COMPARATIVE STUDY ON THE EFFECTS OF COIR FIBER MEDIA ON CONSTRUCTED WETLANDS

Abstract

Infiltration of water in to landfills, percolating-through waste and the squeezing of waste due to self-weight’ results in. n thick liquid, which is, called Leachate. Landfill leachate contain, besides nutrients, several environmentally hazardous and toxic compounds, which pose a sever threat; to surface and ground waters. Therefore, it is important to treat leachate before releasing. Open dumpsite leachate, which ultimately reaches the water bodies, is one of the major problems in Sri Lanka. The disposal of liquid waste into wetland-based systems may be a viable alternative to conventional wastewater treatment technology. However, the pollutant a removing capacities of natural and constructed wetlands are not .efficient enough in sonie situations. Coir fiber is one of the locally available low cost media that has the potential to be used in constructed wetlands to increase the efficiency. Three field laboratory scale constructed wetland jysimeters were installed without wetland plants at Mcewatliura farm, University of Peradeitiya. Three treatments were chosen, namely;coir, coir + soil, soil as media respectively. The sizes of the lysimeters of constructed wetlands are length X surface width X bottom width X depth (5m X 0.82m X 0,44m X, 0:6m). Influent leachate from a dumpsite was used as the effluent to be treated and dosed at a uniform rate of 70 ml/min from one end of the lysimeters. Effluents from lysimeters were analyzed for water quality parameters. The performances of the three lysimeters are similar and considerably high. It seenis that both onaerobic and aerobic conditions prevail and there is significant break down of substrate even without wetland plants. The BOD removal efficiency was slightly above 67%. The influent BOD was 2229 mgll and the stabilized effluent BOD reached 710 mg/l. The removal efficiency is high, perhaps due to anaerobic conditions in the lower layers and.oxidation taking place closer to the surface. Rate of removal efficiency for coir media for (UODj), TDS, TSS and EC was 68.13%, 59.37%, 100%, 57.55% respectively. Considering all the results coir soil combination has a high potential for plant growth in constructed wetlands. There is no significant difference between the results. The duration of the study is not sufficient to predict the most desirable jnedia Tor the wetland lysimeters. Therefore further studies arc necessary to substantiate the findings.