Development of Smart and Compact Advanced Treatment Process for Nutrient Removal — Carrier-Added A2/O Process —

Nagoya City is required to implement advanced wastewater treatment for reducing COD, nitrogen and phosphorus loads in order to preserve the water quality in Ise Bay, a prominent semi-closed water area in Japan. Due to advanced urbanization in the city, however, it is difficult to expand existing treatment facilities to implement such a measure.To solve this problem, Nagoya City conducted an experiment to verify the feasibility of a carrier-added A2/O process for removing nitrogen and phosphorus by modifying the carrier-added recycled nitrification-denitrification process used for nitrogen removal.The targeted objective of the demonstration test was to simultaneously remove nitrogen and phosphorus biologically within an HRT comparable to that of the conventional activated sludge process (6.5 to 8.5 hours), approximately half that of the standard A2/O process. A treatment plant in service, operating the conventional activated sludge process, was remodeled to carry out the demonstration test.This remodeling has proved that it is possible, without converting an existing facility extensively, to greatly improve the quality of treatment effluent in terms of the discharged amounts of nitrogen and phosphorus.This paper reports on these results and on newly observed characteristics of the modified treatment process, such as nitrification rates and denitrification reaction.