Simple solvatochromic spectroscopic quantification of long-chain fatty acids for biological toxicity assay in biogas plants
- 26 Downloads
Oily organic waste is a promising feedstock for anaerobic co-digestion. Free long-chain fatty acids (LCFAs) produced from lipids can inhibit methanogenic consortia, so optimal control of LCFA concentration is the key to successful operation of co-digestion. Most LCFAs are present in the solid phase, making them difficult to be detected and monitored. This study proposes a simple and easy method for detecting LCFAs in both the liquid and solid phases of anaerobic digestate by combining liquid–liquid extraction followed by solid-phase extraction (SPE) and spectrophotometric analysis. The extraction procedure successfully removed impurities that interfere with the absorbance spectrum and ensured high recovery rates of LCFAs. The utility of the pretreatment used for the extraction was discussed using thermodynamic analysis and calculations of phase equilibrium for the solvent extraction system. The absorbance spectrum shift of pyridinium N-phenolate betaine (PNPB) dye-stained solution showed a good correlation with LCFA concentration and enabled highly sensitive measurements. Good quantification was demonstrated in experiments using various digestate samples obtained from the laboratory, pilot, and full-scale reactors.
KeywordsAnaerobic digestion Grease trap waste Inhibitory substance Monitoring Simplified analysis method
We would like to thank Mr. Yuji Yamazaki, Tomoyuki Nara, and Toshitaka Kato of Takenaka Corporation, Japan, for their valuable help in the collection of digestate samples.
- J. Hunter Long, Tarek N. Aziz, Francis L. de los Reyes, Joel J. Ducoste, (2012) Anaerobic co-digestion of fat, oil, and grease (FOG): A review of gas production and process limitations. Process Safety and Environmental Protection 90 (3):231-245Google Scholar
- Lalman JA, Bagley DM (2001) Anaerobic degradation and inhibitory effects of linoleic acid. Water Res 34(17):4220–4228Google Scholar
- M.A. Pereira, A.J. Cavaleiro, M. Mota, M.M. Alves, (2003) Accumulation of long chain fatty acids onto anaerobic sludge under steady state and shock loading conditions: effect on acetogenic and methanogenic activity. Water Science and Technology 48 (6):33-40Google Scholar
- Schwarzenbach RP, Gschwend PM, Imboden DM (2003) Environmental organic chemistry, 2nd edn. John Wiley, HobokenGoogle Scholar
- Yau YH, Rudolph V, Lo CC, Wu KC (2018) Restaurant oil and grease management in Hong Kong. Environ Sci Pollut Res. https://doi.org/10.1007/s11356-018-2474-4