Using slow-release permanganate candles to remediate PAH-contaminated water

Abstract

Surface waters impacted by urban runoff in metropolitan areas are becoming increasingly contaminated with polycyclic aromatic hydrocarbons (PAHs). Slow-release oxidant candles (paraffin-KMnO(4)) are a relatively new technology being used to treat contaminated groundwater and could potentially be used to treat urban runoff. Given that these candles only release permanganate when submerged, the ephemeral nature of runoff events would influence when the permanganate is released for treating PAHs. Our objective was to determine if slow-release permanganate candles could be used to degrade and mineralize PAHs. Batch experiments quantified PAH degradation rates in the presence of the oxidant candles. Results showed most of the 16 PAHs tested were degraded within 2-4 h. Using (14)C-labled phenanthrene and benzo(a)pyrene, we demonstrated that the wax matrix of the candle initially adsorbs the PAH, but then releases the PAH back into solution as transformed, more water soluble products. While permanganate was unable to mineralize the PAHs (i.e., convert to CO(2)), we found that the permanganate-treated PAHs were much more biodegradable in soil microcosms. To test the concept of using candles to treat PAHs in multiple runoff events, we used a flow-through system where urban runoff water was pumped over a miniature candle in repetitive wet-dry, 24-h cycles. Results showed that the candle was robust in removing PAHs by repeatedly releasing permanganate and degrading the PAHs. These results provide proof-of-concept that permanganate candles could potentially provide a low-cost, low-maintenance approach to remediating PAH-contaminated water.

A combined chemical and biological approach to transforming and mineralizing PAHs in runoff water

“…Given that adsorption tests confirmed that neither diphenaldehyde or the ozone-treated benzo(a)pyrene products were adsorbed by the glass beads or glass beads coated with microorganisms ( Figure SM-7), the losses in 14 C recovered confirm that biological mineralization could be achieved in a flow-through system and mineralization rates improved with repeated cycles. Collectively, the results reported in this study, combined with previous chemical-biological approaches (Zeng et al, 1999;Zenaitis et al, 2002;Yerushalmi et al, 2006;Rauscher et al, 2012), support combining ozone with biological treatments for treating PAH-contaminated water. …”

“…Many of these products would be more soluble and thus more available for natural biotic mineralization than the original parent structure, which was evident from our mineralization results ( Figure 6B). Nam and Kukor (2000); Rauscher et al (2012) also found that oxidative treatment of PAHs resulted in more biological products.…”

“…Peak areas from the fluorescence detector were compared to standard calibration curves generated for each PAH. The total run time was ~50 min per sample (Rauscher et al, 2012). 14 C-activity was determined by removing 1 mL subsamples from the batch reactors and mixing with 5 mL of Ultima Gold liquid scintillation cocktail (Packard, Meriden, CT).…”

“…Its drawbacks however, include long treatment times and the fact that higher molecular weight PAHs (>3-rings) are generally resistant to biodegradation (Cerniglia, 1992;Wilson and Jones, 1993). For this reason, many researchers have attempted to couple chemical treatments with biological treatments as a means of transforming hydrophobic contaminants to more hydrophilic products that can then be biodegraded (Zeng et al, 1999;Nam and Kukor, 2000;Zenaitis et al, 2002;Yerushalmi et al, 2006;Rauscher et al, 2012;Wang et al, 2013).…”

Quantum Dots Extraction Coupled With High-Performance Liquid Chromatography for the Determination of Polycyclic Aromatic Hydrocarbons in Water

“…Chemical analysis of PAHs is of great environmental and toxicological importance as many PAHs have been identified as potent mammary carcinogens in experimental bioassays (Elbayoumy, 1992). Exposures to PAHs have been linked to increased cancer risks in epidemiological studies (Mastrangelo et Due to their hydrophobicity, PAHs are inclined to adsorb to and accumulate with particles such as dust, sediment and debris, Atmospheric PAHs may undergo photolytic and chemical (ozone) transformations or be deposited back to land (Rauscher et al, 2012;Xie and Haleegoah, 2016). A primary route of human exposure to PAHs is the ingestion of contaminated water, which is one of the indispensable materials in daily human life.…”