Conductive polyaniline hydrogel enhanced methane production from anaerobic wastewater treatment

Three-dimensional polyaniline (PANI) hydrogel was used as the conductive medium to improve the methane (CH₄) production from the anaerobic degradation of organics in wastewater. The porous structure and hydrophilic surface of the PANI hydrogel promoted the adhesion of the anaerobes. The PANI hydrogel existed as a conductive emeraldine base (EB) form with a conductivity of 0.42 S/cm, and had a good biocompatibility with the microorganisms in the anaerobic system. The conductive PANI hydrogel was added into the anaerobic sludge as the conductive medium of the direct interspecies electron transfer (DIET) between bacteria and archaea, accelerating CH₄ production during the biodegradation of organic pollutants. The results indicated that the CH₄ production rate was increased by 10.50%, 14.21%, 28.77% and 19.30% from the anaerobic system with adding 1000, 2000, 3000 and 4000 mg/L of PANI hydrogel. The proportion of Methanosaeta in the anaerobic sludge with the ability of DIET was increased to 64.74% after adding the PANI hydrogel. The conductive PANI hydrogel served as an electronic channel to enrich the microorganism with the DIET ability, which was responsible for PANI hydrogel improved CH₄ production.