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DISPOSAL OF SOLID WASTES

DISPOSAL OF SOLID WASTES. Dr. Pracheth R. Outline. Importance Solid waste Sources of refuse Storage Collection Methods of disposal. Importance. Solid wastes. Garbage (food wastes) Rubbish (paper, plastics, wood, metal, glass) Demolition products (bricks, pipes)

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DISPOSAL OF SOLID WASTES

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  1. DISPOSAL OF SOLID WASTES Dr. Pracheth R.

  2. Outline • Importance • Solid waste • Sources of refuse • Storage • Collection • Methods of disposal

  3. Importance

  4. Solid wastes • Garbage (food wastes) • Rubbish (paper, plastics, wood, metal, glass) • Demolition products (bricks, pipes) • Sewage treatment residue • Dead animals, manure

  5. Health hazard • Decomposes, fly breeding • Attracts rodents • Pathogens • Water, soil pollution • Unsightly appearance, nuisance- bad odours

  6. Storage • First consideration • Steel dust bin with close fitting cover • Paper sack

  7. Storage • Public bins : • Large number of people • Not covered • Concrete platform : 2-3 inches above ground level

  8. Collection • House- house: best • Dump – public bins

  9. Methods of disposal • Dumping • Controlled tipping • Incineration • Composting • Manure pits • Burial

  10. Dumping • Refuse dumped in low lying areas • Bacterial action- humus • Drawbacks: • Flies, rodents • Nuisance • Loose waste : wind • Water pollution

  11. Controlled tipping (Sanitary landfill) • Most satisfactory : land available • Material placed in trench : covered with earth- day

  12. Trench method • Level ground available • Covered with earth

  13. Ramp method • Sloping

  14. Area method • For filling land, depressions, clay pits • Refuse: in uniform layers • Each layer sealed with mud cover • Sealing: prevents fly, rodent, nuisance

  15. Continued….

  16. Mechanism • Temperature : rises 60 degree C within 7 days : kills • 2-3 weeks to cool down • Complete decomposition: 4-6 months

  17. Incineration • Land unavailable • Hospital refuse • Industrialized countries • India : fine ash • Manure

  18. Composting • Combined disposal of refuse and night soil or sludge • Organic matter -bacterial action : “ Compost” • CO2, H2O, heat • Compost : few pathogens, good manure

  19. Bangalore Method ( Hot fermentation) • Indian Council of Agricultural Research • Trenches : 90 cm deep • Depths >90 cm : slow decomposition • Location: not less than 800 m from city limits

  20. Composting procedure • Layer of refuse : 15 cm thick: at bottom of trench • Over this, night soil : 5cm thick • Alternate layers of refuse and night soil :till heap rises to 30 cm above ground level • Covered -earth

  21. Continued… • Within 7 days : heat generated in compost mass by bacterial action • Heat stays : 2-3 weeks- decomposes refuse and night soil , destroys pathogens • At end of 4-6 months : decomposition is complete , manure formed

  22. Mechanical composting ( Aerobic method) • Compost manufactured on large scale • Refuse first cleared : rags, bones, metal, glass, items • Pulverized : reduce size of particles < 2inches • Then mixed with sewage, sludge/ night soil in a rotating machine, incubated

  23. Continued… • Completed in 4-6 weeks • Developed countries : Holland, Germany • India : Delhi, Nagpur, Hyderabad, Chennai Pune

  24. Manure pits • Rural areas • Thrown around house : soil pollution • Waste: dumped, covered with earth after each days dumping • Two such pits needed : one is close, other use • 5 months : converted to manure

  25. Diagram – manure pit

  26. Burial • Small camps • Trench • At end of each day: refuse covered with earth • When level -40 cm from ground level : filled with earth and compacted, new trench dug out • 4-6 months : used in fields.

  27. Public education • Pamphlets, newspapers, films

  28. Summary

  29. Sewage treatment • Sewage • Sullage • Health aspects • Composition • Aim of purification • Modern sewage treatment plant • Other methods of sewage treatment

  30. Sewage • Waste water- community – solid and liquid excreta: from houses, street, factories, industries Sullage • Waste water- no human excreta • Kitchens, bathrooms

  31. Health aspects • Nuisance, unpleasant odour • Breeding- flies, mosquitoes • Soil pollution, water supply • Food contamination

  32. Aim of purification • Aim: stabilize organic matter- disposed off safely • Convert sewage- EFFLUENT- disposed off-rivers, sea, lands

  33. Decomposition of organic matter • Aerobic process: • Most efficient- reduce organic matter • Requires continuous supply of O2 • Organic matter broken: CO2, water, ammonia, nitrates, nitrites by bacteria action

  34. Continued…. • Anaerobic process: • Sewage highly concentrated, plenty solids • Methane, ammonia, CO2, H2 • Slower, more complex

  35. MODERN SEWAGE TREATMENT PLANT • Purification: action of aerobic, anaerobic bacteria • Primary: solids separated- screening, sedimentation, anaerobic digestion • Secondary: aerobic oxidation

  36. Primary treatment • Screening • Grit chamber • Primary sedimentation

  37. Screening • Pass through metal screen • Intercepts floating objects- wood pieces, rags, garbage mass, dead animals • Prevent obstruction • Vertical bars • Screenings removed : disposed- burial

  38. Grit chamber • Long narrow, detention: 30 s- 1min • Allow settlement- heavier solids • Sewage: pass • Grit: collects at bottom, periodically removed; disposed- dumping

  39. Primary sedimentation • Primary sedimentation tank • Sewage- slowly, 6-8 hrs • Purification: sedimentation- suspended matter • 50-70%: settle down- gravity • 30-40% organisms- reduced

  40. Continued…. • Organic matter settle down: SLUDGE- mechanically removed, without disturbing • Fat and grease- rise to surface : SCUM: removed time to time , disposed off

  41. Secondary treatment • Effluent- contains: organic matter, living organisms • High demand for O2: pollution • Trickling filter method • Activated sludge process

  42. Trickling filter method

  43. Secondary sedimentation

  44. Secondary sedimentation • Oxidized sewage from trickling filter • AERATED/ ACTIVATED sludge- fully aerated • Valuable manure • Part: pumped back to aeration tank • Rest: sludge digestion for treatment, disposal

  45. Activated sludge process • Aeration tank • Aeration- 6- 8 hrs • Organic matter- oxidized • Let into secondary sedimentation tank

  46. Sludge digestion • Digestion: • Incubated , volume- reduced • 3-4 weeks- sludge digested • Manure • Sludge digestion tanks • Sea disposal • Land: composting with town refuse

  47. Effluent disposal • By dilution: • Water sources- rivers, streams- disposal by dilution • Effluent dissolved in water, impurities oxidized • Disposal on land: irrigation purpose

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