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Published on: June 15, 2014
Integrated sludge resources hierarchical recovery: enhancing VFAs production through pilot scale liquid-state
Jing Zhang1, Dong-Shan Yang1, Jia-Yu Yang1
1School of Environment and Ecology, Jiangnan University, Wuxi 214122, China.
Abstract:
Efficient production of volatile fatty acids (VFAs) from waste activated sludge (WAS) is often constrained by limited substrate accessibility and mass-transfer resistance. This study proposed and evaluated a hierarchical resource recovery strategy by systematically comparing conventional whole-sludge fermentation and liquid-state fermentation, with and without biochar addition, in a 30 L pilot-scale digester. Liquid-state fermentation increased VFAs concentration and productivity by 93.2% and 161.7%, respectively, highlighting the decisive role of improved mass transfer and substrate availability. Biochar addition further enhanced VFAs production, increasing VFAs concentration by 34.6% and 29.5%, and VFAs productivity by 33.3% and 25.5% under conventional and liquid-state fermentation, respectively. Economic analysis showed that biochar-assisted liquid-state fermentation achieved a net profit of 4.27 USD/m3, which was 3.36-fold higher than that of the biochar-free scenario. Overall, the proposed hierarchical resource recovery strategy substantially improved VFAs production, maximizing the recovery of carbon and nutrient resources from sludge and representing a highly promising novel sludge resource utilization process.
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