Optimization of anaerobic acidogenesis by adding Fe0 powder to enhance anaerobic wastewater treatment

Acidogenesis is responsible to convert complex organics into volatile fatty acids (VFA), whose metabolic rate and production type have important effects on the whole anaerobic digestion. A novel strategy for enhancing anaerobic wastewater treatment via dosing Fe powder (40 g) in an acidogenic reactor (2 L) is described. The results showed that the hydrolysis/fermentation was accelerated by Fe dosing. As a result, the acidogenic performances in COD removal (45-56%) and VFA production (1170-1340 mg/L) were less affected by shortened hydraulic retention time (HRT) from 6 to 2 h. However, COD removal declined to 25% and VFA production decreased to 661 mg/L in a reference reactor without Fe⁰ dosing (A2). Besides, Fe⁰ dosing optimized fermentation type, namely, the production of propionate was decreased, which was favorable for subsequent acetogenesis and methanogenesis. Fluorescence in situ hybridization (FISH) analysis indicated that Fe⁰ dosing increased the abundance of acidogens, especially acetogens. The methanogenic reactor fed with the effluent of A1 had higher COD removal and treatment stability with almost no propionate detected. These results suggested that the enhancement of acidification by Fe⁰ powder dosing was helpful to accelerate and improve anaerobic acidogenesis to create a favorable feeding condition for the subsequent treatment.