Free Chlorine Disinfection of Full-scale MBR Effluent to Achieve 5-Log Virus Inactivation

In May 2015, Alexandria Renew Enterprises (AlexRenew), a 204,412 m3/d 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 produced from dewatering anaerobically-digested sludge. During the startup period, the ammonia and total nitrogen removal rates averaged 89 percent and 78 percent, respectively. The CPT system startup encountered a number of operational issues including centrate quality, nitrite control, excess polymer and micronutrient deficiency etc. These challenges were identified and addressed primarily through operational and process control measures. The CPT process reached 100% plant centrate production (0.5 kg N/m3/d) after 18 months of startup period. This paper summarized major challenges during the startup phase of the CPT system from an operational standpoint, documented our approaches and learnings to tackle each problem and shed some light on future improvement.