Electrochemical simultaneous denitrification and removing phosphorus from the effluent of municipal wastewater treatment plant using cheap metal electrodes
Nitrate and phosphate in the effluent of municipal wastewater treatment plants (MWTPs) were electrochemically removed with cheap metal (aluminum and iron) electrodes. The effects of electric current density, electrolysis time and electrode material on nitrate and phosphate removal were investigated. The results demonstrated the feasibility of simultaneous removing nitrate and phosphate by electroreduction and electrocoagulation using aluminum or iron electrode. The optimum reaction conditions were determined as follows: the electric current density was 8 mA/cm2 and the electrolysis time was 1.5 h. The best removal performance of nitrate and phosphate could be obtained by using aluminum sheet as cathode and anode. Under above conditions, the removal rate of nitrate and phosphate was 100%, and 85% nitrate converted to nitrogen gas. The XRD and FTIR characterization spectra of the precipitate produced in the electrolytic cell were analyzed, and it was found that the main removal mechanism of phosphate was the co-precipitation of metal ions, phosphate ions and hydroxide ions in solution and the adsorption of phosphate by hydroxyl metal complexes. Compared with iron sheet, aluminum sheet has the less consumption in the electrolysis process with the same treatment effect. In a word, this study provided an economical and efficient alternative method for simultaneous removal of nitrate and phosphorus from the effluent of MWTPs.