Two-Liquid-Phase Slurry Bioreactors To Enhance the Degradation of High-Molecular-Weight Polycyclic Aromatic Hydrocarbons in Soil

Abstract

High-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs) are pollutants that persist in the environment due to their low solubility in water and their sequestration by soil and sediments. The addition of a water-immiscible, nonbiodegradable, and biocompatible liquid, silicone oil, to a soil slurry was studied to promote the desorption of PAHs from soil and to increase their bioavailability. First, the transfer into silicone oil of phenanthrene, pyrene, chrysene, and benzo[a]pyrene added to a sterilized soil (sandy soil with 0.65% total volatile solids) was measured for 4 days in three two-liquid-phase (TLP) slurry systems each containing 30% (w/v) soil but different volumes of silicone oil (2.5%, 7.5%, and 15% [v/v]). Except for chrysene, a high percentage of these PAHs was transferred from soil to silicone oil in the TLP slurry system containing 15% silicone oil. Rapid PAH transfer occurred during the first 8 h, probably resulting from the extraction of nonsolubilized and of poorly sorbed PAHs. This was followed by a period in which a slower but constant transfer occurred, suggesting extraction of more tightly bound PAHs. Second, a HMW PAH-degrading consortium was enriched in a TLP slurry system with a microbial population isolated from a creosote-contaminated soil. This consortium was then added to three other TLP slurry systems each containing 30% (w/v) sterilized soil that had been artificially contaminated with pyrene, chrysene, and benzo[a]pyrene, but different volumes of silicone oil (10%, 20%, and 30% [v/v]). The resulting TLP slurry bioreactors were much more efficient than the control slurry bioreactor containing the same contaminated soil but no oil phase. In the TLP slurry bioreactor containing 30% silicone oil, the rate of pyrene degradation was 19 mg L(-)(1) day(-)(1) and no pyrene was detected after 4 days. The degradation rates of chrysene and benzo[a]pyrene in the 30% TLP slurry bioreactor were, respectively, 3.5 and 0.94 mg L(-)(1) day(-)(1). Low degradation of pyrene and no significant degradation of chrysene and benzo[a]pyrene occurred in the slurry bioreactor. This is the first report in which a TLP system was combined with a slurry system to improve the biodegradation of PAHs in soil.

Solvent selection for enhanced bioproduction of 3‐methylcatechol in a two‐phase partitioning bioreactor

“…A log P value for silicone oil was not found but silicone oil has been successfully demonstrated as an immiscible liquid for a number of twophase applications. Guieysse et al (2001); Villemur et al (2000). Figure 1.…”

“…was selected as it has been shown to be an effective immiscible liquid in two-phase systems (Tikhomiroff et al, 2002;Villemur et al, 2000) demonstrating both biocompatibility and non-bioavailability.…”

Enhanced biodegradation of phenol by a microbial consortium in a solid?liquid two phase partitioning bioreactor

“…This selfimposed metabolic limitation of using pure cultures is somewhat off-set by the fact that, through rational solvent selection (Bruce & Daugulis 1991), an organic delivery phase can be tailored to a substrate/organism pairing, usually with excellent performance. A few studies (Guieysse et al 2001a;Marcoux et al 2000;Villemur et al 2000) have employed silicone oil as a delivery phase, due exclusively to its non-biodegradability, along with mixed cultures, however, the properties of silicone oil are, for better or for worse fixed; silicone oil thus provides no opportunity for enhancing important solvent properties such as substrate solubility, substrate distribution coefficient, viscosity, etc. as different substrates are selected.…”

Ex-Situ Remediation Technologies for Environmental Pollutants: A Critical Perspective

“…Cost increases in the case of post-gas treatment requirements for volatile contaminants (US EPA 2012 ). Villemur et al ( 2000 ) used a three-phase, aerobic slurry system containing 30 % silicone oil and biodegraded 90-98 % chrysene, pyrene and BaP. Wang and Vipulanandar ( 2001 ) observed that 96-99 % naphthalene was rapidly degraded by aerobic slurry bioreactors in 4 days.…”