TEMPORAL VARIATIONS IN PERCHED WATER AND GROUNDWATER QUALITIES AT AN OPEN SOLID WASTE DUMPSITE IN SRI LANKA

Open dumping of municipal solid waste is a common practice in many developing countries and contaminates surface and groundwater in the vicinity. In this study, long-term monitoring was conducted at an abandoned solid waste dumpsite to characterize temporal variations of perched water and groundwater qualities. The dumpsite was located at Udapalatha PS in Central Province of Sri Lanka and consisted of two sections (namely Old and New sections). The Old section was used for waste dumping for seven years from 2003 to 2010, and the New section was used for six months in 2011. Multiple wells were installed at each section and water qualities monitored for two years from May 2013 to March 2015. Water quality parameters such as pH, EC, BOD, COD, TN, TP, major cations, major anions, and heavy metals were measured monthly. Leachate pollution index (LPI) was used to quantify the leachate contamination potential of landfill site. Results showed that groundwater samples from both Old and New sections exhibited relatively low LPI during the monitoring period, whereas perched water samples from New section showed high LPI with fluctuations. At the monitoring site, perched water and groundwater seem to persist as two independent bodies for both Old and New sections. Especially, the dumped waste at lower layer at the Old section was fully washed out by rainfall and surface water after waste dumping and currently carries a low risk of groundwater contamination.