Optimization of C/N and carbon types on the denitrification biofilter for advanced wastewater treatment

In this study, the optimization of carbon-nitrogen ratio (C/N) was investigated with methanol, sodium acetate and glucose as the external carbon source in two denitrification biofilter, which used the secondary effluent treated by triple-channel oxidation ditch in Handan. The Reactor 1 was filled with ceramsite and the Reactor 2 was filled with polyethylene polyhedral hollow ring. It showed that Reactor 1 and Reactor 2 were in stable operation by the method of artificial inoculation after 25 and 30 d, respectively. Results showed that nitrate could be effectively reduced over a wide range of C/Ns. In the case of methanol, sodium acetate and glucose as the additional carbon source, the release of N2O was observed in the 1# and 2# columns, and when the C/N was increased to the optimum one it showed a sudden decline. And the N2O emission factor was the smallest when methanol was used as the carbon source, and the largest when sodium acetate was used as the carbon source. And an optimum C/N of carbon source in this study was obtained. Moreover, the effluent TN of the two filters were under 15 mg/L, meeting the Grade 1A permissible discharge standard of China [18]. Through comprehensive comparison, sodium acetate was more suitable for external carbon source.