– Site stakeholders needed conclusive evidence that biodegradation of benzene and naphthalene was occurring under existing site conditions to accept MNA instead of a more aggressive strategy.
– Stable isotope probing (SIP) studies using Bio-Traps® amended with 13C benzene or 13C naphthalene conclusively demonstrated in situ biodegradation occurred under existing site conditions.
• A site impacted by chlorobenzene was managed by MNA.
• The ISM study provided answers to site managers’ questions at a significant cost savings compared to pilot-scale studies and provided sound support for a pathway to reducing time to closure at the site.
• Groundwater at a former gasoline service station was impacted by leaking underground storage tanks and associated piping. Although contaminant trends and geochemistry suggested that MNA could be an appropriate site management strategy, the need for more rapid site closure led to a decision to enhance biodegradation of BTEX and MTBE aerobically with injection of an oxygen releasing compound.
At a crude oil impacted site, project managers were considering MNA as a site management strategy based on favorable contaminant concentration trends and geochemistry in groundwater. However, additional lines of evidence were required.
Together with contaminant concentration trends and geochemistry, the direct microbial data provided multiple lines of evidence to support a confidant MNA decision resulting in significant cost savings over enhanced remediation.
• QuantArray®-Chlor analysis allowed site managers to have a comprehensive understanding of all relevant microbial processes at the site over time which allowed timely decisions and significant cost savings in site management.
• The ISM study conducted at this site provided clear, actionable evidence that electron donor injection would stimulate reductive dechlorination without the need for expensive bioaugmentation. Further, this evidence was provided in a significantly more cost effective manner than a bench-scale treatability study or a pilot scale study and in a more timely manner.
• A petroleum pipeline release in a remote area had gone undiscovered for a number of years and groundwater was impacted with BTEX. Groundwater monitoring results suggested that BTEX concentrations were decreasing although results were variable.
• Trends in decreasing BTEX concentrations were validated as biological in origin supporting an MNA management strategy and avoiding the greater costs of enhanced remediation.
• A site impacted by PCE and TCE was experiencing an accumulation of cis-DCE (DCE stall). CENSUS® qPCR quantification demonstrated that Dehalococcoides concentrations were too low for effective rates of complete reductive dechlorination.
• Avoiding the expense of bioaugmentation resulted in significant cost savings while achieving treatment goals with biostimulation alone.