Potentiality of Water Quality Improvement in Irrigation Tanks by the Thin Layers of Soil Method

Abstract

One of environmental issues of an irrigation tank as one of closed water areas is water pollution such as organic pollution and eutrophication that is induced by inflow of domestic wastewater from the catchment area. A development of reasonable technique to improve water quality is required in order to conserve water environment, landscape, and habitats of irrigation tanks, because irrigation tanks may provide an open space to take a rest for residents generally.
The objective of this study was to evaluate a performance of the Thin Layers of Soil Method for a technique to improve water quality of an irrigation tank. The Thin Layers of Soil Method was developed to treat drainage from kitchen and its effectiveness was illustrated by several experiments. In this paper, indicators to evaluate the performance of the method for an irrigation tank were COD concentration and T-N and T-P concentration as typical nutritional salts.
As the results of experiments done for several months including summer at two irrigation tanks in which water quality parameter such as COD, T-N, and T-P differed from each other, removal ratio of COD was about 38 percent and removal ratio of T-P was about 34 percent, although T-N removal were not entirely clear. For an improvement of the method to adopt an irrigation tank, to maintain detention time of raw water in the installation and to keep anaerobic environment in the installation were needed.