Abstract
Nitrogen and phosphorus removal from swine wastewater in three bench-scale activated sludge units with limited and non limited aeration processes (LAP and NLAP) was investigated. The ratio of BOD : T-N : PO4-P of wastewater charged was 100:33:4. Operational conditions for the units were the same except for aeration periods; in the conventional method (NLAP), aeration began at the charging, while in the limited aeration processes (LAP-13, LAP-8), thirteen and eight hours after the charging, respectively. These units were operated under the loadings of 0.25 and 0.50 kgBOD·m-3·d-1. High removal efficiencies for BOD and TOC were achieved with both LAPs and NLAP. However, large difference of nitrogen removal between LAPs and NLAP was found: at a BOD loading rate of 0.50kg·m-3·d-1, removal efficiencies for total nitrogen in LAP-13, LAP-8 and NLAP were 52.4%, 53.9% and 19.2%, respectively. The time course analyses during those operations indicated a shortage of aeration for nitrification in LAP-13 at a BOD loading rate of 0.50kg·m-3·d-1, and advance of nitrification was needed to attain higher removal efficiency for nitrogen.
