Kinetic modeling of Methyl Tert-Butyl Ether (MTBE) removal by bacterial isolated from contaminated soils

Abstract

ABSTRACT Methyl Tert-Butyl Ether(MTBE) is among oxygenised additives to gasoline, which has high solubility and leads to pollution of water resources. So far, the microbial species affecting the of high MTBEconcentrationsremoval have been less investigated. This study aimed to remove high concentrations of MTBEusing isolated bacteriafrom contaminatedsoil with petroleum compounds in southern regions of Iran and determine their kinetics. After isolating the bacteria and determining their growth in different concentrations, the effects of the following parameters on the removal percentage were examined: incubation time = 1–7 days, pH = 5.0–7.0, and 9.0, initial MTBE concentration = 1000–5000 mg/L, and C: N:P. Then, the four strains with high efficiency were selected, and their kinetic were analysed by zero-order, first-order, and second-order models. The results showed that the highest growth in MTBE concentration (50,000 mg/L) was observed for Acinetobacter sp, Bacillus sp, Ochrobactrum sp, and Sphingomonas sp. after four days. Then, Ochrobactrum sp.was used as a pure strain as well as a microbial consortium for the next steps, including the effects of nutrient ratio and initial MTBE concentration. In this study, the optimal conditions for incubation time and the initial MTBE concentration were 72 hours and 5000 mg/L, respectively. The kinetic modeling indicated that the second-order model (R2 = 0.95, Root Mean Squared Error = 0.012) and the Micheal-Menten model (R2 = 0.99) were the best modelfor MTBE biodegradation. Overall, the results indicated that pure Ochrobactrum sp. and a microbial consortium consisting of resistant bacteria at high MTBEconcentrations could remove MTBE> 90%.