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Waste Water Treatment

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  • 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.

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