Wednesday, April 20, 2011

Solid waste pollution


Solid wastes consist of discards of households, dead animals, industrial and agricultural wastes and other large wastes like debris from construction site, automobiles, furniture etc. A typical classification of solid waste includes:
1)      Garbage: Putrescibe wastes from food, slaughter houses, canning freezing industries and market refuse. 
2)      Rubbish: Non-putrescible wastes like paper, wood, cloth, rubber, leather etc. which all are combustible. It also includes non-combustible like metals, glass, ceramics, stone etc. 
3)      Ashes: Like fly ash from thermal plants, residues of combustion of soil fuels or residues of incineration of solid wastes by municipal bodies or industries.
4)      Hospital refuse: Cotton, plaster, ampoules, needles and operation theatre wastes. 
5)      Large wastes: Debris from construction site, automobiles, old furniture etc. 
6)      Dead animals: Households, veterinary hospitals and zoo.
7)      Sewage treatment process solids or sludge. 
8)      Industrial solid wastes: Chemicals, paints, sand etc. 
9)      Mining wastes: Tailings slag heaps.
10)  Agricultural wastes: Farm animal manure, crop residue etc. 

Chief methods of disposal of solid wastes: 
1)      Land filling: Many countries have made a start by locating land fills to dump solid wastes. In the US 80% of solid wastes are dumped into 6000 land fills. But land fill sites poses potential threat of pollution to ground water resources. In US, nearly 3 thousand land fill-sites were closed by 1988-1993, some 2 thousand more is estimated to be closed.
2)      Dumping in seas: Dumping in seas is not upheld today because of the threat to poses to aquatic life and their regenerative capacity.  New York still dumps its wastes in Atlantic Ocean. Nearly three million tones of hazardous waste have been transported from US and Western Europe on ships. 
3)  Incineration: Incineration is very hygienic way of disposal of rubbish. It requires a well-designed incinerator that would ensure complete combustion. 
4)    Pyrolysis: Pyrolysis means an operation using intense heat to cause chemical changes but not combustion. Pyrolysis may yield marketable products.
5)      Controlled tipping and sanitary fills: It is the most satisfactory method of disposal of solid wastes. In this method garbage is leveled in layets, compacted and covered with earth. Where the ground is leveled trench method is followed and if there is slope, ramp method is followed.

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