Enhanced biological phosphorus removal from wastewater with synergistic treatment via anaerobic digestion and micro electrolysis

Anaerobic digestion coupled with micro electrolysis was employed to enhance biological anaerobic phosphorus removal. The anaerobic reactor with the micro electrolysis material maintained a relatively lower total phosphorus (TP) in the digestion mixture and a higher PH3 content in the digestion gas than the control system with no filler, which facilitated phosphorus removal due to PH3 formation. The PH3 release was positively correlated with indicators such as H2 content, COD concentration, and activity of the electron transfer system. The addition of Fe-C and Fe-Mn-C fillers promoted the biochemical metabolism of organic substrates, and the digestion systems had lower chemical oxygen demand, total nitrogen, and TP during continuous operation. The average TP in the control system was 7.0 mg L−1 from 11 d to 40 d; however, the mean values in the Fe-C and Fe-Mn-C systems were 5.1 and 4.7 mg L−1, respectively. In a conventional anaerobic digestion system, electrons and hydrogens preferentially transfer to sulfate to produce H2S, resulting in a decrease in reducing power. As micro electrolysis material was added to the wastewater, the dissolved Fe2+ or Mn2+ ions combined with sulfur ions to form sulphide precipitates, mitigating the biological toxicity derived from H2S and reducing the consumption of reactive hydrogen. Hence, electrons and hydrogen accumulate and subsequently facilitate the reduction of PH3 formation and methane synthesis. This study provides new insights into the biological dephosphorisation of wastewater.