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

Abstract

Removal of gasoline vapors from waste air was investigated in a bench-scale perlite biofilter for three aromatic-to-aliphatic mass ratios (62/38, 92/8 and 44/56) under different loads, varied by changing both the substrate inlet concentration and air flow rate. The measurement of concentration profiles along the bed height allowed for an assessment of interactions between the aromatic and aliphatic fractions of gasoline. Variations in both the inlet concentrations and empty bed residence time significantly influenced the removal of aliphatic gasoline components. Except for the lowest organic loads, the whole biofilter bed was required for achieving an acceptable removal efficiency of aliphatic hydrocarbons. The presence of large amounts of aromatics negatively impacted the removal of aliphatics. By contrast, the aromatic gasoline components were near-completely removed from any mixtures; the bulk of them were degraded in the first (out of three) biofilter section, even at high concentrations of aliphatic hydrocarbons. The observed effect was shown to be due to competitive interactions of aliphatic and aromatic components, which is consistent with the biological steps being rate limiting. Mass transfer, particularly for aliphatic components due to their high Henry's law constants, was shown to be rate-limiting under extreme scenarios, such as low loading rates and EBRT.

Biofiltration of gasoline and diesel aliphatic hydrocarbons

“…Dishes with sterilized BSM medium, whose detailed composition is provided elsewhere (Halecky et al, 2012), were solidified with 10 g L −1 of a pure agar and used for a semiquantitative comparison of the hydrocarbon degradation ability of biofilm isolates, by evaluating colony growth. Dishes inoculated with isolates were placed in an airtight glass desiccator containing the vapors of individual pollutants.…”

“…Gasoline measurements were conducted using the procedure described elsewhere (Halecky et al, 2012). A Hewlett-Packard 4890 gas chromatograph (GC) was equipped with an HP-Innowax capillary column (based on cross-linked polyethylene glycol) having a length of 30 m, inner diameter of 0.53 mm, and film thickness of 1 μm (Hewlett-Packard, Palo Alto, CA).…”

“…Gasoline composition (% weight) was determined using GC-mass spectroscopy (MS) and was similar to that described by Halecky et al (2012): n-alkanes, 6.4; isoalkanes, 26.7; cyclo-alkanes, 5.8; aromatic hydrocarbons, 37.4; alkenes, 10; MTBE, 11.4; ethanol, 2; nonidentified, 0.3. The same procedure was applied to diesel hydrocarbons.…”

“…Yet only a few papers on the biofiltration of gasoline and other diverse hydrocarbon mixtures are available (Leson and Smith, 1997;Barton et al, 1997;Wright et al, 1997;Morales et al, 1998;Namkoong and Park, 2003;Namkoong and Park, 2004;Paca et al, 2007). Even fewer studies have tackled the interactions of aliphatic and more biodegradable aromatic compounds in their mixtures (Schindler and Friedl, 1995;Holubar et al, 1999;Lu et al, 2001;Kim, 2003;Hassan and Sorial, 2010;Halecky et al, 2012). Furthermore, neither the order of biofiltration efficiency nor potential substrate interactions within the group of aliphatic hydrocarbons have, to our best knowledge, been investigated and documented.…”

“…This objective was addressed using two novel approaches in the application of biofiltration to complex hydrocarbon mixtures. First, the biofilter was designed to degrade sequentially, in two different stages, (1) the readily biodegradable and then (2) less biodegradable chemicals, which are known to cause the interactions documented earlier (Halecky et al, 2012).…”