Nuclear Magnetic Resonance Spectroscopy Analysis of Anaerobic Microbial Metabolic Response to Benzalkonium Chloride Disinfectant

Featured Application An NMR spectroscopic analysis of an anaerobic digestion can simultaneously detect the presence of quaternary ammonium compounds and the effects of these compounds in the microbial metabolic profile before impacts on biogas production can be measured. This approach may provide an early warning indicator for future microbial upset resulting from exposure to these disinfectant compounds. Quaternary ammonium compounds (QACs) are disinfection agents used in industrial cleaning processes that are known to interfere with the proper functioning of anaerobic waste digestion directly impacting the quality and quantity of the biogas produced (i.e., CO2 and CH4). While the impact of these contaminants on waste digestors are well known, the impact these compounds have on the metabolic profile of an anaerobic digestor is less understood. This paper describes the use nuclear magnetic resonance (NMR) spectroscopy as a non-targeted tool to monitor variations in the metabolic profile of anaerobic bioreactor microcosms simulating the treatment of food production wastewater exposed to benzalkonium chloride (BAC), a key QAC. Using NMR, the variation in the metabolic profile of these wastewater microcosms is compared to variations in the quality and quantity of the biogas produced. A clear development of propionic, isobutyric, isovaleric, and other volatile fatty acids (VFAs) is observed indicating a disruption to the overall ability of the system to convert fatty acids to methane. The ability of NMR to successfully identify the overall metabolic profile, the occurrence of the individual VFAs, and the occurrence of BAC itself in one analysis helps to provide valuable information on the metabolic pathways involved in the disruption of these anaerobic processes.