Evaluation of Contamination Potential and Treatment Techniques of Leachate Generated from Landfill Lysimeter

Abstract

In this study one open dump lysimeter with leachate detection and collection system as well as two sanitary lysimeter having two different types of cap liner were simulated. After designing a reference cell, construction of landfill lysimeter was started in January 2008 and completed in July 2008. In all construction process locally available civil construction materials were used. The municipal solid waste (MSW) of 2800 to 2985 Kg having the total volume of 2.60 m3 (diameter 1.48 m; height 1 .6m) as well as moisture and organic content of 65, 52 %, respectively, was deposited in each lysimeter by applying required compaction energy. This study endeavors to characterize leachate and investigate the tropical climatic influence on leachate characteristics under different seasonal variation. The leachate characteristics, leachate generation and climatic influence parameter had been monitored since June 2008 to Dec. 2010. These periods covered both the dry and rainy season. The leachate generation followed the rainfall pattern and open dump lysimeter-A without top cover demonstrated more leachate generation due to percolation of rainfall than that of sanitary lysimeter-B and C.

Open dump lysimeter-A showed lower concentration of TKN and NH4-N as well as TKN load, while both the concentration and load of COD higher in compared to sanitary lysimeter-B and C. Sanitary lysimeter-B, not only revealed lower leachate generation, but also produced reasonable lower concentration and load of COD in compared with open dump lysimeter-A. Result depicted that lysimeter operational mode had direct effect on leachate quality. In contrary, sanitary lysimeter-C showed higher composition of LFG in compared to sanitary lysimeter-B due to the providing of lower compaction of cap liner in sanitary lysimeter-C. in absence of compacted clay liner (CCL) and hence percolation of rainwater that facilitated rapid degradation of MSW in open dump lysimeter-A and resulted in higher settlement than that of sanitary lysimeter-B and C. In sanitary lysimeter-B and C, leachate generation showed lesser amount than that of open dump lysimeter-A due to the providing of cap liner in lysimeter-B and C, played an important role to reduce the percolation of rainwater. Study revealed leachate pollution index (LPI) and sub-pollution indices (sub-LPI) for lysimeter significantly higher and proper treatment to be necessary before discharging the leachate into the water bodies.

To meet the standard discharge condition lysimeter leachate was treated in the laboratory through the phytoremediation treatment process by using aquatic reactors of duckweed, snail, helencha and topapana, but the removal efficiency was not satisfactory. Then the leachate was treated through the chemical coagulation process by using FeCl3, PAC, FeSO4 and Al2(SO4)3 in various dosages and pH. Result revealed that FeCl3 more effective for removing pollutant. In the laboratory, leachate was further treated by using FeCl3 at optimum dosage and the concentration and consequently the values of LPI of treated leachate were found within the limit of maximum discharge standards. Finally, it can be concluded that leachate generated from lysimeter may be discharge after required level of chemical treatment into the natural streams to maintain the limit of maximum discharge standards.