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

This is a knowledge contribution to the unsatisfactory biodegradation problem, when biotrickling filters are purifying mixed paint solvents. A biotrickling filter manufacturer reported low biodegradation rates during the purification of a hydrocarbon pollutant mix from an industrial paint spraying floor. From a gas chromatograph/mass spectrometer analysis both hydrophilic and hydrophobic solvents were found in the polluted air. It is known that biodegradation is retarded, if the pollutant does not transfer from gas to liquid into the biofilm and it was therefore suspected that hydrophobic pollutants do not sufficiently migrate into the water/biofilm. To test this hypothesis, pure, rather than mixed pollutants, were injected into the abiotic biotrickling filter. When hydrophobic paint solvent (xylene) was sprayed into the biotrickling filter, the solvent load at the outlet of the filter was almost as high as at the inlet. But when pure, hydrophilic paint solvent (PGME) was sprayed into the abiotic biotrickling filter, the solvent load measured at the outlet of the filter was zero, indicating complete dissolution into the circulation water. Carbon/solvent loads at the filter outlet and inlet were measured with a portable flame ionization detector instrument. The experiment confirms that the hydrophobic solvent does not migrate into the liquid phase. This poor mass transfer of hydrophobic solvents is likely to be the reason for the low biodegradation rate. The result is highly relevant to the paint spraying industry and manufacturers of exhaust gas treatment equipment alike, who spend millions in non-sustainable incineration of exhaust gases.

Marine Gel Interactions with Hydrophilic and Hydrophobic Pollutants

Microgels play critical roles in a variety of processes in the ocean, including element cycling, particle interactions, microbial ecology, food web dynamics, air–sea exchange, and pollutant distribution and transport. Exopolymeric substances (EPS) from various marine microbes are one of the major sources for marine microgels. Due to their amphiphilic nature, many types of pollutants, especially hydrophobic ones, have been found to preferentially associate with marine microgels. The interactions between pollutants and microgels can significantly impact the transport, sedimentation, distribution, and the ultimate fate of these pollutants in the ocean. This review on marine gels focuses on the discussion of the interactions between gel-forming EPS and pollutants, such as oil and other hydrophobic pollutants, nanoparticles, and metal ions.

Uptake of monoaromatic hydrocarbons during biodegradation by FadL channel-mediated lateral diffusion

In modern societies, biodegradation of hydrophobic pollutants generated by industry is important for environmental and human health. In Gram-negative bacteria, biodegradation depends on facilitated diffusion of the pollutant substrates into the cell, mediated by specialised outer membrane (OM) channels. Here we show, via a combined experimental and computational approach, that the uptake of monoaromatic hydrocarbons such as toluene in Pseudomonas putida F1 (PpF1) occurs via lateral diffusion through FadL channels. Contrary to classical diffusion channels via which polar substrates move directly into the periplasmic space, PpF1 TodX and CymD direct their hydrophobic substrates into the OM via a lateral opening in the channel wall, bypassing the polar barrier formed by the lipopolysaccharide leaflet on the cell surface. Our study suggests that lateral diffusion of hydrophobic molecules is the modus operandi of all FadL channels, with potential implications for diverse areas such as biodegradation, quorum sensing and gut biology.