Evaluation of Fenton's Reagent and Activated Persulfate for Treatment of a Pharmaceutical Waste Mixture in Groundwater

Soil and groundwater beneath the Kærgård Plantage megasite in Denmark are contaminated with a complex mixture of pharmaceutical wastes, including sulfonamides, barbiturates, aniline, pyridine chlorinated solvents (DNAPL), benzene, toluene, mercury, and cyanide. Regulatory agencies in Denmark are now in the process of evaluating remedial alternatives for source area remediation at the site. As there is no precedent for treating this type of mixture, the feasibility of a variety of in situ remediation technologies are being evaluated in bench tests, including biological, chemical, and thermal techniques. This paper describes the results from the bench tests evaluating treatment of site groundwater and soil using modified Fenton's reagent (MFR) and activated sodium persulfate (ASP). These results have been used to design pilot tests that will form the basis for selecting an optimal remediation technology or series of technologies for a future full-scale remediation system.

The bench tests investigated oxidant stability, oxidation efficiency, toxicity reduction, metal mobilization and, for the persulfate, different activating agents, including NaOH, chelated iron, and modified Fenton's reagent. 126 reactors and more than 650 analyses were used to evaluate the MFR and ASP processes in bench scale. The stability of the oxidants was determined under simulated aquifer conditions, with and without catalyst or activating agents. Efficient activation for both MFR and ASP was observed. Due to a low buffer capacity of the aquifer sediments, pH dropped to within the range of 1 to 3 for all tests.

Due to the presence of significant quantities of mercury and cyanide in the target treatment zone and the lowering of pH, batch and continuous-flow column reactors were used to measure mobilization of the mercury, cyanide, chromium and other metals both within the aqueous and vapour phases. Except the alkaline activation, all the investigated techniques for activating persulfate were able to remove more than 80% of the primary contaminants. Optimization and more dosages led to 98-99% destruction of primary contaminants for both techniques (MFR and ASP). Persulfate activated by MFR also degraded all the analysed barbiturates, sulfonamides, aniline, and pyridine by more than 99.9% or to below detection limits, except sulfonic acid which was reduced by 95%.
The main objective of this presentation will be comparison of the bench scale results for MFR and ASP for treating a complex pharmaceutical waste mixture in the soil and groundwater beneath the Kærgård Plantage megasite.