Abstract:
Municipal Solid Waste (MSW) management is a severe problem in Sri Lanka. As a remedy, a
new sanitary landfill is planning to implement in Aruwakkalu, Puttalam district for dumping the
Colombo MSW. Aruwakkalu area is covering Natural Red Earth (NRE), which considered as a
strong adsorbent. However leachate released from possible MSW dump has significant threat on
the environment. Therefore, this study is aim to identify possible leachate infiltration
characteristics under different density profiles of NRE. The laboratory scale experimental design
was conducted with five filter columns that filled with NRE, which was collected from
Aruwakkalu area. The columns were filled up to 10 inches height under selected density range
that occurred in NRE (1.4 gcm-3-1.6 gcm-3). Leachate from Karadiyana landfill site was diluted
50% and 200 ml of leachates were added to each column while maintaining standard flow,
filtrate were collected from each column for chemical and physical analyses. Approximately two
days interval was maintained between leachate each feeding events and sampling of the filtrate.
Experiment was conducted few months until major physical and chemical changes that occurred
in filtrate and NRE columns. NRE characteristics such as surface chemistry, particle size and
shape were studied using Scanning Electron Microscope (SEM). X-ray Florescence analysis
(XRF) was done to identify total chemistry. Elusion analyses were conducted under different pH
to investigate soluble fractions of NRE. Further, Fourier-Transform infrared spectroscopy
(FTIR) analyses were done to study adsorption sites. X-ray Diffraction analyses (XRD) were
done to identify secondary minerals present in NRE. Cation Exchange Capacity (CEC) was
studied for NRE samples using laboratory experimental setup. Atomic Absorption Spectroscopy
(AAS), multiparameter electrodes and Spectrophotometer were used to study leachate and filtrate
such as Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Dissolved
Solid (TDS), conductivity, pH, salinity, Oxidation-Reduction Potential (ORP), phosphate,
nitrate, and other selected elements (Fe, Zn, Pb, Cu, and Ni). Results indicate a significant
reduction of conductivity and TDS from the filtered leachates in different soil columns. It has
been noted, gradual incensement of TDS and conductivity with the time, however compare to
raw leachate values are small in the filtrate. There were no considerable changes of pH with
time. Selected anionic and cationic parameters reflect progressive and regressive changes during
the period of experiment due to different process in the soil columns. Time taken for the
percolation of leachate from each soil column was increased with the time due to compaction of
soil with the continuous addition of leachate.
