Abstract
In order to remove nitrogen and phosphorus contained in secondary treated swine wastewater, performance of two steps fixed bed reactor process was examined, which consisted of autotrophic denitrification reactor filled with S0－CaCO3－medium (3－5 mm in diameter) and a phosphate absorption reactor filled with autoclaved－light－weight－concrete (ALC)－medium (5－8 mm in diameter). The former medium had coating layer of sulfur－CaCO3 mixture around perlite particle nuclei. The latter medium was byproduct of autoclaved light weight concrete production. Removal rate of NOx－－N by the denitrification reactor increased rapidly during initial about 5 days, and maintained over 95％ removal rate until about 30 days with NOx－－N loading rate of about 1.5 kg/nominal m3・day and nominal HRT of about 9 hours. Consumption of sulfur in the medium was estimated about 2.0 kg for 1 kg nitrogen removal. Phosphate removal rate by ALC medium increased to about 86％ during initial 5 days, and this high removal activity continued until about 50 days with nominal HRT of about 9 hours. The phosphate absorbing activity of used ALC medium was recovered by washing in tap water for 5 minutes with stirring. The phosphate removal reactor had also neutralization effect of acidified effluent from denitrification reactor. Both the denitrification reactor and the phosphate removal reactor had some activity of reducing true color of wastewater. Total reduction rate of true color by the two processes was about 30～40％. These results suggest that simple and stable water quality improvement of secondary treated swine wastewater would be possible by combining the two processes.
