Remediation, bacterial

Bacterial remediation of selenium oxyanions in San Joaquin, California, drainage water is under active investigation (96,97), but has not yet been commercialized. Agricultural drainage rich in selenium is also typically rich in nitrates, so bioremediation must also include conditions that stimulate denitrification (98). Phytoextraction of selenium is also being tested, but is not yet being used on a large scale. 

Pure Ti02 was recently reported to be active in the disinfection of water contaminated by spores of the type Fusarium solani [142], Bacillus anthracis [143], or Cryptosporidium parvum oocysts [144], or when supported as nanocomposites on zeolite H(i for E. coli deactivation [145], and it found applications in water treatment as a replacement for chlorine. Ag-Ti02 immobilized systems were used for inactivation of bacteria, coupling the visible light response of the system and the strong bactericidal effect of Ag [146]. Silver was deposited on hydroxyapatite to form nanocomposites with a high capacity for bacterial adsorption and inactivation [147], or used for airborne bacterial remediation in indoor air [148],... 

CA models are well suited to the modeling of bacterial remediation. The first step is to build a model of a colony of bacterial cells that can reproduce and grow. In doing so, you will need to take into account several factors such as ... 

Srinath T, Verma T, Ramteke PW, Garg SK (2002) Chromium biosorption and bioaccumulation by chromate resistant bacteria. Chemosphere 48 427-435 Stephen JR, Macnaughton SJ (1999) Developments in terrestrial bacterial remediation of metals. Curr Opinion Biotechnol 10 230-233 Tabak HH, Lens P, van Hullebusch ED, Dejonghe W (2005) Developments in bioremediation of soils and sediments polluted with metals and radionuclides 1. Microbial processes and mechanisms affecting bioremediation of metal contamination and influencing metal toxicity and transport. Rev Environ Sci Bio/Technol. 4 115-156... 

More practical questions are whether introduced GEMs will survive in polluted matrices, or whether their continued viability will dramatically affect the success of remediation. A recent development in this area is the isolation of bacterial strains which can respond to selective agents under field conditions. These strains have been called field application vectors or FAVs, since their intended purpose is to express foreign genes in environments not conducive to the use of the parent organism (Lajoie et al., 1993). The proposed use of FAVs illustrates the need to control bacterial growth and survival under the real-world conditions where bacterial remediation has to occur. 

Cathodic protection with impressed current, aluminum or magnesium anodes does not lead to any promotion of germs in the water. There is also no multiplication of bacteria and fungi in the anode slime [32,33]. Unhygienic contamination of the water only arises if anaerobic conditions develop in the slurry deposits, giving rise to bacterial reduction of sulfate. If this is the case, HjS can be detected by smell in amounts which cannot be detected analytically or by taste. Remedial measures are dealt with in Section 20.4.2. 

E. Jurkevitch, Y. Hadar, and Y. Chen, Involvement of bacterial siderophores in the remedy of lime-induced chlorosis in peanut. Soil Sci. Soc. Am. J. 52 1032 (1988). 

Some heavy metal-tolerant bacterial strains and their sorption capacities for Cu and Cd are listed in Table 1. These bacteria show great potential for remediating soils that are contaminated with toxic metals. Our pot culture experiments showed that the growth of tobacco plants in a Cd-polluted Yellow Brown Soil (Alfisol) was significantly promoted by inoculating the soil with P. Putida in comparison with the non-inoculated soil (Fig. 2). 

Bacteria and their composites with soil minerals or organic matter are capable of taking up a wide range and variety of toxic metals in soil environments. Research done over the last decade or so has greatly improved our understanding of the mechanisms on biosorption of metals and bacte-ria-metal-soil component interactions. However, more studies from molecular level are needed in order to enhance the ability of bacteria and their association with soil components to remediate toxic metals-contaminated soils. The focus of future investigations should be on the mechanisms by which metals are sorbed and bound by bacterial cell surfaces and bacteria-soil/mineral composites. In this connection, X-ray absorption spectroscopy (XAS) is a promising technique because it can provide information about... 

If an open system with renewal of substrate, nutrients, water, and electron acceptors can be supplied, the growth rate of the bacteria population is able to continue for an extended period of time until the remediation is complete. The Monod equation describes the type of bacterial growth that can be expected in an open system ... 

Clausen, C.A. (2004b). Improving the two-step remediation process for CCA-treated wood part B. Evaluating bacterial nutrient sources. Waste Management, 24(4), 407 11. 

I believe that many of the same problems exist in the remediation field. Most remediation specialists don t consider what the wastewater treatment people have been doing with bacterial systems for the past 100 years. Not all the work in wastewater treatment may be applicable to remediation, but it does not deserved to be dismissed out of hand either. In many cases, what is happening involves water, oxygen, nutrients, a substrate, and the same soil organisms which are found in wastewater. In fact, one of the ways of... 

Bacteria indigenous to Cr(VI)-polluted areas are Cr(VI) tolerant and/or resistant and have been considered as potential candidates for bioremediation of Cr(VI)-contaminated sites.16 However, the ability of bacteria to reduce Cr(VI) to the less-toxic Cr(III) compounds may produce reactive intermediates (such as Cr(V), Cr(IV), radicals), which are known to be active genotoxins and are likely to be carcinogenic.17 Therefore, the formation and lifetimes of Cr(V) intermediates, produced via bacterial reduction of Cr(VI), need to be evaluated carefully if microorganisms are to be employed as a means for remediation of chromium-polluted subsurface environments. Similarly, Cr(V) accumulation should first be monitored when considering plants and algae as biosorption materials for the bioremediation in the event of chromium pollution.18... 

The major limitations of this technology are those factors that limit bacterial growth, such as temperature extremes, pH (below 3 or above 10), and presence of other contaminants detrimental to bacteria life. Remediation of petroleum contaminants using FyreZyme can be accomplished under both aerobic and anaerobic conditions however, remediation under aerobic conditions is faster and more complete. Other factors that may affect speed and completion of contaminant breakdown include moisture level, soil properties, and microbe mobility. In addition, the shelf life of FyreZyme is reduced from 5 to 2 years at temperatures above 100°F. 

TCE-degrading bacteria is a patented technology for the treatment of soil, groundwater and wastewater contaminated with trichloroethylene (TCE). The particular strain of bacteria used in this technology does not require the addition of a toxic co-substrate to activate the bacterial destruction of TCE. The technology can be used to remediate virtually any media type contaminated with one or more volatile organic compounds (VOCs), including TCE, and can be used for in situ or ex situ bioremediation. 

For reasons that will be explained in a subsequent chapter, the team found that the application of a technology known as bioflitration was considered the best remediation method. The contaminated gas is pumped through a column packed with a material that performs two functions (1) it provides for efficient contact between the air passing through it and water, and (2) it serves as a scaffold for the development of a bacterial colony. Figure 1.7 shows a typical biofiltration arrangement. The team must develop a system that has a very low pressure drop so that the process can be constructed from plastic tanks and low-pressure pumps to save money. In a further effort to save money, the process should have a small footprint. 

The discussion of improved sanitary remediation systems is by no means limited to the Third World. In rural areas of the United States, bacterial contamination of water supplies occasionally makes headlines. 

Although the above studies conducted with packed columns are important from a fundamental standpoint as they relate to the mechanisms of cell sorption to solid surfaces, in situ remediation of contaminants in subsoils requires microbial transport in well-structured soils. The presence of soil macropores that facilitate preferential water flow is well appreciated (Thomas Phillips, 1979). Sorption phenomena are less important when bacterial transport occurs through structured soils in which cells pass unimpeded through relatively large conduits (Smith et al., 1985). 

Nadim, L., Schocken, M.J., Higson, F.J., Gibson, D. T., Bedard, D. L., Bopp, L. H. Mondello, F. J. (1987). Bacterial oxidation of polychlorinated biphenyls. In Proceedings of the 13th Annual Research Symposium on Land Disposal, Remedial Action, Incineration, and Treatment of Hazardous Waste, pp. 395—402. U.S. Environmental Protection Agency, Cincinnati, OH (EPA/600/9-87/015). 

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