Stimulation Of Microbial Urea Hydrolysis In Groundwater To Enhance Calcite Precipitation

Abstract

Addition of molasses and urea was tested as a means of stimulating microbial urea hydrolysis in the Eastern Snake River Plain Aquifer in Idaho. Ureolysis is an integral component of a novel remediation approach for divalent trace metal and radionuclide contaminants in groundwater and associated geomedia, where the contaminants are immobilized by coprecipitation in calcite. Generation of carbonate alkalinity from ureolysis promotes calcite precipitation. In calcite-saturated aquifers, this represents a potential long-term contaminant sequestration mechanism. In a single-well experiment, dilute molasses was injected three times over two weeks to promote overall microbial growth, followed by one urea injection. With molasses addition, total cell numbers in the groundwater increased 1-2 orders of magnitude. Estimated ureolysis rates in recovered groundwater samples increased from < 0.1 to > 25 nmol L(-1) hr(-1). A quantitative PCR assay for the bacterial ureC gene indicated that urease gene numbers increased up to 170 times above pre-injection levels. Following urea injection, calcite precipitates were recovered. Estimated values for an in situ first order ureolysis rate constant ranged from 0.016 to 0.057 d(-1). Although collateral impacts such as reduced permeability were observed, overall results indicated the viability of manipulating biogeochemical processes to promote contaminant sequestration.

Biosequestration of copper by bacteria isolated from an abandoned mine by using microbially induced calcite precipitation

“…This change in pH can be explained by ureolysis that leads to an increase in pH and a shift in bicarbonate equilibrium. Urea hydrolyzing bacteria can promote calcium carbonate precipitation by hydrolyzing urea and producing ammonium and bicarbonate ions, thereby increasing the pH (Fujita et al, 2008). The generation of NH 4 + increases local pH, and the reaction continues spontaneously to form calcium carbonate in the presence of calcium ions and the availability of nucleation sites (Rodriguez-Navarro et al, 2003).…”

Introduction of Microbial Biopolymers in Soil Treatment for Future Environmentally-Friendly and Sustainable Geotechnical Engineering

“…MICP has also been found to be applicable in various other fields, including the remediation of heavy metals [59], CO 2 sequestration [60], and the repair of concrete [61,62].…”

Microbially-induced Carbonate Precipitation for Immobilization of Toxic Metals

“…Most earlier studies on environmental urease have been confined to its significance in soil chemistry and agricultural practice. More recent studies have shown that urease-producing microbes show considerable potential for mediating metal bioprecipitation through the formation of insoluble metal carbonates (Fujita et al, 2000(Fujita et al, , 2004(Fujita et al, , 2008Achal, Pan, & Zhang, 2011;Li, Chen & Guo, 2013;Li et al, 2014Li et al, , 2015.…”

“…MICP has been shown to have potential as a remediation strategy for toxic metals since toxic metals can also be precipitated as insoluble carbonates (Fujita et al, 2000(Fujita et al, , 2004(Fujita et al, , 2008Achal, Pan, & Zhang, 2011;Li, Chen, & Guo, 2013). Furthermore, carbonates can be highly effective in further absorbing toxic metals (Plassard, Winiarski, & Petit-Ramel, 2000;Sipos et al, 2005).…”