Solid Waste Management What is solid waste? -Solid waste is an useless, unwanted or discarded material. -It consists of part of raw materials, intermediate product or finished product which has got no commercial value. -As defined by federal law, “solid waste may be solid, liquid or semiliquid, generated from industries, muncipalities, businesses or home”. - It includes discarded article that is worn out, broaken, packaging or organic wastes or toxic substance produced as a by product of some industrial process.

What is Solid Waste Management? - Solid waste management involves management of activities associated with generation, storage, collection, transfer and transport, processing and disposal of solid waste which is environmentally compatible, adopting principles of economy, aesthetics, energy and conservation. - Solid waste management involves four steps : a) Generation & composition of waste. b) Collection of waste. c) Transportation of waste. d) Disposal of waste.

From where does the waste comes from? - The major sources are mining (75%), Agriculture (12%),Industries (9 %), Muncipalties (3%) & Sewage sludge (1 %). - The composition of each type varies from location to location. Solid Waste Disposal Practices. If waste is either not reused directly or recycled, there are only three places where the waste can be disposed : 1) Into or onto the land (Landfills) 2) Into the air (Incineration) 3) Into the water (Ocean dumping)

Land disposal of waste : Open dumping cost is low Sanitary landfills cost is more According to Resource Conservation & Recovery Act (oct 1976), open dumps are prohibited & directed to develop a complaince schedule to convert open dumps into sanitary landfills. New federal regulations require landfills to be upgraded to meet more strict standards to protect ground water aquifers and other environmental and health factors.

Incineration : - A common method employed in areas with concentrated populations, where land availability is a problem. - A method employed for disposal of toxic waste and waste from hospitals. - Coupling of waste incineration with energy recovery is getting increased attention. Ocean dumping : -For many years, this is practiced as an inexpensive & convenient method of waste disposal. But now, as per Marine Protection & Sancturies Act (1972), permit has to be obtained for ocean dumping.

Disposal on Land : - Suitable for flat land. - Trench of 2 m deep & 2 – 5 m wide is cut. - The excavated soil is used to cover the trench. Trench method

- Quitable in areas where natural depressions exist. -Waste is put in depressions & compacted. - A layer of earth is put on the top. Area method

- Modification of trench & area method. - A ramp of about 15 m wide, 30 m long & of suitable height is created. - At the end refuse is compacted along with soil cover so that it becames a part of ramp. Ramp method

Sanitary landfilling is defined as “method of disposing of refuse on land without creating nuisance or hazards to public health or safety, by utilizing the principles of engineering to confine the refuse to the smallest practical area, to cover it with a layer of earth at the conclusion of each day’s operation or at such more frequent intervals as may be necessary”.

Incineration is defined as a controlled combustion process for burning solid, liquid or gaseous combustible wastes to gases & residues containing non-combustible material. CO 2, water vapour, ash & non-combustibles are the end products. TTT & O are essential for satisfactory incineration. Selectional view of a retort multi-chamber incinerator

A Compost Heap. Compost heaps may be age-scale operations or backyard projects. The critical mix sludge organic matter, oxygen and decomposers. Composers feast on the organic matter and break it down in presence of oxygen into simpler, partly degraded organic mineral components. Compost may then be used as a conditioner.

Flow chart for a mechanical compost plant

Processing methods for the future 1) Pyrolysis : It is the process of heating refuse in a nearly oxygen-free environment to produce oil, gas and/or char as an end product. - A ton of solid waste processed in this manner yields energy approximately equivalent of about one barrel of oil. - It is an endothermic reaction and is carried out at temperatures between 500 – 1000 o C. -The end products have high calorific value and energy recovery can be from 37 to 62%.

2) Biogas production : When solid wastes with a large proportion of organic matter is subjected to anaerobic decomposition, a gaseous mixture (CH 4 & CO 2 ) know as biogas can be produced. - The gas production ranges from 0.29 m 3 /kg of vs added/day to 0.13 m 3 /kg of vs added/day in different seasons. - The sludge has good manurial value (NPK :: 1.6 : 0.85 : 0.93). - Satisfactory detention period is of about 25 days. - Methane, thus produced is also a commercially recoverable fuel. - Los Angeles and california use verted gas from sanitary landfills to proide electricity to 350 and 1,000 homes respectively.

3) Refuse derived fuel systems (RDF system) : In this method, combustibles are separated from non- combustibles. - The combustibles are then shredded and burned in industrial boilers as a primary fuel or as a supplement to fossil fuels. - In US, RDF is used to supplement other fuel sources in a ratio of 20% RDF to 80% fossil fuel. - This method besides reducing cost also helps in reducing the sulphorous emissions.

4) Conversion of SW to protein : - Laboratory investigations conducted at Louisana State Univ. USA, showed that under aerobic conditions, it is possible to convert the insoluble cellulose contained in muncipal waste by using cellulolytic bacteria. - The bacteria are then harvested from media to use as protein. - The process involves size reduction followed by mild allcaline oxidation treatment before aerobic oxidation. - The single cell protein (SCP0, thus produced has a crude protein content of 50 6 % and has been successfully tested on animals. - How ever, the process has yet to be tested on full scale basis.

5) Bioconversion : The decomposition of sw can be accelerated artificially by using an aerobic digeoter. Producing end products CH 4 & CO 2. - The results can be obtained within a week. -A demonstration Bioconversion plant is in operation in Florida, since ) Co-disposal : - An emerging technology cost led as thermal co-disposal. - it involves simultaneous disposal of solid waste and sewage sludge. - It involves the use of energy from burning solid waste to dry the sludge to a point at which it will burn without supplemental fuel or in combination with more refuse. - This method is suggested, because sludge due to its volume & presence of persistant chemicals such as heavy metals, creates problem is disposal and also use of such sludge as fertilizer is questioned moreover, because of its high water content, it can not be burned easily.

7) Other methods : Due to high paper content in the waste from developed countries, a method has been envolved to hydropulp the waste and recover paper fiber from refuse. - This method is used at Ohio.