The nature of gas production patterns associated with methanol degradation in natural aquifer sediments: A microcosm study

With growing global use of methanol as a fuel additive and extensive use in other industrial processes, there is the potential for unintended release and spills into soils and aquifers. In these subsurface systems it is likely that methanol will be readily biodegraded; however, degradation may lead to the production of by-products, most importantly methane possibly resulting in explosion hazards and volatile fatty acids (VFAs) causing aesthetic issues for groundwater. In this study, the formation of these potentially harmful by-products due to methanol biodegradation was investigated in natural sand and silt sediments using microcosms inoculated with neat methanol (100%) ranging in concentration from 100 to 100,000 ppm. To assess the rate of degradation and by-product formation, water and headspace samples were collected and analyzed for methanol, volatile fatty acids (VFAs, including acetic, butyric, and propionic acid), cation (metal) concentrations (Al, Ca, Fe, K, Mg, Mn and Na), microbial community structure and activity, headspace pressure, gas composition (CH