Electrochemical removal of nitrite in simulated aquaculture wastewater

Abstract

Electrochemical removal of nitrite at a concentration of 10 mg l^-1 from synthetic aquaculture wastewater was investigated in this study using a batch reactor. The effects of important operating parameters such as electrode material and applied current density were studied. The highest nitrite removal is achieved with nickel as compared to stainless steel and other electrode materials. Optimum nitrite removal is achieved at a current density of 3.75 mA cm^-2 and an initial pH of 5. Basic pH tends to inhibit nitrite oxidation, which is consistent with the literature. An optimum anode to cathode surface area ratio of 1 and an inter-electrode spacing of 2 cm gave best results, respectively. Nitrite concentrations are reduced to match USEPA’s discharge limit of 1 mg l^-1 within 5 min of experimental runs. This is much better than previously reported results. Nitrate concentrations generated remained within USEPA’s discharge limit of 10 mg l^-1. Further experiments are recommended for the conversion of nitrate to nitrogen. Using operating parameters determined here, it was envisaged that real aquaculture wastewater can also be treated efficiently for the removal of nitrite in both batch and continuous scales of operation.

Key words: Electrochemical oxidation, nitrite removal, aquaculture wastewater.