE TREATMENT PLANT, INCLUDING \

m A TENTATIVE TERTIARY TREATMENT PROCESS,

158


sludges comprise t h e m a j o r i t y o f domestic sludges i n t h e U . S . , so t h e remainder o f t h i s s e c t i o n w i l l d iscuss these types o f sludges.

L i q u i d sewage sludge genera l l y con ta ins between 1-10% t o t a l

s o l ids , w i t h t h e so l i d conten t f a i r l y evenly d i s t r i b u t e d between

i n o r g a n i c and organ ic ma te r ia l s . a r e p r i m a r i l y metals and w i l l remain as a res idue when i n c i n e r a t i o n

i s used f o r sludge disposal .

o rgan ic carbon, n i t rogen, phosphorus, arid s u l f u r contained i n

p a r t i a l l y and conipletely degraded sewage cons t i t uen ts , compounds syn thes ized by microbes du r ing d iges t i on , and dead and l i v e

m i c r o b i a l c e l l s . The average chemical composi t ion o f sewage sludge

samples f rom 10 Ind iana c i t i e s i s shown i n Table V-4.

Sludge hand l ing procedures used a f t e r d i g e s t i o n w i l l p a r t i a l l y

determine t h e elemental composi t ion o f t h e sludge. Dewatering o f

sludge w i l l r e s u l t i n a low concen t ra t i on o f so lub le ions i n t h e

s ludge so l i ds . Na, K , and Nti+4, f o r example, w i l l remain

d i sso l ved i n t h e l i q u i d p o r t i o n o f sludge a f t e r dewater ing by

f i l t r a t i o n , c e n t r i f u g a t i o n , o r g r a v i t y s e t t l i n g . Heat -d ry ing o f

s ludge w i l l evaporate o f f t he water w h i l e l e a v i n g behind t h e Fla and

K , however, which then are concentrated i n t h e sludge so l i ds .

Heat -d ry ing r e s u l t s i n comparable amounts o f these elements be ing

found i n l i q u i d and hea t -d r i ed sludges. Ammonium w i l l v o l a t i l i z e

as ammonia gas du r ing a d r y i n g process, so hea t -d r i ed sludge i s

lower i n N t han l i q u i d sludge.

25-501 o f t h e t o t a l N i n sludge, t h e t o t a l N con ten t o f sludge i s

s t r o n g l y i n f l uenced by t h e processing riiethod used.

The s o l i d p o r t i o n o f sludge conta ins almost a l l t h e

phosphorus, organic n i t rogen , a l k a l i n e - e a r t h metals, and heavy

metals present i n a d d i t i o n t o sinal1 amounts o f Na, K, and NH4

adsorbed on c a t i o n exchange s i t e s .

employed determines t h e t o t a l amount o f n i t r o g e n present i n t h e

sludge, w i t h a c t i v a t e d sludge c o n t a i n i n g about t w i c e as much t o t a l

N as anaerob ica l l y d iges ted sludge. Storage o f d iges ted sludge i n

lagoons decreases t h e N conten t o f sludge i n a d d i t i o n t o reduc ing

t h e concent ra t ions o f v o l a t i l e so l i d s and pathogens. Most n i t r o g e n

i n sludge s o l i d s i s organic n i t rogen, whereas about 50% o f t h e

The ino rgan ic elements, o r ash,

Sludge organ ic ma t te r i s composed o f

Since NH+4 may account f o r

The t ype o f sludge d i g e s t i o n

159

W W TRMT SPNOFFjBIOLOG W TRMT SYSTEMS

Tab le V-4. Chemical composi t ion o f sewage sludge and arnoiint o f elements

added t o s o i l a t an a p p l i c a t i o n r a t e o f 25 d r y tons/acre.

-___ _ _ _--- - -- -- A p p l i e d at

25 dry tons/acre 1 El emen t Concentration

Total N hx:ionium N Plrosplwrus

Sodium Calcium ?!a?gn e s i um S U I fur

1'0 t 3. s :i ium

zinc NO 11 {:;In C' s e C q p e r C a d n r i um Lead Mcrcury C h r om1 um

%

4 . 9 2.1 2.4 0.4 0.8 7 .9 1.2 1 .o

P P" S l O O

750 3 300 I70 770

4 4 300

11) s / R C re 2 4 5 0 1050 1.200

2 00 4 00 3950

600 5 00

(4 00 40 140

8 40

220

160

WW 'TRMT SPNOFF/BIOLOG W TRMT SYSTEMS

t o t a l sludge phosphorus i s inorgan ic P. Since phosphorus i s very

i n s o l u b l e i n water, i t s concent ra t ion i n sludge s o l i d s i s not

g r e a t l y a f f e c t e d by dewater ing o r d r y i n g processes. The heavy metal content o f sewage sludge i s q u i t e v a r i d b l e and

i s s t r o n g l y i n f l uenced by the presence o f i n d u s t r i a l discharges.

Heavy metals t h a t may be present i n sludge i n s u f f i c i e n t q u a n t i t i e s

t o cause h e a l t h o r p o l l u t i o n problems upon d isposa l i nc lude

cadmium, lead, z inc, n i c k e l , mercury, copper, manganese, and

be ry l l i um. The concent ra t ions o f these metals i n sludge l i q u i d s i s

genera l l y l e s s than 1 ppm. Metals are h e l d i n t h e s o l i d pot - t ion o f s ludge by p r e c i p i t a t i o n , sorp t ion , che la t i on , and i o n exchange

reac t ions .

Dur ing t h e sludge d i g e s t i o n process, t he number o f pathogenic

and sewage microorganisms i s reduced t o very low leve ls . Small

numbers o f these microbes w i l l i n e v i t a b l y be present i n any sewage

sludge, however, so sludge t h a t w i l l be so ld as a f e r t i l i z e r

m a t e r i a l i s cormionly hea t -d r i ed t o ensure a more hygenic product.

F u r t h e r research i s needed on the s u r v i v a l o f v i ruses i n d iges ted

sludge. I n general, t he hand1 i n g o f d iges ted sewage sludge does

n o t appear t o pose any major human h e a l t h problem.

Disposal - Digested sewage sludge can be disposed o f i n l i q u i d o r

d r i e d form. Dewatering o f sludge by f i l t r a t i o n , c e n t r i f u g a t i o n ,

f i l t e r beds, o r heat -d ry ing may make i t eas ie r t o handle and reduce

t r a n s p o r t a t i o n costs; t h e sludge s o l i d s can then be inc inera ted ,

l a n d - f i l l e d , o r used as f e r t i l i z e r ma te r ia l . L i q u i d sludge can be

pumped or c a r r i e d by tank t r u c k s t o lagoons o r l and sur faces f o r

d isposa l . sl udge d i sposal i nc l ude 1) $73--dryi ng f o r f e r t i 1 i zer, 2) $69--dewatering and i n c i n e r a t i n y , 3 ) $54--continuous d i g e s t i o n i n a permanent lagoon, and 4 ) $17--d igest ion and a p p l i c a t i o n on land.

From these cos t cons idera t ions alone i t i s obvious why t h e r e i s

increased i n t e r e s t i n land d isposal o f sludge.

Ef fects o f Sludge on Crop Produc t ion - Sludge d isposa l on l and has

been p r a c t i c e d f o r many cen tu r ies around the wor ld w i thout any no t i ceab le de t r imenta l e f f e c t s on p l a n t growth, where neu t ra l pH

Some approximate cos ts per t o n f o r rep resen ta t i ve methods o f


t o t a l sludge phosphorus i s inorgan ic P. Since phosphorus i s very

i n s o l u b l e i n water, i t s concent ra t ion i n sludge s o l i d s i s not

g r e a t l y a f f e c t e d by dewater ing o r d r y i n g processes.

The heavy metal content o f sewage sludge i s q u i t e v a r i a b l e and

i s s t r o n g l y i n f l uenced by the presence o f i n d u s t r i a l discharges.

Heavy metals t h a t may be present i n sludge i n s u f f i c i e n t q u a n t i t i e s

t o cause h e a l t h o r p o l l u t i o n problems upon d isposal i nc lude

cadmium, lead, z inc, n i c k e l , mercury, copper, manganese, and

be ry l l i um.

g e n e r a l l y l ess than 1 ppm.

s ludge by p r e c i p i t a t i o n , sorp t ion , che la t ion , and i o n exchange

r e a c t i ons .

The concent ra t ions o f these metals i n sludge l i q u i d s i s

Meta ls are he ld i n t h e s o l i d p o r t i o n o f

Dur ing t h e sludge d i g e s t i o n process, t h e number o f pathogenic

and sewage microorganisms i s reduced t o very low leve ls . Small

numbers o f these microbes w i l l i n e v i t a b l y be present i n any sewage

sludge, however, so sludge t h a t w i l l be so ld as a f e r t i l i z e r

m a t e r i a l i s commonly heat -d r ied t o ensure a more hygenic product.

F u r t h e r research i s needed on the s u r v i v a l o f v i ruses i n d igested

sludge. I n general, t h e hand l ing o f d iges ted sewage sludge does

no t appear t o pose any major human hea l th problem.

Disposal - Digested sewage sludge can be disposed o f i n l i q u i d o r

d r i e d form. Dewatering o f sludge by f i l t r a t i o n , c e n t r i f u g a t i o n ,

f i l t e r beds, o r heat -d ry ing niay make i t eas ie r t o handle and reduce

t r a n s p o r t a t i o n costs; t h e sludge s o l i d s can then be i nc ine ra ted ,

l a n d - f i l l e d , o r used as f e r t i l i z e r ma te r ia l .

pumped o r c a r r i e d by tank t r u c k s t o lagoons or land surfaces f o r

d isposa l .

s ludge d isposal i nc lude 1) $73--drying f o r f e r t i l i z e r , 2 )

$69--dewatering and i n c i n e r a t i n g , 3 ) $54--continuous d i g e s t i o n i n a

permanent lagoon, and 4 ) $17--d igest ion and a p p l i c a t i o n on land.

From these cost cons idera t ions alone i t i s obvious why the re i s

increased i n t e r e s t i n land d isposal o f sludge.

E f f e c t s o f Sludge on Crop Produc t ion - Sludge d isposal on land has

been p r a c t i c e d f o r many cen tu r ies around the wor ld w i thout any no t i ceab le de t r imenta l e f f e c t s on p l a n t growth, where neu t ra l pH

L i q u i d s ludge can be

Some approximate cos ts per ton fo r rep resen ta t i ve methods o f

162


a p p l i c a t i o n no sewage microbes ( c o l i f o r m s ) cou ld be detected i n the

sludge-contaminated forage.

t reatments. Studies i n I l l i n o i s showed corn y i e l d increses over

convent ional f e r t i l i z e r t reatment du r ing the years 1968-1971 (Table

V-5). s ludge a p p l i c a t i o n (Table V-6).

l and a p p l i c a t i o n o f sludge due t o metal t o x i c i t i e s o r induced

n u t r i e n t d e f i c i e n c i e s caused by h igh concent ra t ions o f meta ls i n

s o i l s . Metal t o x i c i t i e s t o crops are impor tant problems on a c i d

s o i l s , bu t i n neu t ra l and a l k a l i n e s o i l s the metals are l a r g e l y

p r e c i p i t a t e d o r bound w i t h organic mat te r and are not r e a d i l y

ava i l ab le .

c o n t a i n increased metal concent ra t ions , bu t these concent ra t ions

a re genera l l y not found i n the e d i b l e p o r t i o n o f t he crop, t he

except ion being Cd.

general l y not been found.

gradual accumulat ion of heavy meta ls i n s o i l s due t o repeated

sludge app l i ca t i ons .

ex ten t , i t i s not known i f the maintenance o f h igh organic ma t te r

l e v e l s and the proper s o i l pH w i l l prevent t h e i r f r e e movement o r

not. F u r t h e r research i s needed t o determine t h e f a t e and impact

o f these meta ls on s o i l s over long t ime per iods.

of sludge i s a l s o h i g h l y va r iab le , making an ana lys is before

a p p l i c a t i o n essen t ia l .

Impact o f Land Disposal on Environmental Q u a l i t 1 - Two main

environmental concerns w i t h sludge a p p l i c a t i o n t o land are sur face

water contaminat ion by r u n o f f and groundwater contaminat ion by

leaching. Runoff f rom sludge d isposal s i t e s may con ta in h i g h

,concentrat ions o f n i t r a t e s and phosphates and may a l so c o n t a i n some

BOD c o l i f o r m bac ter ia . Runoff should there fore be minimized t o

prevent d e t e r i o r a t i o n and poss ib le contaminat ion o f sur face waters.

groundwater and i s probably the most important environmental

cons ide ra t i on i n sludge app l i ca t i on . Ammonium present i n sludge

S1 udge can increase crop y i e l ds over convent ional f e r t i 1 i zer

Y ie lds o f Coastal bermuda grass have a l so been increased by

Heavy meta ls (e.g., Zn, Cu, N i and Cd) are a major concern i n

Crops grown on sludge-amended s o i l s have been found t o

Y i e l d decreases due t o t o x i c i t i e s have

A more ser ious problem may be the

If the metals do accumulate t o a l a r g e

Metal composi t ion

N i t r a t e leached from sludge-amended s o i l can contaminate


Tab le V-5. Average Annual corn y i e l d s obtained w i t h sludge

appl i c a t i o n . 1

Maximuin A p p l i c a t i o n Rates - - Rate of h@catlon I_--

T o t a l T o t a l dry Year NPK 1 / 4 i n . 1 / 2 in. 1 i n . 1 i q u i d s o l i d s ---

htr lncre i n / y r ton 9 / RC re

1968 6 6 . 3 9 6 . 2 1 1 4 . 2 111.9 6.75 23.0 1369 1 4 2 . 8 149.0 150.2 150 .6 10 .0 2 1 . 1 1970 88.2 119 .3 121.5 137.6 9.0 30.8 19 7 1 9 6 . 6 103.7 110.4 1 2 5 . 6 10.0 43.1

4 y r av. 98.6 1 1 7 . 1 1 2 4 . 1 131 .3 T o t a l 35.75 118.0

'From " I< f fc>cts 011 Corn h y App l t c , t t t on of l l c n t c d Anacrobicnlly Dicested Sludge ," T . D . l l t n c s l y , R. I,. J ones , E . 1,. Z i c g l e r , C o n p s t Science, 1 3 : 4 , 1972.

--

Table V-6. Y i e l d o f Coastal bermuda grass f e r t i l i z e d w i t h NPK and sewage

s l udge.l

SSuiKe- Rate, I n c h e s --I

Year C o n t r o l :n'K 0.25 0.5 1 .oo 2 .oo __-__-_---_------ y e ( 111 f; /*IC re) -----__- -- ____

1969 590 5,6002 7,400 10 ,400 10 ,900 10 ,400

1970 1 , 000 11 ,800 7,400 11,500 12,300 11 ,400

lSource: J . Ilnviron. Qual , 1: 325-329,

2200, 3 3 ,ind 83 l b s l n c r c of N , P , and K, r e s p e c t i v e l y .

'320, 100, and 200 l b s / a c r e of N , P , and K , respectively.

----- ___.-- - I_c--

1972.


i n i t i a l l y and ammonium re leased from sludge so l i d s d u r i n g

decomposit ion i s o x i d i z e d t o n i t r a t e by s o i l microbes. The

water -so lub le n i t r a t e i o n i s r e a d i l y leached through t h e s o i l

p r o f i l e and can e n t e r t h e groundwater.

t o t h e water t a b l e by l each ing w i l l depend on t h e amount o f N a p p l i e d i n the s ludge which i s removed by the growing crop.

Research has i n d i c a t e d t h a t leachates f rom sludge-amended s o i l s

c o n t a i n more n i t r a t e s than those from un t rea ted s o i l s . Heavy

meta ls may a l s o be leached and e n t e r t h e groundwater, bu t t h i s

seems t o be a minor problem except i n acid, sandy s o i l s . I n

general, t h e metals a re t i g h t l y bound t o t h e s o i l and do no t leach

as l ong as t h e pH i s near neu t ra l and t h e organic mat te r con ten t o f t h e s o i l i s not t o o low.

The amount o f n i t r a t e l o s t

D. S i t e S e l e c t i o n and Management

Cropland i r r i g a t i o n w i t h wastewater and sludge has great p o t e n t i a l

f o r h e l p i n g t o so l ve our domestic waste d isposa l problems, as w e l l as

r e c y c l i n g a va luab le resource back t o the land.

v a r i a t i o n s t h a t e x i s t throughout the count ry i n waste composit ion, s o i l s ,

c l ima te , and groundwater geology, it i s impossible t o devise one " p e r f e c t "

t rea tment system t h a t w i l l work everywhere. A few gu ide l i nes can be

es tab l i shed, however, t o p rov ide a framework f o r developing and e v a l u a t i n g

t rea tment systems. Proper s i t e s e l e c t i o n and good management a re t h e most

impor tan t c o n d i t i o n s f o r a s u c c e s s f u l l y o p e r a t i n g l and t rea tment system.

Complete d e t a i l s on s i t e s e l e c t i o n are presented i n t h e Land Disposal

Spi n o f f .

Because o f the tremendous

Soi 1 s

The " i d e a l " s o i l f o r a d isposa l s i t e would be one t h a t : 1 ) has a

h i g h i n f i l t r a t i o n ra te , 2 ) i s permeable f o r good water movement bu t not so

permeable as t o not f i l t e r t h e water, 3 ) i s deep t o groundwater o r rock

l a y e r s t o prevent groundwater contamination, 4 ) i s n e a r l y l e v e l t o prevent

r u n o f f and e ros ion hazards, 5 ) i s i n an upland area w i t h no danger o f

165


f l ood ing , 6 ) has h igh water- and n u t r i e n t - h o l d i n g capac i t i es . Since t h e

i d e a l d isposa l s i t e w i l probably not be found, a p p l i c a t i o n r a t e s and o t h e r

management p r a c t i c e s w i l l need t o be ad jus ted t o f i t t h e s i t e l i m i t a t i o n s .

F o r example, drainage systems may need t o be i n s t a l l e d i n areas o f h igh

water tab les , and s to rage areas may be needed i f s o i l t ype and c l i m a t e

prevent w i n t e r a p p l i c a t i o n o f waste. There should a l s o be a procedure f o r

m a i n t a i n i n g aerob ic c o n d i t i o n s i n t h e s o i l , s i nce anaerobic c o n d i t i o n s

cause many problems such as increased metal a v a i l a b i l i t i e s , s o i l c logging,

and decreased i n f i l t r a t i o n rates.

The Cooperat ive S o i l Survey provides s o i l naps and r e p o r t s t h a t show

t h e l o c a t i o n o f d i f f e r e n t s o i l s , descr ibes t h e i r p roper t i es , and p r e d i c t s

how t h e s o i l s w i l l r eac t t o var ious uses. Th is i n f o r m a t i o n i s a v a i l a b l e i n

pub l i shed s o i l surveys and, i n unpublished form, from l o c a l S o i l and Water

Conservat ion D i s t r i c t o f f i c e s .

Waste Composition

To manage t h e treatment system p roper l y and not over load t h e s o i l ,

t h e composi t ion o f t he waste m a t e r i a l s niust be known.

concern are 1 ) n i t r a t e concent ra t ions , 2 ) s a l t concent ra t ions , 3) heavy

metal concent ra t ions , 4) o rgan ic ma t te r content, 5 ) organisms present, and

6 ) n u t r i e n t imbalances. Since n i t r a t e i s so lub le and can contaminate

groundwater and r u n o f f , t h e p l a n t a v a i l a b l e N a p p l i e d i n sludge should no t

g r e a t l y exceed t h e amount o f n i t r o g e n t h a t can be taken up and removed by

t h e crops. Excessive s a l t concent ra t ions may induce a water s t r e s s which

adverse ly a f f e c t s p l a n t growth, and my a l s o proniote s o i l puddl i ny , thus

reduc ing water i n f i l t r a t i o n i n t o t h e s o i l .

S i x major areas o f

The e f f e c t o f heavy nietals on crops and water q u a l i t y i s not f u l l y

understood. When t h e s o i l o rgan ic ma t te r con ten t i s kept h igh and t h e s o i l

pH i s kept n e u t r a l o r a l k a l i n e , however, meta ls a re most ly complexed i n

i n s o l u b l e and unava i l ab le forms. Before l a r g e q u a n t i t i e s o f sludge h igh i n

meta ls a re a p p l i e d t o s o i l , i t s e f f e c t s on c rop composit ion, animals t h a t

e a t t h e crops, and water q u a l i t y should be determined as much as poss ib le

and s p e c i f i c recommendations should be obtained from s t a t e h e a l t h o f f i c i a l s

o r a g r i c u l t u r a l ex tens ion s p e c i a l i s t s . Care fu l mon i to r i ng o f metal

166 WW TRMT SPNOFFIRIOLOG W TRMT SYSTEMS

concent ra t ions i n crops and s o i l s should he lp prevent any poss ib le

t o x i c i t i e s before they devel op.

have been proposed by EPA, and these can be used as gu ide l ines u n t i l

f u r t h e r research i s completed. These l i m i t s are designed t o p r o t e c t

crop land from poss ib le metal contaminat ion. The t o t a l amount o f sludge

t h a t can be app l ied t o a p a r t i c u l a r land area i s determined by the

f o l l o w i n g equat ion:

Some t e n t a t i v e l i m i t s on metal contents o f sludges app l ied t o cropland

t o t a l sludge ( d r y tons) /acre = 32,600 x CEC ppm ZN + 2(ppm Cu) + 4(ppm N i ) - 300

CEC - c a t i o n exchange capac i t y o f the unsludged s o i l i n meq/lOOg

ppm = mg meta l /kg d r y weight o f sludge

The s o i l should be mainta ined a t a pH o f 6.5 o r g rea ter f o r a t l e a s t 2

years a f t e r t h e f i n a l sludge a p p l i c a t i o n t o prevent immediate leach ing o f

metals. I n add i t i on , t he sludge must have a Zn/Cd r a t i o i n excess o f

1OO:l.

sludges and s o i l s . Metal concent ra t ions genera l l y l i m i t t he l i f e t i m e o f a

d isposa l system, whereas n i t rogen concent ra t ions l i m i t t he y e a r l y

a p p l i c a t i o n rates.

heavy amounts o f some s low ly degradable organics can seal t h e s o i l sur face

and prevent water and a i r f rom enter ing. A p p l i c a t i o n ra tes should be

ad jus ted f o r t he nature o f t he organic m a t e r i a l s present and the a b i l i t y o f

t h e s o i l t o a s s i m i l a t e them. A f t e r t he sludge has d r i e d on the s o i l

sur face, i t can be plowed o r disked i n t o the s o i l t o he lp prevent sur face

s e a l i n g and encourage s o i l aggregat ion. There i s genera l l y no r e a l h e a l t h

problem w i t h disease-producing b a c t e r i a i n d igested sludges, but as an

added s a f e t y p recaut ion they should not be app l i ed t o l e a f y vegetables o r

e d i b l e r o o t crops near harvest time. N u t r i e n t imbalances which r e s u l t i n

poor crop growth may be caused by the a p p l i c a t i o n o f some sludges, such as

those low i n potassium. This type o f imbalance can be e a s i l y cor rec ted by

su ppl ement a1 K f e r t i 1 i zat i on.

Table V - 7 shows some rep resen ta t i ve t o t a l load ing r a t e s f o r var ious

Organic mat te r content can be a concern w i t h sludge a p p l i c a t i o n , s ince


Table V-7. To ta l a p p l i c a t i o n i n dry tons of sewage sludges based on t h e

z i n c equivalancc formula [Dry Tons = Ca t ion Exchange Capacity

x 32,600 3 (Zn + 2Cu + 4Ni - 300)l .

Cation Exclinnge Capacity of So i l (meq/100p;)

Heavy Metals (ppm) 5 10 1 5 20 25 30 (zn + 2cu + 4 ~ 1 )

2000 4000 6000 8000

10000 12000 14000 16000 111000 20000 22000 24000 26000 2 ROO0 30000

96 44 29 21 17 14 12 10 9 8 8 7 6 6 5

192 88 57 42 34 28 24 21 1 u 1 7 15 14 13 12 11

2 88 132 86 64 50 42 36 31 28 25 2 3 21 19 18 16

384 176 114 85 67 56 48 42 37 33 30 28 25 24 22

479 220 14 3 106 84 70 59 52 4 6 41 38 34 32 29 27

575 2 64 172 12 7 100 84 71 62 55 50 45 41 38 35 33

168

W W TRMT SPNOFF/BIOLOG W TRNT SYSTEMS

Crops

The crops chosen f o r a land d isposal system can g r e a t l y a f f e c t i t s

success, s ince n u t r i e n t uptake and removal i n harvested crops i s t h e bas is

o f t h e system.

requirements and a l s o t o l e r a n c e t o wet s o i l cond i t ions , n u t r i e n t u t i l i z a -

t i o n , s e n s i t i v i t y t o metals and s a l t s , l e n g t h o f t h e crop growing season,

and s u s c e p t i b i l i t y t o i n s e c t s and diseases brought on by increased s o i l

moisture. Whi le almost any type o f crop can be grown a t a t reatment s i t e ,

some w i l l remove more n i t r o g e n and are thus b e t t e r renovators.

grasses seem t o be t h e best f o r d isposal s i t e s because o f t h e h igh amounts

o f n u t r i e n t s , e s p e c i a l l y n i t rogen, t h a t they remove, t h e i r f i b r o u s r o o t

system which helps main ta in s o i l s t r u c t u r e and aera t ion , and t h e i r l o n g

growing season. Studies o f crops i r r i g a t e d w i t h e f f l u e n t i n Pennsylvania

showed t h a t corn s i l g a g e removed 160 pounds N per acre per year w h i l e reed

canary grass removed 408 pounds N per acre per year.

fescue are a l s o h i g h users o f n i t rogen. I f two crops are grown, a w i n t e r

cover c rop could a l s o be used t o increase t h e e f f i e i n c y o f t h e renovat ion

systern. Removing t h e crops froin t h e growing s i t e makes t h e most e f f i c i e n t

use o f t h e a p p l i e d n u t r i e n t s and reduces t h e p o s s i b i l i t i e s o f p o l l u t i o n .

on Water Q u a l i t y o f t h e S t a t e s ' c r i t e r i a f o r land a p p l i c a t i o n and o t h e r

uses o f wastewater and sludge. The i n f o r m a t i o n was compiled f rom

i n d i v i d u a l responses t o t h e i r u t i l i z a t i o n o f s e c t i o n 201(a) - (e ) o f PL

92-500, f rom a t a b l e on land a p p l i c a t i o n prepared by M e t c a l f & Eddy, from

s p e c i f i c S t a t e regua la t ions i n t h e Environmental Reporter, and froin

te lephone contacts.

Table V-8 l i s t s t h e r e s t r i c t i o n s t o land a p p l i c a t i o n and whether

s p e c i f i c r e g u l a t i o n s are used. F i r s t , i t i s h e l p f u l t o s t a t e t h e

l i m i t a t i o n s o f t h i s tab le . It was assumed t h a t a small percentage of

s t a t e s do no t have r e g u l a t i o n s i f they d i d not appear i n t h e S t a t e

responses t o t h e NCWQ i n q u i r y o r t h e Environi i iental Reporter.

indeed have formal h e a l t h department r e g u l a t i o n s not i n d i c a t e d i n Table

V-8. Also, a p o l i c y regard ing land a p p l i c a t i o n o f wastewater was nUt

ob ta ined f rom 5 s t a t e s , and froin 19 s t a t e s regard ing sludges.

t e r r i t o r i e s ; 22 o r 41 percent have formal regu la t ions . T h i r t y - e i g h t s t a t e s

Some f a c t o r s t o consider when s e l e c t i n g crops are water

Perennia l

Orchard grass and

F o l l o w i n g i s a summary (Table V-8) compiled by t h e Nat iona l Commission

Some may

F o r land a p p l i c a t i o n o f wastewater, froro a t o t a l o f 54 s t a t e s and


STATZ - Table V-8. Land A p p l i c a t i o n o f Wastewater and Sludge

SLVDCE I_

‘r! I 3’; f .*A A R R - -- . . - - i q u - Tre.rtment and 0th.r Rep- 1Atlons Res tfict ions lations Restrictions

Ala-. . . . S O U a 3 k a . . . . . . . . . . * Y e s Arizona. . . . . . . . . . . Yea Arkansas . . . . . . . . . . No California . . . . . . . . . Yes Colorado . . . . . . . . . . No Connecticut. . - - . . - - . No -1AWarO . - . - . Yes D . C . . . . . . . . . . . . Ye8 Florida . . . . . . . . . . Y e s Georgia. . . . . . . . . . . Ye. G u m . . . . . . . . . . . . Y e s

Idrho. . . . . . . . . . . . Yes Illinois . . . . . . . . . . res Ind1.m. . . . . . . . . - . N O xm.. . . . . . . . . . . No Kansas.. . . . . . . . . .No Kentucky . . . . . . . . . . No Louisiana. . . . . . . . . . No Maine . . . . . . . . . . . Yar Uryland . . . . . . . . . . No nicNgm..........No

fiUAii . . . . . . . . . . . YES

Msr.churotU - - * No

ninnesota . . . . . . . . . Yes nirslssippi . . . . . . . . No

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Yes No No NO Yes Yes No No No uo No

OkldhOIM. a . NO Oregon. . . . . . . . . . . No Pennsylvania . . . . . . . . Yes

Pueeo Rico . . . . . . . . South Carolina . . . . . . . Tennessee . . . . . . . . . Trust territories . - gt&. . . . . . . . . . . . VerZvnt . . . . . . . . . .

R h o d m Islmd * . - - . . South DJkOt. . . . . . . . . TexAa . . . . . . . . . . .

!a0 NO No No NO Yes No Yes Yes

Virginia. . . . . . . . . . Yes ;Jsshington. . . . . . . . . Draft West Virginia . . . . . . . No UisconrLn . . . . . . . . . Yes WyOmFnp . . . . . . . . . . NO

Secondary Treament Secondary or Advance1

Secondary

Secondary C Disinfection M Hoc Basis Secondary 5 Disinfection Prohibited Secondary to Advanced Secondary C Disinfection M R o ~ Basis Secondarj C Disinfection Secondary or Sec. 6 D i s h

I . &rimary to Advanced

Secondary - not Generhlly Practiced Secondary Secondary C Disinfection Secondary Secondary Disinfection Secondary

Prohibited; OK sacondary 6 DishLeetion Sscondary C Disinfection

-

I

Sccond;lry C Dishfection

Not Currectly Practiced M Hoc by Permits Secondary C Disinfection Secondary - Toxics Prohib. Secondary - Dishfection Advanced C Diginfection Sect-ndary If not cost effective - no Secondary Secondary C Disinfection or

Secondary 6 Disinfectlon

-

disposal

mora stringent

- DisCouragcd Ad HOC Basis Secondary C Dlslnfection Secondary C Disinfection Secondary or Secon. L Disin. Ad Hac Basis

Secondary 6 Disinfection to

Secni!ary h Dl3infection Secondary 6 Disinfection

Secondary & Disinfection Secor.dary

Secondary

Prohibited

-

No No No No No No No No lilo No No

NO Yes Yes No No Yes NO No

No No

Yes Yes No NO Yes Yes No N o - NO Yes Yes

Yes Yes

Ye3

No Yes Yes NO Yes Yes

Yes Yes

-

- Permit Required - - Ad Roc Basis Nloued in Ladfills - Landfill - Ad HOC Landfill - M Hoc

- - -

Heat treatment M Hoc Basis Stabilized Landfill if muatered M Hoc Basis - Landfill Ad Woc Basis Ad Hoc Basis - - Lmdfill - Ad BOC Ad Hoc Basis

Guidelines in EreTaration Stabilized - Ad HOC

Landfill if &watered Landfill if Dewatered - - Pernit - Ad Hoc Basis Landfill - mixed vi th refuse

Ad Hoc Basis Ad Hoc Basis Landfill

-

Landrill - ~d aoc

Landfill - Ad Hoc Landfill - Permit Landfill - P e h t , Lf digested

C Dewater4

Landfill - Ad Hoc -

” . * A d Hoc Basis Devaterinq Landfill - Ad Hoc Digested or more Stringent Undfill - Ad Hoc

-

Stabilized or more Stringent - - Digestion as A .(inhum -

Source: Ccnpilcd by the Nitihna1 Ccxission on Water Quality. -

170


o r 70 percent r e q u i r e a minimum o f secondary t reatment o r more s t r i n g e n t

requirements.

d iscouraged i n Rhode I s land , and genera l l y not p r a c t i c e d i n Nebraska, Ohio,

and Iowa.

For land d isposal o f sludge, 21 s t a t e s or 39 percent have some form o f

formal regu la t ions . O f t he 35 s t a t e s w i t h p o l i c i e s rga rd ing sludge

d isposa l , 18 s ta tes o r 51 percent a l l ow o r regu la te d isposal i n l a n d f i l l s ;

20 o r 57 percent eva lua te d isposal on an ad hoc o r case-by-case bas is ; 5 o r

14 percent r e q u i r e dewatering; M i s s i s s i p p i and Ind iana r e q u i r e some form of

s t a b i l i z a t i o n ; Wisconsin requ i res d iges t i on ; Idaho requ i res heat t reatment ;

and Pennsylvania requ i res d i g e s t i o n f o r l a n d f i l l d isposal .

needs and p o t e n t i a l i n fo rma t ion sources concerning land a p p l i c a t i o n can be

found i n Table V-9.

A p p l i c a t i o n i s p r o h i b i t e d i n the D i s t r i c t o f Columbia,

I n fo rma t iona l

E . Operat ional C h a r a c t e r i s t i c s

To f o l l o w are genera l l y app l ied opera t ing cond i t i ons f o r the systems

i d e n t i f i e d and discussed i n Sec t ion C.

1. Ac t i va ted Sludge Systems

A. Conventional

1)

2)

Loading Fac tor ( l b . BOD/da )

l b . BOD/day = - F = 1 b. MLVSS M

I 7 J m E d .

3 ) Aera t ion Per iod (hours)

4) S e t t l i n g Per iod (hours)

5 ) 6 ) Return Sludge Rates ( X ) 7 ) Sludge S o l i d s Turnover (days)

Dissolved oxygen i n ae ra t i on bas in (mg/ l )

B. Contact S t a b i l i z a t i o n

1) Loading Fac tor ( l b . BOD/day) 1000 cu. ft.

2 ) lb . BOD/day = - F = l b . MLVSS M

3 ) Ae ra t i on Per iods (hours)

4) S e t t l i n g Per iod (hours)

5 ) D isso lved oxygen i n ae ra t i on bas in (mg/ l )

30 t o 40 Ave. 35

0.2 t o 0.5

4 t o 8 2 t o 3

1 t o 3 25 t o 30

3 t o 4

30 t o 70 Ave. 40

0.2 t o 0.5

6 t o 9

2.5 t o 3.5

1 t o 3


6 ) Return Sludge Rate (%)

7 ) Sludge S o l i d s Turnover (days) C . Extended a e r a t i o n / o x i d a t i o n d i t c h

1) Loading F a c t o r J l b . BOD/day) 1000 cu. f t .

2 ) l b BOD/da = F = d a 3) Aera t ion P e r i o d s ( h o u r s ) 4 ) S e t t l i n g P e r i o d s ( h o u r s )

5 ) 6 ) Return Sludge Rate (7,) 7 ) Sludge S o l i d s Turnover (days)

Dissolved oxygen i n a e r a t i o n b a s i n (mg/l)

2. Contact S u r f a c e A. T r i c k l i n g F i l t e r (High Rate)

100 18 t o 20

10 t o 30 Ave. 20

0.05 t o 0.2

20 t o 30 3 t o 4 1 t o 3 100 16 t o 20

30 t o 60 Ave. 45 1) Loading Range lb . BOD/da

2 )

w BOD removal c o n s t a n t ( spm/f t3 of packing m a t e r i a l )

b ) s l a u g h t e r house waste 0.044 c ) d a i r y wastewater 0.030

a ) gpm/sq. f t . ( h i g h r a t e ) 0.15 t o 0.5 b ) Mil g a l / a c r e / d a y 5 t o 30

4 ) Sludge Return from f i n a l 0.5 t o 3.5 i n r a t i o w i t h h y d r a u l i c f low

a ) canning waste 0.021

3 ) Hydraul i c Loadi n y

B. R o t a t i n g Bio logica l Contac tors 1 ) Loading f a c t o r ( l b . BOL)/day)

1000 sq. f t . 5 t o 10

2 ) Deten t ion time ( h o u r s ) 5 t o 8

3. Ponds/Lagoons A. B. Deten t ion t ime

Temperature nust be above 15OC

1) S t a b i l i z a t i o n 2 ) Aera t ion

1 ) In Nothern reg ions 2 ) In Southern r e g i o n s

C. Loading f a c t o r

3 t o 6 months 25 t o 35 days

20 l b . BOD/acre 50 1 b. BOD/acre

172


D. Ma in ta in adequate d i sso l ved oxygen i n sys tem. Above 1.0 mg/l

4. Aerobic D i g e s t e r A. So l i ds l oad ing 0.1 t o 0.2 l b .

v o l a t i l e s o l i d s /

cu. f t . /day

B. Deten t ion t ime 10 t o 20 days

C. Best r e t e n t i o n t ime f o r s o l i d s concen t ra t i on 4 t o 6 days

D. Oxygen requ i rement 1.5 t o 2.0

l b s / l b o f

v o l a t i l e s o l i d s

degraded

up t o 40% E . Pro jec ted v o l a t i l e s o l i d s reduc t i on

5. Land I r r i g a t i o n P r a c t i c e s (See Next Page)

6. Anaerobic Lagoon

A. Water sur face should be covered

B. Deten t ion t ime

C. Loading f a c t o r

D. Minimum opera t i ng temperature

E . BOD r e d u c t i o n

7. Anaerobic D i a e s t e r

4 t o 20 days

20 lh. BOD/1000 cu. f t . /day

22oc

65 t o 75%

A. So l i ds l oad ing

1 ) Conventional Rate

2 ) High Rate

B. Methane Produc t ion

C. V o l a t i l e so l i d s reduced

D. Temperature o f ope ra t i on

E . Retent ion Time (days)

v o l a t i l e s o l i d s

cu. f t . /day

0.03 t o 0.10 l b

0.1 t o 0.4 l b .

8 t o 12 cu. ft./

l b . v o l a t i l e

s o l i d s degraded

50 t o 60%

30 t o 40OC

20 t o 30

5. Land I r r i g a t i o n P r a c t i c e s

D i s p e r s a l Impact on S u i t a b l e of Applied Q u a l i t y of

P r o c e s s O b j e c t i v e S o i l s Water Applied Water

Over l a n d Flow

Ridge and Fur- row I r r i g a t i o n

High Rate Spray I r r i g a - t i o n

I n f i l t r a t i o n - P e r c o l a t i o n

Maximize water t r e a t m e n t . Crop i s i n c i d e n t a l .

Maximize a g r i - c u l t u r a l pro- d u c t i o n .

Maximize water t r e a t m e n t by e v a p o t r a n s p i r a - t i o n and perco- l a t i o n w i t h c r o p p r o d u c t i o n a s import an t s i d e b e n e f i t .

Recharge w a t e r a f t e r s o i l perco- l a t i o n ; c r o p s u s u a l l y not grown.

Slow p e r m e a b i l i t y Most t o s u r f a c e BOD and SS g r e a t l y and/or h i g h water r u n o f f . Some t o reduced . N u t r i e n t s t a b l e . e v a p o t r a n s p i r a - reduced by f i x a t i o n

t i o n and ground- and c r o p growth. water. TDS i n c r e a s e d

S u i t a b l e f o r Most t o evapo- BOD and SS removed. i r r i g a t e d a g r i - t r a n s p i r a t i o n . Pi0 s t n u t r i e n t s c u l t u r e .

' water; l i t t l e o r f i x e d . TDS Some t o ground- consumed i n c r o p

o r no r u n o f f . g r e a t l y i n c r e a s e d .

More permeable Evapot ranspi ra - BOD and SS n o s t l y s o i l s s u i t a b l e t i o n and ground- removed. N u t r i e n t s f o r i r r i g a t e d water; l i t t l e reduced. TDS sub- a g r i c u l t u r e ; o r no r u n o f f . s t n a t i a l l y i n c r e a s e d . may u s e margina l s o i l s i f c o a r s e texture.

Highly permeable To groundwater , BOD and SS reduced . sands and g r a v e l s . some evapot rans- L i t t l e change i n TDS.

p i r a t i o n ; no r u n o f f .

-i

cn -0 z 0 7 n


Tab1 e V-9. INFORMATIONAL NEEDS AND POTENTIAL INFORMATION SOURCES CONCERNING LAND APPLICATION

1 POTENTIAL SOURCES

p R E LI M I NARY I NFO R MAT IO N -

SOIL TYPE SOIL DRAINABILITY SOIL DEPTH SOIL DEPTH TO GROUNDWATER -- PHYSICAL CHARACTERISTICS OF SOIL: -

1. PH 2. Cation Exchange Capacity 3. Water-holdtng Capachy 4. Drainability/lnfil!ration Capacity

L_

__.-

- -___-_____ DEPTH TO GROUNDWATER (PERMANENT) Of PTH TO BEDROCK _-- -____

~

IRREGULARITIES IN SOIL: 1. Fissures -~ 2. Limestone Are*

3. Fracturing of Bedrock _- SOIL SLOPE -- LAND USE P U N S

AGRICULTURAL POTENTIAL 6 COVER CROP SENSITIVE ENVIRONMENTAL AREAS -

LANE REOUIREO 6 LAND AVAILABILITY GROU&r3 WATER OUALlrY 6 MONITORING

~.

REOUIAEMEMS GROUNDWATER VOLUME GROUNDWATER MOVEMENT:

1. Direction

2. Speed WASTEWATER CHARACTERISTICS:

1. Volume of Wastewater (MGO) 2. Nltrogen. Phosphorus Concentration

DISTANCE FROM TREATMENT PLANT TO SITE(S) CONSTRUCTION COSTS OPERATING COSTS:

1. Personnel 2. Power (Electricity)

HEALTH HAZARDS PUBLIC ATTITUDE CLIMATE AND RAINFALL FLOODING FREOUENCY __-

I Local I County Stale6 Federal

SOURCE: EPA, Technolopy Transfer Seminar Publications; Design Faclors 11. Jan. 1976.

175 WW TRMT SPNOFF/RIOLOG W TRMT SYSTEMS

BIOLOGICAL WASTE TREATMENT SYSTEMS

F. Bib1 iography

General References

Hammer, Mark J . , 1975. "Waste Vater Process ing" I n "Water and Waste Water Technology" publ i shed by Wiley and Sons, I n c . , New York.

CH2M, 1976. "Wastewater Treatment" a v a i l a b l e from CH2M, H i l l , Box 428, C o r v a l l i s , Oregon 97330.

Aerobic Type Systems

Cheremisinoff , P.N., A . J . Perna , and E.R. Swaszek, 1975. " C o n t r o l l i n g Organic P o l l u t a n t s i n I n d u s t r i a l Wastewaters" , I n d u s t r i a l Wastes , Sept . /Oct . i s s u e , p. 26-35.

Environmental P r o t e c t i o n Agency Technica l T r a n s f e r S e r i e s

1. Flow E q u a l i z a t i o n , 1974. EPA 625/4-74-006

2 . Upgrading Lagoons, 1 9 7 3 . EPA 62514-73-0016

3 . Wastewater Treatment Ponds, MCD-14

The MCD-14 p u b l i c a t i o n i s a v a i l a b l e from:

General S e r v i c e s Adminis t ra t ion (8FFS) C e n t r a l i z e d Mail ing L i s t Services Bui ld ing 41, Denver F e d e r a l Center Denver, Colorado 80225

E t t e r , Eugene R . , 1974. "Oxidat ion and Aerated Lagoon Operat ion" i n DEEDS & DATA publ i shed by Water Pol lu t i .on Cont ro l F e d e r a t i o n , May i s s u e , p . 2-3.

Gromiec, M . J . , 1978. Ppaer f e a t u r e s i n f o r m a t i o n on t h e o p e r a t i o n a l parameters f o r t h e o x i d a t i o n d i t c h . t h e Dairy I n d u s t r y i n Poland." p . 22-26.

" I n d u s t r i a l Waste Management i n I n d u s t r i a l Wastes, Mar./Apr. i s s u e ,

L a n c a s t e r , Edward A . , 1971. "A gu ide t o waste t r e a t m e n t methods" i n Food i n Canada, Vol. 31 ( 7 ) , p . 15-25.

Middlebrooks, E . J . , D.H. Falkenborg, R.F. L e w i s and D . J . Ehre th , 1974. "Upgrading Wastewater S t a b i l i z a t i o n Ponds t o Neet New Discharge Standards" i n t h e Symposium Proceedings h e l d August 21-23, 1974 a t Utah Water Research Laboratory Col lege of Engineer ing Utah S t a t e U n i v e r s i t y Logan, Utah 84322

Pescod, M.B. and J . V . Nair, 1972. " B i o l o g i c a l Disc F i l t r a t i o n f o r T r o p i c a l Waste Treatment", Water Research, Vol. 6 , p . 1509-1523.

ACKNOWLEDGEMENTS

The development of this program and the preparation of the modules resulted from the collaboration of Drs. Roy E. Carawan, N.C. State University, James V. Chambers, Purdue University, Robert R. Zall, Cornell University and Roger H. Wilkowske, SEA-Extension, USDA. Financial support which supported the development of this project and the modules was provided by the Science and Education Administration- Extension, U.S.D.A., Washington, D. C., and the Cooperative Extension Services of North Carolina, New York and Indiana.

STAFF AND PART-TIME PARTICIPANTS

An Advisory Committee made up of individuals from the food processing industry, equipment manufacturers, regulatory agencies and the legal profession assisted in the planning and development of these materials. The authors appreciate their advice and support.

Much of the information presented in these documents has been gleaned from the remarks, presentations and materials of others. Their cooperation and assistance is appreciated.

Ms. Torsten Sponenberg (Comell University) provided support in developing several modules and chapters. The authors appreciate her interest, enthusiasm and dedication.

Ms. Jackie Banks (Comell University) provided many hours of typing and proof-reading needed to pull together the wide array of material in the different documents. The authors appreciate her contributions.

Mr. V. K. (Vino) Chaudhary (Purdue University) provided support in developing the materials on pretreatment and treatment.

Ms. Cindy McNeill (N. C. State University) provided support in the preparation of the final documents.

Mr. Paul Halberstadt (N. C. State University) provided support in the development of many of the modules. H e also was the principal reviewer and editor for these materials. The authors acknowledge his contribution to this program.

Mrs. Gloria Braxton (N. C. State University) provided typing for several of the modules.

Mrs. Judy Fulp (N. C. State University) served as secretary for the project. She is primarily responsible for typing the materials in the many modules. The authors deeply appreciate her invaluable contribution. Only through her interest, dedication and hard work were the authors’ notes turned into these documents.

Sets of the modules are available from:

Publications Office N. C. Agricultural Extension Service Ricks Hall N. C. State University Raleigh, North Carolina 27650

Documents

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