Performances of low – cost reactive materials as permeable reactive barrier media to treat landfill – leach ate

Abstract

The landfill-leachate is deemed to be one of the most serious pollution problems because landfill- leachate- polluted ground water riches in various hazardous contaminants. Permeable reactive barriers (PRBs) are considered a low cost and effective alternative for remediating contaminated sites. The availability and the cost are important criteria in selecting a reactive material. Therefore in this study a laboratory scale column experiment was conducted to study the feasibility of a PRB with low cost- locally available reactive materials such as coconut coir fibre, rice straw, saw chips and rice husks to remedy the landfill- leachate. The leachate was collected from the Galle-municipal-council dumpsite. The column experimental set-up consisted of 4 columns each with 35 cm height and 8.9 cm diameter. The initial length of the reactive media was 26 cm in each column. The influent which was stored in an overhead tank was loaded on to the column via a shower. An application rate of approximately 0.4 mL/s was maintained by adjusting a valve. The effluent was collected in an effluent tank kept below each column. Influent and effluent were characterized in terms of several wastewater parameters. Each reactive material was mixed with laterite soil so that soil to reactive material ratio became 2:1 on weight. Adsorption and biological uptake could be the dominant treatment mechanisms of organic matter. Rice straw and saw chips reduced COD concentration to greater than 80 percent within two days of application. In considering the overall removal of organic matter, saw chips were the best at both adsorption and biodegradation; coconut coir fibre and rice husks were the best at biodegradation; both rice straw and saw chips were equally good at adsorption. Ammonia could be treated mainly by adsorption and nitrification. Based on the results, rice husks could be the most supportive reactive media for nitrification. Though there were enough carbon sources and anaerobic zones, denitrification was not significant. Adsorption could be the dominant mechanism for chloride removal in all media that equally performed in removing chloride with greater than 90 percent removal.