Characterization of landfill leachate from municipal solid waste landfills in Sri Lanka.

Abstract

Open dumping of municipal solid waste (MSW) is the most common way of handling solid waste in Sri Lanka due to high cost involved with advanced technologies for landfilling, lack of technical capacity, lack of knowhow to manage landfill sites, and so on. Landfill leachate generated from the MSW landfill sites must be treated before dispose into the environment as it creates many social and environmental problems. Characterization of landfill leachate is important to identify the most critical pollutants present in the leachate and thereby to introduce suitable and applicable treatment technologies such as in-situ permeable reactive barrier technologies for contaminant remediation. Therefore, the objective of this research is to characterize landfill leachate collected from several MSW landfills in Sri Lanka. The leachate samples were collected from 12 landfill sites located in Matale, Hambantota, Kataragama, Bandaragama, Kolonnawa, Gampola, Gohagoda, Wennappuwa, Rathnapura, Negombo, Galle, and Matara. For the collected samples, general water quality parameters (pH, EC, DO, ORP, and SS), organic pollutants (BOD5, COD, TOC, IC, TN, TP), typical anions and cations (Cl- , SO4 2- , NH4 + , K+ , Mg2+, Ca2+, etc), and heavy metals (Cr, Mn, Fe, Se, Pb, etc) were measured. The results showed that most of the pollutants (F- , Cl- , PO4 3- , NH4 + , Fe, Se, Pb, BOD5, and COD) exceeded the maximum tolerance limits in Sri Lankan Standards. It was found that the BOD5/COD ratio ranged from 0.01 to 0.6 for the most samples and the highest value of 0.6 was observed in the Kolonnawa sample. Measured EC values for all samples were high and varied ranging from 4.5 to 38.3 mS/cm, indicating the biological treatment system alone would not be effective in reducing the pollutants especially for heavy metals. The results of this study will be used in developing site specific remediation technologies in landfill leachate treatment.