Formatted Title
Full-Scale Application of ERD following ISCO/S-ISCO® for Treatment of NAPL Pharmaceutical Waste Mixture
Background/Objectives
The Kaergaard Plantation megasite on the western coast of Denmark represents one of the most difficult remediation challenges in Scandinavia. Disposal of an estimated 280,000 metric tons of pharmaceutical wastes at the site from 1956 to 1973 resulted in the development of a complex mixture of contaminants in soil and groundwater, including sulfonamides, barbiturates, aniline, pyridine, chlorinated solvents (chloroethenes), fuel hydrocarbons, mercury, cyanide, lithium and other compounds. Although the waste pits were excavated down to the water table, residual dense non-aqueous phase liquid (DNAPL) beneath the water table continues to dissolve an impact underlying groundwater. Contaminants in groundwater are estimated to discharge into the ocean, and public health concerns have prompted the closing of a 1.4-kilometer section of beach at the site. The primary remedial goal for the site is to substantially reduce the mass flux of chlorinated solvents migrating from four of the waste pits to downgradient areas.
Approach/Activities
A detailed evaluation of the hydrogeology and mass distribution in each waste pit, and a series of bench and field pilot tests were previously completed to find the most cost-effective solution. This process identified sequenced application of in situ chemical oxidation (ISCO) using peroxide activated persulfate (ASP) for areas with significant DNAPL, followed by enhanced reductive dechlorination (ERD) for areas with less contaminant mass. One waste pit was used to demonstrate the full-scale application and confirmatory monitoring approaches. This was initiated with a series of ISCO injection events in the shallow intervals of the waste pit, along with an ERD amendment injection event in the deeper zone. This approach was intended to initiate treatment in both the shallow and deep intervals of the waste pit. Multiple lines of evidence have been used to evaluate the performance of each technology, including evaluating initial distribution of amendments, changes in geochemical conditions and bacterial populations, and changes in contaminant mass and mass flux. Surfactant-enhanced In-Situ Chemical Oxidation (S-ISCO®) has also been used in areas with significant DNAPL impacts. In 2021, following success of ISCO/S-ISCO in the first waste pit, ERD was initiated. This included recirculation with first soluble amendments (lactate, bicarbonate, KB-1) to initiate geochemical conditions conducive to ERD, and then injection of long-term amendments (EVO, neutral zone, KB-1) to maintain longer term treatment.
S-ISCO is a patented, proprietary technology owned by Ethical Solutions LLC (EthicalChem).
Results/Lessons Learned
This presentation will focus on the successful approach used to transition from ISCO/S-ISCO® to ERD, and observations and lessons learned from this treatment train implementation. This will include a description of the laboratory and pilot tests, and the full-scale implementation, including amendments distribution and treatment performance of ERD. This project has shown the importance of a flexible approach in remediation and demonstrated the success of a multi-component remedy in treating a complex DNAPL source using ISCO, S-ISCO® and ERD.