Optimizing electrochemical methods for fish wastewater treatment in recirculating aquaculture systems

Abstract

Aquaculture operations generate substantial wastewater containing organic matter, total dissolved solids, emerging contaminants, and uneaten food pellets, leading to significant environmental issues. In this study, electrooxidation (EO) treatment methods using a boron-doped diamond (BDD) electrode was employed to remove soluble chemical oxygen demand (sCOD), ammonia (NH3-N), nitrate (NO3--N), nitrite (NO2--N), total dissolved phosphorus (TDP), and total dissolved nitrogen (TDN) from aquaculture wastewater. Response surface methodology (RSM) was used to design experiments and optimize operating parameters. The experiments were tested as follows; pH of 6-8, current density of 30-50 mA/cm(2), and electrolysis time of 20-60 min. The results showed that >93 % removal of NH3-N, NO3--N, NO2--N, TDN, and 86.85 % of sCOD were achieved. TDP removal rate was lower than compared to other pollutants and was found to be 79.41 %. The model estimation values and experimental values agreed with an average coefficient of determination (R-2) of >0.98, and all models were found significant (p < 0.05). The optimized treatment conditions were a pH of 6.97, a current density of 42.36 mA/cm(2), and an electrolysis time of 60 min. Under these conditions, responses were achieved at 87.86, 96.52, 99.18, 94.71, 94.78, and 77.78 % for sCOD, NO2--N, NH3-N, NO3--N, TDN, and TDP. In addition, the kinetic model results confirmed that the operating parameters provided a significant reduction of parameters in the EO process. The results indicated that the EO process can efficiently treat the aquaculture effluent.