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SOLID WASTE DISPOSAL

SOLID WASTE DISPOSAL. Dr Navya N Assistant Professor Department of Community Medicine Yenepoya Medical College. INTRODUCTION. Term “solid waste” includes- garbage (food wastes) -rubbish (paper, plastics, wood, metal, throw

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SOLID WASTE DISPOSAL

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  1. SOLID WASTE DISPOSAL Dr Navya N Assistant Professor Department of Community Medicine Yenepoya Medical College

  2. INTRODUCTION • Term “solid waste” includes- garbage (food wastes) -rubbish (paper, plastics, wood, metal, throw away containers, glass - demolition products( bricks, masonary, pipes) - sewage treatment residue (sludge and solids from the coarse screening of domestic sewage) - dead animals -manure - other discarded material

  3. HEALTH HAZARDS • Solid waste if allowed to accumulate , is a health hazard : • It decomposes and favours fly breeding • It attracts rodents and vermin • Pathogens in the solid waste may be conveyed back to man’s food through flies and dust. • There is a possibility of water and soil pollution • Heaps of refuse present an unsightly appearance and nuisance from bad odours

  4. SOURCES OF REFUSE • Refuse collected -street cleansing service or scavanging- street refuse • Refuse - collected from market – market refuse • Refuse collected from stable- stable litter • Industrial refuse- completely inert to highly toxic and explosive compounds • Domestic refuse- ash, rubbish, garbage.

  5. STORAGE AND COLLECTION • Galvanized steel dustbin with close fitting cover – suitable • Capacity – depends - no of users and frequency of collection • Recent innovation – western countries- paper sack • Public bins – large no of people • India – without cover • Kept-concrete platform – raised above ground level – prevent flood water • Municipalities – handled and emptied mechanically – lorries fitted with cranes • Method of collection – funds available • House to house collection – best method

  6. METHODS OF WASTE DISPOSAL • Principal methods of refuse disposal : • Dumping • Controlled tipping or sanitary landfill • Incineration • Composting • Manure pits • Burial

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  8. Dumping • Refuse - dumped in low lying areas • Bacterial action decreases the volume of refuse – converted gradually into humus • Kolkata disposes- refuse- dumping and reclaimed land is leased out for cultivation • Drawbacks: • Refuse is exposed to flies and rodents • Source of nuisance from smell and unsightly appearance • Loose refuse - dispersed by the action of the wind • Drainage from dumps - pollution- surface and ground water.

  9. Controlled Tipping / Sanitary Landfill • Most satisfactory method of refuse disposal. • The material is placed in a trench or other prepared area , adequately compacted and covered with earth at the end of the day. • Modified sanitary landfill- compaction & covering done once or twice a week • 3 methods are used : • The trench method • The ramp method • The area method

  10. Controlled Tipping / Sanitary Landfill The trench method : • When level ground available • A long trench is dug out- 2-3m (6-10ft) deep and 4-12m(12-36ft) wide • Refuse- compacted and covered with excavated earth The ramp method : • When terrain is sloping Area Method : • Filling land depressions , disused quarries, clay pits • Refuse – deposited, packed, consolidated- uniform layers – 6-8 ft deep • Disadvantage – supplemental earth

  11. Controlled Tipping / Sanitary Landfill • Chemical, bacteriological and physical changes- buried refuse • Temperature rises over – 60 degree celsius within 7 days • Kills all pathogens and hastens decomposition process • 2-3 weeks – cool down • 4-6 months – complete decomposition of organic matter- innocuous mass • Tipping of refuse in water should NOT be done

  12. Controlled Tipping / Sanitary Landfill

  13. Incineration • Burning • Method of choice- suitable land not available • Hospital waste – incineration • A preliminary separation of dust or ash is needed • All this involves – heavy outlay and expenditure • Disposal of refuse by burning - loss to the community in terms of manure • In India limited application.

  14. Composting • Combined disposal of refuse and nightsoil or sludge. • Process of nature – organic matter breaks down under bacterial action- formation of relatively stable humus- like material • Considerable manurial value for the soil • Principal by- products- carbon dioxide , water and heat • Heat produced – 60 deg C or higher , over a period of several days • Destroys eggs and larvae of flies, weed seeds and pathogenic agents. • End product compost- contains few or no disease producing organisms good soil builder containing small amounts of major plant nutrients such as nitrates and Phosphates

  15. Composting and Vermicomposting

  16. Methods of composting • Bangalore Method ( Anaerobic method) • Mechanical composting (Aerobic method) Bangalore Method ( Hot fermentation process) • Trenches are dug 90cm( 3ft) deep , 1.5- 2.5m (5-8ft) broad , 4.5-10m(15- 30 ft ) long • Depths greater than 90cm (3ft) not recommended- slow decomposition • Pits should be located not < 800m (1/2 mile) from city limits . Composting procedure is as follows : • A layer of refuse about 15cm (6in) thick- spread at the bottom of the trench • Over this nightsoil is added -to a thickness of 5cm (2in) • Alternate layers of refuse and nightsoil are added in the proportion of 15cm(6in) and 5cm(2in) tilll heap rises 30 cm ( 1 ft) above the ground level

  17. Bangalore Method ( Hot fermentation process) • The top layer should be of refuse – atleast 25cm(9in) thickness • Within 7 days due to bacterial action heat (over 60deg C) is generated • Intense heat persist over 2-3 weeks – decomposes refuse and nightsoil – destroys all the pathogenic and parasitic organisms. • At the end of 4-6 months – decomposition is complete • Resulting manure- well decomposed Odourless innocuous material of high manurial value

  18. Mechanical Composting • Compost manufactured in a large scale by: • Processing raw materials and turning out a finished product • The refuse is cleared of : rags, bones ,metals , glass- interfere with grinding operation • Pulverised in a pulverising equipment- reduce the particles to < 2inches • Pulverised refuse- mixed with sewage , sludge or nightsoil in a rotating machine and incubated • Carbon- nitrogen ratio, temp, moisture , Ph and aeration • Entire process complete in 4-6 weeks • This method used in – Holland, Germany, Switzerland , Israel

  19. MECHANICAL COMPOSTING

  20. Manure Pits • Rural areas • The garbage, cattle dung , straw and leaves- dumped into manure pits • Covered with earth after each day’s dumping • 2 such pits will be needed • 5-6 month’s time- refuse converted into manure – returned to fields

  21. Burial • Suitable for small camps • A trench 1.5m wide and 2 m deep is excavated • At the end of each day refuse is covered with 20-30cm of earth • When the level in the trench is 40cm from ground level – trench filled with earth and compacted • A new trench is dug out

  22. SUMMARY • Definition of solid waste • Health hazards of solid waste • Sources of solid waste • Methods of collection and Storage • Methods of waste disposal

  23. THANK YOU

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