Removal of ammonium-N from a recirculation aquacultural system using an immobilized nitrifier

Various immobilization methods were evaluated for the removal of ammonium-N from recirculating aquacultural water. Ba-alginate, Ca-alginate, carrageen an, and agar beads were prepared with nitrifer consortium from the activate d sludge of a sewage treatment facility in Sooyoung, Pusan, South Korea. Ba tch bioreactor tests for the determination of the effectiveness of the:immo bilized nitrifier and the optimum hydraulic retention time (HRT) were carri ed out. The nitrifiers immobilized in Ba-alginate and Ca-alginate showed th e most effective nitrification, while those immobilized in the carrageenan and agar beads showed reduced activities. Ninety five percent of the ammoni a (20 mg/l) added to the batch bioreactor was nitrified in 6 h when immobil ized Ba-alginate or Ca-alginate nitrifiers were used. In order to apply the immobilized nitrifier to an aquaculture facility, a continuous bioreactor was used with synthetic aquacultural water containing 2 mg/l ammonia. Using immobilized Ba-alginate and Ca-alginate beads, 94 and 87% of loaded ammoni a were removed with in 3.4 h of HRT, respectively. The amounts of ammonia r emoval per day were in the range of 2.5-82 g ammonia/m(3) per day depending on HRT. The highest ammonia removal rate of 82 g/m(3) per day was observed when HRT was 0.3 h (18 min). (C) 2000 Elsevier Science B.V. All rights res erved.