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Abstract:
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Leachate from an untreated landfill or landfill with damaged liners
will cause the pollution of soil and ground water. Here an attempt was made
to generate knowledge on concentrations of all relevant pollutants in soil
due to municipal solid waste landfill leachate and its migration through soil
and also to study the effect of leachate on the engineering properties of soil.
To identify the pollutants in soil due to the leachate generated from
municipal solid waste landfill site, a case study on an unlined municipal
solid waste landfill at Kalamassery has been done. Soil samples as well as
water samples were collected from the site and analysed to identify the
pollutants and its effect on soil characteristics. The major chemicals in the
soil were identified as Ammonia, Chloride, Nitrate, Iron, Nickel,
Chromium, Cadmium etc.. Engineering properties of field soil samples
show that the chemicals from the leachate of landfill may have effect on the
engineering properties of soil.
Laboratory experiments were formulated to model the field around an
unlined MSW landfill using two different soils subjected to a synthetic
leachate. The Maximum change in chemical concentration and engineering
property was observed on soil samples at a radial distance of 0.2 m and at a
depth of 0.3 m. The pollutant (chemicals) transport pattern through the
soil was also studied using synthetic leachate. To establish the effect of
pollutants (chemicals) on engineering properties of soil, experiments were
conducted on two types soils treated with the synthetic chemicals at four
different concentrations. Analyses were conducted after maturing periods of
7, 50, 100 and 150 days. Test soils treated with maximum chemical
concentration and matured for 150 days were showing major change in the
properties.
To visualize the flow of pollutants through soil in a broader sense, the
transportation of pollutants through soil was modeled using software ‘Visual
MODFLOW’. The actual field data collected for the case study was used to
calibrate the modelling and thus simulated the flow pattern of the pollutants
through soil around Kalamassery municipal solid waste landfill for an extent
of 4 km2. Flow was analysed for a time span of 30 years in which the
landfill was closed after 20 years. The concentration of leachate beneath the
landfill was observed to be reduced considerably within one year after
closure of landfill and within 8 years, it gets lowered to a negligible level.
As an environmensstal management measure to control the pollution
through leachate, permeable reactive barriers are used as an emerging
technology. Here the suitability of locally available materials like coir pith,
rice husk and sugar cane bagasse were investigated as reactive media in
permeable reactive barrier. The test results illustrates that, among these, coir
pith was showing better performance with maximum percentage reduction
in concentration of the filtrate. All these three agricultural wastes can be
effectively utilized as a reactive material.
This research establishes the influence of leachate of municipal solid
waste landfill on the engineering properties of soil. The factors such as type
of the soil, composition of leachate, infiltration rate, aquifers, ground water
table etc., will have a major role on the area of influence zone of the
pollutants in a landfill. Software models of the landfill area can be used to
predict the extent and the time span of pollution of a landfill, by inputting
the accurate field parameters and leachate characteristics. The present study
throws light on the role of agro waste materials on the reduction of the
pollution in leachate and thus prevents the groundwater and soil from
contamination |