Extremely effective self-sufficient sugar factory wastewater treatment plant and its methanogenic microbial consortium

• Dobrzelin WWTP is energy self-sufficient and has a closed water circuit. • Methane synthesis occurred using all known pathways. • The role of selected syntrophic bacteria in methane synthesis was proposed. • Produced biogas showed desirable properties as a fuel source. This study introduces a novel contribution to the long-term goal of limiting global climate change by energy recovery and reduction of associated emissions in industrial-scale wastewater treatment facilities. The upgrades implemented at the Dobrzelin sugar factory WWTP have enabled it to achieve complete water and electricity self-sufficiency by fully reusing the biogas produced from sugar fabrication wastewater. Despite substantial technological process changes, no significant differences were detected in the composition of the microbial community present in the anaerobic chamber before and after modernization (9,483 vs 9,437 species). Concurrently, the efficiency of biogas production per kg of reduced pollutant load improved by an average of 3.4%, with the methane content increase reaching 10.5%. All currently known methane synthesis pathways are present, with CO₂ and acetate-related pathways being the most dominant. The modernisation of the Dobrzelin WWTP represents a previously unreported achievement within the context of large-scale sugar waste treatment and, more broadly, for fully operational industrial wastewater treatment facilities.