Nitrification/denitrification in an intermittent aeration process for swine wastewater

Abstract Nitrogen removal by a methane fermentation plus activated sludge process with the intermittent aeration was presented based upon a full‐scale pig farm experiment. Swine wastewater had a T‐N/BOD ratio from 0.2–0.29. The BOD concentration input to the process ranged from 1050–1608 mg l‐1 and the T‐N concentration from 273–350 mg l‐1. More than 90% of organic carbon was removed in each experimental run. Only small concentrations of NO3‐N were found in the effluent and higher than 60% of the T‐N and 73% of NH4‐N which were loaded to the intermittent aeration tank was removed. The nitrogen balance of each run was calculated. Denitrification was estimated to be accountable for 45–90% of the T‐N removed in the intermittent aeration tank. Denitrification rate increased as the BOD concentration increased (> 1300 mg l‐1). The T‐N removal percentage was a function of the T‐N/BOD ratio of the influent. Although higher DO concentration (> 3 mg l‐1) did not enhance the denitrification rate, nitrification did m...