Effect of Nanoscale Zero-Valent Iron Treatment on Biological Reductive Dechlorination: A Review of Current Understanding and Research Needs

Abstract

Nanoscale zero-valent iron (nZVI) is a strong non-specific reducing agent that is used for in situ degradation of chlorinated solvents and other oxidized pollutants. However, there are significant concerns regarding risks posed by the deliberate release of engineered nanomaterials 20 into the environment, which have triggered moratoria, for example, in the United Kingdom. This critical review focuses on the effect of nZVI injection on subsurface microbial communities, which are of concern due to their important role in contaminant attenuation processes.Corrosion of ZVI stimulates dehalorespiring bacteria, due to the production of H 2 that can serve as an electron donor for reduction of chlorinated contaminants. Conversely, lab studies show 25 that nZVI can be inhibitory to pure bacterial cultures, although toxicity is reduced when nZVI is coated with polyelectrolytes or natural organic matter. The emerging toolkit of molecular biological analyses should enable a more sophisticated assessment of combined nZVI/biostimulation or bioaugmentation approaches. While further research on the consequences of its application for subsurface microbial communities is needed, nZVI continues 30 to hold promise as an innovative technology for in situ remediation of pollutants. It is particularly attractive for the remediation of subsurface environments containing chlorinated ethenes because of its ability to potentially elicit and sustain both physical-chemical and biological removal despite its documented antimicrobial properties.

Assessment of biostimulation and bioaugmentation for removing chlorinated volatile organic compounds from groundwater at a former manufacture plant

“…threaten the health of human beings and other organisms (Mattes et al 2010). To remove CVOCs from the contaminated sites, several effective remediation technologies have been applied, such as air-stripping (Nelson et al 1997), zero-valent iron degradation (Bruton et al 2015), granular activated carbon absorption (Yang et al 2009) and biodegradation (Cope and Hughes 2001;Scheutz et al 2008). Considering the cost and efficiency, biodegradation was one of the promising approaches to resolve CVOCs problems in the field.…”

The ecotoxic potential of a new zero-valent iron nanomaterial, designed for the elimination of halogenated pollutants, and its effect on reductive dechlorinating microbial communities

“…The formulation ingredients (coatings, suspending agents, stabilization materials) of NZVI preparations can also serve as a source of electron donors supporting biological dechlorination (He et al, 2010;Kirschling et al, 2010;Su et al, 2012;Wei et al, 2012). Despite toxic effects of NZVI on natural microflora and dechlorinating microorganisms (Barnes et al, 2010;Bruton et al, 2015;Kumar et al, 2014b;Velimirovic et al, 2015;Xiu et al, 2010aXiu et al, , 2010b, the combined use of abiotic dechlorination with NZVI and biological dechlorination can result in synergetic effects, positive for the remediation process (Bruton et al, 2015;He et al, 2010;Kocur et al, 2015;Su et al, 2012). High pH conditions developing during anaerobic ZVI corrosion as well as acidification due to fermentation of formulation ingredients being unfavourable for biological processes have to be taken into account during field applications (Bruton et al, 2015;Velimirovic et al, 2015).…”

“…On the other hand, hydrogen is consumed by hydrogenotrophic bacteria, acting as a sink for hydrogen and mitigating the problem of gas clogging. Moreover, hydrogen is an excellent electron donor for supporting biological reductive dechlorination (Bruton et al, 2015;Lohner et al, 2011;Lohner and Tiehm, 2009;Velimirovic et al, 2015). Biological reductive dechlorination represents an environmental friendly, sustainable and cost-efficient option for removal of e.g.…”

Transient Performance of Two-Electron Regime Bioreactors That Contained Unacclimated Biocatalysts After Feeding Perchloroethylene

“…ZVI can create ecological niches that possibly would improve the microbial activities favorable to chlorinated organic compounds removal (Bruton et al 2015).…”