Valorization of pretreated waste activated sludge to organic acids and biopolymer

Alice Muhorakeye, Roent Dune Cayetano, A. Naresh Kumar, Jungsu Park, Ashutosh Kumar Pandey, Sang Hyoun Kim

Research output: Contribution to journalArticlepeer-review

Abstract

Polyhydroxybutyrate (PHB) is a natural polyester that may be made by utilizing volatile fatty acids (VFAs) as a substrate. VFA generated by continuous anaerobic fermentation of waste activated sludge (WAS) was fed into bioreactors for PHB synthesis in this work. Series of optimization tests were conducted to increase the biodegradability and hydrolysis of waste activated sludge. It was found out that 0.05 g/g TS of SDBS (sodium dodecylbenzene sulfonate), 70 °C (heat treatment) and 2hr (time) as pretreatment condition would give the highest solubilization. Impact of pH adjustment on the acidogenesis of pretreated WAS was evaluated in batch experiments at varying initial pH (4–10). The result indicated that when operational pH was between 7.5 and 8, the VFA yield was increased by 5.3–18.1%. Continuous acidogenic operation validated the SDBS pretreatment and pH adjustment warranted stable VFA conversion from WAS at a yield of 47% in COD basis. Firmicutes, Actinobacteria and Proteobacteria were affiliated as dominant bacterial phyla in the continuous acidogenesis. The effluent of the continuous acidogenesis was converted to biopolymer with the average yields of 0.23 g PHB-COD/g VFAadded-COD in the feast mode and 0.34 g PHB-COD/g VFAadded-COD in the famine mode. In feast and famine cycle, the average VFA utilization was 55% and 60% respectively. The sequential SDBS pretreatment, acidogenesis and PHB production would produce 162 g of PHB from 1 kg of WAS as COD basis.

Original languageEnglish
Article number135078
JournalChemosphere
Volume303
DOIs
Publication statusPublished - 2022 Sep

Bibliographical note

Funding Information:
The research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government ( Ministry of Science & ICT, Republic of Korea ) (No. NRF-2019M3E6A1103839, NRF-2020R1A2B5B02001757 ).

Publisher Copyright:
© 2022 Elsevier Ltd

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Environmental Chemistry
  • Chemistry(all)
  • Pollution
  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis

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