Design of a recirculating aquaculture system based on mass balance

Quick removal of the water soluble ammonia and increase of dissolved oxygen are the core issues of system design. The system design calculating formula and basic processes ammonia and dissolved oxygen balance equation were established using mass balance relations, and the system design formula was derived. Some formulas were modified according to project practice experience. A group of appropriate design parameters closer to practical situation were obtained, for example: system compensated water volume, oxygen supply quantity, recirculation quantity, cycle-index, effective volume of biological filter and so on. At the same time, a basic flow for designing intensive recirculating aquaculture system was also constructed. A case design of a high-density recirculating aquaculture system for catfish（Ictalurus）with an annual output of 50 tons and rearing density of 50 kg/m³ was conducted. The calculated results show that the system compensated water volume is 30 m³/d with the water compensation ratio of 6%, system oxygen supply quantity is 11.0 kg/h, system recirculation quantity 740 m³/h, cycle-index is 36 times per day, effective volume of biological filter is 44.2 m³.