Combination of highly efficient microflora to degrade paint spray exhaust gas

Abstract

Spray paint exhaust gas contains recalcitrant volatile organic compounds (VOCs), such as benzene, toluene and xylene (BTX). Treating BTX with a biofilter often achieves unsatisfactory results because the biofilter lacks efficient microbial community. In this work, three strains for BTX degradation were isolated and identified as Pseudomonas putida, Bacillus cereus and Bacillus subtilis by using 16S rRNA sequencing technology. A consortium of highly efficient microbial community was then constructed on a stable biofilm to treat BTX in a biofilter. A relatively suitable ratio of P. putida, B. cereus and B. subtilis was obtained. An efficiency of over 90% was achieved in the biofilter with VOC concentration of 1000 mg/m 3 through inoculation with the microbial community after only 10 days of operation. Thus, fast start-up of the biofilter was realised. Analysis of intermediate products by gas chromatographymass spectrometry indicated that BTX was degraded into short-chain aldehydes or acids via ring opening reactions. Paint spray exhaust gas includes volatile organic compounds (VOCs), such as benzene, toluene and xylene (BTX), and even more complicated compounds, i.e. chlorinated benzenes and toluenes 1,2 , all of which can cause great harm to humans 3,4. The indiscriminate discharge of large amounts of paint spray exhaust gas also exerts a negative impact on the atmospheric environment 5,6. Therefore, efficient technologies should be developed to treat paint spray exhaust gas and address its effects. Although several technologies for paint spray exhaust gas treatment exist, some of these methods are difficult to apply on a large scale because of their shortcomings 7. Biofiltration and biotrickling filters have received wide attention because they are low-cost and occupy a small space. Moreover, the activity of microorganisms can remain comparatively stable 8-10. Leili et al. found that the biofiltration system shows good performance in terms of removing BTEX 11. In theory, VOCs can completely mineralise during biofiltration. However, it is restricted by the microorganism type and the operating parameters in practise. Thus, the effect remains unsatisfactory 12. The toxicants in waste gas could be degraded with a specific strain by acclimation, which can be applied to the biofilters to improve their efficiency. A removal efficiency of higher than 98% was achieved by Bacillus firmus when the concentration of ketone (acetone and methyl ethyl ketone) and benzene in paint spray exhaust gas was lower than 3000 mg/m 3 13. Mohammad et al. used Exophiala sp. as inoculum for biofilter, which had a good removal effect on BTEX 14. However, because the composition of the exhaust gas might be complex, a single strain may not always obtain satisfactory results, resulting in unstable removal rates 15,16. The microbial community has been studied to promote biofilter operation. Archaea and bacteria effectively remove printing press VOCs in an anaerobic bioscrubber 17. Xue et al. used a biotrickling filter to treat complex odorous gas...

Gas-to-aqueous Phase Transfer for Three Paint Solvents Injected into an Abiotic, Industrial Biotrickling Filter Measured with a Flame Ionization Detector

“…Similarly, the pharmaceutical industry encountered difficulties treating mixed VOC exhaust gases [19,20]. And a mix of paint spray exhaust containing benzene, toluene and xylene (BTX) is considered difficult to biodegrade, unless an appropriate microbial community is inocculated [21]. Even though degradation of single, aromatic VOCs is possible [21], this may not be so if other, more microbially accessible VOCs are present at the same time.…”

“…And a mix of paint spray exhaust containing benzene, toluene and xylene (BTX) is considered difficult to biodegrade, unless an appropriate microbial community is inocculated [21]. Even though degradation of single, aromatic VOCs is possible [21], this may not be so if other, more microbially accessible VOCs are present at the same time. When two alcohols and an ether are simultaneously present in the exhaust air, the ether (ethoxy-2-propanol) is much harder to degrade than the two alcohols due to catabolite repression [22].…”