5 phases in which the whole process of waste treatment takes place
Phase 1:
The waste decomposes aerobically, until the oxygen that was present in the freshly-placed fill is used up by the aerobic microorganisms.
Phase 2:
The anaerobic conditions prevail and H2 and C02 are evolved.
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Phase 3:
Methanogenic population of bacteria takes place and is the beginning of methanogenic activity. The bacteria decompose the matter to methane and C02.
Methane is highly poisonous and highly explosive when mixed with air in concentrations from 5 to 15 per cent.
Phase 4:
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The methanogenic activity becomes stabilized.
Phase 5:
Image Source: mde.state.md.us/programs/Water/wwp/PublishingImages/UICblowup1.JPG
The methanogenic activity decreases, representing depletion of organic matter and finally, the system returns to aerobic conditions again.
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The hazardous potential of methane should thus, be given due consideration. The carbon dioxide so produced reacts with water to form carbonic acid. The acidic environment thus, produced helps in dissolution of minerals and salts of Ca, Mg, Fe, Pb, Cd, Hg, Zn and various elements present in the wastes. These dissolved salts if percolate to ground water, they increase hardness and heavy metal toxicity of water.
The rate of decomposition in sanitary landfills depends on several factors. The weather condition, however, is not in our hand. The other factors however, can be controlled by introduction of proper technology.
The aerobic decomposition rate will decrease if the wastes are compressed too tightly, so the wastes should be compacted in such a manner so as to have adequate amount of oxygen available.
Also, the generation of methane and carbon dioxide should not get reduced. Again, if there should be proper ventilation, a venting system to collect and vent the blocked gas to the outer surface in a controlled manner, in order to prevent explosion. The large amount of methane that is produced in the landfill can be tapped and used as a fuel.