摘要:

Chlorate (CIO3−) and perchlorate (CIO4−) have been manufactured in large quantities, and therefore it is not surprising that they have been found at high concentrations (>50 mg/L and >1000 mg/L, respectively) in surface waters and groundwaters around the world. These compounds are chemically stable in water, and they are difficult to remove using typical physical-chemical water treatment technologies. Fortunately, chlorate and perchlorate can be removed by biodegradation to low levels in water. Both compounds are highly oxidized and can serve as electron acceptors for several strains of microorganisms under anoxic conditions. Although it has been known for more than 40 years that chlorate can be reduced by mixed cultures, several bacteria have been isolated recently that are able to respire using either chlorate or perchlorate. The purpose of this paper is to review the characteristics of these mixed cultures and isolates in order to assess their future potential for biological water and wastewater treatment processes.

ISSN:1088-9868    

DOI:10.1080/10889869891214222

出版商:TAYLOR & FRANCIS    

年代:1998

数据来源: Taylor

摘要:

Since the discovery of perchlorate in the ground and surface waters of several western states, there has been increasing interest in the health effects resulting from chronic exposure to low (parts per billion [ppb]) levels. With this concern has come a need to investigate technologies that might be used to remediate contaminated sites or to treat contaminated water to make it safe for drinking. Possible technologies include physical separation (precipitation, anion exchange, reverse osmosis, and electrodialysis), chemical and electrochemical reduction, and biological or biochemical reduction. A fairly unique combination of chemical and physical properties of perchlorate poses challenges to its analysis and reduction in the environment or in drinking water. The implications of these properties are discussed in terms of remediative or treatment strategies. Recent developments are also covered.

ISSN:1088-9868    

DOI:10.1080/10889869891214231

出版商:TAYLOR & FRANCIS    

年代:1998

数据来源: Taylor

摘要:

The explosive 2,4,6-trinitrotoluene (TNT) is widely used and results in widespread soil contamination. The white-rot fungusPhanerochaete chrysosporiumhas been shown to degrade TNT, using the peroxidase enzyme. In this study, we report peroxidase-independent degradation of TNT by non-ligninolyticP. chrysosporium. Significant disappearance of TNT from highly contaminated soil usingP. chrysosporiumhas been observed. Soil highly contaminated with TNT (2270 ppm [10 mM]) was diluted to 100 ppm (0.44 mM) with malt extract medium. Pregrown (48 hours) mycelial pellets ofP. chrysosporiumwere added in 100 mL malt extract medium and incubated in Gledhill flasks. Analysis by high-performance liquid chromatography (HPLC) was conducted on soil extracts at specific time points to estimate the disappearance of TNT from contaminated soil incubated withP. chrysosporium. When the pregrown mycelial pellets were added, TNT disappeared within 48 hours. The dissolved concentration of 2-amino-4,6-dinitrotoluene (2Am-DNT) increased up to the third day, then declined before its final disappearance by day 10. Results show that the pregrown mycelial pellets ofP. chrysosporiummineralized up to 17.3±6.3% [14C]-TNT within 30 days.

ISSN:1088-9868    

DOI:10.1080/10889869891214240

出版商:TAYLOR & FRANCIS    

年代:1998

数据来源: Taylor

摘要:

Subsurface microorganisms from McClellan Air Force Base (AFB) were grown in batch aquifer microcosms on methane, propane, and butane to evaluate the potential for aerobic trichloroethylene (TCE) cometabolism. Microorganisms stimulated on all three substrates indicated the existence of a subsurface microbial community capable of utilizing alkanes as growth substrates. Initial growth substrate utilization lag periods of 2 weeks for methane and 3 weeks for propane and butane were observed. Methane- and propane-utilizers were active toward TCE cometabolism, whereas butane-utilizers showed no ability to transform TCE. Gradually increasing TCE concentrations were effectively transformed with uniform additions of methane and propane for up to 1 year. TCE was transformed most rapidly during active methane utilization, and continued at a slower rate for approximately 1 week after methane was consumed. Propane microcosms maintained first-order TCE transformation for up to 4 weeks after propane was consumed. The microbial communities remained active toward primary substrate utilization as the TCE concentration was gradually increased. Both methane- and propane-utilizers showed positive correlations between TCE transformation rates and primary substrate utilization rates. Observed maximum TCE transformation yields were 0.068 g TCE/g methane and 0.048 g TCE/g propane. The methane-utilizers also transformed chloroform (CF) but not 1,1,1-trichloroethane (1,1,1-TCA). Propane-utilizers transformed both CF and 1,1,1-TCA, indicating they were better suited for cometabolizing chlorinated aliphatic hydrocarbon mixtures in the McClellan AFB subsurface.

ISSN:1088-9868    

DOI:10.1080/10889869891214259

出版商:TAYLOR & FRANCIS    

年代:1998

数据来源: Taylor

摘要:

Benzene-amended microcosms prepared with saturated soil or sediment from five hydrocarbon-contaminated sites and one pristine site were monitored for a year and a half to determine the rate of benzene biodegradation under a variety of electron-accepting conditions. Sustainable benzene degradation was observed under specific conditions in microcosms from four of the six sites. Significant differences were observed between sites with respect to lag times before the onset of degradation, rates of degradation, sustainability of the activity, and environmental conditions supporting degradation. Benzene degradation was observed under sulfate-reducing, nitrate-reducing, and iron(III)-reducing conditions, but not under methanogenic conditions. The presence of competing substrates such as toluene, xylenes, and ethylbenzene was found to inhibit anaerobic benzene degradation in microcosms where sulfate or possibly nitrate was the electron acceptor for benzene degradation, but not in microcosms from where iron(III) was the electron acceptor. The presence of organic matter, indicated by a high fraction organic carbon (foc), also appeared to inhibit the biodegradation of benzene; microcosms constructed with soils with the highest focexhibited the longest lag times before the onset of benzene degradation. The initial extent of hydrocarbon contamination did not appear to correlate with anaerobic benzene-degrading activity.

ISSN:1088-9868    

DOI:10.1080/10889869891214268

出版商:TAYLOR & FRANCIS    

年代:1998

数据来源: Taylor

摘要:

A genetically engineered strain ofEscherichia colithat expresses organophosphorus hydrolase (OPH) was immobilized in a polyvinyl alcohol (PVA) cryogel to form a porous biocatalyst that successfully degrades organophosphorus (OP) neurotoxins. The impacts of both diffusion and reaction on biocatalyst efficiency were determined to enable prediction and optimization of the biocatalyst performance. The kinetic rate parameters and activation energies of pure OPH, free cell suspensions, and the immobilized cell biocatalyst were compared. Diffusion was a determining factor for paraoxon hydrolysis because of the very rapid OPH kinetics for its model substrate. Both the paraoxon diffusion through the PVA matrix and the diffusion associated with microbial transport of paraoxon were shown to impact the biocatalyst reaction. However, the enhancement in storage stability resulting from diffusional limitations provides an advantage to diffusion-limited operation. This research may serve as a guide to define the influence of diffusion in biological reaction systems. The broad substrate specificity and hydrolytic efficiency of OPH coupled with the ability to genetically engineer the enzyme for specific target OP neurotoxins enhance the suitability of OPH-based technologies for detoxification of these compounds. Cryoimmobilization provides a suitable vehicle as a cost-effective, efficient technology for bioremediation of environmental media contaminated with OP compounds.

ISSN:1088-9868    

DOI:10.1080/10889869891214277

出版商:TAYLOR & FRANCIS    

年代:1998

数据来源: Taylor