18-Month Operation of Sidestream Deammonification - Ready for Mainstream Anammox Seeding?

In May 2015, Alexandria Renew Enterprises (AlexRenew), a 54 MGD advanced resource recovery facility, started up a centrate pretreatment (CPT) system. This system utilizes the sidestream deammonification process (DEMON®) to remove nitrogen in the centrate that results from dewatering anaerobically-digested sludge. Ammonia removal rate has averaged 90% ranging between 77% and 97% and TN removal has averaged 78% within a range of 58%-89%. The CPT process is removing 10% of the secondary treatment ammonia loading without any methanol addition and utilizing 38% of the oxygen as compared to conventional nitrification, presenting an opportunity for great savings in energy and chemical consumption. During the startup period, the CPT process has encountered a number of challenges including poor centrate quality, high polymer carryover from dewatering, micronutrient deficiency and instrument maintenance etc. These challenges have been addressed via operational measures or are studied through lab tests. After almost 1.5 years of operation, our CPT process reliably reached 100% of centrate loading. This paper summarizes the startup of our CPT process by documenting the issues encountered as well as approaches taken to resolve each problem, observed seasonal impacts and microbial population transition during periods of process upset.