Abstract
This study investigated the aerobic biodegradation of methyl tertiary-butyl ether (MTBE) by a microbial consortium in a continuous up-flow packed-bed biofilm reactor using tezontle stone particles as a supporting material for the biofilm. Although MTBE is toxic for microbial communities, the microbial consortium used here was able to resist MTBE loading rates up to 128.3 mg L-1 h-1, with removal efficiencies of MTBE and chemical oxygen demand (COD) higher than 90%. A linear relationship was observed between the MTBE loading rate and the MTBE removal rate, as well as between the COD loading rate and the COD removal rate, within the interval of MTBE loading rates from 11.98 to 183.71 mg L-1 h-1. The metabolic intermediate tertiary butyl alcohol (TBA) was not detected in the effluent during all reactor runs, and the intermediate 2-hydroxy butyric acid (2-HIBA) was only detected at MTBE loading rates higher than 128.3 mg L-1 h-1. The results of toxicity bioassays with organisms from two different trophic levels revealed that the toxicity of the influent was significantly reduced after treatment in the packed-bed reactor. The packed-bed reactor system used in this study was highly effective for the continuous biodegradation of MTBE and is therefore a promising alternative for detoxifying MTBE-laden wastewater and groundwater.
Highlights
Methyl tertiary butyl ether (MTBE) is an oxygenated chemical that is widely used as a gasoline additive to improve the octane number and increase the combustion efficiency of gasoline by supplying extra oxygen during the combustion process, thereby reducing carbon monoxide and volatile organic carbon (VOC) emissions from internal combustion engines and air PLOS ONE | DOI:10.1371/journal.pone
The microbial consortium is mainly composed of five gram-negative bacterial species, which were molecularly identified by sequence analysis of the 16S rRNA genes and designated as Pseudomonas delhiensis IPN-TA, Ochrobactrum sp
The above results indicated significantly reduced toxicity in the effluents from the packedbed bioreactor following treatment and demonstrated that the microorganisms were more sensitive to MTBE and MTBE-degradation metabolites compared to L. sativa. These results suggested that the lower hydraulic retention times (HRT) (5.8 h) necessary for the effective and efficient operation of the packed-bed reactor resulted in high MTBE and chemical oxygen demand (COD) removal efficiencies and rates, as well as less toxic effluents obtained relative to the influent
Summary
Methyl tertiary butyl ether (MTBE) is an oxygenated chemical that is widely used as a gasoline additive to improve the octane number and increase the combustion efficiency of gasoline by supplying extra oxygen during the combustion process, thereby reducing carbon monoxide and volatile organic carbon (VOC) emissions from internal combustion engines and air PLOS ONE | DOI:10.1371/journal.pone.0167494 December 1, 2016Biodegradation of MTBE in a Packed-Bed Reactor pollution [1,2]. Extensive MTBE use has resulted in frequent soil, surface water and groundwater pollution, mainly due to accidental fuel leakage during storage and transportation [3,4], raising serious concerns about human and environmental health. MTBE concentrations of 11.5 mg m-3 [7] and 4.4 ppb [8] in air were recorded at a service station and emissions of on-road vehicles, respectively. Maximum MTBE concentrations of 0.88 and 0.3 mg kg-1 were found in soils at oil distribution and storage stations, respectively [9,10]. There is no legislation in Mexico that regulates gasoline releases or that defines MTBE limits in groundwater; all reported concentrations are higher than the Environmental Protection Agency advisory limit of 20 μg L-1 [11]
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