Effect of effluent addition to a freshwater reservoir on the filter clogging capacity of irrigation water

This paper deals with the effect of the addition of effluents to a shallow freshwater reservoir used for irrigation, on the clogging capacity of the water. The clogging capacity was estimated with an instrument that measures the increasing differential pressure needed to maintain a constant flow of water through a 30 μm screen filter. The dependence of the clogging capacity on plankton composition and suspended solids concentration was studied by means of multiple regression analysis, on four different arrangements of the matrix of data. The addition of effluents raised the clogging capacity sharply and quickly. The phenomenon was primarily due to an increase in the number of large algae and zooplankton species. These large species partially substituted for the small ones which were dominant before the entry of effluents. The concentration of suspended solids also affected the clogging capacity, but to a much lower extent. A relationship between the clogging capacity and the total number of plankton organisms was not found. The addition of plankton filter-feeding fish to the reservoir is recommended.