Effect of iron powder on hydrogen sulfide reduction and phosphate removal in semi-continuous anaerobic digestion treating primary sludge

Abstract

BACKGROUND: To our best knowledge, no experimental study has previously investigated the simultaneous effects of adding Fe powder for the decrease of hydrogen sulfide (H2S) in biogas and the removal of phosphate (PO4-P) in continuous anaerobic digestion (AD). This study investigated the effects of iron (Fe) powder (5 g L−1) in AD to remove H2S and PO4-P. A comparative experiment was conducted using two semi-continuous-flow anaerobic digesters treating primary sludge at decreasing hydraulic retention times (HRTs) of 20 to 10 days. RESULTS: The addition of Fe powder to AD removed > 98% of H2S at all HRTs, and removed 64–72% of PO4-P, with the highest removal efficiency at HRT = 10 d. The addition of Fe powder to AD had no noticeable effect on biogas production or pH, but it increased the CH4 content (62.7–66.0% in Fe-treated vs 58.2–60.4% in the Control) partly due to the greater presence of Methanoregulaceae. The relative abundance of the microbial groups was more affected by HRT than by the addition of Fe powder. The presence of Fe powder notably increased the abundance of Spirochaetaceae and Syntrophaceae. CONCLUSION: As shown, the addition of Fe powder can improve the management of both H2S in the biogas and PO4-P in the digested sludge in the AD system. © 2024 Society of Chemical Industry (SCI). © 2024 Society of Chemical Industry (SCI).