Ultrasonically enhanced delivery and degradation of PAHs in a polymer–liquid partitioning system by a microbial consortium

Abstract

The current study examined the effects of ultrasonic irradiation on mass transfer and degradation of PAHs, by an enriched consortium, when delivered from polymeric matrices. Rates of release into methanol under sonicated conditions, relative to unmixed cases, for phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene were increased approximately fivefold, when delivered from Desmopan 9370 A (polyurethane). Similar effects were observed in Hytrel and Kraton D4150 K polymers as well as recycled Bridgestone tires. Enhancements were also displayed as shifts to higher release equilibria under sonicated conditions, relative to non-sonicated cases, agreeing with current knowledge in sonochemistry and attributed to cavitation. Ultrasonic effects on microbial activity were also investigated and cell damage was found to be non- permanent with consortium re-growth being observed after sonic deactivation. Finally, the lumped effect of sonication on degradation of phenanthrene delivered from Desmopan was examined under the absence and presence of sonication. Rates of degradation were found to be increased by a factor of four demonstrating the possibility of using ultrasonic irradiation for improved mass transport in solid-liquid systems. Cellular inactivation effects were not evident, and this was attributed to the attenuation of sonic energy arising from the presence of solid polymer materials in the medium. The findings of the study demonstrate that sonication can be used to improve mass transport of poorly soluble compounds in microbial degradations, and alleviate limiting steps of soil remediation processes proposed in previous research.

Sonication Effects on Atrazine Dissipation in Vadose Zone Sediment Slurries

“…Once a day sonications for 10 min, or twice a day sonications for 5 min did not affect atrazine concentrations, while the increase in the sonication time to twice a day for 20-30 min may already have inhibited microbial atrazine degradation. Similarly, 20 min sonications at the intervals of 120/240 min have enhanced microbial phenantrene degradation in a solid-liquid system, but not 25 min sonications at intervals of 205 min in two-liquid-phase systems (sonication horn, 42 kHz, 70 W) [24,34]. Biological activity started to decrease after 5 min sonication (40 kHz, 0.115 W/cm 3 ) in the regeneration of biological activated carbon [35].…”

“…It is not known, however, whether microbial atrazine degradation can be enhanced by sonication. For instance, the microbial phenantrene degradation rate was increased fourfold by intermittent sonication in a solid-liquid system [24]. The enhanced degradation was attributed to the improved mass transport of phenantrene between the solid and liquid phase, which increased phenantrene bioavailability to microorganisms.…”

Mass transport and thermodynamic analysis of PAHs in partitioning systems in the presence and absence of ultrasonication

“…Studies have shown that although lower molecular weight PAHs are not acutely toxic, increasing molecular size correlates well with carcinogenicity, environmental persistence, and chronic toxicity. [1][2][3] Currently, 16 PAHs are present in the US Environmental Protection Agency priority pollutant list. 2 The removal and destruction of PAHs has been studied through numerous technologies.…”

“…[4][5][6][7] Two-phase partitioning bioreactors (TPPBs) are a technology platform recently explored for biological degradation of PAHs. [8][9][10][11][12][13][14][15][16] In TPPB setups, an aqueous phase containing degrading micro-organisms co-exists with an immiscible second phase acting as a reservoir for high concentrations of hydrophobic pollutants. 17 Low levels of contaminants are then transported and partitioned into the aqueous phase, where microbes degrade these toxic substrates.…”

Biodegradation of Endocrine Disruptors in Solid-Liquid Two-Phase Partitioning Systems by Enrichment Cultures

“…Furthermore, consortia can more readily adapt to environment changes or variations in bioprocess operating conditions (32)(33)(34). Microbial consortia were used for the degradation of PAHs, phenolic compounds, and benzene, toluene, ethylbenzene, and xylene (BTEX) in solid-liquid TPPBs (19,20,22,24,33,(35)(36)(37)(38)(39). However, the biodegradation adaptations of these consortia were performed in the absence of the immiscible phase.…”