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Module 2

Module 2. Wastewater Treatment Technologies. I Flow Sheets of Water Treatment. Sample 1 - Sample 7. Indian Standards for Drinking Water Quality. Unit Operations and Processes Screening Aeration Sedimentation Coagulation Flocculation Filtration (Rapid sand/ Slow sand) Water softening

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Module 2

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  1. Module 2 • Wastewater Treatment Technologies

  2. I Flow Sheets of Water Treatment

  3. Sample 1 - Sample 7

  4. Indian Standards for Drinking Water Quality

  5. Unit Operations and Processes • Screening • Aeration • Sedimentation • Coagulation • Flocculation • Filtration (Rapid sand/ Slow sand) • Water softening • Disinfection

  6. Unit Operations and Processes • Equalisation • Neutralisation • Grit removal • Flotation • Chemical ppn • Ion exchange • Adsorption • Biological processes (aerobic / anaerobic) • Chemical/ advanced oxidation processes • Wet air oxidation • Filtration processes (RO/UF/NF)

  7. Factors considered for evaluating & selecting Unit Operations & Processes • Process applicability • Applicable flow range • Applicable flow variation • Influent ww characteristics • Inhibiting constituents • Climatic constraints • Process sizing based on reaction kinetics • Process sizing based on mass transfer rates

  8. Factors considered for evaluating & selecting Unit Operations & Processes 9 performance • treatment residuals • Sludge processing • Envi constraints • Chemical requirements • Energy requirements • Other resource requirements • Personnel requirements • O&M requirements • Ancillary processes • Reliability • Complexity • Compatibility • Adaptability • Economic life cycle analysis • Land availability

  9. (a) Surface Water Chlorination Storage Turbidity <10 NTU No odour, No colour

  10. (b) Ground Water Chlorination Turbidity <10 NTU No odour, No colour

  11. (c) Surface Water Plain Sedimentation Slow sand filtration Chlorination Turbidity >50 NTU Sufficient area available

  12. (d) Surface Water Highly polluted water with algae and microorganisms) Chlorination (pre) sedimentation Aeration Coagulation Flocculation Chlorination (Post) Rapid sand Filtration

  13. (e) Water with excessive hardness Softening Rapid Sand Filtration Chlorination (Post) Excessive Hardness

  14. II Flow Sheets of Wastewater Treatment

  15. Effluent Disposal and utilisation • Water body, land ( disposal ) • Reclamation ( industrial reuse ) • Reuse in agriculture, horticulture • GW recharge

  16. SOLIDS( Raw sewage=99.9% water+0.1% solids) • Solids = 50% suspended + 50% dissolved • Solids = 70% organic + 30% inorganic

  17. Sewage characteristics (Major Pollutants) • Suspended solids • Biodegradable organics • Pathogens • Nutrients • Dissolved inorganic solids • Waste + Oxygen Oxidised waste + New bacterias bacteria

  18. Typical composition of domestic waste water

  19. Indian Standards Related to Disposal of Treated Effluents

  20. Basic design considerations • 1.Degree of treatment (Water Act1974) • 2.Design period (30 years) • 3.Population (future population) • 4.Sewage Flows (Peak, Average, Min) • 5.Sewage characteristics

  21. Basic design considerations (cont.) • 6.Effect of industrial wastes • 7.Effluent disposal and utilization • 8.Unit operations & processes for treatment • 9.Design of process flow sheets for treatment • 10. Choice of processes

  22. Design of process flow sheets for treatment

  23. Unit Operations and Processes • Physical (screening, grit removal & sedimentation) • Chemical (Coagulation, flocculation) • Biological [suspended / attached growth, aerobic / anaerobic]

  24. Typical wastewater treatment process Pre-treatment Eg: physical/chemical treatment, solids separation Treatment Biological treatment Eg : aerobic/ anaerobic suspended/attached batch/continuous Post-treatment Eg:filtration, adsorption Discharge of clean effluent BIOREACTOR

  25. Aerobic Biological Treatment Processes • Suspended Growth • Activated sludge • Oxidation ditches/ponds • Aerated lagoons, stabilization ponds • Attached Growth • Trickling filters • Rotating Biological Contactors (RBCs)

  26. Process SS(%) BOD (%) Total coliform (%) • Primary Treatment (sedimentation ) 45-60 30-45 40-60 2. Chemical Treatment 60-80 45-65 60-90 3.Secondary Treatment • Standard trickling filters • High rate trickling filters a. Single stage b. Two stage • Activated sludge plants • a.Stabilisation ponds (Single Cell) b. Stabilisation ponds (Two cells) 75-85 75-85 90-95 85-90 80-90 90-95 70-90 75-80 90-95 85-95 90-95 95-97 80-90 80-90 90-60 90-96 90-95 95-98 CHOICE OF PROCESSES

  27. Activated Sludge • Process in which a mixture of wastewater & microorganisms is agitated & aerated • Leads to oxidation of dissolved organics • After oxidation, sludge is separated from wastewater • DT = approximately 6 - 8 hr

  28. Trickling Filters • Rotating distribution arm sprays primary effluent over circular bed of rock or other coarse media. • Air circulates in pores between rocks. • “Biofilm” develops on rocks and micro-organisms degrade wastes as they flow past

  29. Trickling Filters Filter Material

  30. RAW TREATED GRIT CHAMBER BIOLOGICAL REACTOR SCREEN S.S.T P.S.T WASTE WATER WASTE WATER RECYCLED SLUDGE ANAEROBIC DIGESTOR TO SLUDGE HANDLING AND DISPOSAL SUPERNATANT DIGESTED SLUDGE (CH4 CO2) PROCESS FLOWSHEET OF CONVENTIONAL DOMESTIC WASTEWATER TREATMENT

  31. RAW TREATED OXIDATION DITCH SCREEN S.S.T WASTE WATER WASTEWATER RECYCLED SLUDGE EXCESS SLUDGE DRIED SLUDGE PROCESS FLOWSHEET INCORPORATING OXIDATION DITCH SLUDGE DRYING

  32. RAW TREATED AERATED LAGOON SCREEN WASTEWATER WASTEWATER PROCESS FLOWSHEET EMPLOYING AERATED LAGOON

  33. RAW TREATED WASTE STABILISATION POND SCREEN WASTE WATER WASTE WATER PROCESS FLOWSHEET USING WASTE STABILISATION POND

  34. RAW GRIT CHAMBER SCREEN ANAEROBIC REACTOR SETTLING WASTE WATER TREATED WASTE WATER PROCESS FLOWSHEET EMPLOYING ANAEROBIC TREATMENT DEVICES

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