Biofiltration of paint solvent mixtures in two reactor types: overloading by hydrophobic components

Abstract

Steady-state performance characteristics of a trickle bed reactor (TBR) and a biofilter (BF) in loading experiments with increasing toluene/xylenes inlet concentrations while maintaining a constant loading rate of hydrophilic components (methyl ethyl and methyl isobutyl ketones, acetone, and n-butyl acetate) of 4 g m⁻³ h⁻¹ were evaluated and compared, along with the systems' dynamic responses. At the same combined substrate loading of 55 g m⁻³ h⁻¹ for both reactors, the TBR achieved more than 1.5 times higher overall removal efficiency (RE(W)) than the BF. Increasing the loading rate of aromatics resulted in a gradual decrease of their REs. The degradation rates of acetone and n-butyl acetate were also inhibited at higher loads of aromatics, thus revealing a competition in cell catabolism. A step-drop in loading of aromatics resulted in an immediate increase of RE(W) with variations in the TBR, while the new steady-state value in the BF took 6-7 h to achieve. The TBR consistently showed a greater performance than BF in removing toluene and xylenes. Increasing the loading rate of aromatics resulted in a gradual decrease of their REs. The degradation rates of acetone and n-butyl acetate were also lower at higher OL(AROM), revealing a competition in the cell catabolism. The results obtained are consistent with the proposed hypothesis of greater toxic effects under low water content, i.e., in the biofilter, caused by aromatic hydrocarbons in the presence of polar ketones and esters, which may improve the hydrocarbon partitioning into the aqueous phase.

Preferences in removal of aliphatic and aromatic gasoline components by biofiltration under varied loading

“…A similar improvement of aromatic hydrocarbons' partitioning into water in the presence of polar solvents was shown earlier. [32] The co-partitioning of aromatic hydrocarbons caused by polar solvents was much more pronounced than the subtle effects observed in the current work, apparently due to much greater solubility of oxygenated aliphatics in water compared to hydrocarbons.…”

“…The rate-limiting step identification is not straightforward because C5-C6 aliphatic hydrocarbons are characterized by both low biodegradability and high Henry's constants. [24,32] The same problem pertains to the first reactor section. in section I either under large excess of aromatics (HGF) or at low EBRT.…”

A two-stage combined trickle bed reactor/biofilter for treatment of styrene/acetone vapor mixtures

“…Our previous studies confirmed different removal characteristics of individual pollutants in trickle-bed reactors and biofilters treating mixtures of hydrophobic and polar pollutants including styrene and acetone [1,4] as well as a paint solvents mixture. [2,5] Either BFs or TBRs were shown to be more efficient under specifically varied conditions, particularly for specific patterns of substrate loading.…”

Transformation of microflora during degradation of gaseous toluene in a biofilter detected using PCR-DGGE

“…Sphingobacterium multivorum (closest strain of bands 8 and 9) is able to use the toluene as the sole carbon and energy source for growth. In fact, Paca et al (2010) investigated the performance of a biofilter using several toluene-degrading bacteria including S. multivorum. Weelink et al reported that Alicycliphilus denitrificans, which is the closest strain of the excised band 13 can degrade benzene aerobically (Weelink et al, 2007).…”