26-10-2016, 02:43 PM
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ABSTRACT
Asian countries are facing municipal solid waste management problems due to the rapid growth in solid waste generation rate and open dumping practices. There is a need for dumpsite reclamation processes to solve the environmental problems associated with dumpsites. Chennai is the fourth largest metro city in India with the current population of 6 millions, generating 3700 t/d of municipal solid waste. The wastes are disposed by open dumping at Perungudi and Kodungaiyur dumping grounds.
Assessment of reclamation and hazard potential of these dumpsites was carried out. Detailed investigations on solid waste characteristics, leachate quality and methane emission potential of the dumpsites were used to assess the reclamation potential. Hazard potential was assessed based on heavy metal speciation pattern in the solid waste samples and their mobile fraction having adverse environmental effects due to their leaching potential. An integrated risk based approach was also developed for the rapid assessment of the hazard potential of the dumpsites, which will be useful for prioritization of rehabilitation activities of the existing dumpsites.
The soil fraction of the mined waste collected from Perungudi and Kodungaiyur dumping grounds are 30-40% and 56-68%, respectively. The physico- chemical properties of the soil fractions are similar for samples collected from Perungudi and Kodungaiyur dumping ground. Chromium, Cu, Hg, Ni and Pb contents
of the soil fraction of the solid wastes are exceeding the Indian compost quality standards but less than the compost quality standards specified by the United States Environmental Protection Agency. Heavy metal speciation studies of the soil fraction of the solid waste samples into exchangeable, acid extractable, reducible, oxidizable and residual fraction for the metals Cu, Cr, Cd, Fe, Pb, Ni, Mn and Zn showed that less than 60% of the total metal contents are bioavailable (mobile fraction). Bioavailability is restricted to a maximum of 40% in the case of Cr, Pb, Cu and Fe. The soil fraction (40-60%) of the waste can be reclaimed as compost or cover material.
Leachate quality data showed that chemical oxygen demand and total dissolved solids are exceeding the Indian standards for disposal of treated leachates into inland surface water while biochemical oxygen demand, pH and heavy metals are less than the specified standard limits. Leachate treatment systems and protection liners will be useful to prevent the leachate contamination to surface and ground water. Methane content of both the borehole and the ambient air samples from the dumpsites varied between 0 and 220 ppm.
Validation of the developed decision making tool to access the hazard potential of the dumpsite to Perungudi and Kodungaiyur dumping grounds resulted with scores of 569 and 579 out of 1000, respectively. This indicates that both sites have moderate hazard potential and need to be rehabilitated. Based on the present study suggestions and remedial measures for environmentally sound solid waste disposal are proposed.