Long-term operation of a reactor enriched in Accumulibacter clade I DPAOs: performance with nitrate, nitrite and oxygen

摘要

The microbiology of denitrifying enhanced biological phosphorus removal systems has been ansubject of much debate. The question has centred on the affinities of different types ofnCandidatus Accumulibacter PAOs, type I and type II, towards different electron acceptors such asnoxygen, nitrate and nitrite. This study used a propionate anaerobic/anoxic/aerobic lab-scalensequencing batch reactor where a microbial culture was successfully enriched in Accumulibacterntype I organisms (approx. 90%). The culture was able to take up phosphorus using nitrate, nitritenand oxygen as electron acceptors, although experiments with oxygen led to the fastest P removalnrate. The phosphorus uptake to nitrogen consumed ratio (P/N ratio), when using both nitrate andnnitrite, was shown to be affected by pH in the range of 7–8.2, achieving higher values for lowernpH values (7.0–7.5). The effect of pH on P removal seems to follow a similar trend for both nitratenand nitrite. To our knowledge, this is the first study where the impact of pH in the phosphatenremoval stoichiometry using the three most significant electron acceptors is shown for such anhigh enrichment in Accumulibacter type I.