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.

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This study evaluated the effect of pre-pasteurization (70 oC for 45 min) on the performance of temperature-phased anaerobic digestion (TPAD) in horizontal comparison with standalone mesophilic and thermophilic anaerobic digestion...

Anaerobic digestion stabilizes municipal sludge through total solids reduction and biogas production. It is generally accepted that hydrolysis accounts for the rate‐limiting step of municipal sludge anaerobic digestion, impacting the overall rates of solids reduction and methane production. Technically, the sludge hydrolysis rate can be enhanced by the application of thermal hydrolysis pretreatment (THP) and is also affected by the total solids concentration, temperature, and solids retention time used in the anaerobic digestion. This study systematically analyzed and compared ways to take these four factors into the consideration of modern anaerobic digestion system for achieving the maximum solid reduction. Results showed that thermophilic anaerobic digestion was superior to mesophilic anaerobic digestion in terms of solids reduction but vice versa in terms of the methane production when integrated with THP. This difference has to do with the intermediate product accumulation and inhibition when hydrolysis outpaced methanogenesis in THP‐enhanced thermophilic anaerobic digestion, which can be mitigated by adjusting the solids retention time. Practitioner points THP followed by TAD offers the greatest solids reduction rate. THP followed by MAD offered the greatest methane production rate. FAN inhibition appears to be an ultimate limiting factor constraining the methane production rate. In situ ammonia removal technique should be developed to further unblock the rate‐limiting step.