Fuzzy-control parameters for nitrogen removal of saline sewage in SBR process

Abstract

In order to investigate the feasibility and validity of using fuzzy-control strategy for nitrogen removal of saline sewage in the sequence batch reactor (SBR) process, the real saline sewage was treated firstly in this experiment and the variation patterns of dissolved oxygen (DO) and pH value during the removal of organic matter, nitrification and denitrification were studied in detail with fresh sewage and saline sewage at salinity 10 g·L, 20 g g·L, 35 g g·L during steady state and salinity shock periods. The results showed that the characteristic points and platforms of pH value detected in saline sewage were repeated very well and had the same regularity but DO curve changed a lot with different regularities. The characteristic points a (break point), b (ammonia valley), c (nitrate apex)could indicate the completion of organic matter degradation, nitrification and denitrification. Points a and b would appear late in the sewage with a high salinity. During the salinity shock periods, the pH value also changed with the same regularity though the characteristic points appeared in different times. However, when the salinity was above 30 g g·L the pH curve became flat. Points a and b would not appear until the aeration time was prolonged but c was influenced little. Because during the shock periods the nitrification oxidation bacteria were inhibited at first, then were ammonia oxidation bacteria, and the denitrification bacteria were inhibited at last. pH should be used as the fuzzy-control parameter for nitrogen removal of saline sewage in sequence batch reactor (SBR) process