This document discusses the process of sewage treatment. It begins by defining sewage and its characteristics such as being mostly water with small amounts of waste matter. It then outlines the various steps of sewage treatment including preliminary treatment using screens and grit chambers, primary treatment using sedimentation to remove solids, and secondary treatment using activated sludge processes with microorganisms to reduce organic content before final treatments like anaerobic digestion and chlorination. Flow diagrams and tables with treatment details are provided.

1. SEWAGE TREATMENT:
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By-
VIJAY KARHALE
SHANKAR DHADAM
AKASHAY ZENDE
SHAILESH BANGAR
GAJANAN GUTTHE

2. Sewage:
It is an domestic sewage comprises spent water from kitchens ,bathrooms,
lavatories etc.
Sewage is nearly 99.9% water and 0.1% waste matter.
It is this small amount of effluents that bring about grossly polluted
conditions.
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3. Sewage Characteristics
Physical Characteristics
Chemical Characteristics
Biological Characteristics
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4. Sewage Characteristics Table:
Item Range Of Value Contributed in Waste
Water(mg/l)
BOD5 170-250
COD (1.6-1.9) BOD5
Total Solids 600-800
Suspended Solids 400-600
Grit 20-55
Oil and Grease 60-120
Phosphorus 03-15
Nitrogen 40-80
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5. Pollutional Effects Of Sewage
The Following materials can cause pollution
1) Organic Matter
2) Suspended Solids
3) Oils and Greases
4) Micro Organisms
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6. Treatment Of Sewage
Preliminary Treatment
Primary Treatment
Secondary Treatment
Tertiary Treatment
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7. Preliminary Treatment
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It consists of Screens and Grit Chambers units.
1) Screens
Coarse Screens(50mm to 75mm)
Medium Screens(20mm to 50mm)
Fine Screens(Less than 20mm)
2) Grit Chambers
It removes sand, gravel, silt, cinders, broken glass, inorganic solids,
eggshells, bone chips, etc.

8. Primary Treatment
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The tanks are used to settle sludge while grease and oils rise to the surface
and are skimmed off.
Fig. Primary Sedimentation tank.

9. Primary Sedimentation Tank:
BOD removal is 30 to 35 %
Suspended solids removal 50 to 60 %
Detention Time 2 to 2.5 hours
Average Over flow Rate is 35 to 50 m3/m2/D
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10. Secondary Treatment
It consists of Activated sludge process and Secondary Sedimentation.
Activated sludge process:
It is an aerobic process, in which oxygen is supplied from outside.
In this process microorganism convert or reduce organic content of sewage.
1) Oxidation:
COHNP + O2 + Microorganism CO2+ H2O + NH3 + End Products +
(Organic Matter) +Energy
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11. Activated Sludge Process
2) Synthesis:
COHNP + O2 C5H7O2N
(Organic Matter) (Bacteria)
3) Auto Oxidation:
C5H7O2N + O2 CO2 + H2O + NH3 + End Products + Energy
(Bacteria)
Design Parameters:
f/m=0.2 to 0.4, MLSS= 1500-3000mg/l, HRT= 4-8 Hours, Qr/Q=0.25-0.5,
O2 required= 1 Kg/Kg Of BOD destroyed, Efficiency= 85-92%
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12. Activated Sludge Process
12 Fig:- Activated Sludge Process

13. Anaerobic Digester
Anaerobic digestion is a collection of processes by which microorganism
break down organic material in the absence of oxygen.
In this process there are two processes as follows:
1) Standard rate digester
2) High rate digester
Following activities takes place in anaerobic digester
1) Hydrolysis
2) Acid Formation
3) Alkaline Fermentation
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14. Standard and high rate Anaerobic Process
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15. Sludge Drying Bed
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Sludge is dewatered to reduce the volumes so that it is easy for
transportation to disposal site.

16. Chlorination
The purpose of chlorination in the treatment of waste water is to
substantially reduce the number of microorganisms in the water to be
discharged back into the environment for the later use of drinking,
bathing, irrigation, etc.
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17. Flow Diagram For Sewage Treatment
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18. References:
Sewage manual
http://nzic.org.nz/ChemProcesses
http://water.worldbank.org/shw-resource-guide/infrastructure/menu-technical-
options/wastewater-treatment
http://www.fao.org/docrep/t0551e/t0551e05.htm
http://www.actew.com.au/Water%20and%20Sewerage%20Systems/ACT
%20Sewerage%20System/What%20is%20sewage/Sewage%20Treatment%
20Process.aspx
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