The main aim of this study was to investigate the qualitative changes of the rainbow trout effluent as water supply in a drip irrigation system. Two drip irrigation systems with a hydro-cyclone filter, sand filter and screen filter for using freshwater (control treatment) and fish farm effluent were tested in Kurdistan province (northwest of Iran) in 2017. In addition, the effect of lateral drainage at the end of each irrigation event was also studied. Two emitter types with different discharge flows were used for each treatment. In the 16 irrigation events carried out, samples were collected from the different water sources (dam, well, and river), filter outlets and lateral locations for measuring total suspended solids (TSS), particle size, pH, electrical conductivity, different compounds (Fe, Na, K, Ca, Mg, NO3, PO4, HCO3) and the number of coliform bacteria. The results showed changes in the TSS and the number of coliform bacteria, but the remaining parameters had slight changes. In both control and effluent treatments, the filtration system significantly reduced TSS, having the screen filters the greatest effect on this decrease and hydro-cyclone and sand filter the least. To achieve higher removals, it is recommended to use finer grains in sand filters. The filtration of both control and effluent treatments increased the number of bacteria. The highest number of bacteria in the control treatment was measured after the sand filter and in the effluent treatments after the screen filter.
