Enhanced nitrogen removal of aerobic denitrifier using extracellular algal organic matter as carbon source: application to actual reservoir water

Man-made organic matter acting as carbon source for oligotrophic aerobic denitrification has been studied extensively, while less attention has been paid to the actual organic matter derived from drinking water reservoir. In this study, the effect of extracellular organic matter (EOM) released from Microcystis aeruginosa and Chlorella sp. and organic matter in actual reservoir water on aerobic denitrification performance of Acinetobacter johnsonii strain WGX-9 has been investigated, by measuring nitrogen removal and determining changes in the properties of organic matter. Results indicated that the Acinetobacter johnsonii strain WGX-9 showed effective nitrogen removal efficiency when cultural conditions were low C/N of 5, pH of 5–11, and low temperature of 8 °C. The nitrate removal efficiency with EOM as the sole carbon source was relatively higher than that with intracellular organic matter or natural organic matter as the sole carbon source. This is probably due to that EOM exerts a lower molecular weight and better ability of donating electrons. Besides, the findings can elucidate that nitrate and total organic matter removal efficiency with actual high-density algal water as the carbon source was higher than that with actual low-density algal water as the carbon source. This was attributed to that more EOM was released in high-density algal water, which highlighted the aerobic denitrification performance of Acinetobacter johnsonii strain WGX-9. This study will provide a reference for the application of aerobic denitrifier in drinking water reservoirs.