Effects of acetate and nitrite addition on fraction of denitrifying phosphate-accumulating organisms and nutrient removal efficiency in anaerobic/aerobic/anoxic process
(1) Department of Chemical Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan;(2) Mayekawa Mfg. Co. Ltd. Moriya Factory, Research and Development Center, 2000 Tatsuzawa, Moriya City, Ibaraki 302-0118, Japan
Abstract:
The effects of acetate and nitrite on the performance of sequencing batch reactors (SBRs) employing an anaerobic/aerobic/anoxic (AOA) process were investigated. Three types of SBR operations were used: sodium acetate addition at the start of anoxic condition for heterotrophic denitrification (Type 1); sodium acetate addition at the start of aerobic condition for anoxic phosphate removal by denitrifying phosphate-accumulating organisms (DNPAOs) (Type 2: conventional AOA process); and nitrite addition at the start of aerobic condition for inhibition of phosphate-accumulating organisms (PAOs) (Type 3). A track experiment shows that Type 2 led to the best performance of SBRs among the three types. An analysis by fluorescence in situ hybridization (FISH) revealed that nitrite addition decreased the ratio of PAOs with a decrease in phosphorus removal efficiency. The fraction of DNPAOs in Type 2 was the highest at 13%, indicating that Type 2 is suitable for the simultaneous nitrogen and phosphorus removal in the AOA process.