A Laboratory-scale Model for Evaluating

8/18/2019 A Laboratory-scale Model for Evaluating

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Wat. Res. Vol. 24, No. 6, pp. 717-723, 1990 0043-1354/90 $3,00 + 0.00

Printed in Great Britain. All rights reserved Copyright © 1990 PergamonPress plc

A L A B O R A T O R Y S C A L E M O D E L F O R E V A L U A T I N G

E F F L U E N T T O X I C IT Y IN A C T IV A T E D S L U D G E

W A S T E W A T E R T R E A T M E N T P L A N T S

DONALD J. VERSTEEG* and DANIEL M. WOLTERING

Environmental Safety Department, The Procter & Gamble Company, Ivorydale Technical Center,

Cincinnati, OH 45217, U.S.A.

First received M ay 1989; accepted in revised orm December 1 989)

Abstract--Laboratory-scale wastewater treatment systems were used to assess the potential contribution

of a specific waste source, a detergent manufacturing plant, to wastewater treatment plant (WWTP)

effluent toxicity. Laboratory-scale, continuously-fed activated sludge treatment systems (CAS units) were

established and seeded with sludge from one of two activated sludge WWTPs. The CAS units were fed

influent from these WWTPs supplemented with detergent manufacturing plant waste (plant waste). CAS

unit effluent toxicity was measured with the 7 day

Ceriodaphnia dubia

survival and reproduction test and

the 4 day Selenastrum capricornutum population growth test. Control (ambient W~VTP nfluent) CAS unit

and actual WWTP effluentshad similar toxicity, indicating the CAS units generated effluent oxicologically

similar to actual effluent for the two species tested. Untreated WWTP influent was supplemented with

atypically high concentrations of plant waste in an attempt to establish a dose--response relationship

between influent plant waste levels and effluent toxicity. However, there was no trend toward increasing

effluent toxicity to Ceriodaphnia or algae with increasing influent plant waste concentrations. Thus, the

detergent manufacturing plant waste is not contributing to the toxicity of the municipal WWTP effluent.

This case study demonstrated the utility of CAS units for assessing the impact of WWTP influent sources

on final effluent toxicity.

Key words--wastewater treatment, effluent toxicity, algae, invertebrates, Ceriodaphnia, surfactants,

manufacturing plant

INTRODUCTION

The U.S. Envir onment al Protection Agency water

quality based toxics control strategy promotes the

utilization of toxicity data on single species to assess

and control the discharge of toxic substances into

receiving waters (U.S. EPA, 1985). Whole effluent

toxicity tests with the daphnid, Ceriodaphnia dubia,

a green algae, Se lenas t rum capr icornuturn and the

fathead minnow, P i m e p h a l e s p r o m e l a s , are recom-

mended to assess potential chronic effluent impacts

on in-stream communities (Horning and Weber,

1985).

Municipal wastewater treatment plant (WWTP)

effluents have been observed to be acutely an d chron-

ically toxic to aquatic organisms, with up to 79% of

effluents reported to be acutely toxic to aquatic life

(Tebo, 1986; Neiheisel et al . , 1988). Effluents exceed-

ing permitted toxicity limits may be required to

reduce effluent toxicity. Effluent toxicity reduction

can be accomplished through a toxicity identification

and reduction evaluation (TI/RE) in which toxicants

are identified and toxicity is ameliorated by aug-

mented treatment processes and programs designed

to restrict sources of toxic compounds (Mount and

Anderson-Carnahan, 1988), At municipal WWTPs,

*Author to whom all correspondence should be addressed.

the TI/RE process may involve going up the pipe

to identify industrial or commercial sources of toxic-

ity (U.S. EPA Science Advisory Board, 1988). But,

how should toxicity info rmati on on untreat ed waste

be obtained and interpreted to accurately reflect

toxicity in the final treated effluent? Toxicity tests on

untr eated wastes may no t accurately assess the contr i-

bution of a waste to final effluent toxicity, especially

in waste streams containi ng compound s removed by

treatment processes. Knowledge of total waste

treatability (e.g. BOD removal) might not always be

useful as effluent levels of residual toxic compounds

will not be known. The key parameter to understa nd

is the quan tity of final effluent toxicity a specific waste

source contains. In this study, model waste treatment

systems were used to assess the con tribut ion of a

detergent manufac turin g plant waste to final effluent

toxicity. This approach has been used successfully to

evaluate the effect of treatment on the toxicity of a

number of compounds (Horning

et a l . ,

1984; Botts

e t

al. , 1989).

Predicting the potentia l contribu tion of the manu-

facturing plant waste to WWTP effluent toxicity is

complicated by: (1) the chemical complexity of the

manu fac tur ing plan t waste; (2) the differential

WWTP removal of manuf actur ing plant waste com-

ponents; and (3) the potential for toxicological inter-

actions among components of the final WWTP

717


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718

INFLUENT/SLUDGE

SOURCE

D O N A LD J V ER S TEEG a n d D A N IEL M W O LTER IN G

W W T L , - - - J I

; , N . L U E . .A O . L U O O E I [ ' . F L U ' A . O S ' U O 0 '

MANUFACTURING

PLANTASTE

DOSING

~_~ Mnnufacturlng

Plant aste

4X

C A S U N I T S ~ ~ ~ ~ ~ ~

TOXICITY

TESTS

EFFLUENT EFFLUENT EFFLUENT EFFLUENT EFFLUENT EFFLUENT

Fig . 1 . F low d iagram of the exper imenta l des ign demons tra t ing the source o f s ludge and in f luen t , the

add i t ion o f m anufac tu r ing p lan t was tes and the use o f CAS un i t e ffluen ts fo r tox ic i ty te st ing .

e f f lu e n t . T o c o n d u c t t h e m o s t r e l e v a n t t e s t i n g p o s s-

i b l e, w e r e a s o n e d t h a t e f f lu e n t t o x i c i t y s h o u l d b e

a s s es s e d f o l l o w i n g a c t u a l o r s i m u l a t e d w a s t e w a t e r

t r e a t m e n t o f th e m a n u f a c t u r i n g p l a n t w a s t e .

T h i s r e s e a r c h h a d t w o p u r p o s e s . F i r s t , t o a s se s s t h e

f e a s i b il i t y o f c o u p l i n g a l a b o r a t o r y - s c a l e w a s t e t r e a t -

m e n t s y s t e m w i t h e f f l u e n t c h r o n i c t o x i c i t y a s s a y s t o

d e t e r m i n e t h e c o n t r i b u t i o n o f a n i n f l u e n t s o u r c e t o

f i n a l W W T P e f f lu e n t t o x i c it y . T h i s r e s e a r c h w a s

c o n d u c t e d u s i n g a d e t e rg e n t m a n u f a c t u r i n g p l a n t

w a s t e a s a ca s e s t u d y . T h e m a n u f a c t u r i n g p l a n t

r e l e a s e s w a s t e s a l o n g w i t h o t h e r d o m e s t i c , c o m m e r -

c i a l a n d i n d u s t r i a l s o u r c e s to a m u n i c i p a l W W T P .

E f f lu e n t f r o m t h e m u n i c i p a l W W T P w a s o b s e r v e d to

b e t o x i c t o a q u a t i c l i f e a n d t h e i ss u e w a s t h e l e v el o f

f i n al e ff l u e nt to x i c i t y c o n t r i b u t e d b y t h e m a n u f a c t u r -

i n g p l a n t. T h e s e c o n d o b j e c t i v e o f t h is s t u d y w a s t o

d e t e r m i n e , u n d e r a r e a l i s t i c w o r s t c a s e s c e n a r i o , i . e . a

W W T P r e c ei v in g b o t h d o m e s t i c w a s te a n d d e t e r g en t

m a n u f a c t u r i n g p l a n t w a s t e , w h e t h e r s u r f a c t a n t s , t h e

m a j o r c o m p o n e n t s o f t h e m a n u f a c t u r i n g p l a n t w a s te ,

a r e li k e l y t o c o n t r i b u t e t o m u n i c i p a l W W T P e f f lu e n t

t o x i c i t y .

MATERIALS AND METHODS

Wastewater sources

Two was tewate r t rea tment p lan t s ludges and in f luen t

sources (A and B) were used to es tab l ish and opera te s ix

CAS (con t inuous ly -fed ac t iva ted s ludge) un i ts . WWTP A is

an appro x . 20 mil l ion ga l lons pe r day conven t io na l ac t iva ted

s ludge t rea tm ent p lan t rece iv ing was te f rom dom es t ic (90 )

and indus tr ia l (10 ) sources . The indus tr ia l inpu t includes

w a s te s f ro m th e d e te rg e n t m a n u fa c tu r in g p l a n t . WWT P B

is a 1 mil l ion ga l lon pe r day , ex tended ae ra t ion ac t iva ted

s ludge p lan t rece iving w as tes en t i re ly f rom dom es t ic sources .

C S units

T h re e C A S u n i t s w e re se ed e d w i th s lu d g e f ro m W W T P A

(Fig . I ) . One un i t was opera ted with WW TP A in flUent on ly .

This in f luen t con ta ins ambien t leve ls o f the de te rgen t m anu-

fac tu r ing p lan t was te . In f luen t to the o the r two CAS un i ts

w e re s p ik ed w i th a d d i t io n a l d e t e rg e n t m a n u fa c tu r in g p l a n t

was te a t 4 and 16 t imes the typ ica l level o f p lan t was te in

WWTP A in f luen t (F ig . 1 ) . Three CAS un i ts were se t up

w i t h s l u d g e f r o m W W T P B a n d o p e r a t e d w i t h W W T P B

inf luen t . One un i t was opera ted with un trea ted in f luen t

a lone ( i .e . normal load in g o f domes t ic was te and n o de te r-

gen t manufac tu r ing p lan t was te ) . In f luen t to the o the r two

uni ts were sp iked with 4 an d 16 t imes the p lan t was te leve ls

in W W TP A influent (Fig. 1).

Each labora to ry-sca le CAS un i t cons is ted o f a p lex ig las

aeration basin and a 21. cylindrical c larifier (Fig. 2). The

aera t ion bas in con ta ined 61 . o f ac t iva ted sludge d ispe rsed by

two ae ra t ion tubes . The ae ra t ion bas in d ischarged th rough

an ov erf low tube in to a c la r i f ie r s ti r red by a sha f t m ixer . The

Pump

Influsn

Plus

PlantWaste

4o c )

Compressed

Air ~

Aeration

Section

/

Effluent

Pump

Waste

Solids ecycle

Pump

Fig . 2 . Schematic d iagram of the CAS un i ts used in the

trea tment o f the in f luen t and th~ was te f rom a de te rgen t

m a n u fa c tu r in g p l a n t .


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W a s t e c o n t r i b u t i o n t o e f f l u e n t t o x i c i ty

719

c l a r if i e r h a d a r e cy c le d i s c h a r g e t u b e i n t h e b o t t o m a n d a n

over f low fo r e f f luen t d i scharge . S ludge se t t l ing in the c la r i f i e r

w a s p e r i o d i c a l l y re c y c le d (1 5 m i n p e r h ) t o t h e a e r a t i o n b a s i n

b y a p e r i s t a l t ic p u m p . E f f l u e n t f ro m t h e c l a r i f ie r w a s c o r n -

p o s i t e d i n a 2 0 1 . p o l y p r o p y l e n e p a i l f o r t o x i c o l o g i c a l a n d

a n a l y t i c a l s a m p l i n g .

G r a b s a m p l e s o f W W T P i n f t u e n t s w e r e c o l l e c te d tw i c e

w e e k l y , t r a n s p o r t e d t o t h e l a b o r a t o r y a n d s t o r e d i n

p o l y p r o p y l e n e c o n t a i n e r s a t 4 °C . S a m p l e s w e r e f e d i n t o

C A S u n i t s i m m e d i a t e l y u p o n r e c e ip t a t t h e l a b o r a t o r y . D u e

t o t h e i n f l u e n t f e e d ra t e , a p o r t i o n o f i n f l u e n t s a m p l e s w e r e

4 d a y s o l d w h e n t r e a t e d . I n f l u e n t w a s f e d b y p e r i s t a l t ic

p u m p t o t h e C A S u n i t s a t a m e a n f lo w r a t e o f 1 6 .6 m l / m i n .

O p e r a t i o n a l p a r a m e t e r s i n t h e C A S u n i t s w e r e d e s ig n e d t o

b e s i m i l a r t o a c t u a l c o n v e n t i o n a l w a s t e w a t e r t r e a t m e n t

p l a n t s ( T a b l e 1 ) ( M e t c a l f & E d d y , 1 9 79 ; N a m k u n g a n d

R i t t m a n n , 1 9 8 7 ) . W a s t i n g o f s l u d g e w a s c a r r i e d o u t a s

n e e d e d t o m a i n t a i n t h e m i x e d l i q u o r s u s p e n d e d s o l i d s

( M L S S ) l i m i t s . I n fl u e n t , e ff l u e nt a n d m i x e d l i q u o r t o t a l

s u s p e n d e d s o l i d s , a n d i n f l u e n t a n d e ff l u e n t p H a n d t o t a l

o r g a n i c c a r b o n w e r e r o u t i n e ly m o n i t o r e d d u r i n g t h e d o s i n g

p e r i o d .

I n i ti a l ly , C A S u n i t s w e r e o p e r a t e d f o r 1 4 d a y s w i t h

u n t r e a t e d i n f l u e n t o n l y . T h i s p r e d o s e p e r i o d a l l o w e d t h e

C A S u n i t s t o r e a c h a s t a t e o f e q u i l i b r i u m b e f o r e d o s i n g w i t h

p l a n t w a s t e . A f t e r t h e p r e d o s e p e r i o d , i n f l u e n t s w e re s u p p l e -

m e n t e d w i t h d e t e r g e n t m a n u f a c t u r i n g p l a n t w a s t e t o a p -

p r o x i m a t e i n c r e a s e s o f z e r o ( a m b i e n t i n f l u e n t ) , 4 a n d 1 6

t i m e s th e l e ve l o f m a n u f a c t u r i n g p l a n t w a s t e i n W W T P A

i n f l u e n t . T h e e x a g g e r a t e d d o s e s o f p l a n t w a s t e s w e r e i n -

t e n d e d t o g e n e r a t e e f f lu e n t s f o r t o x i c it y t e s t i n g w h i c h c o u l d

b e c o m p a r e d i n a d o s e -r e l a te d m a n n e r . O b s e r v a t i o n o f a

d o s e - r e s p o n s e r e l a ti o n s h i p b e tw e e n t h e c o n c e n t r a t i o n o f t h e

m a n u f a c t u r i n g p l a n t w a s t e a n d e f f l u e n t t o x i c i t y w o u l d b e

s u b s t a n t i a l e v i d e n c e o f a c a u s e a n d e f f ec t r e l a t i o n s h i p . T h e

d o s i n g p e r i o d l a s t e d f o r 3 2 d a y s a l l o w i n g s u f f i c ie n t ti m e f o r

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

t o p l a n t w a s t e u n d e r l a b o r a t o r y c o n d i t i o n s . C o n t r o l C A S

u n i t e f f lu e n t s am p l e s w e r e c o l l e ct e d f o r a c u t e t o x i c i t y t e s t i n g

d u r i n g t h e e n t i r e d o s i n g p e r i o d . E f f l u e nt s a m p l e s f o r c h r o n i c

t o x i c i t y te s t i n g w e r e c o ll e c t e d d u r i n g t h e l a s t 7 d a y s o f t h e

d o s i n g p e r i o d .

T o x i c i t y t e s t s

C o n t r o l C A S u n i t i n f l u e n t s a n d e f f lu e n t s w e r e t e s t e d f o r

a c u t e t o x i c it y t o Cer i o d a p h n i a d u b i a b y t h e m e t h o d o f P e l ti e r

a n d W e b e r ( 1 9 8 5 ) . G r a b s a m p l e s o f i n f l u e n t a n d 2 4 h

c o m p o s i t e s a m p l e s o f e f f l u e n t w e r e u s e d . T o x i c i t y t e s t s w e re

i n i t i a t e d i m m e d i a t e l y a f t e r s a m p l i n g a n d t e s t s a m p l e s w e r e

c h a n g e d a f t e r 2 4 h w i t h a f r e s h g r a b s a m p l e o f i n f l u e n t a n d

a secon d 24-h comp os i te o f e f fluen t . Th ese t e s t s were

c o n d u c t e d t o d e t e r m i n e t h e v a r i a b i l i t y i n i n f l u e n t t o x ic i t y

a n d t h e a b i l i t y o f C A S u n i t s t o r e m o v e t o x i c i t y ,

E f f lu e n t s h o r t - t e r m c h r o n i c t o x i c it y t e s ts w i t h

C e r i o d a p h -

nia dubia

a n d

S e l en a s t ru m ca p r i co rn u t u rn

were used to assess

t h e c h r o n i c t o x i c i t y o f C A S e f f lu e n t s a n d f i n a l e ff l u en t s f ro m

W W T P s A a n d B . C e r i o d a p h n i a w e r e c h o s e n d u e t o t h e i r

g e n e r a l l y g r e a t e r s e n s i t i v it y t h a n f i sh t o W W T P e f f lu e n t s

( d a t a n o t s h o w n ) . S e l e n a s t r u m w a s s e l e c te d d u e t o t h e

s e n s i t iv i t y o f a l g a e t o s u r f a c t a n t s , t h e s h o r t d u r a t i o n o f

t o x i c i t y t e s t s w i t h a l g a e , a n d t h e i r c r i t i c a l p o s i t i o n i n t h e

e c o s y s t e m . T h e s e t e s t s w e r e c o n d u c t e d a c c o r d i n g t o t h e

Table 1. Operational conditions of the CAS units

Parameter

Aeration tank volume (litres) 6.0

Aeration rate (l/min) 6.0

Wastew ater flow (I/d) 23.9

Hydraulic retention time (h) 6.0

Sludge retention time (d) 12.0

Mixed l iquor suspended so lids MLS S (m g / l ) 200 0-3 000

Sludge volume inde x SVI (ml/I) < 100

m e t h o d s o f H o r n i n g a n d W e b e r ( 1 9 8 5 ) w i t h t h e e x c e p ti o n

t h a t C e r i o d a p h n i a w e r e c u l t u r e d a n d t e s t e d i n i n d i v i d u a l

30 ml p las t i c cups f i l l ed wi th 20 ml o f t e s t so lu t ion . F i l t e red

L i t t l e M i a m i r i v e r w a t e r, a r e l a ti v e l y c l e a n s o u r c e o f n a t u r a l

d i l u t i o n w a t e r , w a s c o l l ec t e d a t X e n i a , O h i o a n d u s e d f o r

C e r i o d a p h n i a a n d S e l e n a s tr u m c u l t u r e a n d a s d i l u t i o n w a t e r

i n t o x i c it y t e st s . D u r i n g C e r i o d a p h n i a 7 d a y c h r o n i c t o x i c it y

t e s t s , d a i l y 2 4 - h c o m p o s i t e d s a m p l e s f r o m e a c h C A S u n i t

e f f lu e n t w e r e u s e d t o m a k e t h e d a i l y r e n e w a l s o f t e s t

s o l u t i o n s . O b s e r v a t i o n s o n t h e s u r v i v a l a n d r e p r o d u c t i o n o f

C e r i o d a p h n i a w e r e m a d e d a i l y a t t h e t i m e o f t r a n s f e r .

T h e 4 d a y a l g a l t e s t s w e r e r u n c o n c u r r e n t l y w i t h t h e

C e r i o d a p h n i a t o x i c i t y t e s ts . T e s t s o l u t i o n s w e r e n o t r e n e w e d

d u r i n g t h e te s t . A l g a e w e r e i n c u b a t e d a t 2 4°C a n d 8 6 E s - 1

m - 2 ( e q u i v a l e n t t o 4 0 0 f t - c c o o l w h i t e f l u o r e s c e n t l i g h t) o n

a s h a k e r t a b l e o s c i l l a t i n g a t 1 0 0 r p m . A f t e r 4 d a y s o f

i n c u b a t i o n , p o p u l a t i o n g r o w t h w a s a s s e s s e d b y q u a n t i f y i n g

a l g a l b i o m a s s ( c h l o r o p h y l l a ) f l u o r o m e t r i c a l l y o n a T u r n e r

m o d e l 1 11 f l u o r o m e t e r ( A P H A , 1 9 85 ).

A n a l y t i c a l

S u r f a c t a n t a n a l y t i c a l s a m p l e s w e r e 2 4 h c o m p o s i t e s o f

C A S e f f l u e n t s . S a m p l e s c o l l e c t e d f o r a n i o n i c a n d n o n i o n i c

s u r f a c t a n t a n a l y s e s w e r e p r e s e r v e d w i t h 1 % f o r m a l i n a n d

s t o r e d a t 4 °C . S a m p l e s c o l l e c t e d f o r c a t i o n i c s u r f a c t a n t

a n a l y s e s w e re p r e s e r v e d w i t h 1 % f o r m a l i n a n d 5 m g / l o f

alkyl ethoxylate (C14_15A E 7 ), a n d s t o r e d a t 4 °C . T h e s a m p l e s

w e r e a n a l y z e d f o r t o t a l n o n i o n i c s u r f a c t a n t s b y a m o d i f ic a -

t i o n o f t h e c o b a l t t h i o c y a n a t e a c t i v e s u b s t a n c e m e t h o d

( A P H A , 1 9 8 5 ) , l i n e a r a l k y l b e n z e n e s u l f o n a t e s ( L A S ) b y

d e s u l f o n a t i o n g a s c h r o m a t o g r a p h y ( O s b o r n e , 1 9 86 ), a n d t h e

f o l l o w i n g c a t i o n i c s u r f a c t a n t s b y a m o d i f i c a t i o n o f t h e

m e t h o d o f W e e ( 19 8 4) ; d i t a l l o w d i m e t h y l a m m o n i u m c h l o -

r id e , m o n o t a l l o w t r i m e t h y l a m m o n i u m c h l o r i d e a n d d o d e -

c yl t ri m e t h y l a m m o n i u m c h l o r i d e . N o t e t h a t t h e a n a l y t ic a l

m e t h o d f o r t h e n o n i o n i e s u r f a c t a n t s i s a n o n s p e c if i c c o l o r i-

m e t r i c m e t h o d r e p o r te d t o o v e r e s t i m a t e t h e c o n c e n t r a ti o n o f

n o n i o n i c s u r f a c t a n t i n W W T P e f f l u e n t s ( G l e d h i l l et a l .

1 9 89 ). T h u s , r e s u l ts o f n o n i o n i c s u r f a c t a n t a n a l y s e s a r e

r e p o r t e d i n g e n e r a l t e r m s o n l y .

W a t e r q u a l i t y p a r a m e t e r s i n c l u d i n g h a r d n e s s , a lk a l i n i t y ,

d i s s o l v e d o x y g e n , t o t a l o r g a n i c c a r b o n , t o t a l s u s p e n d e d

s o l i d s , a m m o n i a , c o n d u c t i v i t y a n d p H w e r e m e a s u r e d i n

d i l u t i o n w a t e r a n d C A S i n f l u e n t a n d e f f l u e n t b y a c c e p t e d

m e t h o d s ( A P H A , 1 9 85 ). C A S u n i t s l u d g e v o l u m e in d e x

( S V I ) w a s m e a s u r e d a c c o r d i n g t o A P H A ( 1 9 8 5 ) u s i n g a

3 0 m i n s e t t l i n g ti m e . W a t e r q u a l i t y p a r a m e t e r s w e r e m e a -

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

C e r i o d a p h n i a t e s t i n g .

S t a t i s t i c s

S u r v i v a l d a t a w e r e a n a l y z e d b y t h e m e t h o d s d e s c r i b e d i n

P e l t i e r a n d W e b e r ( 1 9 8 5 ) . C e r i o d a p h n i a y o u n g p r o d u c t i o n

a n d a l ga l p o p u l a t i o n g r o w t h d a t a w e r e a n al y z e d b y n o n l i n -

ea r mul t ip le regress ion ana lys i s on SAS (SAS, 1986) .

T o x i c i t y t e s t r e s u l t s a r e s u m m a r i z e d i n t h i s s t u d y a s t h e

e f fe c t iv e c o n c e n t r a t i o n o f e f f lu e n t r e d u c i n g b i o l o g i c a l re -

s p o n s e , s u r v i v a l o r r e p r o d u c t i o n , b y 5 0 % ( E Cs 0 v a l u e s ) w i t h

95% conf idence in te rva l s . The ECs0 s ta t i s t i c was se lec ted to

iden t i fy e f f luen t concen t ra t ions caus ing a spec i f i c l eve l o f

t o x i c i t y a n d d o e s n o t i n d i c a t e a t o x i c i t y t h r e s h o l d o r

b i o l o g i c a l r el e v a n c e i n t h e r e c e i v i n g e n v i r o n m e n t . I n u s i n g

n o o b s e r v e d e f f ec t ( N O E C ) a n d f i r st o b s e r v e d e f fe c t c o n c e n -

t r a t i o n s ( F O E C ) , b i o l o g i c a l e f f e c t s v a r i e d g r e a t l y a m o n g

C A S u n i t t r ea t m e n t s w i t h s i m i la r N O E C s a n d F O E C s .

O t h e r s h a v e o b s e r v e d t h i s e f f e c t a n d r e c o m m e n d t h e u s e o f

a d o s e - r e s p o n s e s t a t i s ti c a l a p p r o a c h i n p l a ce o f t h e h y p o t h -

e s is t e s t i n g a p p r o a c h ( K r u m p , 1 9 84 ; B a r n t h o u s e e t a l .

1 98 7) . T h u s , t o m a k e m e a n i n g f u l c o m p a r i s o n s a m o n g C A S

u n i t t r e a t m e n t s i n t h i s s t u d y , b i o l o g i c a l e f f e c t s w e r e h e l d

c o n s t a n t a t 5 0 % .

F o r C e r i o d a p h n i a c h r o n i c t e s t s , E C s 0 v a l u e s w e r e c a lc u -

l a t e d b a s e d o n s u r v iv a l a n d y o u n g p r o d u c t i o n . T h e l o w e r o f


4/7

7 2 0 D O N A L D J . V E R ST E EG a n d D A N I E L M . W O L T E R I N G

T a b l e 2 . C o n c e n t r a t i o n [ m e a n ( m g / l ); ( S D ) ; n = 4 ] o f s u r f a c t a n t s * i n C A S u n i t s a n d a c t u a l W W T P e f f lu e n ts

T r ea tm e n t s ys te m D T D M A C M T T M A C C I : T M A C L A S

W as t e wat e r t r e a t m e n t p l an t s

W W T P A e f fl u en t ( n = 7 ) 0 . 0 38 ( 0 .0 1 8) < 0 . 0 1 2 t < 0 . 0 1 0 t < 0 . 0 5 0 t

W W T P B e f f l u e n t ( n = 3 ) 0 . 0 2 5 ( 0 . 0 2 7 ) < 0 .0 0 5 I < 0 . 0 0 5 t 0 . 1 3 0 t

C S u n it s

W W T P A c o n t r o l 0 . 7 6 0 ( 0 .3 9 ) 0 . 0 0 9 ( 0 . 00 2 ) < 0 . 0 0 5 t 0 . 0 7 0 ( 0 . 03 2 )

W W T P A 4 × p l a n t w a s t e 4 . 5 3 (0 . 8 4 ) 0 . 0 0 8 (0 . 0 0 3 ) < 0 . 0 0 5 t 0 . 3 9 0( 0 . 04 2 )

W W T P A 1 6 x p l a n t w a s t e 2 0 .3 ( 4 .5 7 ) 0 . 0 2 4 ( 0 . 00 1 ) < 0 . 0 0 5 t 3 . 10 ( 1 . 4 6 )

W W T P B c o n t r o l 0 . 5 5 0 ( 0 .2 8 ) 0 . 0 1 0 ( 0 . 00 5 ) < 0 . 0 0 5 t 0 . 1 4 0 ( 0 . 01 0 )

W W T P B + 4 x p l a n t w a s t e 2 . 9 8 ( 1 . 4 1 ) 0 . 0 1 1 ( 0 . 0 0 5 ) 1 0 0 % , b u t w a s g e n e r a l l y l es s t o x i c th a n W W T P

i n f l u e n t B ( T a b l e 3 ). W W T P B i n fi u e n t w a s c o n s i s -

t e n t l y a c u t e l y t o x i c t o C e r i o d a p h n i a ; L C s 0 v a l u e s

w e r e l es s t h a n 5 0 % . E f f lu e n t s fr o m c o n t r o l C A S u n i t s

w e r e c o n s i s t e n t ly o f l o w a c u t e t o x i c i t y i n d i c a t i n g

C A S u n i t s e f fe c ti v e ly r e m o v e d a c u t e l y to x i c c o m p o -

n e n t s . M o r e s e n si t iv e c h r o n i c e n d p o i n t s , t h o u g h ,

w e r e n e e d e d t o d i s t i n g u i s h e f fl u en t t o x i c i t y a m o n g

C A S u n i t s .

C h r o n i c t o x i c i t y

T o x i c i t ie s o f W W T P A a n d B e ff lu e n ts w e r e s i m i l a r

t o C e r i o d a p h n i a ( T a b l e 4 ) . E C 50 c o n c e n t r a t i o n s w e r e

2 4 a n d 2 2 °/ '0 e f f lu e n t in W W T P A a n d B , r e s p e c t i v e l y .

C o n t r o l C A S u n i t a n d a c t u a l e f f l u e n t s a l s o h a d

s i m i l a r t o x i ci t ie s . F o r W W T P A , c h r o n i c E C s 0 c o n -

c e n t r a t i o n s w e r e 2 4 % i n t h e a c t u a l W W T P e f f l u e n t

a n d 3 3 % i n t h e c o n t r o l C A S u n i t e f f l u e n t t o C e r i o -

d a p h n i a . F o r W W T P B , e ff lu e n t E C s 0 c o n c e n t r a t i o n s

w e r e 2 2 a n d 1 6 % i n th e a c t u a l W W T P a n d c o n t r o l

C A S u n i t e f f l u e n t s , r e s p e c t i v e l y .

I n W W T P A C A S u n i t s , C e r io d a p h n i a c h ro n i c

e f fl u e n t E C s0 c o n c e n t r a t i o n s w e r e 3 3 % f o r t h e c o n t r o l

C A S u n i t , 4 6 % f o r th e C A S u n i t re c e i v in g 4 x p l a n t

w a s t e a n d 1 3 % f o r t h e 1 6 x p l a n t w a s t e C A S u n i t

( T a b l e 4 ) . I n W W T P B C A S u n i t s , c h r o n i c e f f l u e n t

C e r i o d a p h n i a E Cs 0 c o n c e n t r a t i o n s w e r e 1 6 % f o r t h e

c o n t r o l C A S u n i t , 3 5 % f o r t h e C A S u n i t r e c e i v i n g

T a b l e 3 . T h e a c u t e t o x i c i ty o f i n f lu e n t s a n d e f f l u e nt s f r o m c o n t r o l C A S u n i t s t o Ce r i odaphn i a dub i a

4 8 - h L C s 0 v a l u e ( % )

S a m p l e t y p e W e e k : 1 2 3 4 5

W W T P A c o n t r o l

i n f l u e n t 2 2 . 2 > 5 0 > 1 0 0 > 1 0 0 - -

( 1 6 . 5 - 2 9 . 6 )

ef f luen t > 100 > 100 > 100 > 100 > 100

W W T P B co n t ro l

i n f l u e n t 4 4 . 6 1 6 . 0 3 8 . 0 < 2 5 - -

( 3 2 . 9 - 9 2 . 3 ) ( 1 2 . 0 - 2 5 . 0 ) ( 2 5 . 0 - 5 0 . 0 )

ef f luen t 52 .9 > 100 > 100 > 100 > 100

( 0 - 1 0 0 )


5/7

Waste contribution to effluent toxicity

721

Table 4. Effect on the survival and reproduction of Ceriodaphnia

dubia and the growth of Selenastrum caprieornutum of effluents rom

WWTPs and CAS units

Ceriodaphnia Selenastrum

ECs0 ECs0

Treatment ( ) ( )

Wastewater treatment plants

WWTP A effluent 24 > 100

(16.8-36.9)

WWTP B effluent 22 13

(8.4-58.4) (9.0-17.8)

CAS u n i t s

WWTP A control 33 > 100

(25.0-50.0)

WWTP A + 4 x plant waste 46 > 100

(25.0-50.0)

WWTP A + 16 × plant waste 13 > 100

(9.6-18.7)

WWTP B control 16 72

(12.5 25 .0 ) (60.8-86.1)

WWTP B + 4 x plant waste 35 59

(27.6-45.3) (46. 74.8)

WWTP B + 16 x plant waste 28 58

(20.5-37.1) (49.4-67.0)

4 x plan t waste and 28 for the 16 x plant waste

CAS unit effluent (Table 4).

Toxicities of WWTP A and B effluents to

S e l e -

n a s t r u m c a p r i c o r n u t u m

differed (Table 4). The ECs0

concentr ations were > 100 in WW TP A effluent

and 13 in WW TP B effluent. The control CAS units

reflected this difference in effluent toxicity. Ef fluent

from the WWTP A control CAS unit were also

nontoxic to algae with 4-day ECs0 concentrat ions

exceeding 100 effluent. With WWT P B influent, the

control CAS unit effluent was less toxic to algae than

the actual WWT P effluent. The ECs0 concentrati on of

the WWTP B effluent was 13 effluent while the

control CAS unit effluent EC50 level was 72 .

In WW TP A CAS units, all algal CAS un it effluent

ECs0 concentr ations exceeded 100 effluent (Table

4). In WWTP B CAS units, algal chronic ECs0

concentr ation s were similar at 72, 59 and 58 in the

ambien t, 4 x and 16 x pla nt waste units (Table 4).

Regression of effluent toxicity to Cer ioda phnia and

Selenastrum on infiuent manufacturing plant waste

levels and effluent surfactant concen trat ions indicated

the lack of a statistically significant relationship

between toxicity and the level of plant waste com-

ponents in the influent or effluent (Table 5).

DISCUSSION

Federal and state agency regulati on of effluents has

expanded to include the moni torin g and regulation of

whole effluent toxicity (U.S. EPA, 1984, 1985). Tech-

Table 5. Regressionstatistics (r; Pearsoncorrelation

coefficients) describing the regression of toxicity

(ECs0) to Ceriodaphniaand Selenastrumon influent

manufacturingplantwaste levelsand effluentsurfac-

tant concentrations

Correlation coefficient(r)

Species lnfluent Effluent

Ceriodaphnia 0.03 0.05

Selenastrum 0.28 0.15

niques used to control whole effluent toxicity at

municipal WWTPs include utilization of alternative

treatment options to remove final effluent toxicity

and chemical identification and remediation of efflu-

ent compounds causing toxicity (U.S. EPA, 1985;

Mount and Anderson-Carnahan, 1988). These tech-

niques are useful and effective a t controlling effluent

toxicity. However, in some cases a more cost effective

and direct approach to cont roll ing effluent toxicity,

source reduction, is recommended (U.S. EPA Science

Adviso ry Board, 1988). In this approach , the waste

streams contributing to final effluent toxicity would

be identified and regulated.

Interpretation of the results of toxicity tests on

municipal WWTP influent waste streams is not

straightforward. Due to the potential chemical com-

plexity of a waste stream, the differential impact of

treatment on the components of the waste, and the

effect of the effluent matrix on the toxicity of waste

components, the waste treatment process should be

incorporated in evaluating the contribution of a

waste stream to final effluent toxicity.

Laboratory-scale, con tinuou sly fed activated

sludge treatment systems (CAS units) have been

validated as effective models of the activated sludge

process giving removals of conventio nal parameters

and consumer product chemicals similar to actual

WWTPs (King, 1980; Vashon

e t a l .

1982). In this

study, we demonstrated the utility of CAS units to

assess the contribution of a specific WWTP influent

waste stream to post-treatment toxicity by verifying

that, for Ceriodaphnia and Selenastrum, CAS units

generate effluent toxicologically similar to actual

WW TP effluents. For Ceriodaphnia, effluent toxicity

in the control CAS units and the actual WWTPs were

similar for both influent sources. For algae, although

some differences between toxicity in the WWTP s and

the control CAS unit effluents were observed, effluent

toxicities were comparable for an influent source. At

WWTP A, both control CAS unit and the actual

WWTP effluents had similar toxicity to algae with

ECs0 conce ntrat ions exceeding 100 effluent. The

WWTP B control CAS uni t effluent was less toxic to

algae tha n the actual WW TP effluent. However, given

the possible variability in effluent toxicity and in the

toxicity test, algal toxicity of the control CAS units

and the actual WWTP effluents were comparable.

Effluents of increasing manufactur ing plant waste

strength were generated by exaggerating influent

plant waste loadings to CAS units. There was no

overall effect of plant waste components on toxicity.

However, effluent from W WT P A CAS un it receiving

the 16-fold addition of plant waste and having the

highest effluent total surfactant concentrations did

have increased toxicity to Ceriodaphnia relative to

effluent from the WWTP A control CAS unit. A

4-fold addition of manufacturing plant waste to

untreated influent had no effect on the toxicity of the

WWTP A CAS unit effluent. Thus, the current level

of detergent manufacturing plant waste being re-


6/7

722 DONALD J. VERSTEEGand DANIELM . WOLT RING

c e i v e d a t W W T P A i s n o t i m p a c t i n g e f fl u e n t t o x i c it y .

I n f a c t , a 4 - f o l d i n c r e a s e i n i n f lu e n t p l a n t w a s t e l e v e l s

w o u l d n o t b e e x p e c t e d t o i m p a c t e f f l u e n t t o x i c i t y .

I n t h e W W T P B C A S u n i t s , i n c r e a s e s i n p l a n t

w a s t e l e v e l s i n c l u d i n g t h e 1 6 - f o l d a d d i t i o n d i d n o t

a d v e r s e l y im p a c t e f f lu e n t t o x i c it y t o a l g a e o r C e r i o -

d a p h n i a . T h e r e a s o n f o r t h e 1 6 x p l a n t l e ve l c o n -

t r i b u t i n g t o e ff lu e n t t o x i c i ty i n W W T P A b u t n o t

W W T P B is n o t k n o w n b u t m a y h a v e b e e n d u e t o

i n c r e a s e d le v e ls o f m a n u f a c t u r i n g p l a n t w a s t e i n t h i s

ef f luent .

D u e t o a d d i t i o n o f p l a n t w a st e s to C A S u n i t

i n f l u e n t s , C A S u n i t e f f l u e n t s c o n t a i n e d g r e a t l y i n -

c r e a s e d c o n c e n t r a t i o n s o f t w o d e t e r g e n t a c t i v e s ,

l i n e a r a l k y l b e n z e n e s u l f o n a t e a n d d i t a l l o w d i m e t h y l

a m m o n i u m c h l o ri d e D T D M A C ) , i n c o m p a r i s o n t o

t h e a c t u a l W W T P s T a b l e 2). D e s p i t e t h e s e g r e a t l y

e l e v a t e d c o n c e n t r a t i o n s o f s u r f a c t a n t s , e f f l u e n t t o x i c -

i t y t o a l g a e a n d C e r i o d a p h n i a w a s n o t a f f e c te d e x c e p t

i n t h e C A S u n i t w i t h t h e g r e a t e s t e f f l u e n t s u r f a c t a n t

c o n c e n t r a t i o n i .e . W W T P A 1 6 × p l a n t w a s t e C A S

uni t ) .

I n a l l C A S u n i t e f f l u e n t s , l i n e a r a l k y l b e n z e n e s u l -

f o n a t e c o n c e n t r a t i o n s r e m a i n e d b e l o w l e v e ls re p o r t e d

t o b e t o x i c t o a q u a t i c o r g a n i s m s M a k i , 1 97 9; H o l -

m a n a n d M a c e k , 1 9 8 0 ; T a y l o r , 1 9 8 5 ) . H o w e v e r , C A S

u n i t e ff lu e nt co n c e n t r a t io n s o f D T D M A C e x c ee d e d

l e v e ls r e p o r t e d t o b e t o x i c . L e w i s a n d W e e 1 9 8 3 )

o b s e r v ed t h a t D T D M A C c o m p l e t e ly i n h i b it e d S e l e -

n a s t r u m c a p r i c o r n u t u m g r o w t h E C l0 0 o r a l g i s t a t i c

c o n c e n t r a t i o n ) a t c o n c e n t r a t i o n s r a n g i n g f r o m 0 .7 t o

2 . 6 m g / l i n f i l t e r e d r i v e r w a t e r . I n a c h r o n i c t o x i c i t y

t e s t c o n d u c t e d i n r i v e r w a t e r , t h e D T D M A C E C s0

c o n c e n t r a t i o n t o D a p h n i a m a g n a w a s a p p r o x .

1 .0 m g /1 . I n o u r s t u d y , D T D M A C c o n c e n t r a t i o n s u p

t o 2 0 . 3 m g / l i n a C A S u n i t e f f l u e n t h a d n o e f f e c t s o n

S e l e n a s t ru m . F o r C e r i o d a p h n i a , a c o n g e n e r i c sp e c ie s

t o D a p h n i a , t h e ef fl u en t D T D M A C c o n c e n t r a t io n a t

t h e E C s 0 l e v e l o f e ff l u e n t r e a c h e d a m a x i m u m o f

3 . 0 m g /1 . T h e s e o b s e r v a t i o n s i n d i c a t e t h a t t h e w a s t e

t r e a t m e n t p r o c e s s a n d e f f lu e n t m a t r i x m a y h a v e r e -

d u c e d t h e a p p a r e n t t o x i ci t y o f D T D M A C . T h i s ef fe ct

o n t o x i c i ty i s p r e s u m e d t o b e d u e t o a n e f f ec t o n

D T D M A C s p e c ia t i o n a n d b i o a v a i la b i l it y . S i m i l ar

r e s ul t s o n t h e a m e l i o r a t i o n o f t h e t o x i c i t y o f c a t i o n i c

c o m p o u n d s b y s u s p e nd e d s o l id s an d o r g a n i c c a rb o n

h a v e b e e n r e p o r t e d C a r y e t a l . 1987) . S ince the se

f a c t o r s a f fe c t t h e t o x i c i t y o f th e s e c o m p o u n d s i n t h e

e n v i r o n m e n t , i t i s i m p o r t a n t t o u t i l i z e t h e m o s t

e n v i r o n m e n t a l l y r e l e v a n t m e t h o d t o i n t ro d u c e t h e s e

c o m p o u n d s i n t o a q u a t i c t o x i c i t y t e s t s y s t em s . T h e s e

r e s u l t s s u g g e s t t h a t C A S u n i t s a r e a n e f f e c ti v e m e t h o d

f o r g e n e r a t i n g i n c r e a s e d c o n c e n t r a t i o n s o f t e s t m a t e -

r i a ls in a n e n v i r o n m e n t a l l y r e a li s ti c m a t r i x a n d t h a t

r e l e v a n t s a f e t y d a t a c a n b e o b t a i n e d w i t h t h e s e

m e t h o d s .

I n t h i s c a s e s t u d y , e f f l u e n t c o n c e n t r a t i o n s o f t h e

m a j o r p l a n t w a s t e c o m p o n e n t s c o u l d b e m e a s u r e d .

H o w e v e r , i f p l a n t w a s t e c o m p o n e n t s c o u l d n o t b e

m e a s u r e d d u e t o t h e n u m b e r o f c o m p o u n d s o r t h e

i n a b i l i t y to a c c u r a t e l y q u a n t i f y s p e ci fi c c o m p o n e n t s ,

t h e C A S u n i t a p p r o a c h w o u l d r e m a i n v a li d . D u e t o

t h e a b i l i t y to m a n i p u l a t e i n f lu e n t w a s t e l o a d i n g s , t h e

C A S u n i t a p p r o a c h c a n b e a p o w e r f u l t o o l t o a s s e s s

t h e c o n t r i b u t i o n o f w a s t e c o n t r i b u t o r s t o e f f lu e n t

t o x i c it y . In u t i li z i n g t h i s a p p r o a c h , c a r e s h o u l d b e

e x e r c i s e d t o a v o i d e f f e c t s o f t h e w a s t e o n t h e t r e a t -

m e n t p r o ce s s . A d d i t i o n o f w a s t e a t a b n o r m a l l y h i g h

l e v e ls c o u l d c a u s e e f f ec t s i n c l u d i n g t o x i c i t y t o a c t i -

v a t e d s l u d g e o r g a n i s m s , a l t e r n a t iv e s u b s t r a t e u t i l iz a -

t i o n o r d i l u t i o n o f i n fl u e n t a n d m i x e d l i q u o r s t re n g t h .

T h e s e , a n d o t h e r p o t e n t i a l e f f ec ts , c o u l d a m e l i o r a t e o r

p o t e n t i a t e t h e o b s e r v e d t o x i c i t y o f t h e w a s t e . T h e

i n c i d e n c e o f t h e s e e f f e c t s c a n b e r e d u c e d b y p r o p e r

s e l e ct i o n o f i n f lu e n t w a s t e l e v el s a n d m o n i t o r i n g o f

a c t i v a t e d s l u d g e p r o c e s s e s .

CONCLUSIONS

U s e o f l a b o r a t o r y - s c a l e , c o n t i n u o u s a c t i v a t e d

s l u d g e u n i t s c o u p l e d w i t h e f f l u e n t t o x i c i t y te s t p r o c e -

d u r e s w e r e e ff e c ti v e m e t h o d s t o a s s e s s t h e c o n t r i b u -

t i o n o f a n i n f lu e n t s o u r c e t o f in a l W W T P e f fl u en t

t o x i c it y . C A S u n i t s p r o v i d e d t r e a t m e n t o f i n fl u e n t

w a s t e s t r e a m s a n d g e n e r a t e d t o x i c o l o g i c a l l y r e l e v a n t

e f fl u en t s f o r C e r i o d a p h n i a a n d S e l e n a s tr u m . A m a j o r

c o m p o n e n t o f th e d e t e r g e n t m a n u f a c tu r i n g p l a n t

w a s te , D T D M A C , w a s l es s t o x ic as a c o m p o n e n t o f

a C A S u n i t e f f l u e n t t h a n h a s b e e n r e p o r t e d i n t h e

l i t e r a t u r e i n c o n v e n t i o n a l l a b o r a t o r y t o x i c i t y t e s t s

s u g g e s ti n g t h a t c o m p o n e n t s o f W W T P e f fl u e nt s a m e -

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

s t u d y , t h e d e t e r g e n t m a n u f a c t u r i n g p l a n t w a s t e w a s

n o t a s i g n i fi c a n t c o n t r i b u t o r t o W W T P e f fl u e nt to x i -

c i ty a t c u r r e n t r a t es o f m a n u f a c t u r i n g p l a n t w a s t e

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