DESIGN CONSIDERATIONS FOR SBRs USED IN DIGESTION LIQUOR SIDESTREAM TREATMENT

There is a growing need amongst practitioners for a rigorous approach for designing sidestream treatment processes. Sequencing batch reactor (SBR) systems are a convenient vessel configuration to conduct sidestream treatment, since reactions are performed along the time axis and the duration of each process step can be more accurately controlled than a continuous flow process. Presented results demonstrate the multi-task-capabilities of SBR systems: Design objectives of all 3 different side-stream treatment options – nitritation/denitritation, deammonification and bioaugmentation – can be implemented in the same SBR layout. The suggested design volumetric loading rate of 0.6 kg NH4-N/m3 and a HRT of 2 days can provide a sufficient safety factor, since difference in SRT requirement match typical sludge production rates of these systems. Full- and pilot-scale data and the applied biokinetic model demonstrate the sensitivity of the minimum SRT of 20 days (30°C) for deammonification against TSS concentration in the influent. In case of nitritation/denitritation high ammonia concentrations can lead to limiting OUR conditions. For bioaugmentation the carbon demand can be partly covered by the RAS stream recycled for AOB enrichment with recycle rate limits also given in this paper.