Solid Waste Management and its Steps

STEPS INVOLVED IN SOLID WASTE MANAGEMENT : 

1. Solid Waste Generation. 

2. Collection of Waste

3. Transportation 

4. Storage           

5. Segregation of  Wastes - Home Separation For Recycling.

6. Disposal Wastes.

Methods Of  Disposal Of Solid Waste : 

1. Landfill.

2. Incineration.

3. Composting. 

I) LANDFILL :

Solid wastes are placed in sanitary landfill system in alternate layers of 80cm thick refuse, covered with selected earth fill of 20cm thickness. After two or three years, solid waste volume shrinks by 25 -30 % and the land is used for parks, roads and small buildings. 

The most common and cheapest method of waste disposal is dumping in sanitary land - fills which is invariably employed in Indian cities. land - fill structure is built either into the ground or on the ground into which the waste is dumped. The method involves spreading the solid waste on the ground, compacting it and then covering it with soil at suitable intervals

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II) INCINERATION (or) THERMAL PROCESS :

It is the hygienic way of  disposing solid waste. It is more suitable if the waste contains more hazardous material and organic content. It is a Thermal process and is very effective for detoxification of all combustible pathogens. It is an expensive technology compared to land fill and composting because incinerators are costly.

In this method the municipal solid wastes are burnt in a furnace called incinerator. The Combustible substances such as rubbish, garbage, dead organisms  and  the non combustible matter such as glass, porcelain, metals are separated before feeding to incinerators. The non - combustible materials can be left out for recycling and reuse. The left out ashes and clinkers from the incinerators may be accounted for only about 10 to 20% which need further disposal either by sanitary landfill or by some other means. 

The heat produced in the incinerator during the burning of refuse is used in the form of steam power for generation of electricity throughout the turbines. The municipal solid waste is generally wet but has a very high calorific value. So it has to be dried up first before burning. The waste is dried in preheater from where it is taken into large incinerating furnace called destructors which can incinerate about 100 to 150 tones per hour. The temperature normally maintained in a combustion chamber is about 700*C and may be increased to about 1000*C when electricity is to generated.

III) COMPOSTING :

It is another popular method practiced in many cities in our country. In this method, bulk organic waste is converted into fertilizing manure by biological action. 

The separated compostable waste is dumped in underground earthen trenches in layers 1.5 m and is finally covered with earth of about 20cm and left over for the decomposition. Sometimes certain microorganisms such as actinomycetes are introduced for active decomposition. Within 2 to 3 days biological action starts, the organic matters are being destroyed by actinomycetes and lot of heat is liberated increasing the temperature of the compost by about 75*C and finally the refuse is converted to powdery brown colored odorless mass known as humus and has a fertilizing value which can be used for agricultural field. The compost contains lot of nitrogen essential for plant growth apart from phosphates and other minerals.