Abstract: In response to increasing strict regulations on aquatic product quality, organic matter and nitrogen discharge, industrial recirculating aquaculture systems (RASs) are getting more and more application because of their minimal environmental impact and controlled operation. As a core unit of RASs, marine biofilters play an important role in controlling water quality. It is important to establish a scientific, reasonable and efficient design to improve the purifying efficiency of the biofilters. In this paper, the production situation of a certain farm was taken as an object to design a moving bed biofilm reactor using material balance principle and water purification facilities construction technology. Under the guidance of the balance principle of nitrogen, the maximum ammonia production rate, maximum allowable ammonia nitrogen concentration in culture ponds, quantity of exchanged water, and oxygen demand of the tank and biofilter were calculated based on the oxygen consumption rate of aquaculture organisms, oxygen consumption of nitrification and the dissolved oxygen balance. The three flow rates required for removal of target ammonia nitrogen and for dissolve oxygen in the culture tank and biofilter were calculated. On the basis of the above calculation, several key parameters were precisely established according to the water treatment facilities construction technical specifications and production experience, including the flow rate, volume, circulation, hydraulic retention time, quantity of exchanged water and filtration equipment. The main technical parameters were determined as the circulated flow rate of 286 m3/h, volume of 140.59 m3in four biofilters of each 4 m×4 m×2.5 m, the water level of 2.2 m, hydraulic retention time of 29 min, exchanged water of 1.16 m3/h, at a rate of 20 times a day, the diameters of 300 and 200 mm in total and branch inlet pipe, blower volume of 1716 m3/h and the carrier Kaldnes K3 filling with 40%. It is put forward to provide a complete design method for the proper design of biofilter with the above process. The findings provide a good reference for the design of moving bed biofilter reactor in recirculating aquaculture system.
2018, Vol. 33 
