A comprehensive method for the evaluation of biological nutrient removal potential of wastewater treatment plants

An evaluation method based on the supply and demand of carbon source in the biological nutrient removal (BNR) process, combined with an index of difficulty of nutrient removal (DNR), was put forward to achieve comprehensive assessment and analysis of the BNR potential of wastewater treatment plants (WWTPs). Twenty-five full-scale municipal WWTPs with different BNR processes were evaluated over a period of 12 months in Shanghai (China). Statistical analysis results showed that the DNR index had significant positive correlation (r > 0.790, p < 0.01) with total nitrogen, total phosphorus concentrations in the effluent, and yielded higher correlation coefficient with BNR efficiency than the C/N and C/P ratios that were conventionally used to estimate carbon source supply conditions. According to the WWTPs ranking by DNR evaluation, the number of WWTPs with low, medium, high, and extremely high DNR level was 8, 10, 6, and 1 among the 25 WWTPs, respectively. The developed method can evaluate and analyze the BNR potential scientifically and objectively, and the ranking results can be used to guide level-to-level management, upgrading, and optimization of WWTPs under different discharge standards.