Comprehensive assessment of system performance in a full-scale wastewater treatment plant with an anaerobic/anoxic/aerobic membrane bioreactor combined with the ozonation process

: The system performance, economic cost and environmental impact of a full-scale anaerobic/anoxic/aerobic/membrane bioreactor (3AMBR) combined with the ozonation process were evaluated. The 3AMBR/ozonation process removed biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids, NH4-N and total phosphorus efficiently, with removal percentages above 94%, while the total nitrogen removal percentage was only 70%. The multiple linear regression analysis showed that hydraulic retention time (HRT) had a significant effect on nitrogen removal. A low HRT benefited nitrogen removal. Ferrous sulfate dosage close to the optimal value and a high mixed liquid suspended solid could enhance the phosphorus removal. The electricity cost accounted for 88% of the total economic costs. Greenhouse gas (GHG) emissions from the BOD oxidation and endogenous decay accounted for more than 50% of total emissions. The second largest GHG emission source was electricity consumption, accounting for 41%. The key to reduce the eutrophication was to enhance nitrogen removal. The composite cost of the 3AMBR/ozonation process was 251 CNY/t CODeq removed, among which economic cost accounted for 82.5%, while environmental impact cost accounted for a small proportion.