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Why wastewater treatment? Policy on Wastewater Separation Types of sanitation systems

IMPROVED RURAL SANITATION CONCEPTS By Dhanesh Gunatilleke SPECIALIST (SEWARAGE DESIGNS) NWSDB 1 st April 2014. Why wastewater treatment? Policy on Wastewater Separation Types of sanitation systems Design of onsite sanitation systems in compliance to SLS 745 Part II:2009

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Why wastewater treatment? Policy on Wastewater Separation Types of sanitation systems

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  1. IMPROVED RURAL SANITATION CONCEPTSByDhanesh GunatillekeSPECIALIST (SEWARAGE DESIGNS)NWSDB1st April 2014

  2. Why wastewater treatment? Policy on Wastewater Separation Types of sanitation systems Design of onsite sanitation systems in compliance to SLS 745 Part II:2009 Further Treatment Options Presentation Outline 2

  3. 1 WHY WASTEWATER TREATMENT ? • Protect the environment from; • high loads of suspended solids & organic matter • eutrophication & groundwater pollution • Substantial load of hazadous and non biodegradable compounds • Serious contamination with microorganisms • …in order to • establish/maintain healthy environment for flora & fauna • allow mankind to use water resources for different purposes • prevent transmission of waterborne diseases/improve public health

  4. Definition of Safe Sanitation • Collection, Transport, Treatment & Disposal or reuse of human excreta, domestic wastewater and solid waste, and associated hygiene promotion Ref: water supply and sanitation collaborative council

  5. Pollution from human beings • 45-60 g BOD/person/day • 8- 14 g N/person/day • 0.6-2.5 g P/person/day • Virus • Medical residues

  6. Eutrophication & it’s impacts • Increase in rate of supply of organic matter to an ecosystem resulting nutrient built up (N, P) • Massive algae growth, anaerobic conditions, oxygen depletion • Changers in the structure and functioning of the lake and marine ecosystem • Reduction in biodiversity, fish and shellfish harvesting • Increase risk of poisoning by algal toxins

  7. DO Sag Curve Wastewater 7.83mg/l at 280C DOsat Distance (Km)

  8. Health Problems • In some areas in the developing world, 75 -80% of human illness is related to water and water pollution • Discharge of wastewater represents the greatest risk for pollution of potable water

  9. Ref: A.J. Arcivala

  10. Ref: A.J. Arcivala

  11. Ref: Metcalf & Eddy

  12. 2. Wastewater Separation Rainwater Harvesting/Surface Drainage System Rainwater Onsite/Sewerage Reticulation System Grease Interceptor Restaurants WW of Domestic Nature Separate them in concentrated form in separate plumbing system Treat/Dispose as Hazardous WW Hazardous WW

  13. X-Ray Processing AgCl+NaOH AgO • Dental Wastewater (Amalgam) Ag, Pb, Sn • Radioactive Iodine Treatment Mutagenic • Full Blood Count Test (Cn) • Blood Urea Test • Total Protein Test • Albumin Test • Liver Functional Test • Cholesterol Test • Sugar Test • Skin Preparation (Salicylic, Benzoic Acid, yellow parafin) • Bottle Washing (Antibiotics) • Molecular Biology Research • (Ethidium BromideMutagenic) • Formalin (preservative for biological specimens)

  14. CONCEPT FOR HOSPITAL Storm Water/ Rain Water To the Existing Surface Drainage System Kitchen WW Sewerage System Grease Trap Other WW of Domestic Nature Pumping Station Existing Oxidation Ditch & Settling tank will be converted to a Floting wetland Retention (As per CEA/AEA Recommendation) Effluent from Radiation Treatment (Iodine) Rat/ Mora WWTP Disposal as Hazadous Wastewater (GeoCycle) • X- Ray Processing • (Dark Room) • Dental WW • Laboratory WW Collection to Containers in concentrated form with separate plumbing system

  15. HazardousWW Disposal-Preconditioning

  16. Ref: National Institute of Minamata Disease

  17. Ref: National Institute of Minamata Disease

  18. Ref: National Institute of Minamata Disease

  19. 3. Types of Sanitation Systems • On site sanitation systems (>90%) • Septic tank associated effluent disposal systems • Off Site Sanitation Systems (>2.5%) • Wastewater collection, treatment & Disposal • Decentralized System

  20. How it Works PRODUCTION PRE TREATMENT DISPOSAL EVAPOTRANSPIRATION Drainage field GREASE TRAP SOIL ABSORBTION SEPTIC TANK PURIFICATION Unsaturated Zone GROUND WATER WATER TABLE Saturated Zone Schematic cross-section through a conventional septic tank soil disposal system for on-site disposal and treatment of domestic liquid waste

  21. Onsite Sanitation Systems SIMPLE PIT LATRINE Manual 1:Latrine Construction Technical Manual Series on Rural Water Supply & Sanitation NORAD-Helvetas Sri Lanka 29

  22. VENTILATED IMPROVED PIT LATRINE Manual 1:Latrine Construction Technical Manual Series on Rural Water Supply & Sanitation NORAD-Helvetas Sri Lanka 30

  23. On Site Sanitation WATER SEAL POUR – FLUSH LATRINE (Off-set Pit Type) Manual 1:Latrine Construction Technical Manual Series on Rural Water Supply & Sanitation NORAD-Helvetas Sri Lanka 31

  24. DRY COMPOST LATRINES • Environmentally friendly • Designed to keep the faeces separate from the urine and water used for anal cleansing • Is usually an elevated construction • Urine/water drained into an evaporative plant bed or a cultivation plot • To eliminate bad odour and nuisance from flies a handful of ash, lime or soil has to be sprayed into the pit Manual 1:Latrine Construction Technical Manual Series on Rural Water Supply & Sanitation NORAD-Helvetas Sri Lanka 32

  25. ECOSAN-BANGALIDESH/TAMIL NADU 33

  26. Onsite Sanitation Systems SEPTIC TANK / SOKAGE PITS/SOKAGE TRENCES Manual 1:Latrine Construction Technical Manual Series on Rural Water Supply & Sanitation NORAD-Helvetas Sri Lanka 34

  27. GREAZE INTERCEPTOR

  28. Service Stations • Primary treatment by Grease Interceptors • Subsequent Pre treatment by • Coagulation • Flocculation • Sedimentation • Disposal of Oil • As furnace oil Muthugala Service Station- Kurunegala

  29. Nippon Steel Cor.

  30. 38 Frazer Thomas-NZ

  31. Frazer Thomas-NZ 39

  32. BIO TOILET-JAPAN 40

  33. Problems in on site systems? Faulty design & construction of septic tanks Inadequate water depth for solid separation Failure in construction/water tightness Faulty design of soakage arrangements Seasonal high ground water table Presence of non favorable soils Presence of shallow rock Prone for flooding Overloading 41

  34. 4. Treatment Options SLS 745:Part I: 2004 Part I- Small systems disposing to ground SLS 745:Part II: 2009 Part II-Systems Disposing To Surface, Systems For On-site Effluent Reuse And Larger Systems Disposing To Ground 42

  35. SEPTIC TANK Inspection port Inspection port 150mm 150mm To further treatment 750mm minimum(internal dimension) INLET Access openings 500mm min. PLAN Vent pipe Access openings Inspection port dia . 25mm min. 500mm min. 150mm Dia.100mm Dia.100mm min. min. Free board Opening To further treatment INLET 200mm min. . 25mm min 50mm min. 300mm min. Liquid level Min. 20% of liquid depth Partition Opening . 100mm min First compartment approx. 2/3 length Second compartment approx. 1/3 length Total length between 2 – 4 times width SECTION Ref: SLS745 Part II 43

  36. SEPTIC TANKS Design Requirements SLS 745:Part I: 2004 SLS 745:Part II: 2009 Main functions Free board Vent pipe & cowl Access Commissioning Desludging 44

  37. DESIGN CRITERIA The Design and Construction of Septic Tank and Associated Effluent Disposal Systems (SLS 745 Part I : 2004) Design for All Wastewater No of members in a family = 5 Per capita Water Consumption = 140 liters/person/day Per Capita Wastewater Flow = 140 * 0.8 liters/person/day = 112 Average daily WW flow Q = 112 * 5 Q = 0.56 m3/day Septic Tank Assume initial BOD = 200 mg/l Assume reduction in BOD = 55% Minimum depth of septic tank = 1m Minimum width of Septic Tank = 0.75m Length to Width Ratio = 2 to 4 45

  38. SEPTIC TANK DESIGN FOR 5 PERSONS (DE-SLUDG PERIOD 5 YEARS) 1.1) Volume required for settling, Vs (All Waste) Vs = ts.Q Time required for settling ts = (1.5-0.3 log Q) days 1.58 = days Should be > 0.2 d OK Vs 0.88 = m3 1.2) Volume required for sludge digestion Vd (All Waste) Vd = qs. Td. P Volume of fresh sludge per person qs 0.001 = m3/day (for all wastewater) days Time required for sludge digestion td = (for an ambient Temperature of 20 0C) 33 Population equivalent for all wastewater p = Q(m3/day) / 0.2(m3/p/day) 2.8 = Vd 0.092 = m3 td =1853T-1.25 46

  39. 1.3) Volume required for sludge storage Vst (All Waste) Vst = r.p.n Volume of digested sludge per person per year for all wastewater r = 0.04 m3/year Desludging interval>1 n = 5 year Vst = 0.56 m3 1.4) Volume required for scum storage = 0.5 Vst Volume required for scum storage 1.5)Total Volume required for septic tank = Vs+Vd+1.5*Vst m3 V = 1.81 m3 ( 1m3 < V < 12m3 ) Take Depth, H = 1 m ( Minimum Depth 1m) Then, Surface Area A = 1.81 m2 Assume width, W = 0.75 m Then Length L = 2.42 m L/W = 3.23 ( 2<L/W<4 ) Hence ok Assume rate of BOD removal in septic tank = 55% BOD of effluent = 90 mg/l 47

  40. SIZING OF SEPTIC TANKS 48

  41. Sludge Judge Sludge judge 49

  42. SOKAGE PITS Soakage pits • Soak septic tank effluent • Effluent get treated before reaching GW Applicability • GWT below 2.5m (seasonal fluctuation) • Soil percolation rate between 25mm/h to 125mm/h Location • At least 18m away from nearest well/drinking water source • At least 5m away from the nearest building

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