Enhancement of post-anoxic denitrification for biological nutrient removal: effect of different carbon sources

Previous research has demonstrated that post- anoxic denitrification and biological nutrient removal could beachievedintheoxic/anoxic/extended-idlewastewatertreat- ment regime. This study further investigated the effect of different carbon sources on post-anoxic denitrification and biological nutrient removal. Acetate, propionate (volatile fatty acids (VFAs)), glucose (carbohydrate), methanol, and ethanol (alcohol) were used as the sole carbon source, respectively. The experimentalresults showedthatVFA substratesled to an improvement in nitrogen and phosphorus removal. The total nitrogen and phosphorus removal efficiency values driven by acetate achieved 93 and 99 %, respectively. In contrast, glu- cose present in mixed liquor deteriorated total nitrogen and phosphorus removal efficiency values to 72 and 54 %. In the reactors cultured with methanol and ethanol, 66 and 63 % of the total nitrogen were removed, and phosphorus removal efficiency values were 78 and 71 %, respectively. The mech- anism studies revealed that different carbon sources affected the transformations of intracellular polyhydroxyalkanoates (PHAs) and glycogen. PHAs are the dominant storages for microorganisms cultured with VFA substrates. Though gly- cogen is not the favorable energy and carbon source for polyphosphate-accumulating organisms, it can be consumed by microorganisms related to biological nitrogen removal and is able to serve as the electron donor for post-anoxic denitrification.