Continuous-flow aerobic co-treatment of municipal sludge derived hydrothermal liquefaction aqueous phase with wastewater in treatment plants

Abstract

Aerobic treatment of hydrothermal liquefaction (HTL) aqueous phase from municipal sludge is a potential on-site treatment option that could help overcome a major challenge, effectively managing HTL aqueous phase. In this study, HTL aqueous phase, derived from mixed sludge cake at 332°C, 16.9¿min, was blended with synthetic wastewater in a 1:1000 volumetric ratio representative of sludge processing at a full-scale treatment plant. This mixture was then fed into a bench-scale activated sludge unit, comprised of aeration and settling tanks, under organic loading rates of 1.2–1.6¿kg BOD/m3·d. Results revealed that blending HTL aqueous phase into influent wastewater resulted in significant changes in chemical oxygen demand (COD), five-day biochemical oxygen demand (BOD5), total ammonium nitrogen (TAN), PO43--P, and total phenolics concentrations of influent wastewater. There was no evidence of inhibition on aerobic biomass throughout the testing period. However, significant increases in COD (40–45¿%), TAN (10–14¿%), PO43--P (8¿%), and total phenolics concentrations (75–87¿%) were detected in the treated effluent while the BOD5 of treated effluent was not affected by HTL aqueous phase blending. Although the sludge volume index of biomass significantly increased after blending HTL aqueous phase into the wastewater, the total suspended solids concentration of the settling underflow and sludge recycle were not affected. Finally, recalcitrant compounds were found to increase the UV254 absorbance. The techno-economic analysis showed that returning the HTL aqueous phase to the activated sludge process would increase aeration cost by 22.5¿%, while overall treatment cost would decrease by 13.5¿% through HTL integration.

This research was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) and Metro Vancouver Industrial Research Chair Program in Advanced Resource Recovery from Wastewater (IRCPJ 548816-18). The authors acknowledge the help of Jacky Takeuchi, research technician at the Bioreactor Technology Group, School of Engineering, University of British Columbia, for analysis of organic compounds using GC-MS. We respectfully acknowledge the Syilx Okanagan Nation and their peoples, in whose traditional, ancestral, unceded territory this research was conducted.

Peer Reviewed

9 - Indústria, Innovació i Infraestructura

11 - Ciutats i Comunitats Sostenibles

6 - Aigua Neta i Sanejament

11.6 - Per a 2030, reduir l’impacte ambiental negatiu per capita de les ciutats, amb especial atenció a la qualitat de l’aire, així com a la gestió dels residus municipals i d’altre tipus

Postprint (published version)