Remediation of Polyaromatic Hydrocarbons (PAHs) through Landfarming with Biostimulation and Bioaugmentation

Abstract

Many soils contaminated with high molecular weight hydrocarbons (HMW PAHs) contain PAHdegrading microorganisms. These microbes are often limited in their degradation capability because of some limiting environmental factors (i.e., low aqueous solubility of PAHs, low bioavailability of PAHs, nitrogen or other nutrient limitation, high co-contamination levels such as pentachlorophenol [PCP] that can inhibit PAH biodegradation, etc.). Microcosm studies were done using biostimulation (addition of ground rice hulls as a bulking agent and dried blood as a slow-release nitrogen source) and/or bioaugmentation (addition of Pseudomonas aeruginosa strain 64, a biosurfactant-producer on a vermiculite carrier). Soil from the POPILE, Inc. Superfund site (PAHs at 13,000 mg/kg, average and PCP at 1,500 mg/kg, average) was used. After 11 months, control microcosms (no treatment) showed a 23% decrease in total PAHs and a 48% decrease in total BaP toxic equivalents. The biostimulated microcosms showed a 34% decrease in total PAHs and a 57% decrease in total BaP toxic equivalents, while the biostimulated and bioaugmented microcosms revealed an 87% decrease in total PAHs and a 67% decrease in total BaP toxic equivalents. Pseudomonas aeruginosa strain 64 is not a PAHdeg rader, t herefore, this redu ction in PAHs was due to stimulated deg rada tion by the autochthonou s mic robial community. Pan studies were designed t o tes t the imp roved bioremediation of HMW PAHs Acta Biotechnol. 23 (2003) 2 -3, 179 -196 using biostimulation and/or bioaugmentation on a larger scale. Drywells were used to monitor soil microbial respiration, soil moisture was maintained at 50-80% of the soil field moisture capacity (FMC), cultivation was carried out weekly with rototillers, and microbial biomass and community composition (indigenous microbiota and augmented soil) were determined by PLFA profiles. An initial rapid decrease in PAH concentration was observed in the pan receiving both bioaugmentation and biostimulation (50% degradation at six months). The pan that was biostimulated only achieved the 50% level at seven months. After 16 months, the control pan showed a 12% decrease in PAHs, while biostimulated only and both biostimulated and bioaugmented pans showed an 86 and 87% removal, respectively. These two pans developed similar microbial communities, and these communities were different from that in the control pan 1. Supplementing autochthonous bacterial communities, using slow-release nitrogen fertiliser and bulking agent has great potential for improving landfarming of PAH-contaminated soils.

On-site and in situ remediation technologies applicable to petroleum hydrocarbon contaminated sites in the Antarctic and Arctic

“…Treatment strategies vary for landfarms and can be tailored according to site-specific characteristics including climate, location, soil type and temperature (Paudyn et al 2008). Nutrient amendments, pH buffers and bulking agents may be applied to stimulate aeration of co-substrates, microbial metabolism or bacterial inoculations and can significantly increase remediation efficiency (Straube et al 2003;Paudyn et al 2008;Filler et al 2009). The success of landfarming in temperate environments is well reported (McCarthy et al 2004); however, landfarming trials in cold regions are comparatively scarce and field trials from the Antarctic and Arctic have revealed conflicting results (Delille 2000;Aislabie et al 2004;McCarthy et al 2004;Paudyn et al 2008;Chang et al 2010).…”

Potential of the soil microbial biomass C to tolerate and degrade persistent organic pollutants

“…It is known that many soils contaminated with PAHs contain PAH-degrading microorganisms. These microbes are often limited in their degradation capacity because of some limiting environmental factors such as aqueous solubility of PAHs, low bioavailability of PAHs, nitrogen or other nutrient limitation, high co-contamination levels that can inhibit PAH biodegradation (Straube et al 2003). This fact could be a partial explanation why PAHs degraded well in the soil Polluted-PAH and partly also in the soil Control-PAH, whereas no decrease was found in the sewage sludges amended soil Polluted-sew.sl-PAH.…”

“…On the other hand, the microbes are often limited in their degradation capability because of some limiting environmental factors (i.e., low aqueous solubility of PAHs, low bioavailability of PAHs, nitrogen or other nutrient limitation, high cocontamination levels such as pentachlorophenol (PCP) that can inhibit PAH biodegradation, etc.) (Straube et al 2003).…”

Rhamnolipid Biosurfactants Produced by Pseudomonas Species

“…DS10-129, increased the bioremediation process in an oilcontaminated soil (Rahman et al 2002). Similarly, Straube et al (2003) reported that adding P. aeruginosa strain 64 enhanced the bioremediation in a soil contaminated with PAHs and pentachlorophenol. Kumar et al (2008) reported that a crude biosurfactant from the Pseudomonas DHT2 strain isolated from an oil-contaminated soil enhanced the solubility of PAHs in a dosedependent manner.…”