Short Notes on Dumping of Hazardous Wastes

(iii) Property values decrease as a result of illegal dumping.

(iv) Public nuisance is created by illegal dump sites.

Land dumping :

Solid wastes are dumped in low-lying areas outside the city/town limits. These areas have no provision of leachate collection and treatment. Moreover, land fill gas is neither collected nor used.

Advantages:

(i) It requires no planning.

(ii) It is cheaper.

Disadvantages:

(i) The waste is untreated, uncovered and not segregated. It is the breeding ground for flies, other insects, rats etc. that spread diseases.

(ii) Rainwater run-off from these dump sites contaminate nearby land and water there by spreading diseases.

Landfills :

Landfill site is a pit that is dug in the ground. The solid waste is dumped and the pit is covered with a layer of soil to form a cell. The process is repeated every day so that many cells completely fill the landfill site. Finally, about 1 m of earth layer covering is done.

Advantages:

(i) Breeding of insects is prevented.

(ii) Landfill sites can be developed as a park or a parking space. Disadvantages:

(i) All types of wastes are dumped in land fill sites without segregation. When rainwater seeps through them, it gets contaminated and in turn pollutes the surrounding area, and ground water.

Sanitary landfills :

Sanitary landfill sites have liner systems and other safeguards to prevent ground water contamination. These sites are consistent with the economic considerations, hydro geological requirements, climatic conditions and topography.

Advantages:

(i) The site is well above the ground water table, so underground water pollution is avoided.

(ii) The site is easily accessible so process is low in cost.

(iii) The site is at least 1.5 km down wind from the commercial and residential areas so it is not offensive to the surrounding environment.

(iv) The finished sanitary landfill can be used for the development of regions of recreation like parks, golf-courses etc.

Disadvantages:

(i) Leach ate from sanitary landfill site can contaminate the ground water.

(ii) The sites cannot be used in future as a productive farm land.

(iii) In a sanitary landfill, about 60% of the methane gas (odourless) is generated. When its concentration in air reaches about 5%, it is explosive and so very hazardous.

(iv) Aesthetic problems may arise as a result of poorly operated landfill operations.

Combustion :

Solid waste is burned at high temperature in combustion facilities. Advantages:

(i) Energy is generated.

(ii) Amount of waste is reduced by up to 90% in volume and 75% in weight.

Disadvantages:

(i) Cost increases with rise in the moisture content of solid waste. This is because energy is required for preheating the solid waste.

(ii) Ash formed after combustion has high concentrations of dangerous toxins such as dioxins and heavy metals. It results in air and water pollution.

Incineration :

The controlled combustion of organic solid wastes so as to convert then into incombustible residue and gaseous products the weight and volume of solid waste is reduced and often energy is also produced

Advantages:

As the volume of the waste is reduced so to take the waste to the ultimate disposal site, less transportation cost is required.

Larger wastes can be accomodated in a given land fill area because incineration reduces the land requirement to one-third.

Disadvantages:

(i) Not applicable for radioactive wastes.

(ii) High capital and operational costs.

(iii) Air pollution chances if incineration is not properly done.

(iv) Highly trained man-power is needed.