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Abstract
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This study aims to investigate the performance of disc, conventional screen, and automatic screen filters when rainbow trout fish effluent is used for irrigation. The experiments were performed in a fish farm, located in the north-west of Iran. The disc and conventional screen filters were tested at pressures of 150 and 300 kPa, and the automatic screen filter at 200 and 300 kPa. The filtration experiments continued until the backwashing was reached. The results showed that (1) the initial head loss of disc and conventional screen filters was 40 kPa, while for the automatic screen filter was 5 kPa. (2) In the disc filter, with increasing working pressure, the filtered volume significantly (P< 0.05) increased from 9.7 to 14.5 m3 m−2 (10 kPa)−1, but for conventional and automatic screen filters, it was constant at 5.5 and 7.0 m3 m−2 (10 kPa)−1, respectively, and all of them had significant (P < 0.05) differences. (3) In the disc filter, with increasing the working pressure, the filtered volume o reach backwashing significantly (P < 0.01) increased from 80.9 to 104.4 m3 m−2, while in the conventional screen filter increased from 14.1 to 16.4 m3 m−2. This volume at two working pressures was 29.5 m3 m−2 for the automatic screen filter. These volumes were significantly different (P < 0.01) between filters. (4) The mass retention for the disc, conventional, and automatic screen filters were 28.88, 9.11, and 7.72 g min−1 m−2, respectively, and tended to increase at lower working pressures. Based on this index, the difference in the performance of the filters was significant (P< 0.01). (5) Overall, the best performance was for the disc filter, and after that was the automatic screen filters, but the period of time to operate for the filters until backwashing time was less than half an hour, which is not applicable under farm conditions.
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