Removal of Mercury from Chemical Wastewater by Microoganisms in Technical Scale

Abstract

The enzymatic reduction of Hg(II) to water insoluble Hg(0) by mercury resistant bacteria has been used for removal of mercury from wastewater in technical scale. Pure cultures of seven mercury resistant strains of Pseudomonas were immobilized on carrier material inside a 700 L packed bed bioreactor. Neutralized chloralkali electrolysis wastewater with a mercury concentration of 3−10 mg/L was continuously fed into the bioreactor (0.7 m3/h up to 1.2 m3/h). A mercury retention efficiency of 97% was obtained within 10 h of inoculation of the bioreactor. At optimum performance, bioreactor outflow concentrations were below 50 μg Hg/L, which fulfill the discharge limit for industrial wastewater. In combination with an activated carbon filter, outflow concentrations below 10 μg Hg/L were always obtained. The retention efficiency of the bioreactor was not affected by fluctuations in inflow conductivity (between 20 and 105 mS/cm), pH (between 6.5 and 7.5), or mercury concentration (between 3 and 10 mg/L) and was between 95% and 99%. Temperature increases up to 47 °C did not impair bioreactor performance. Standby periods up to 6 h could be tolerated without loss in activity. A simple, effective, and robust biotechnology for remediation of mercury polluted wastewater is thus demonstrated.

A conservative region of the mercuric reductase gene (merA) as a molecular marker of bacterial mercury resistance

“…Recently, the microbial mercury resistance, dependent of MerA mechanism, has been used for the remediation of mercury contaminated wastewater (3,7,27). Therefore, the identification of Hg resistant strains is essential to the technological development of mercury bioremediation strategies.…”

Technology Evaluation for Waterborne Mercury Removal at the Y12 National Security Complex

“…A pilot test has demonstrated the use of aerobic biological treatment to convert soluble Hg 2+ to elemental mercury (Wagner-Dobler et al, 2000). The reaction is catalyzed by enzymes such as mercuric reductase.…”

U.S. Department of Energy and Polish Institute for Ecology of Industrial Areas Joint Coordinating Committee for Environmental Systems FY00 Annual Report

“…Wagner-Doebler et al [51] Meagher [52,53] engineered several plant species, for example: Arabidopsis, tobacco, canola, yellow poplar, rice, to express the bacterial genes, merB and/or merA, under the control of plant regulatory sequences. These transgenic plants acquired remarkable properties for mercury remediation.…”