Methyl tertiary-butyl ether (MTBE) biodegradation in batch and continuous upflow fixed-biofilm reactors

Abstract

MTBE was effectively biodegraded under oxidizing environmental conditions in the presence of an acclimated mixed culture isolated from a petrochemical biotreater. MC-1 (Gram-positive coccus), MC-2 (Acinetobacter lwoffii) and MC-3 (Bacillus sp.) were present in the culture medium, with MC-1 being the predominant organism. The presence of other easily assimilated carbon sources in the culture medium influenced MTBE biodegradation. In batch studies, 62–73% MTBE was biodegraded in 144–192 hours at an initial concentration of 100 ppm as the sole carbon source, with the ORP ranging from 191–274 mv, and at a temperature of 29°C. The overall K rate constants and the specific k rate constants were evaluated using a first order rate equation. Mean values determined were 1.79×10-1 day-1 and 1.66×10-2 day-1/(mg/L cell mass), respectively. Continuous upflow fixed biofilm reactor studies were performed at retention times of 0.25, 0.5, and 1 day at an initial MTBE concentration of 150 ppm. Results indicated that approximately 53% MTBE was biodegraded for the 0.25 day retention time and 70% for both the 0.5 and 1.0 day retention times. Three kinetic models were evaluated for all experimental retention times. These included: Model I (Eckenfelder); Model II (Arvin) and Model III (first-order biphasic). Results indicated that model III yielded the highest and most consistent correlation coefficients for all retention times evaluated.