Electrochemically assisted sulfate reduction autotrophic denitrification nitrification integrated (e-SANI®) process for high-strength ammonium industrial wastewater treatment

Large amount of high-strength ammonium industrial wastewater was discharged in China causing serious environmental pollution. In this work, an electrochemically assisted sulfate reduction autotrophic denitrification and nitrification integrated (e-SANI) process was developed by coupling a microbial electrolysis cell (MEC) with a conventional SANI process for high-strength ammonium wastewater treatment. In the e-SANI process, the MEC cathode was used for hydrogen-oxidizing autotrophic denitrification and simultaneously for pH elevation, while the MEC anode oxidized residual sulfide in effluent for elemental sulfur recovery. As a key operational parameter, the cathode potential was controlled at -0.8, -0.9 and -1.0 V (vs. Ag/AgCl, saturated KCl) to evaluate the total nitrogen removal efficiency in the e-SANI process. The results indicated the maximum total nitrogen removal efficiency was significantly improved in the e-SANI system (56.9 +/- 1.4% at -1.0 V) compared to the conventional SANI system (34.8 +/- 2.3%). With the assistance of the anode, residual sulfide in effluent can be significantly eliminated through oxidation to elemental sulfur. Furthermore, microbial community in the e-SANI system was analyzed and Bacteroides and Thiobacillus were identified as the predominant denitrification bacteria in the cathode chamber. Conclusively, the developed e-SANI system extends the application of the SANI process and can be a promising technology for high-strength ammonium wastewater treatment.