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 hydrocyclone 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. In order to achieve higher removals, 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
Abstract. Stepped spillways are employed to reduce excess energy encountered with exiting ow from high hydraulic structures. Study of local scour evolution downstream of stepped spillways wilt, therefore, provide the required information to reap the bene ts made from these structures to minimize the scour hole dimensions. This paper provides the results of 67 experiments downstream of some stepped spillways subjected to di erent Froude numbers, basin lengths, tail-water depths, sediment sizes, and two di erent sloped spillways. The experiments were continued for 6, 8, 12, and 24 hours from which 824 pro les and 85000 data points were recorded and analyzed. The results show that, in certain circumstances, the dimensions of scour hole increase in accordance with particle Froude number. It was also observed that an increase in the slope of spillway would result in reduction in the geometries of scour hole. Under certain conditions, as the tail-water increases, the depth of scour hole increases and elongates the hole. The relations of duration of scour evolution downstream of stepped spillway are presented in this paper. Finally, it was observed that the stepped spillway would considerably decrease the dimensions of scour hole compared with ogee spillways, re ecting the excess energy downstream loss of stepped spillway.
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 m 3 m -2 (10 kPa) -1 , but for conventional and automatic screen filters, it was constant at 5.5 and 7.0 m 3 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 to reach backwashing significantly (P<0.01) increased from 80.9 to 104.4 m 3 m -2 , while in the conventional screen filter increased from 14.1 to 16.4 m 3 m -2 . This volume at two working pressures was 29.5 m 3 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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