Hydrogen peroxide pretreatment of aqueous phase product of hydrothermal sludge liquefaction for enhanced anaerobic and aerobic biodegradability

Abstract

Wastewater treatment plants (WWTP) generate municipal sludge (MS) that contains high organic and inorganic matter, creating disposal challenges. Hydrothermal liquefaction (HTL) is a promising method for converting sludge into value-added products (biocrude oil, hydrochar) but generates a large volume of aqueous by-product (HTLaq) with soluble inhibitory organics to downstream biological treatment. This creates a bottleneck to incorporate HTL to WWTPs. This study investigated hydrogen peroxide (H2O2) pretreatment of HTLaq to improve its biodegradability for downstream treatment. Pretreatment with H2O2 dosages of 0.25, 0.50, and 0.75 g H2O2/g chemical oxygen demand (COD) of HTLaq, followed by quenching with sodium carbonate (Na2CO3), significantly reduced total COD (tCOD) and phenolic compounds. The highest tCOD removal (18%) occurred with 0.75 g H2O2/g COD, while the 0.25 g H2O2/g COD with Na2CO3 quencher showed the highest (63%) increase in cumulative methane yield under thermophilic conditions. Aerobic biodegradability index, quantified by biochemical oxygen demand (BOD)/tCOD ratio, also increased from 0.75 to 0.85. The results suggest that lowdosage H2O2 pretreatment enhances the biodegradability of HTLaq, making it more amenable for downstream biological treatment.

The authors gratefully acknowledge the generous support of Metro Vancouver and the Natural Sciences and Engineering Research Council of Canada (NSERC) under the Industrial Research Chair Program in Advanced Resource Recovery from Wastewater (IRCPJ 548816–18). The authors thank Jacky Takeuchi (research technician) and Dr. Parmila Devi (research engineer) at the Bioreactor Technology Group, School of Engineering, University of British Columbia, for their help with the analysis of organic compounds using GC-MS and some of the laboratory procedures & set-up. The authors also acknowledge the Syilx Okanagan Nation for the use of their unceded ancestral traditional territory, the land on which the research was conducted.

Peer Reviewed

7 - Energia Assequible i No Contaminant

6 - Aigua Neta i Sanejament

9 - Indústria, Innovació i Infraestructura

11 - Ciutats i Comunitats Sostenibles

Postprint (published version)