Study on sludge characteristics of modified A2/O activated sludge-biofilm coupling process at low temperature

Abstract

To investigate the correlation between the pollutant removal efficiency of the modified anaerobic/ anoxic/oxic (A2/O) activated sludge biofilm coupling process at low temperature and sludge characteristics, experimental studies were carried out. The study used the A2/O process coupling with biofilm, and the biofilm carrier was placed in the reactor, and the test temperature was controlled at 13°C ± 1°C. Through 180 d of operation, the average removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH4+ –N), total nitrogen (TN), total phosphorus (TP) were 86.37%, 92.09%, 74.85%, and 92.76%. The modified A2/O activated sludge-biofilm coupling process could operate stably for 180 d under low temperature condition and had excellent treatment performance. The results of the study of the sludge characteristics of the system showed that the values of extracellular polymeric substances (EPS) content between compartments differed little for activated sludge and significantly for biofilm. Dehydrogenase activity values (DHA) remained similar along the course, but the activated sludge in the system had higher dehydrogenase activity. The research results of nitrification and denitrification rate of each of compartments showed that: O2 was the leading site where nitrification taken place, but the activated sludge in the O1 compartment had a more significant absorption capacity for dissolved oxygen (DO) than O2, the higher nitrification rate in the O1 compartment resulted in a higher NH4+ –N removal rate in the O1 compartment.