Evaluation of Performance and Optimization of Horizontal Roughing Filter (HRF) to Reduce Turbidity and Suspended Solids from the Wastewater Treatment Plant Outflow for Agriculture Use

One of the influential processes on Total Suspended Solids (TSS) and Turbidity (TUR) removal can behorizontal roughing filter (HRF). Lack of water resources has addressed using of treated wastewater as one of the approaches to solve the problem. Therefore, low cost and natural methods are considered to improve polluted water quality. In this paper, HRF performance was evaluated in pilot scale with four compartments of difference size of sand and also in three filtration rates of 0.5, 1 and 1.5 meter per hour. The performance of constructed HRF was monitored throughout the pilot operation period under the effect of effluent from a wastewater treatment plant which contains TSS and TUR exceeding the Iranian Environment Protection Organization limits(even for agricultural use which its permissive standard is more than the allowable one for discharging surface water). Comparing the three filtration rates indicated that maximum efficiency, which is equal to 72 percent, has occurred in 0.5 meter per hour. Analyzing of samples in the rate of 0.5 meter per hour showed that as filter operation time (T) increases, at first, TSS and TUR removal rise to 72 and 54 percent until the third month of T and then falls to 39 and 33.5 percent to the end of T, respectively. It was demonstrated that the four compartments HRF, in comparison with three compartments in previous studies improve system efficiency. Moreover, according to Iranian Environment Protection Organization standards, outlet TSS from the HRF with four compartments (40 mg/L) was within the allowable limits to discharge surface water and suitable for use in agriculture and irrigation.