Implementation of a Full-Scale Anammox-Based Facility to Treat an Anaerobic Digestion Sidestream at the Alexandria Sanitation Authority Water Resource Facility

The 204,000 m³/day Alexandria Sanitation Authority (ASA) Water Resource Facility (WRF) is currently being upgraded to meet an annual average total nitrogen (TN) waste load based on a concentration of 3 mg/L at its current design capacity. The State-of-the-Art-Nutrient-Upgrade-Program (SANUP) includes a system to treat the high nitrogen solids handling sidestream from dewatering anaerobically digested solids. The centrate pretreatment (CPT) system is being implemented as a sequencing batch reactor (SBR) capable of operating in three modes: (1) nitrification/denitrification, (2) nitritation/denitritation, and (3) partial nitritation/Anammox according to the “Universal Tank” concept. The design concept and basis for the facility are presented, along with the physical layout. It is being implemented using a conventional design-bid-build approach. Design is complete and construction is currently in the bid phase. Construction is expected to begin in the second quarter of 2011 and to be complete by December 2012. The estimated construction cost is $US 14.1 million. The design incorporates a number of innovations, including: (1) accounting for variations in process loading and anticipated operating modes over the life of the facility, (2) provision of a 10 percent capacity daughter reactor to facilitate process optimization and testing, and (3) inclusion of a cyclone to selectively retain the slow growing Anammox bacteria. It is anticipated that the facility will start up in the nitritation/denitritation mode, while the daughter reactor is used to acclimate biomass and finalize the operating strategy for the partial nitritation/Anammox mode.