Solid slow-release carbon sources improve the simultaneous nitrification and denitrification processes in low carbon resource wastewater.

In this study, A Acinetobacter pittii sp. was isolated with high efficiency for heterotrophic nitrification and aerobic denitrification (HN-AD). The boundary conditions for total nitrogen (TN) removal were as follows: C/N ratios 8-14, temperature 25-35 °C, initial pH 7-9, and shaker speed 100-120 rpm. Addition of mixed carbon resources achieved 97.38 % ammonia-N and 91.50 % TN removal, which was higher than that of the group with sole carbon resources. The ammonia-N and TN removal profiles matched well with first-order kinetics in the rapid response period and zero-order kinetics in the slow reaction period. Meanwhile, enzyme activity related to nitrogen conversion would remarkably increase with mixed carbon resources. Furthermore, proposed a possible relationship between the solid carbon source, hydrolysis, soluble small molecule organic matter, microbial activity, and heterotrophic nitrification and aerobic denitrification (HN-AD). This study provides a new strategy for improving nitrogen removal in wastewater with low-carbon resources.