Enhancing energy recovery and microbial stability in blackwater anaerobic digestion with graphite felt

Abstract

Maximizing energy recovery from blackwater (toilet wastewater) helps the sustainable development of human society. This study introduces a novel approach by integrating graphite felt in anaerobic baffled reactor for enhanced blackwater treatment under room temperature. During the 382-day operation, incorporating graphite felt effectively mitigated hydrolysis and methanogenesis constraints, resulting in a 1.26 to 3.53-fold increase in methane yield compared to the control. The maximum energy recovery was attained at a hydraulic retention time of 1.59 d and an organic loading rate of 2.68 kg COD/m3reactor/d, with a methane production rate of 371 ± 55 NL CH4/m3reactor/d and a methanization rate of 39.44 ± 5.58 % in graphite felt amended reactor. Our findings revealed that graphite felt augmented the efficiency of microbial and enzymatic interactions with the substrate, and enriched hydrolysis fermentation-associated bacteria for efficient solid matter degradation. Further analysis unveiled that graphite felt strengthened the activity of hydrogenotrophic methanogens and fortified the syntrophic relationship between bacteria and archaea. This led to the promotion of a combined syntrophic acetate oxidation and hydrogenotrophic methanogenesis pathway, which guaranteed a stable and efficient methane production process. Overall, this approach offers a cost-effective and efficient strategy to support sustainable development in less-developed, resource-constrained regions.