Abstract:
The objective of this research is to suggest the appropriate treatment system for aquaculture ponds. The two-step processes (rapid sand and slow sand filter) were applied for treating the wastewater from a tilapia pond. The results showed that, the optimum overflow rate of sedimentation tank was obtained at 4.07 m/hr from the removal suspended solid efficiency of 70 %. The highest treatment efficiency (93%) and moderate filtration performance (130 minutes operating time, 445 L volume of effluent and 13.2 m/hr filtration rate) can be obtained with the combination of media between anthracite (D10 2 mm and 0.15 m in depth) and sand (D10 0.5 mm and 0.55 m in depth). However, this process cannot remove nitrate in the wastewater. Therefore, slow sand filter was examined for the treatment of nitrate. Firstly, a conventional sand filter (using filtration rate of 0.4 m/d) was operated; no nitrate removal was observed in this system. Therefore, ethanol was used as a carbon source to stimulate microbial growth that could assist in denitrification. Wastewater was added with ethanol before entering the slow sand process. Moreover, in this part, optimum C/N ratio and filtration rate were 2.1: 1 and 0.2 m/hr. Finally, the daily operation area of the rapid processes (61.34 m2) was significant lower than that of sedimentation and coagulation-flocculation process (119.05 m2 and 155.1 m2) for treating 1,000 m3 of water.