Application of Electrochemical Treatment for the effluent from Marine Recirculating Aquaculture Systems

An actual wastewater from a western king prawn (Penaeus latisulcatus) culturing tanks located in Zhoushan (Eastern coast of China) was investigated through electrochemical process. Under an electrical field, ammonia and nitrite were indirectly oxidized by electro-generating HOCl, whereas organic compounds were directly oxidized at the anode surface. To achieve simultaneous removal of total ammonia nitrogen (TAN), nitrite (NO2-N) and Chemical oxygen demand (COD), the current density had to be controlled over 23.4 A/m2. Concurrently, finely suspended particles (SS) were effectively separated from wastewater by electroflotation, while the current density was below 25 A/m2. The retention time had insignificant effect on TAN, NO2-N and SS removal. However, the removal efficiency of COD was highly related with the retention time. Experimental results indicated the optimum operating conditions: 25 A/m2 of current density, and 40 minutes of retention time. Under these conditions, the energy consumption was 1.75 kWh/m3 wastewater.