BIOLOGICAL TREATMENT OF WASTE WATER

&

DESIGN CALCULATION OF SEQUENCING

BATCH REACTOR PROCESS A Technical Seminar Report

Submitted to

Mewar University, Chittorgarh

Towards the Part Time of

The degree of

Master of Technology

In

Environmental Science & Engineering

Session: -2013-2016

Submitted to Submitted by

Mr. Mahboob Alam Ajay Kumar

(Assistant Professor) MUR 1302657

Faculty of Engineering & Technology

Department of- Chemical Engineering

2

August– 2015

DECLARATION

In accordance with the requirements for the degree of Master of Technology

in Environmental Science &Engineering in Faculty of Chemical

Engineering I present this Seminar report Entitled “Biological treatment of

waste water & Design calculation of Sequencing Batch Reactor process”

This report is completed under the Supervision of Mr. Mahboob Alam

I declare that the work presented in the report is my own work except as

acknowledged in the text and footnotes, and that to my knowledge this

material has not been submitted either in whole or in part, for a degree at this

University or at any other such Institution.

Date -9/8/15 Ajay Kumar

MUR 1302657

Faculty of Engineering & Technology

Department of: - Chemical Engineering

Mewar University

Chittorgarh (Raj.)

3

August-2015

ACKNOWLEDGEMENT

I Express My Sincere Thanks to Mr. Mahboob Alam (Assistant Professor,

Department of Chemical Engineering) for their kind Co-Operation for

presenting the seminar.

I also extend my sincere thanks to all the authors of books whose I read

duration of seminar report preparation.

Ajay Kumar

4

ABSTRACT

Biodegradable constituent of waste water treated by biological treatment

process. Biological treatment carried out by several biological treatment

units. The Sequencing batch Reactor (SBR) is a fill and draw Activated

sludge system in which all steps of conventional process take place in

sequences one by one. In the system almost process of waste water treatment

carried out in reactor such as- Equalization, aeration and clarification.

Normally the SBR process occurs in batch process so does not require

secondary clarifier.

5

CONTENTS PAGE

I –INTRODUCTION

1.1- Introduction of biological treatment 7

1.2- Role of microorganisms in waste water treatment 7

1.3- Objectives of biological treatment 8

1.4- Classification of treatment process 8

II-Sequencing batch reactor process

2.1- Concept 11

2.2- Mechanical Equipments 11

2.3 – Process Description 13

2.4-Design Calculation 14

III- Conclusion 24

IV- References 26

6

CHAPTER 1

INTRODUCTION

7

1.1- Introduction of biological treatment:

After primary treatment removes large floating materials, Grits and a large portion of the

heavy inorganic suspended solids which present in the waste water. The colloidal and

dissolved solids, mainly organic in nature, still remain in the effluent. Remain content

use by population of microorganisms. Microorganisms are able to utilize the colloidal

and dissolved biodegradable organic matter as food for their growth and multiplication.

Microorganisms found in biological treatment system where they does break down waste

organics and remove organic matter from solution.

1.2- Role of Microorganisms in waste water treatment

The Microbes convert these solids into simpler end products like water (H2O) and carbon

dioxide (CO2) and synthesize their own new cells. These cells are known as biomass or

biological floc. As the floc thus produced has a specific gravity which slightly greater

than that of water, it settles easily by gravity. Therefore, the new cells produced are

removed by settling process and settle sludge known as biological sludge or secondary

sludge.

(Settle biological sludge)

8

Organic material + O2 + NH3 + PO4 New cells + water + carbon dioxide

1.3- Objectives of Biological treatment

1- To coagulate and remove both organic and inorganic non – settleable colloidal

particles which do not get removed in primary treatment.

2- To Stabilize the dissolved organic matter ( normally Carbonaceous BOD) that remains

in the effluent from primary treatment.

1.4-Classification of treatment process

The biological process or treatment system have been broadly classified into two

categories.

Process according to operational condition

(1) Aerobic Process: - The process that essentially required the presence of molecular

oxygen for metabolic activity of microorganisms is called an aerobic process. The

process can be designed to supply required oxygen either naturally ( such as in

trickling filter, aerobic stabilization pond) or by artificial/mechanical means ( as

in activated sludge process, aerated lagoons) in the reactor. The process normally

fails in the absence of the oxygen.

(2) Anaerobic process:- The process that operates in the absence of molecular oxygen

in the reactor for the growth of microbes and normally fails in the presence of

excessive oxygen is called an anaerobic process e.g. anaerobic sludge digester,

and anaerobic up flow filters.

(3) Facultative process :- The process that can operate both in the presence or

absence of oxygen in the reactor for the growth of facultative bacteria is called a

facultative process, e.g. facultative stabilization ponds

(4) Anoxic process: - This is the biological process in which microbes convert nitrate

nitrogen of waste water into nitrogen gas in the absence of oxygen . it is also

known as denitrification process.

9

Process According to microbial maintenance in the system

(1) Suspended growth process :- When the microorganisms are maintained as

suspension in the reactor by an appropriate mixing method , the process is

known as suspended growth process,

Following process use in suspended growth process

Activated sludge process

Extended aeration system

Aerated lagoons

Waste Stabilization ponds

Sequencing batch reactor

(2) Attached growth or fixed film process:- In this case , the microorganisms in

the reactor remain attached to some inert packing material or medium ,

Following process use in Attached growth process

Trickling filter

Rotating biological contactor

10

CHAPTER 2

DESIGN CALCULATION OF SEQUENCING BATCH REACTOR

PROCESS

2.1 Concept

11

A reactor or basin in which four steps viz. filling, aeration, settling (clarification) and

decanting for the biological treatment of waste water are carried out in a sequence is

known as sequencing batch reactor (SBR) when the activated sludge process is used for

treatment of waste water in SBR, it is known as SBR process.

Normally two or four basin are provided for aerobic biological treatment of waste water

by SBR process.

2.2 Mechanical Equipments

Typically bellow type of mechanical equipment eructed in SBR

2.2.1- Diffuser grid

The basins are usually designed completely to provide the diffuser system for aeration.

2.2.2- Air blower: - Air blower to supply the air

12

2.2.3 -Return Activated sludge pumps& surplus activated sludge pumps

Pumps for return and surplus activated sludge.

2.2.4-Decanter

Decanters use for Withdraw the clarified or settled effluent

13

2.3 process Description

the complete operation of SBR divided into a number of cycles that will be carried per

day in single reactor or basin , the duration of each cycle is 3-6 hours and each cycle

comprises of the following phase which are repeated.

Fill

Aeration

Settling

Decanting

The following operation are performed during these steps

The waste water is filled in the basin up to a predetermined operating level

The waste water is aerated by the diffuse aeration system as per designed

duration

After the aeration is completed, the biomass or MLVSS is allowed to

settle down by keeping the basin flow quiescent

After settling duration is over, the supernatant (clarified effluent) is

removed from the surface of basin using a decanter

14

Excess or surplus sludge is wasted during decanting of supernatant while

recycling of sludge is carried out during the aeration process.

Schematic diagram of a typical cycle of SBR Process

2.4 Design calculation

Treated water Flow– 20 MLD

Primary Influent parameter

BOD5 250 mg/L

COD 450 mg/L

TSS 320 mg/L

TKN 22 mg/L

TP 5/mg/L

Temp. 25 C

Desired treated effluent Para meter

BOD5 < 10 mg/L

COD < 50.0 mg/L

TSS < 10.0 mg/L

TKN <5.0 mg/L

TP <1.0 mg/L

15

Considered following design data

Filling & aeration period – 2.0 hr

Settling period – 0.5 hr

Decantation period -0.5 hr

Total cyclic time -3.0 hr

Total number of basin -4

No. of basin receiving the flow simultaneously- 2

No. of basin aerated simultaneously- 2

No. of basin decanted simultaneously- 2

MLSS in aeration tank – 4000 mg/L

MLVSS aeration tank –3200 mg/L

F/M ratio -0.12

a) Total volume of the Basin

V= flow (m3/d)* Bod (mg/L) / MLVSS *f/m

= 20,000 ((m3/d) X 200 (mg/L)

3200 (mg/L) X 0.12 (d−1)

= 10416.66 m3

b) No. of Basin – 4

Volume of each basin

= 10416.66

4

= 2604.16 m3 ~ 2700 m3

b) Providing depth - 6 m

c) Area of each basin

16

= Volume Depth

= 2604.16

6

= 434.02 m2

d) Providing length - 30 m

e) Width of basin - 434.02

30

14.46 ~ 15 m

f) Size of each Basin -15 X 30 X 6 ( 0.5 m free board )

g) HRT For The Basin

= V Q 4 X 2700

20,000

0.54 d

0.54 X 24

12.96 hr ~ 13 hrs

I) Design of Anoxi Zone (for removal of nitrogen (TKN) by Denitrification)

Flow rate of anoxic zone of each basin

V = Q X T

Q = V

T

Q = 2700

13

Q= 207.69 ~ 208 m3/hr

Providing recirculation ratio (Qr ¿ of 25% of flow rate

Flow rate to anoxic zone to each basin = Q + Qr

17

= 208 + (0.25 X 208) m3/hr

= 259 .25 ~ 260 m3/hr

Providing HRT 1 hrs

Volume of anoxic zone = Q + Qr X HRT

= 260 m3/hr X 1 hr

= 260 m3

Providing depth – 6 m

Providing length – 15 m

Width of anoxic zone -

= 260

6 X 15

= 2.88 ~ 3 m

Total volume provide for Anoxic zone

= 6 X 15 X 3 = 270 m3

J) Determination of O2 required at given flow condition

O2 For BOD removal

1.2 kg O2/ kg BOD

Inlet BOD- 250

Out let BOD – 10

BOD Removed – 240

Kg of BOD Removed

= BOD X flow

= 240 X 20 X106

106

= 4800 kg / d

Safety factor theoretical kg O2 required per kg of BOD – 10 %

= 1.2 X 110

18

100

= 1.32

Kg O2 required for BOD lode

= 1.32 X 4800

= 6336 kg/day

O2 For N Removal

Inlet Total kjeldhal nitrogen

( Ammonical –N + Organic N )

22 mg/ L

Out let Ammonical Nitrogen = 1mg/L

Out let nitrate nitrogen – 10 mg/L

NH 3-N Removed in day

22-1 = 21 mg/L

4.6 kg O2 / NH 3-N kg

Kg of NH 3-N Removed in day

= 20 X 21

= 420 kg /d

Kg O2 required for NH3-N removed

= 4.6 X 420 = 1932 kg /d

2.86 kg O2 released during denitrification

Assuming 75 % of nitrification occurs

NO3- N Generated

20 X 21 X 0.75

= 315 kg / d

Amount of NO3- N in treated water

20 X 10

= 200 kg / d

Quantity of nitrate – nitrogen that is denitrified

19

= 315 – 200

= 115 kg /d

2.86 kg O2 released during denitrification

= 115 X 2.86

= 328.9 kg / d

Total kg of O2 required /day

= 6336 + 1932

= 8268 kg / d

=8268-328.9 (O2 from denitrification)

= 7939.1 kg /d

Safety factor 10%

= 7939 X 110

100

= 8733.01 kg/d

k) Determination of Quantity of air required at standard condition

Total oxygen required (actual) O2 required AOR- 8733.01 kg/d

Total O2 required at standard condition, SOR, for the field condition is given by

equation:

SOR = AOR

( βC ' sw - C) / (C sw) X ƒ X α X 1.024(T−20)

β = salinity correction factor = 0.95

α = oxygen transfer correction factor =0.65

ƒ = fouling factor = 0.90

C ' sw = solubility of oxygen in tap water at 25 ℃ = 840 mg/L

20

C sw = solubility of oxygen in tap water at 20 ℃ = 9.17 mg/L

C = DO Concentration in aeration basin = 2.0 mg/L (Assumed)

T = Operating temperature in aeration basin = 25 ℃

SOR = 8733

0.95 X 8.40-2 X 0.65 X 0.90 X 1.024(25−20)

9.17

= 2079.85 kg/d

Standard oxygen transfer efficiency of diffuser per meter depth = 5.6 % / m

Liquid level of aeration basin = 6 m Height at which diffuser are kept = 0.4 m Effective aeration depth = 6-0.4= 5.6 m SOTE ( Standard oxygen transfer efficiency ) the above aeration depth

= 5.6 X 5.6 100 = 31.36

Fraction of O2 in air = 23.2 % Specific gravity of air = 1.204 Air required at field condition per basin (consider 4 basin )

= 8733 4 = 2183 kg = 2183 X 100 X 100

21

31.36 X 23.2 X 1.204 = 24920.87 NM 3/ d/ basin

Hours of aeration time per basin per day= 12 hrs /d/basin Air required per hours per basin

= 24920.87

12

= 2076.73 NM 3 /hr/basin Number of operating blower any time in

Basin -2

2076.73

2

= 1038 NM 3/hrl) Calculation for air blower

Assume 70 % of capacity of at standards condition and blowers are capable 1.5 kg per KWH at standard condition.

So power required = 2183

0.7 X 1.5

= 2079.04 kWh

= 2785.92 hp ∵ 1 kilowatt = 1.34 hp

M) Sludge generates & wasted calculation

Sludge generated – 0.80 kg/kg BOD Kg of BOD removed in a day – 4800 kg /d sludge generated per day

0.8 X 4800 = 3840 kg/d Number of basin -4

3840 4 = 960 kg/d/basin

Consistency of sludge solids – 0.8 % Specific Gravity of sludge - 1.5 Density of water - 1000 kg/M 3

Total volume of sludge wasted

22

3840 X 100 1000 X 1.5 X 0.8

= 320 M 3/d

Sludge wasted per basin

320/ 4 = 80 M 3/d

Number of cyclic per day per basin – 8

Sludge wasted per cycle per basin

960 /8 = 120 kg /d

80/8 = 10 M 3/d

n) Pump capacity

Assuming pump running period per cycle – 15 min

Pump capacity

Volume X 60 Running time

= 10 X 60

15 = 40 M 3/hr

Provide 2 nos (1 working + 1 stand by) each capacity 45 M 3/hr

CHAPTER -3

23

CONCLUSION

3.1 Conclusion

24

Removal of suspended solid & colloidal suspension is achieved by

physicochemical treatment whereas reduction of soluble organic solid is achieved

by microbial biosorption and their further degradation and stabilization by

microbes

Biological process classified according to operational condition are : aerobic,

anaerobic , facultative and anoxic process

Biological process classified according to microbial maintenance in the system

are: suspended growth and attached growth processes

The quantity of air and oxygen required for waste stabilization can be provided by

surface or diffuse aeration system

The settling characteristic of activated sludge or MLSS is measured in term of

sludge volume index . it is the ratio of volume of sludge settled after 30 minutes

of settling in a one litre cone to the MLSS concentration of a wastewater sample

Biological treatment carried out by several biological treatment units

The Sequencing batch Reactor (SBR) is a fill and draw Activated sludge system

All steps of conventional process take place in sequences one by one. In the

system almost process of waste water treatment carried out in reactor such as-

Equalization, aeration and clarification.

SBR process occurs in batch process so does not require secondary clarifier

CHAPTER- 4

25

REFERENCES

4.1 References

26

1. Dr. B.C. Punmia , Arun Kumar jain , Ashok Kumar Jain : Waste

water Engineering , Laxmi publication (p) ltd ,volume -I

(2011 edition)

2. Santosh kumar Garg : water supply Engineering , khanna Publishers,

Volume- I,II,( 16th revised 2012 edition )

3. G.L. Karia , R.A. Christian : PHI Learning Private Limited

(2013 edition)

4. Metcalf & Eddy , Inc. : Waste water Engineering Treatment ,Disposal

& Reuse ,Tata McGraw Hill New Dehli ( 4th 2003 edition)