Absorption and Adjustment Process of Zinc (Zn) Using Rice Bran on the Returned-Water in the Semi-Intensive Rainbow Trout Oncorhynchus mykiss Culture Systems

This study was done using rice bran for absorption of Zinc from returned-water of semi-intensive Trout culture systems in concrete ponds, Mazandaran province, Iran. The sampling period was 4 months and well's water used for ponds; 90% of returned-water was reused as input water, after purification and absorption of suspended solids using "Media system" and sedimentation's pool. Zinc metal was detected and evaluated from output water of six octagonal ponds using Photometer (Palintest-7000) and flame atomic absorption method (Thermo-MS). Rice bran was used as a natural Zinc adsorbent in 4 concentrations (0 as control, 10, 15 & 20 gr/l) and 5 treatment times (5, 15, 30, 90 & 120 min). The results showed that there are no difference between amount of Zn in well, input and output waters with 0.11±0.01, 0.13±0.02 and 0.12±0.01 mg/lit, respectively (P>0.05). There was any absorptions at the times of 5 & 15 minutes (P>0.05). The results also showed that the optimum absorption of Zn was occurred with 0.28±0.05 mg/lit (70.0%) at 90 min and 15 g/l and the minimum absorption was obtained with 0.07±0.02 mg/lit (17.5%) at 30 min and 20 g/l of concentration (P