EVALUATING BIOREMEDIATION: Distinguishing Fact from Fiction

Abstract

Bioremediation options encompass diverse types of biochemical mechanisms that may lead to a target's mineralization, partial transformation, humification, or altered redox state (e.g. for metallic elements). Because these various mechanisms produce alternative fates of the targeted pollutants, it is often necessary to use diverse evaluation criteria to qualify a successful bioremediation. Too often target depletion from a treated matrix can be mistakenly ascribed to biological activity when in fact the depletion is caused by abiotic losses (e.g. volatilization, leaching, and stripping). Thus, effective, and therefore convincing, evaluation requires that experimental and engineering designs anticipate all possible routes of target depletion and that these routes be carefully monitored.

Reduction of hexavalent chromium by Ochrobactrum intermedium BCR400 isolated from a chromium-contaminated soil

“…Effective physico-chemical methods have been developed for reduction of Cr(VI) to Cr(III), however, they suffer from limitations of use of chemicals and sludge generation with subsequent disposal problems. Biological processes on other hand are considered eco-friendly and less expensive (Losi et al 1994; Saleh et al 1989; Shannon and Unterman 1993). Several reports on microbial biotransformation of Cr(VI) to less toxic Cr(III) through direct enzymatic reaction or indirectly through metabolites exist in literature (Saleh et al 1989; Puzon et al 2002).…”

Integrative approaches for assessing the ecological sustainability ofin situbioremediation

“…These studies have led to a general acceptance of bioremediation as being an environmentally benign, efficient and economic measure for pollutant removal and restoration of contaminated sites (Watanabe, 2001;Paul et al, 2005). Bioremediation methods are based on the exploitation of metabolic potential for attenuation of the toxic effects of the pollutant(s) by (1) transformation to lesser toxic products; (2) complete mineralization of pollutants; and (3) immobilization of the pollutant (Shannon & Unterman, 1993;Snellinx et al, 2002;Lovley, 2003;Diaz, 2004;Parales & Haddock, 2004). Most of the living beings including plants and higher animals exhibit a minimal basal level of detoxification ability that is expressed via the above mechanisms; however, microorganisms have been studied in greater detail for carrying out the detoxification activities (Watanabe & Baker, 2000;Zhong & Zhou, 2002).…”

Interactions of earthworms with indigenous and bioaugmented PCB-degrading bacteria

“…Bioremediation is an environmentally sound, and potentially low cost method to clean up soils that are contaminated with polychlorinated biphenyls (PCBs) [1]. Nonetheless, there is still concern over the reliability and general e⁄cacy of bioremediation that has precluded the commercial application of these methods [2^4], and there is a consensus that further improvements will require a better understanding of the biological processes that facilitate bioremediation [2,5,6]. Bioremediation can employ either bioaugmentation in which additional bacteria are added to the soil, or may be achieved by biostimulation of contaminant degrader populations within the indige-nous soil micro£ora.…”