Phase separation as a strategy to prevent sulfide-related drawbacks in methanogenesis: performance and energetic aspects

This study investigated the impacts of removing SO42- during fermentation on the performance of a second-stage methanogenic continuous reactor (R2), comparing the results with those obtained in a single-stage system (R1) fed with SO42--rich wastewater (SO42- of up to 400 mg L-1, COD/SO42- of 3.12-12.50). The organic load (OL) was progressively increased to 5.0 g COD d-1 in both reactors, showing completely discrepant performances. Sulfate-reducing bacteria outperformed methanogens in the consumption for organic matter during the start-up phase (OL = 2.5 g COD d-1) in R1, directing up to 73% of the electron flow to SO42- reduction. An efficient methanogenic activity was established in R1 only after decreasing the OL to 0.625 g COD d-1, after which methanogenesis prevailed by consuming ca. 90% of the removed COD. Nevertheless, high sulfide proportions (up to 3.1%) were measured in biogas. Conversely, methanogenesis was promptly established in R2, resulting in a methane-rich (> 80%) and sulfide-free biogas regardless of the operating condition. From an economic perspective, processing the biogas evolved from R2 would be cheaper, although the techno-economic impacts of managing the sulfur pollution in the fermentative reactor still need to be understood.PMID:38625470 | DOI:10.1007/s11356-024-33277-y
Source: Environmental Science and Pollution Research International - Category: Environmental Health Authors: Source Type: research