Effect of the Acetate and Propionate Ratio on the Structure of the Community of Denitrifying Phosphate-Accumulating Microorganisms and on the Efficiency of Simultaneous Phosphorus and Nitrogen Removal

Denitrifying phosphate-accumulating microorganisms (DPAO) play the key role in the processes of simultaneous nitrogen and phosphorus removal during biological wastewater treatment. The present work investigated the effect of the acetate-to-propionate ratio on the efficiency of phosphorus and nitrate removal and on the structure of the DPAO microbial community in a laboratory SBR reactor operating in the cyclic anaerobic-anoxic mode. An increased share of propionate was shown to decrease the rate of anaerobic phosphate release (from 90 to 32.36 mg P–PO4/L) and the rates of anoxic phosphate and nitrate consumption. This was accompanied by redistribution of the dominant taxa of phosphate-accumulating organisms (PAO): relative abundance of Dechloromonas decreased from 41.2 to 8.99%, while that of Ca. Accumulibacter increased from 0.3 to 27.5%. These results indicate that varying the ratios of acetate and propionate has a significant effect on the DPAO structure and functional activity, which should be considered when optimizing biological nitrogen and phosphorus removal.