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)