Model-based study of nitrite accumulation with OUR control in two continuous nitrifying activated sludge configurations

摘要

Achievement of partial nitrification relies on the different characteristics of the microorganismsninvolved in the two steps of nitrification (AOB, ammonium oxidizing bacteria and NOB, nitritenoxidizing bacteria). Several configurations and conditions have been used to achieve partialnnitrification taking into account their different responses in front of some environmentalnconditions like pH, temperature (T), dissolved oxygen (DO) and the inhibitory compounds freenammonia (FA) and free nitrous acid (FNA). This work is a theoretical study about the utilization ofna control strategy based on controlling OUR by manipulating the influent flow-rate together withnadditional changes in T, pH or DO for achieving stable partial nitrification. Two differentnconfigurations were simulated. Configuration A consisted of three continuous stirred-tanknreactors in series plus a settler, while configuration B consisted of a single reactor with the samentotal volume and a settler. The developed control system was shown as a good tool to achievenpartial nitrification with both configurations. Nevertheless, configuration A showed better resultsnand partial nitrification was obtained even under theoretically unfavourable conditions asnT ¼ 158C, pH ¼ 8.3 and DO ¼ 3mgO2 L21n.