Department of Civil, Construction and Environmental Engineering, Marquette University, P.O. Box 1881, Milwaukee, Wisconsin 53201, USADepartment of Civil, Construction and Environmental Engineering, Marquette University, P.O. Box 1881, Milwaukee, Wisconsin 53201, USADepartment of Civil, Construction and Environmental Engineering, Marquette University, P.O. Box 1881, Milwaukee, Wisconsin 53201, USA
Saba Seyedi;Kaushik Venkiteshwaran;Daniel Zitomer
Pyrolysis process is a thermochemical technology that can be used to recover energy from wastewater biosolids while reducing harmful environmental impacts as well as health concerns from biosolids reuse. The process transforms biosolids into biochar, py-gas and pyrolysis liquid. Pyrolysis liquid can contain both bio-oil and an aqueous condensate. Bio-oil can be processed and used as fuel; however, the condensate (non-catalyzed), which is a high-COD water solution containing aromatic organics and nitrogen-containing compounds, has no apparent use. Autocatalytic pyrolysis (i.e. using biochar as catalyst) is one method to increase py-gas while decreasing or eliminating bio-oil volume; however, condensate (catalyzed) may still be produced and must be managed. Co-digesting condensate in anaerobic digesters at municipal water resource recovery facilities is a possible way to manage condensate and recover energy in the form of biomethane. However, ammonia-nitrogen (NH3-N) and some organics present in the condensate can be inhibitory to anaerobic microorganisms. In this study, sustainable anaerobic digester organic loading rates for condensate of 0.01 to 0.05 kg COD/m~3-day were detenuined for unacclimated biomass using anaerobic toxicity assays (ATAs). Organic constituents in condensate caused significant methane production inhibition alone or in combination with NH_3-N. Continuous co-digestion of both catalyzed and non-catalyzed condensates and synthetic primary sludge was also performed. Co-digesters fed aerated non-catalyzed condensate produced statistically more methane than the control digesters that were fed only synthetic primary sludge. Therefore, some organic constituents in condensate are convertible to methane by unacclimated biomass. However, co-digesters fed catalyzed condensate (both aerated and unaerated) produced significantly less methane than control digesters. Microbial community analysis showed a decrease in Archaeal community diversity when condensate was co-digested.