Successful establishment of partial denitrification by introducing hydrolytic acidification of slowly biodegradable...

Partial denitrification (PD, nitrate → nitrite) was successfully established in this study by introducing hydrolytic acidification (HA) of slowly biodegradable organic matter (SBOM). A high selectivity for the nitrate over nitrite as electron acceptors was obtained during a 178-day long-term operation, with the nitrate to nitrite transformation ratio climbing to 81.3% at an influent SBOM of 286 mg/L and low-strength nitrate of 40 mg/L. Acetate (33.9%) and dissolved saccharide (19.3%), as the major SBOM HA products, indeed facilitated high-efficiency nitrite production by serving as favorable electron donors. This was well explained by the metagenomic analysis that the dominant Dechloromonas and Thauera denitrifying genera, which hold 3.9 times higher abundance of nitrate reductase than nitrite reductase, also played a key role in carbon glycolysis and acidification. This study provides new insight into PD development in multiple types of wastewater for the versatile carbon/nitrogen metabolism of functional bacteria.