The use of aqueous film-forming foam (AFFF) has resulted in the widespread occurrence of per-and polyfluoroalkyl substances (PFAS) in groundwater, drinking water, soils, sediments, and receiving waters throughout the United States and other countries. We present the research and development efforts to date by the Strategic Environmental Research and Development Program (SERDP) and the Environmental Security Technology Certification Program (ESTCP) to measure PFAS in the environment, characterize AFFF-associated sources of PFAS, understand PFAS fate and behavior in the environment, assess the risk to ecological receptors, develop in situ and ex situ treatment technologies for groundwater, treat soils and investigation-derived wastes, and examine the ecotoxicity of PFAS-free fire suppression formulations.
Focus articles are part of a regular series intended to sharpen understanding of current and emerging topics of interest to the scientific community.
Both Pseudomonas putida F1 and a mixed culture were used to study TCE degradation in continuous culture under aerobic, non-methanotrophic conditions. TCE mass balance studies were performed with continuous culture reactors to determine the total percent removed in the reactors, and to quantify the percent removed by air stripping and biodegradation. Adsorption of TCE to biomass was assumed to be negligible. This research demonstrated the feasibility of treating TCE-contaminated water under aerobic, non-methanotrophic conditions with a mixed-culture, continuous-flow system. Initially glucose and acetate were fed as primary substrates. Pnenol, which has been shown to induce TCE-degrading enzymes, was fed at a much lower concentration (20 mg/L). Little degradation of TCE was observed when acetate and glucose were the primary substrates. After omitting glucose and acetate from the feed and increasing the phenol concentration to 50 mg/L, TCE biotransformation was observed at a significant level (46%). When the phenol concentration in the feed was increased to 420 mg/L, 85% of the incoming TCE was estimated to have been biodegraded. Under the same conditions, phenol utilization by the mixed culture was greater than that of P. putida F1, and TCE degradation by the mixed culture (85%) exceeded that of P. putida F1 (55%). The estimated percent-of-TCE biodegraded by the mixed culture was consistently greater than 80% when phenol was fed at 420 mg/L. Biodegradation of TCE was also observed in mixed-culture, batch experiments.
Alkaline hydrolysis has been used in several laboratory studies and field demonstrations for the treatment of energetic compounds (particularly, 2,4,6-trinitrotoluene (TNT), dinitrotoluene (DNT), and hexahydro-1,3,5trinitro-1,3,5-triazine (RDX)) in soil. The application of alkaline hydrolysis for treatment of soil involves mixing a caustic source material with soil. Two caustic materials have been explored, calcitic hydrated lime [Ca(OH) 2 , HL] and sodium hydroxide (NaOH). Evaluation of explosives removal is routinely performed using SW-846 Method 8330. This method was developed before the advent of alkaline hydrolysis treatment, and recent studies have indicated that some errors can occur when this method is applied to alkaline hydrolysis samples. This report documents the results of a field study conducted to demonstrate the issue of false degradation in field-collected samples. The field study was followed by two laboratory studies: the first to confirm false degradation as a phenomenon and the second to develop an appropriate acid neutralization method. Results proved that false degradation can occur with alkaline hydrolysis (AH) samples, particularly if residual caustic material and moisture are present in the sample. Treatment systems using HL are more prone to extraction errors than systems using NaOH, although neutralization improves the accuracy of both treatment approaches. ERDC-EL has developed a neutralization method that can be used for alkaline hydrolysis approaches using up to 10% caustic addition (most systems are less than 5%) and a combination of H 3 PO 4 and NaH 2 PO 4. For remedial actions using alkaline hydrolysis, the scope of work for the action should include neutralization of all post-treatment samples, with appropriate control samples prepared in order to ensure that neutralization is achieved. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.
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