Abstract:
This study aims to investigate the roles of nitrification process in aquaponics system. Three experiments were included in this study i.e. 1) ammonium and nitrate utilization of the Green Oak lettuce (Lactuca sativa), 2) to design and study the function of water treatment systems based on nitrification process for recirculating aquaculture system (RAS), and 3) to evaluate an inorganic nitrogen and phosphorous removal efficiency of the RAS-aquaponics with and without nitrification treatment system. It was found that Green Oak lettuce was able to utilize both ammonia and nitrate forms for growth. However, the plant preferred ammonia over nitrate so the utilization of nitrate was found after ammonia depletion. To induce nitrate accumulation in RAS-aquaponics system, suspended solid filter and moving bed nitrification media were installed in the water treatment tank. Ammonia removal rate of 1.09 mg-N/d was obtained and aeration strongly enhanced the nitrification process. As expected, higher nitrate concentration in the water was found in the treatment tank with nitrification biofilter. However, long term operation of RAS-aquaponics system revealed that the nitrification process in fish and vegetable tanks was enough to perform complete nitrification treatment after 20 days of operation.