Arsenic bioremediation

A major concern when remediating wood-treatment sites is that pentachlorophenol was often used in combination with metal salts, and these compounds, such as chromated copper—arsenate, are potent inhibitors of at least some pentachlorophenol degrading organisms (49). Sites with significant levels of such inorganics may not be suitable candidates for bioremediation. 

In several wood-preserving facilities, other wood preservatives such as creosote and chromate-copper—arsenate (CCA) have been used in addition to PCP (e.g., Lamar Glaser, 1994 Mueller et al., 1991a Mahaffey et al., 1991). Environmental contamination by chemical mixtures is likely in these sites. When PCP has been dissolved in an organic carrier such as oil, soil is also contaminated with the solvent (Trudell et al., 1994 Lamar Dietrich, 1990). Chlorinated dimeric impurities in technical CP formulations are also found in contaminated soil. Design of successful bioremediation must address the effects of other chemicals on CP biodegradation. 

Like water, arsenic in contaminated soils, sediments, and even solid wastes may be treated with plants, fungi, bacteria, or other biological organisms. The applications, limitations, and advantages of biological treatment methods with solid materials are often similar to those with water. To be exact, many bioremediation methods are designed to simultaneously treat contaminants in soils, sediments, and water (e.g. phytoremediation). 

Alvarado, S., Guedez, M., Lue-Meru, M.P., Nelson, G., Alvaro, A., Jesus, A.C., and Gyula, Z. 2008. Arsenic removal from waters by bioremediation with the aquatic plants water hyacinth (Eichhomia crassipes) and lesser duckweed (Lemna minor). Bioresource Technology, 99(17) 8436 0. 

Zouboulis, A.I. and Katsoyiannis, LA. 2005. Recent advances in the bioremediation of arsenic-contaminated groundwaters. Environment International, 31(2) 213-19. 

The metalloregulatory protein arsR was overexpressed in Escherichia coli and resulted in both elevated levels of arsenite bioaccumulation leading to severe reduction in cellular growth (Kostal et al, 2004), and the efficacy of this strain at low arsenic levels. Equivalent strains overexpressing PC synthase genes and arsR could be developed to have arsenic hypertolerant strains with higher bioaccumulation, valuable for the bioremediation of arsenic. 

It is well established that microbiota plays a very significant role in the various transformations of arsenic, including mineralization/immobilization, oxidation/ reduction, and methylation/demethylation. Some of these biotransformations lead to less toxic forms of arsenic that can be used in the detoxification of the arsenic-contaminated environments. Biomethylation of arsenic results in formation of mono-, di-, and trimethylarsines which are volatile however, these gaseous arsenic forms are also toxic. In developing a bioremediation strategy to clean the... 

This book contains conttibutions from world-renowned international scientists on topics that include toxicity of arsenic, analytical methods for determination of arsenic compounds in the environment, health and risk exposure of arsenic, biogeochemical conttols of arsenic, Peatment of arsenic-contaminated water, and microbial ttansformations of arsenic that may be useful in bioremediation. 

Chapter 16 focuses on the methylation and volatilization of arsenic. Bio-methylation of arsenic results in formation of mono-, di- and trimethylarsine, which are volatile gases. In developing a bioremediation strategy to clean the environment of arsenic, special attention must be paid to the toxic nature of mi-crobially transformed arsenic compounds. This chapter covers the environmental parameters that promote arsenic volatilization under natural and engineered conditions. 

Her most recent scientific contributions were in the areas of bacterial selenium and arsenic metabolism. Her interest in bioremediation began with selenium-contaminated water found in the San Joaquin Valley in California, from which she isolated the first bacterium able to respire with selenate (reducing it to selenite and then to elemental selenium) using acetate as the electron donor/ carbon source. This organism was found to represent a new genus and named Thauera selenatis. She studied the organism extensively for the purpose of selenium bioremediation. This involved the design and implementation of lab-scale and then pilot-scale reactors. 

Wilson, X T. Kampell, D. H. Weaver, X W Imbrigiotta, B. Ehlke, T. (1996) A review of intrinsic bioremediation of trichloroethylene in ground water at Picatinny arsenal. New Jersey and St. Jospehs, Michigan. In Proceedings of Symposium on Natural Attenuation of chlorinated Organics in Ground Water, Dallas, Texas, Sept. 1996, EPA/540/R-96/509, 11-14. 

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