Toxicity and biodegradability of caffeic acid in anaerobic digesting sludge

Authors

  • JE Hernandez 1. Chemical and Environmental Engineering Department, Bioinspired Engineering Research Group, University of Nottingham, Malaysia, Jalan Broga, Semenyih, Selangor, 43500, Malaysia; 2. Chemical and Environmental Engineering Department, University of Nottingham, United Kingdom
  • RGJ Edyvean Department of Chemical and Process Engineering, University of Sheffield, Kroto Institute, North Campus Broad Lane, Sheffield, S3 7HQ, United Kingdom

DOI:

https://doi.org/10.4314/wsa.v44i1.04

Keywords:

anaerobes, anaerobic digestion, biogas, biomass, caffeic acid, graphene, inhibition, polyphenols, renewable energy, toxicity, wastewater

Abstract

Caffeic acid in waste comes from a variety of industries, and its disposal is likely to increase due to emerging processes such as graphene production and use in healthcare products. The current sustainable option to treat waste caffeic acid and prevent its natural transformation in soil to greenhouse gases, is anaerobic digestion. However, little is known about the toxic and inhibitory effects of caffeic acid on biogas production as well as its ultimate anaerobic biodegradability; or about the reactive adsorptive processes taking place with caffeic acid in sludge, metabolic intermediates, thermodynamic limitations and the effects on extracellular polymeric substances (EPS). Standard methods revealed that 80% of biogas production (EC80) from a readily digestible biomass was inhibited at 389 mg caffeic acid·g-1 VSS. Up to 52% of caffeic acid was biodegraded. β-oxidation and reductive dehydroxylation were the initial activation reactions transforming caffeic acid into typical polyphenol structural units (protocatechuic acid and 4HBA). Adsorption of caffeic acid (53.3% and 28.6%) to the sludge occurred even at inhibitory concentrations. The EPS structure remained unchanged regardless of the increase in concentration of caffeic acid. Reasonable concentrations of caffeic acid could be co-digested with a similar readily digestible biomass with an expected reduction in biogas production. It is feasible to treat waste caffeic acid by anaerobic digestion and adsorption of its derivates, in order to reduce the contribution to global warming and to protect the environment. 

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Published

2018-01-31

How to Cite

Hernandez, J., & Edyvean, R. (2018). Toxicity and biodegradability of caffeic acid in anaerobic digesting sludge. Water SA, 44(1 January). https://doi.org/10.4314/wsa.v44i1.04

Issue

Section

Research paper