Anaerobic fermentation of hydrothermal liquefaction wastewater of dewatered sewage sludge for volatile fatty acids production with focuses on the degradation of organic components and microbial community compositions

Hydrothermal conversion (HTC) is a promising technology for the treatment of dewatered sewage sludge to produce bio-fuels including bio-oil and hydrochar. At the same time, a huge amount of wastewater (HTCWW) was produced. The present study investigated the organic compositions of HTCWW obtained at different HTC temperatures (170-320 degrees C) and volatile fatty acids (VFAs) yields through anaerobic fermentation. Results showed that the highest VFAs yield of 0.59 gCODVFA/gCOD was obtained from HTCWW obtained at 170 degrees C (HTCWW 170). Higher amount of easily biodegradable organics including proteins and carbohydrates were present in HTCWW 170 degrees C, which resulted in the highest VFAs yields. With the increase of HTC temperature, recalcitrant organic compounds were produced as revealed by 3D-EEM and GC-MS analysis, which resulted in lower VFAs yields. Furthermore, microbial analysis showed that different compositions in the HTCWW led to the enrichment of different microbial communities, which affected the VFAs yields. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

Hydrothermal conversion is a promising technology for producing bio-fuels from dewatered sewage sludge, but it also generates a significant amount of wastewater. The composition of organic compounds in the wastewater obtained at different temperatures affects the yields of volatile fatty acids through anaerobic fermentation.