Wastewater treatment involves multiple processes to remove contaminants from water and make it suitable for discharge. It begins with preliminary treatment to remove large solids through coarse screening and grit removal. Primary treatment uses sedimentation to remove settleable solids. Secondary treatment uses bacteria and protozoa to break down organic matter biologically. Tertiary treatment provides disinfection and additional nutrient removal. Sludge treatment involves anaerobic digestion to reduce solids volume, composting, and dewatering the sludge for use as fertilizer.

1. Wastewater Treatment
BY SUSHIL KUMAR

2. What is wastewater ?
 Water that has been utilized in some capacity that
negatively impacts the quality of water.
 Sewage is a subset of wastewater that is contaminated
with feces or urines.

3. Where does wastewater come
from?
 Residences (kitchen, bathroom)
 Rainfall, Highway drainage
 Industrial institution

4. Wastewater Constituents
 Water (more than 95%)
 Pathogens (bacteria, viruses and parasitic worms)
 Non-pathogenic bacteria
 Organic particles(feces, hair, food, paper fiber, plant materials)
 Soluble organic (urea, protein, sugar ,drug)
 Inorganic particles (sand, grit, metals, ceramics etc.)
 Soluble inorganic (ammonia, hydrogen sulfide, thiosulfates etc.)
 Toxins (pesticides, poisons, herbicides etc.)

5. What is wastewater treatment?
 process of removing contaminants from wastewater,
both runoff and domestic and making it suitable to
discharge back into the environment.
 Municipal wastewater treatment
Industrial wastewater treatment

6. How can we say water is pure?
 Physically
a) Total solid (tested by boiling water)
b) Odors
c) Colors
d) Turbidity
 Chemically
a. Biological oxygen demand (BOD)
b. Chemical oxygen demand (COD)

7. Methods involved in wastewater
treatment
 Wastewater Treatment
 Mechanical (Physical) Treatment
a) Preliminary
b) Primary
 Secondary (Biological) Treatment
 Tertiary (Chemical) Treatment
 Sludge Treatment

8. Preliminary Treatment
 The objective of preliminary treatment is the removal of
coarse solids and other large materials often found in raw
wastewater.
 Removal of these materials is necessary to enhance the
operation and maintenance of subsequent treatment unit.
 Coarse Screening
 Grit Removal

9. Coarse Screening
 Removal of large non biodegradable and floating solids
(e.g. rags, clothes, woods, plastics, papers etc.)

10. Grit Removal
 Grit particles which are smaller than the aperture of the
coarse screen will pass through and may cause
abrasive problems to pipes and pumps.
 In grit removal process, velocity is so controlled that grit
may settle but most of the organics are retained in
suspension.

11. Primary Treatment
 Objective is the removal of settelable organic and
inorganic solids by Sedimentation, and the removal of
the material that will float (scum) by skimming.
 Around 25-50% of the incoming BODs, 50-70% of the
total suspended solids and 65% of oil and grease are
removed during primary treatment.

12. Secondary Treatment
 Biological Treatment
• Secondary treatment is designed to substantially degrade the biological content of the
sewage which are derived from the human waste, food waste, soaps and detergents etc.
• Aerobic bacteria and protozoa consume biodegradable soluble organic contaminants
(e.g. sugar, fats, short chain carbon molecules etc.) and binds much of the less soluble
fractions into floc.
 Secondary sedimentation
• Microorganisms must be separated from the treated water by sedimentation to produce
clarified secondary effluent.
• Biological floc is settled out in secondary clarifier and the secondary sludge is then sent to
sludge treatment unit.

13. Nutrients Removal
 Wastewater may contain high level of nutrients (N or P
compounds) which excessive release to environment
may cause eutrophication.
 Overgrowth of weeds, algae, blue-green algae
(cyanobacteria).
 DE oxygenation
 Toxins produced by some algae may contaminate
drinking water supply.

14. Nitrogen Removal
 Nitrification
• Biological oxidation of nitrogen from ammonia to nitrate.
I. Ammonia to nitrite using Nitrosomonas
II. Nitrite to Nitrate using Nitrobacter ssp.
 DE nitrification (anoxic condition)
• Nitrate is converted into nitrogen gas and released into air.

15. Phosphorus Removal
 Biologically
• Using Polyphosphate Accumulating Organism (PAOs)
• The process is called “Enhanced biological phosphorus
removal”.
 By chemical precipitation
• Using salts of irons (e.g. ferric chloride) or aluminium
(e.g. alum) or lime.

16. Tertiary Treatment
 Purpose is to provide a final treatment stage to further improve the
effluent quality before it is discharged to the receiving environment.
 Nutrients removal
 Disinfection
• to reduce the number of microorganisms
 Chlorination
 Ultraviolet radiation
 Ozone
 Odor control

17. Odor Control
 Odor emitted by wastewater treatment are typically an
indication of anaerobic or septic condition.
 Generally arises due to hydrogen sulfide.
 Controlled by adding iron salts or hydrogen peroxide or
calcium nitrate.

18. Sludge Treatment
 This process describes the management and disposal of
primary and secondary sludge.
 processes involved are
 Anaerobic digestion
 Composting
 De watering

19. Anaerobic Digestion
 Anaerobic bacteria acts on sludge and produces large
amount of waste solids and biogas ( high concentration
of methane).
 Methane can be used to generate electricity and run
few pumps.
 Solid waste (containing water) is sent for composting.

20. Composting
 An aerobic process that involves mixing of wastewater
solids with sources of carbons such as sawdust, straw or
woodchips.
 Aerobic bacteria digests both wastewater solids and
carbon source and produce large amount of heat.
 Resultant solid is then sent for dewatering.

21. DeWatering
 Water is removed from solid waste for volume reduction.
 Using drying beds
 Mechanically filtering often through cloth screens.
 Centrifugation.
The sludge is now ready to be used off sites as fertilizers.