Deammonification efficiency in combined UASB and IFAS system for mainstream WWT

Abstract: The study is about Nitrogen removal from the low concentrated mainstream wastewater after Upflow Anaerobic Sludge Blanket reactor process (UASB) by single-stage Partial Nitritation/Anammox process in a pilot scale reactor at Hammarby Sjöstad in Stockholm. A mixture of various concentrations of dissolved oxygen and different aeration methods have been tested in the pilot scale reactor in five months divided into five periods where the temperature was set at 15° C throughout the study. The best result was in period 4, the average nitrogen removal efficiency was 52% varying between 40 and 60 % with aeration method of the ratio R = 1/3 (R = 20 minutes with aeration to 40 minutes without aeration) and a dissolved oxygen concentration of 1.3 mg/L. Partial nitritation/Anammox is considered more environmentally friendly due to reduced energy requirements for aeration, no need for an external carbon source. The process also allows for a more cost-effective nitrogen removal from wastewater.