Engineered and subsequent intrinsic in situ bioremediation of a diesel fuel contaminated aquifer

Abstract

A diesel fuel contaminated aquifer in Menziken, Switzerland was treated for 4.5 years by injecting aerated groundwater, supplemented with KNO 3 and NH 4 H 2 PO 4 to stimulate indigenous populations of petroleum hydrocarbon (PHC) degrading microorganisms. After dissolved PHC concentrations had stabilized at a low level, engineered in situ bioremediation was terminated. The main objective of this study was to evaluate the efficacy of intrinsic in situ bioremediation as a follow-up measure to remove PHC remaining in the aquifer after terminating engineered in situ bioremediation. In the first 7 months of intrinsic in situ bioremediation, redox conditions in the source area became more reducing as indicated by lower concentrations of SO 4 2À and higher concentrations of Fe(II) and CH 4 . In the core of the source area, strongly reducing conditions prevailed during the remaining study period (3 years) and dissolved PHC concentrations were higher than during engineered in situ bioremediation. This suggests that biodegradation in the core zone was limited by the availability of oxidants. In lateral zones of the source area, however, gradually more oxidized conditions were reestablished again, suggesting that PHC availability increasingly limited biodegradation. The total DIC production rate in the aquifer decreased within 2 years to about 25% of that during engineered in situ bioremediation and remained at that level. Stable carbon isotope analysis confirmed that the produced DIC mainly originated from PHC mineralization. The total rate of DIC and CH 4 production in the source area was more than 300 times larger than the rate of PHC elution. This indicates that biodegradation coupled to consumption of naturally occurring oxidants was an important process for removal of PHC which remained in the aquifer after terminating engineered measures. D

In vitro degradation of benzene by the use of ubiquitous bacteria

“…Table 9.Rate of supply (F) and rates of consumption (∆F) of species involved in microbial processes in the subsurface (Hunkeler et al, 2002 In this study, benzene is completely converted to cyclohexane under normal conditions, it is also noted that the concentration of cyclohexane decreases without the formation of other toxic secondary products.…”

“…However, the total flux of dissolved petroleum hydrocarbons decreased from 5 mol/day at the beginning to 0.2 mol/day at the end of the study (Hunkeler et al, 2002 (Kao and Prosser, 2001). Table 6.The scores of each species identified by MALDI-TOF (or even the meanings of the scores in Table 7 above).…”

Monitoramento de indicadores geoquímicos e avaliação de biodegradação em área contaminada com óleo diesel

“…Assim, mediante o acompanhamento da evolução espacial e temporal da concentração desses indicadores geoquímicos presentes na água subterrânea, é possível verificar como está ocorrendo a biorremediação natural de um local contaminado. Além dos aceptores de elétrons, outras variáveis podem ser relacionadas a processos biológi-cos, como o pH e o potencial redox (Vroblesky e Chapelle, 1994;Borden et al,1995;Corseuil e Alvarez, 1996;Walt e McNab, 1999;Azadpour-Keeley et al, 1999;Kao e Wang, 2000;Silva et al, 2002;Bhupathiraju et al, 2002;Röling e Versevel, 2002;Hunkeler et al, 2002, Cheon et al, 2004. Como limitações da biorremediação natural são apontadas principalmente o longo tempo necessário, o risco da pluma de contaminação não ser atenuada antes de atingir pontos de abastecimento de água (Corseuil e Marins, 1997) e a aprovação pelo órgão ambiental (Mariano, 2006).…”

Evidence for in situ degradation of mono-and polyaromatic hydrocarbons in alluvial sediments based on microcosm experiments with 13C-labeled contaminants

“…In practice, often two or more independent approaches are combined (Smets and Pritchard, 2003;Watanabe and Hamamuray, 2003), among these are evidence of concentration decrease of contaminants over time and distance (Wiedemeier et al, 1999), enrichment of heavy stable isotopes in the remaining fraction of organic contaminants (Hunkeler et al, 2002;Meckenstock et al, 2002;Sherwood Lollar et al, 1999), radiotracer studies (Bianchin et al, 2006;Conrad et al, 1997), succession of redox zones in the field (Kuhn and Suflita, 1989;Vroblesky and Chapelle, 1994); accumulation of signature metabolites (Beller, 2002;Elshahed et al, 2001), investigation of the intrinsic microbial biodegradation potential in microcosm studies e in parts with 14 C-labeled substrates e (Aelion and Bradley, 1991;Ambrosoli et al, 2005;Lovley, 2001); characterization of the bacterial community by molecular techniques (Amann et al, 1995;Bakermans et al, 2002), tracing 13 C in fatty acid profiles of bacteria (Geyer et al, 2005), and detection of bacterial enzymes (Hanson et al, 1999;Heinaru et al, 2005;Hendrickx et al, 2006;Löffler et al, 2000). Each of these methods has its advantages and limitations, and therefore it is advisable to base investigations on several approaches, even more when dealing with complex field sites.…”