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.