Microbe–Mineral Interaction-Induced Microorganism-Augmented Permeable Reactive Barriers for Remediation of Contaminated Soil and Groundwater: A Review

Abstract

Conventional zerovalent iron permeable reactive barriers (PRBs) are limited by unknown iron corrosion kinetics and permeability loss, hindering access to desirable remediation targets. Against this background, microbe−mineral interactioninduced microorganism-augmented PRBs (Bio-PRBs) are considered a promising cutting-edge technology for increasing reaction rate k and enhancing removal efficiency η. This study provides original insights into the various active media and microbial carriers and the mechanisms of interaction among microorganisms, active media, and various contaminants. The results showed that microorganism-activated and microorganism-immobilized Bio-PRBs increased k and η by 40−2650% and 25−400%, respectively. In Bio-PRBs, the removal of contaminants involves the coupling of biodegradation, chemical reduction, and adsorption processes. Microorganisms promote the liquefaction of metal minerals into metal ions, thus forming a positive cycle by "microbe−mineral" interaction. Moreover, nonmetallic fillers affect k through synergistic effects of biodegradation, biological reduction, and electron donor groups. Microorganisms accelerate the e − transfer to promote the contaminants' transformation, and nonmetallic fillers are also conducive to improving diversity and abundance. Furthermore, some suggestions are made regarding the development and application of Bio-PRBs. Bio-PRBs provide efficient and novel approaches and strategies for eliminating soil and groundwater contamination based on microbe−mineral interaction and stimulation.

Cr(VI) Reduction and Sequestration by FeS Nanoparticles Formed in situ as Aquifer Material Coating to Create a Regenerable Reactive Zone

“…Hexavalent chromium [Cr­(VI)] is one of the most commonly detected metal contaminants in groundwater. , Approximately 11% of the polluted sites on the U.S. National Priorities List are contaminated by Cr­(VI), and persistence of Cr­(VI) contamination at concentrations above the maximum contaminant level (MCL) is common, even after decades of remediation. ,, Cost-effective management of long-term contamination of groundwater at low concentrations is particularly challenging. − Most of the remedial technologies designed for fast removal of Cr­(VI) (e.g., in situ precipitation or chemical reduction) are less efficient for lasting large plumes of low contaminant concentrations. − Permeable reactive barriers have been used, and yet the loss of permeability due to biofouling or mineral precipitation limits their applicability. , Currently, pump and treat is still the most commonly used approach in dealing with low-level residual Cr­(VI) at many contaminated sites, but the generation of large quantities of wastewater and the long-term operating costs hinder its feasibility. , …”