Bioremediation of selenium‐contaminated sediments and water

Abstract

Selenium (Se) is a contaminant of agricultural irrigation-drainage water in the western United States, and the cause of wildlife deaths and grotesque deformities. Some approaches in reducing the toxic Se concentrations from contaminated sediments and water have been proposed, but most of these tend to be costly or ineffective. Bioremediation through microbial transformations of toxic Se species into nontoxic forms is being considered as an effective remedial alternative. The microbial reduction of toxic oxyanions of Se (SeO(4)(2-) and SeO(3)(2-)) into insoluble Se(0) or methylation of these species to dimethylselenide (DMSe) has been accepted as a potential bioremediation strategy for cleanup of Se-contaminated water and sediments. By conducting a series of laboratory, bench-scale and field studies, we have thoroughly investigated the remedial potential of these approaches. It was observed that microorganisms, particularly Enterobacter cloacea, are very active in reduction of Se oxyanions present in irrigation drainage water, into insoluble Se(0) and, by monitoring various environmental conditions and addition of organic amendments, the process could be stimulated manifold. Similarly, the process of biomethylation of Se in soil sediments and water was found active and highly dependent on specific carbon amendments (pectin and proteins), pH, temperature, moisture, aeration and activators (cofactors). Moreover, Se biomethylation was protein/peptide-limited rather than nitrogen-, amino acid- or carbon-limited. Crude casein and its components were equally stimulatory producing a >50-fold enhancement in DMSe yield. Methionine and methyl cobalamin stimulated DMSe production by Alternaria alternata, indicating that the coenzyme may mediate the transfer of a methyl group to the Se atom. An acute toxicity test involving inhalation of DMSe by rats revealed that DMSe is nontoxic. Experiments were scaled up from laboratory studies to field plots to verify the feasibility of this bioremediation approach. Based upon the promising results of these studies, a biotechnology prototype was developed which could be applicable for cleanup of polluted sediments and water throughout the western United States.

A review on completing arsenic biogeochemical cycle: Microbial volatilization of arsines in environment

“…fungal strains (Srivastava et al, 2011). These results not only proposed the application of fungi cultivation for As removal and bioremediation, also supposed that the amount of released arsines from soils, sediments and waters by indigenous fungi may be enhanced by the optimization of environmental parameters affecting volatilization, such as the addition of soil nutrients and moisture and aeration regulation (Thompson-Eagle et al, 1989;Frankenberger and Arshad, 2001). …”

Ecology and Biotechnology of Selenium-Respiring Bacteria

“…Microbial volatilization opens perspectives for recovering selenium via the gas phase, which is thus free from cells and other metal contaminants. For a long time, microbial volatilization was considered a slow process (129,130,(133)(134)(135) that was unsuitable for industrial applica- , and heavy metals from wastewater or process water. In the BSer process, SeO 4 2Ϫ and SeO 3 2Ϫ are reduced to elemental selenium by biofilms of propriety microorganisms, using molasses as the carbon source and electron donor (117).…”

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides: 2. Field Research on Bioremediation of Metals and Radionuclides

“…The central valley of California has a notorious problem with Se buildup in ponds in wetlands in the area, which have proven to be toxic for local wildlife. Studies by Terry et al ((DE SOUZA et al 2001)) and Frankenberger et al (FRANKENBERGER and ARSHAD 2001;FRANKENBERGER and KARLSON 1994;FRANKENBERGER and KARLSON 1995) demonstrated that from 30 to 70% of the Se coming into the wetlands are volatilized. Microalgae and bacteria were shown to be responsible in a number of studies that added fungicides and bacteriocides to the wetlands water.…”