The role of DPB at anoxic stage in a novel package type BNR process with batch settler.

In this research, package type BNR process was developed to remove nutrients as well as suspended solids from domestic sewage. The effect of HRT reduction of settler on the removal of pollutants as well as the role of DPBs at anoxic reactor were investigated. The proposed package system was composed of sludge denitrification tank, anaerobic, anoxic, oxic, and batch settler. This system could remove nitrogen and phosphorus effectively at low COD/N ratio and also remove SS more effectively than other ordinary BNR system having the conventional settlers. The removal efficiency of total nitrogen (T-N) in optimal condition was about 75.1% under the TCOD/TKN ratio as low as 5.7. The average concentration of the effluent TCOD, ortho-P, NH4+-N, NO3- -N and SS in the package type BNR system of 2 h settler retention time were 15.6. 1.38, 1.4, 10.3 and 3.9 mg/L, respectively. In anoxic state, denitrifying dephosphatation, that is uptaking phosphate by using nitrate-nitrogen as an electron acceptor was observed. The removed NO3- -N concentration by denitrifying dephosphatation was 1.62 mg NO3- -N/mg PO4(3-)-P.