Removal of Organic and Ammonium Nitrogen Pollutants in Swine Wastewater Using Electrochemical Advanced Oxidation

In this study, tests were performed to examine the effects of with/without chloride addition, electrolyte (NaCl vs. Na2SO4), anode material (boron-doped diamond (BDD) vs. PbO2), current density (0.10-0.50 A/cm(2)), and anode area (2-6 cm(2)) on the electrochemical abatements of organic pollutants (in terms of total organic carbon (TOC) or chemical oxygen demand (COD)) and ammonia nitrogen in swine wastewater. The results showed that the TOC degradation was greater in the absence of chloride, but an opposite trend was observed for NH3-N electrochemical abatement. A similar phenomenon was also observed when replacing chloride with sulfate. In the presence of chloride, the NH3-N removal efficiencies were similar on BDD and PbO2, although the former anode was better for TOC degradation than the latter. The removal of both COD and NH3-N increased with increasing current density or anode area on BDD. During the electrolysis of the wastewater, nitrite was not detected in the presence of chloride except in the absence of chloride, in the presence of Na2SO4, or on PbO2 at 0.25 A/cm(2) and on BDD at 0.50 A/cm(2) in the presence of chloride. In the presence of chloride, the concentration of nitrate increased and then decreased with increases in electrolysis time for almost all the tested conditions. At 25 degrees C and 0.25 A/cm(2), the pseudo-first-order rate constants for COD and NH3N removal were 7.05x10(-4) and 6.40x10(-4) 1/s, respectively, while the general current efficiency and specific energy consumption were 15% and 9 kWh/kg-COD, respectively on BDD (4 cm(2)).