Contribution of P-bacteria in biological nutrient removal processes to overall effects on the environment

P-bacteria can combine denitrification and P-uptake. This category of P-bac teria is abbreviated DPB. Use of DPB in BNR processes, instead of obligate aerobic PAOs, reduces oxygen consumption. Moreover, less COD is needed for the nitrogen removal. Non-required COD can be removed by presettling and us ed for methanation. This leads to a lower sludge production. As a result, C O. emissions are reduced owing to less net energy consumption. Simulation f or a planned WWTP with the BCFS (R) process indicates that DPB can save 53- 59% of required COD. The optimal ratios of COD/N and COD/P for simultaneous N and P removal are determined to be 3.9 similar to4.5 and 32.2 similar to 35.2 at 12-20 degreesC. 80-95% of particulate COD can be removed from the influent, thereby CH4 production is increased by 154-271%, and the total vo lume of reactors can be reduced by about 50% compared to a minimised proces s design. Less net energy consumption over the whole WWTP contributes to a net reduction of the total CO2 emissions up to 16-21%. The energy productio n from CH4 is excessive enough to balance the energy consumption from aerat ion, dewatering and incineration. It is concluded that contribution of P-ba cteria to saving COD has overall positive effects on the environment.