Application of a Smart Pilot Electrochemical Systems for Recycling Aquaculture Seawater

Abstract The energy cost and the harm of the residual chlorine by-produced in the electrochemical processes are main hinders for the extensive use of the electrochemical recirculating aquaculture systems (ERAS). The present study conducted shrimp-culture experiments using pilot electrochemical systems to investigate the effects of current density, geometric feature, timing, and other parameters on the effective control of inorganic nitrogen, pathogens, and residual chlorine in aquaculture water. The 50-L electrochemical batch reactor, which featured 154 cm2 (area) of Ti-RuO2 / Ti electrodes and 66 mA/cm2 of current density, eliminated inorganic nitrogen and Vibrio in rearing seawater collected from a shrimp farm with an initial ammonia concentration of 1.2–4.0 mg/L in 5 min. Air strippings were used to resolve residual chlorine derived from electrooxidation, finding hypochlorous acid decreased from 5.0 mg/L initially to 2.5 mg/L in 2 h of continuous of air aeration to the batch reactor. In the experiments of shrimp culture, The ERAS equipped with a 50-L batch reactor and 500-L shrimp tank effectively keep the inorganic nitrogen concentration in rearing water as required when applying 4.3 g of nitrogen loads transformed from a daily quota of commercial prawn feeds. By precisely controlling the times of intermittent processes of electrooxidation and air stripping, an electrochemical recirculating aquaculture system can achieve both the removal of inorganic nitrogen and residual chlorine, disinfection and reduction of energy cost.