Laboratory studies on nitrogen and phosphorus removal from swine wastewater by iron electrolysis

Biological process-free ("Bio-free") treatment of swine wastewater (pH 8.5 or above) for the removal of nitrogen and phosphorus was examined. In this study centrifugal separation of solids and liquids was followed by iron electrolysis, which enables removal of nitrogen and phosphorus when iron is set as the cathode and anode, respectively. The manner in which the treatment efficiency varies according to the current ratio of iron anode to iron cathode (R-ac) was investigated. Nitrogen was removed to a level below 60 mg l(-1) in a 3-h treatment when R-ac., was above 75% and phosphor-us was removed I( a level below 8 mg l(-1) in the same period, irrespective of R-ac. Nitrogen removal efficiency was 60 kWh kg-N-1, which is 6 times higher than that of the same electrolytic treatment when used after aerobic biological treatment ("Post-bio").