Performance Assessment of a New Type of Membrane Bioreactor under Steady State and Transient Operating Conditions

Methyl-t-butyl ether (MTBE) is an additive to gasoline that serves as an oxygenate to increase the octane rating and improve combustion efficiency. Assessment of MTBE biodegradation under aerobic conditions was performed in lab-scale biomass concentrator reactors (BCRs). These reactors were bench-scale microcosms that retain and concentrate biomass thereby enabling biodegradation to sub-mu g/L level. The BCRs were run under low hydraulic retention times with a synthetically prepared feed containing 500 mu g/L of several oxygenates, MTBE, diisopropyl ether (DIPE), ethyl-t-butyl ether (ETBE), t-amyl methyl ether (TAME), t-amyl alcohol (TAA), and the primary gasoline constituents benzene, toluene, ethyl benzene, and p-xylene (BTEX). The BCRs were effective in the removal of the aforementioned contaminants to concentrations lower than the targeted 5 mu g/L, which is below the U.S. Environmental Protection Agency (EPA) taste and odor threshold of 20-40 mu g/L. Reactor performance was also evaluated under shock loading and intermittent feeding (starvation tests) of the contaminants of concern to evaluate the reactor's robustness in recovering from such stresses. The BCRs were found to be highly resilient to fluctuations in substrate and flow conditions. DOI: 10.1061/(ASCE)EE.1943-7870.0000392. (C) 2011 American Society of Civil Engineers.