Removal of nitrogen and phosphorus from swine wastewater by intermittent aeration processes

Nitrogen and phosphorus removal in a methane fermentation plus activated sludge method type pig farm (M-III) with an intermittent aeration process (IAP) was evaluated in comparison with a continuous aeration process (CAP) based on the full-scale and bench-scale experiments. Operation conditions for the treatment system were the same except for the aeration program (in the CAP), a consecutive 24-hr aeration was used, whereas in the IAP, the aeration and non-aeration periods were alternated at intervals of 3:1 hr. BOD and TOC removal efficiencies with the intermittent aeration were as high as those with the continuous operation (92-98%). In the removal of nitrogen and phosphorus, large differences between IAP and CAP were observed. At an influent T-N/TOC ratio of 0.1, removal efficiencies for T-N in the bench-scale IAP was 70%, and for T-P was 22%, respectively. At an even higher influent T-N/TOC ratios of 0.3-1.0, the removal efficiencies for T-N were decreased to about 59-61%, whereas that for T-P were -0.3-13%. In a full-scale plant, removal efficiencies for T-N with IAP and CAP were 42% and -0.09%, respectively. The results of this study show the successful performance of a simple IAP for piggery wastewater: simultaneous, one-sludge denitrification with nitrification in single-activated sludge reactor in a pig farm.