Water quality improvement through vegetative landscape.

Abstract

Water, the valuable natural resource, is contaminated by irresponsible disposal of solid and liquid wastes from residences and industries. Proper wastewater and solid wastes management is necessary for conservation of water resources in Sri Lanka. Lack of low cost and environmental friendly techniques is one of the main reasons for discharging wastewater directly into the environment. Natural attenuation and bioremediation can be used for domestic wastewater treatment for peri-urban areas through natural vegetative landscape. In order to elucidate the potential of vegetative landscape, a study was conducted in a small valley at Nation Builders Association, Kundasale in Kandy during February to May in 2007. The domestic wastewater cum runoff from the Kundasale new town flows through a series of ponds along the valley (Jayakody, B. V., 2004) which is reforested by the combination of trees, shrubs and grasses for last 15 years. Water samples were collected at different locations in the valley and tested for Biochemical Oxygen Demand (BOD), NO3-- Nitrogen, PO/, NH/- Nitrogen, Total Suspended Solids (TSS), pH, Salinity, Total Dissolved Solids (TDS) and Electrical Conductivity (EC) in weekly interval. Groundwater levels were monitored using peizometers to find the groundwater flow direction. Surface flows were measured. Rainfall data was collected from School of Agriculture, Kundasale. BOD values at the upstream pond were higher than the standard value of 30 mg/I for discharge wastewater into the environment. However, the BOD has reduced through the system. The removal rates of BOD and NH/- Nitrogen were between 79% and 92%, and 85% and 99%, respectively. The removal rate of Po/- was between 51 % and 96 % during the study period. Nitrate concentration was found within the desirable drinking water quality level. This quality improvement is due to the combined effect of plant uptake, microbial degradation, dilution and filtration. Therefore, this vegetative landscaping is an ideal system to treat domestic wastewater.