Two-step activated carbon cloth enhances microbial interactions and methane production during anaerobic digestion of municipal sludge

Abstract

This study investigated the effects of two-step activated carbon cloth (CC) on the syntrophic microbial associations during anaerobic digestion (AD) of municipal sludge. A simple two-step activation, acid pretreatment (H2SO4/HNO3) followed by air calcination (550 °C), was used to convert commercial untreated CC (U-CC) into high performance activated CC (A-CC). Biochemical methane potential (BMP) assays conducted at different CC dosages indicated that A-CC, at a dose of 0.80 g A-CC {1.48 g A-CC/g-VS (volatile solids)substrate}, enhanced methane yield from by 3.7× and reduced the lag phase up to 15.6-fold, compared to non-CC Control within 3 days. Characterization of CC surfaces and kinetic modeling indicated indicated that A-CC pore size area increased by 435× a (Barrett, Joyner, and Halenda, BJH) with the potential to promote electron transfer and accelerate kinetic rates of methane production. Consistent with these results, microbial community composition profiles of CC surfaces indicated rapid adherence of methanogenic archaea and bacterial syntrophs to A-CC within 3 days. Multi-variate statistical analyses indicated that these populations were highly enriched on 0.80 g A-CC dosage compared to U-CC and Controls. Based on these results it can be concluded that A-CC provides a robust selective environment for syntrophic energy metabolism driving enhanced methane production from municipal sludge.