AEG Event 2/20/25: In-situ Groundwater Remediation

One professional development hour (pdh) for continuing education credit
(CEC) will be awarded for attending the presentation.

SRPLB Approval for One Hour of LSRP Technical CEC will be requested.

ABSTRACT
Treatment of groundwater contaminated with heavy metals can be challenging because the mechanisms operative in adsorption, precipitation, and co-precipitation of metals vary with the metal of concern.  Groundwater is often contaminated with both heavy metals and solvents. Treatments that perform well on metals may not be effective for degradation of chlorinated organic compounds. For example, certain alkaline reduction treatments that effectively remove hexavalent chromium may increase the solubility of arsenic, while having little impact on chlorinated organics. Similarly, a treatment based on enhanced reductive dechlorination, through biostimulation with organic carbon substrates, may effectively reduce chlorinated solvent concentrations but at the same time mobilize heavy metals by altering the oxidation reduction potential (ORP) and pH.
 
Precipitation of many soluble heavy metals as metal sulfides or iron-metal-sulfides can be promoted by ensuring an adequate supply of soluble iron and free sulfide under appropriate pH and Eh conditions.  Soluble metals can also be removed by adsorption through direct addition of iron oxides or stimulation of biogenic iron oxide formation. The same minerals that mediate removal of metals can also support reductive dechlorination of organic compounds.
 
This talk will review common approaches to treatment of heavy metals from the perspectives of contaminant chemistry, site geochemistry, permanence and sustainability. Performance data from comparative bench-scale testing, pilot-scale demonstration, and full-scale groundwater treatment will be presented.
 
The objective of this presentation is to develop a better understanding of the mechanisms involved in removal versus mobilization of heavy metals and degradation of chlorinated solvents and thereby promote good decision-making in selection of reagents and treatment methods.
 

BIOGRAPHY
Dr. Lakhwala serves as the Key Accounts Manager within Evonik’s Soil and Groundwater business unit. He holds M.S. and Ph.D. degrees in Chemical Engineering with a minor in Environmental Science. He has 30 years of experience in the area of site remediation with activities in technology development, remedial design and engineering, site characterization, treatability studies, project management and business development. He has worked with environmental technology companies, research laboratories and environmental consulting firms.

In the past 20 years, Dr. Lakhwala's focus has been on the design and application of in situ chemical oxidation (ISCO), in situ chemical reduction (ISCR), enhanced reductive dechlorination (ERD), NAPL stabilization and treatment of heavy metals in soil and groundwater. Besides the US, he has worked on projects in several Asia Pacific and European countries.