Bi-bio-selective simultaneous phosphorus and nitrogen removal (BBSPN) novel process

The current municipal wastewater treatment processes are difficult to remove nitrogen and phosphorus simultaneously, especially for domestic wastewater characterized with low C/N. Based on traditional A/O process, a novel Bi-bio-selective simultaneous phosphorus and nitrogen removal (BBSPN) process was developed through adding two-stage biological selectors before A/O process. An anaerobic selector was adopted to provide the most appropriate environment for biological phosphorus release; an anoxic selector was added to avoid nitrate of return sludge influencing phosphorus release and to prevent filamentous bulking. The removal efficiency of COD, ammonia nitrogen and total phosphorus was 88%, 90% and 97% in the steady-state under the condition of influent COD/TN=4.4, COD/TP=33. The effluent qualities can achieve Grade A standard of 'urban sewage treatment plant emission standards'. Hereto, 35% of total phosphorus was removed by denitrifying dephosphatation. Moreover, the linear relationship between nitrate and anoxic phosphorus uptake in anoxic compartment was established. 1 mg NO ₃ ^--N consumption corresponds to 1.8 mg P-uptake, which can be used as a key controlling parameter for this novel denitrifying dephosphatation process.