Integrated Chemical-Biological Treatment of Benzo[a]pyrene

Abstract

Benzo[a]pyrene of natural and anthropogenic sources is one of the toxic, mutagenic, polycyclic aromatic hydrocarbons (PAHs) listed as priority pollutants. This study focuses on an integrated treatment of benzo[a]pyrene involving sequential chemical oxidation and biological degradation. The objectives are to (1) provide mechanistic details in the ozone-mediated degradation of benzo[a]pyrene in the aqueous phase, (2) test the biodegradability of resultant intermediates, and (3) test the feasibility for the coupled chemical-biological treatment of the five-ring PAH. Batch and packed column reactors were used to examine the degradation pathways of benzo[a]pyrene subject to ozonation in the aqueous phase. After different ozonation times, samples containing reaction intermediates and byproducts from both reactors were collected, identified for organic contents, and further biologically inoculated to determine their biodegradability. The O 3 -pretreated samples were incubated for 5, 10, 15, and 20 days; afterward biochemical oxygen demand (BOD), chemical oxygen demand (COD), and E. coli toxicity tests were conducted along with qualitative and quantitative determinations of benzo[a]pyrene, intermediates, and reaction products by GC/FID and GC/ MS methods. Prevalent intermediates identified at different stages included ring-opened aldehydes, phthalic derivatives, and aliphatics. The degradation of benzo[a]pyrene is primarily initiated via O 3 -mediated ring-opening, followed by O 3 and hydroxyl radical fragmentation, and ultimately brought to complete mineralization primarily via hydroxyl radicals. Intermediates formed during chemical oxidation were biodegradable with a measured first-order rate constant (k 0 ) of 0.18 day -1 . The integrated chemical-biological system seems feasible for treating recalcitrant compounds, while pretreatment by chemical oxidation appears useful in promoting soluble intermediates from otherwise highly insoluble, biologically inaccessible benzo[a]pyrene.

Aqueous photodegradation and toxicity of the polycyclic aromatic hydrocarbons fluorene, dibenzofuran, and dibenzothiophene

“…Bioremediation is most often the treatment used for the removal of PAHs from contaminated water and soil because it's generally found to have cost and technical advantages (Zeng et al, 2000). Advanced oxidation processes (AOPs) including ozone, hydrogen peroxide, UV radiation, and combinations of these processes were also shown to degrade various PAHs (Zeng et al, 2000;Beltran et al, 1996;Miller and Olejnik, 2001).…”

Photolysis, oxidation and subsequent toxicity of a mixture of polycyclic aromatic hydrocarbons in natural waters

“…Among the engineered processes bioremediation is generally considered having cost and technical advantages [5]. Advanced oxidation processes (AOPs), by which hydroxyl radicals are generated in order to destroy the organic contaminant, were also studied as an alternative to or in combination with biodegradation for removal of PAHs from aqueous solutions [6][7][8][9][10].…”

Degradation of Benzo[ a ]pyrene by Mycobacterium vanbaalenii PYR-1

“…Because of these properties, PAHs have been included in the U.S. Environmental Protection Agency's list of priority pollutants. The removal of PAHs from soil is necessary during soil remediation to comply with relevant cleanup standards and is based on individual PAH standards (4,14,22,33).…”