Activated carbon (AC) has been shown to remove precursors of halogenated disinfection byproducts. Granular and powdered activated carbon (GAC, PAC) were investigated for their potential to adsorb N-nitrosodimethylamine (NDMA) precursors from blends of river water and effluent from a wastewater treatment plant (WWTP). At bench scale, waters were exposed to lignite or bituminous AC, either as PAC in bottle point experiments or as GAC in rapid small-scale column tests (RSSCTs). NDMA formation potential (FP) was used as a surrogate for precursor removal. NDMA FP was reduced by 37, 59, and 91% with 3, 8, and 75 mg/L of one PAC, respectively, with a 4-h contact time. In RSSCTs and in full-scale GAC contactors, NDMA FP removal always exceeded that of the bulk dissolved organic carbon (DOC) and UV absorbance at 254 nm. For example, whereas DOC breakthrough exceeded 90% of its influent concentration after 10,000 bed volumes of operation in an RSSCT, NDMA FP was less than 40% of influent concentration after the same bed life of the GAC. At full or pilot scale, high NDMA FP reduction ranging from >60 to >90% was achieved across GAC contactors, dependent upon the GAC bed life and/or use of a preoxidant (chlorine or ozone). In all experiments, NDMA formation was not reduced to zero, which suggests that although some precursors are strongly sorbed, others are not. This is among the first studies to show that AC is capable of adsorbing NDMA precursors, but further research is needed to better understand NDMA precursor chemical properties (e.g., hydrophobicity, molecular size) and evaluate how best to incorporate this finding into full-scale designs and practice.
Certain unregulated disinfection byproducts (DBPs) are more of a health concern than regulated DBPs. Brominated species are typically more cytotoxic and genotoxic than their chlorinated analogs. The impact of granular activated carbon (GAC) on controlling the formation of regulated and selected unregulated DBPs following chlorine disinfection was evaluated. The predicted cyto- and genotoxicity of DBPs was calculated using published potencies based on the comet assay for Chinese hamster ovary cells (assesses the level of DNA strand breaks). Additionally, genotoxicity was measured using the SOS-Chromotest (detects DNA-damaging agents). The class sum concentrations of trihalomethanes, haloacetic acids, and unregulated DBPs, and the SOS genotoxicity followed the breakthrough of dissolved organic carbon (DOC), however the formation of brominated species did not. The bromide/DOC ratio was higher than the influent through much of the breakthrough curve (GAC does not remove bromide), which resulted in elevated brominated DBP concentrations in the effluent. Based on the potency of the haloacetonitriles and halonitromethanes, these nitrogen-containing DBPs were the driving agents of the predicted genotoxicity. GAC treatment of drinking or reclaimed waters with appreciable levels of bromide and dissolved organic nitrogen may not control the formation of unregulated DBPs with higher genotoxicity potencies.
Per-and polyfluoroalkyl substances (PFASs) are fluorinated organic chemicals that are concerning due to their environmental persistence and adverse human and ecological effects. Remediation of environmental PFAS contamination and their presence in consumer products have led to the production of solid and liquid waste streams containing high concentrations of PFASs, which require efficient and cost-effective treatment solutions. PFASs are challenging to defluorinate by conventional and advanced destructive treatment processes, and physical separation processes produce waste streams (e.g., membrane concentrate, spent activated carbon) requiring further post-treatment. Incineration and other thermal treatment processes are widely available, but their use in managing PFAS-containing wastes remains poorly understood. Under specific operating conditions, thermal treatment is expected to mineralize PFASs, but the degradation mechanisms and pathways are unknown. In this review, we critically evaluate the thermal decomposition mechanisms, pathways, and byproducts of PFASs that are crucial to the design and operation of thermal treatment processes. We highlight the analytical capabilities and challenges and identify research gaps which limit the current understanding of safely applying thermal treatment to destroy PFASs as a viable end-of-life treatment process.
Research on per- and polyfluoroalkyl substances (PFASs) released from aqueous film-forming foams (AFFFs) has primarily focused on soil and groundwater contamination, or atmospheric transport. However, gas-phase PFAS release from AFFF has not been well examined. We investigated the presence of volatile PFASs in the headspace above agitated AFFF concentrate produced within the past two years using two analytical techniques. One method utilized polyurethane foam and XAD resin with liquid chromatography mass spectrometry to quantify 30 PFASs and is similar to methods used by others to measure PFASs in air. A second, more exploratory approach used a thermal desorption sampler and gas chromatography and mass spectrometry (GC-MS) to measure 22 PFASs. Sixteen PFASs were detected in the headspace, including five fluorotelomer alcohols (0.5–38.1 μg/m3), 10 perfluorinated carboxylic acids (0.4–13670 μg/m3), and one fluorotelomer sulfonate (72.1 μg/m3). The most abundant PFAS detected in the headspace was perfluorooctanoic acid (13670 μg/m3), although it was detected only by GC-MS. Five additional fully fluorinated, iodinated, and ethenyl fluorocarbons were identified but not quantified. It is likely that firefighters are exposed to these compounds, but the risk is not yet known.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.