Numerical assessment of nitrogen removal from swine wastewater in activated sludge systems: Comparison between continuous and intermittent aeration

Abstract An activated sludge model was created using numerical simulations to determine the appropriate conditions required for nitrogen (N) removal from swine wastewater (SW). Additionally, the performance of a continuous stirred-tank reactor (+settler) was assessed. Air supply was considered through continuous or intermittent aeration (CA vs. IA), and several BOD5-to-N ratios were assumed for the SW. Considering CA and low dissolved oxygen (DO) levels, N removal via nitrite short-cut method and simultaneous nitrification–denitrification was determined to be feasible. This method also assessed IA at higher DO ranges. N removal via nitrite was shown to help conserve energy for aeration. However, regardless of the aeration method, critical DO controls will be required, particularly when the SW BOD5-to-N ratio is low. This study assessed the operational conditions required to meet N standards when biologically treating SW and may help identify situations where post-treatment will be needed to reduce the N-content before further discharge.