Nutrient removal from separated pig manure digestate liquid using hybrid biofilters

In this study, laboratory-scale hybrid biofilters were set up to treat the separated pig manure digestate liquid at two loading rates of 0.12 and 0.07 kg N m(-3) per day. The hybrid biofilters were operated with a sequencing batch reactor mode. Over the operation of 136 days, 84% and 88% of total nitrogen was removed on average in addition with complete nitrification at the high loading rate and low loading rate, respectively. In the anoxic phase, the nitrate reduction rates were 0.31 and 0.24 mg L(-1) min(-1); and in the aerobic phase, nitrification rates were 0.29 and 0.18 mg L(-1) min(-1) at the high loading rate and low loading rate, respectively. It was found that in the hybrid biofilters, biofilm biomass had much higher nitrification and denitrification activities than suspended growth biomass. Phosphorus removals achieved were up to 88%. The results show the hybrid biofilter technology is valid for high nutrient pig manure digestate liquid treatment.