Benzene Diffusion and Partitioning in Contaminated Drinking Water Pipes under Stagnant Conditions.

Benzene contamination in drinking water systems affected by wildfires is a problem of emerging concern. Polyethylene pipes used in service lines and premise plumbing are vulnerable to permeation by benzene and can potentially cause challenges in sampling and remediation of contaminated systems. However, the kinetics and equilibria of the uptake of benzene by and release of benzene from pipes of differing polyethylene types and manufacturers are not well studied, leading to additional uncertainty when interpreting sampling data and selecting remediation options. This work addresses this data gap by providing diffusion and partitioning data for benzene and several varieties of polyethylene pipes, including field samples from water distribution systems. All polyethylene pipes that were studied exhibited similar partitioning behavior during benzene uptake and release, but some differences in kinetics were observed among pipes. However, these differences were of minor practical importance in the pipe contamination scenario examined in this work. The results of this study can be used in conjunction with diffusion modeling to inform remediation decisions for benzene-contaminated, polyethylene service lines, and premise plumbing.

Polanyi adsorption potential theory for estimating PFAS treatment with granular activated carbon.

Per- and polyfluoroalkyl substances (PFAS) are a group of chemicals that have gained interest because some PFAS have been shown to have negative health effects and prolonged environmental and biological persistence. Chemicals classified as PFAS have a wide range of chemical moieties that impart widely variable properties, leading to a range of water treatment process efficacies. The Polanyi Potential Adsorption Theory was used to estimate Freundlich isotherm parameters to predict the efficacy of granular activated carbon (GAC) treatment for 428 PFAS chemicals for which the vast majority had no previously published treatment data. This method accounts for the physical/chemical characteristics of the individual PFAS beyond molecular weight or chain length that have previously been employed. From a statistical analysis of available data and model results, many of the 428 PFAS were predicted to be effectively treatable by GAC. Although not directly applicable to full-scale design, the approach demonstrates a systematic method for predicting the effectiveness of GAC where isotherm or column data are not available. This then can be used to prioritize future research.

Modeling PFAS Removal Using Granular Activated Carbon for Full-Scale System Design.

Per- and polyfluoroalkyl substances (PFAS) are increasingly of interest to drinking water utilities due to state regulations, the release of federal and state health advisories, and public concern. Pilot-scale data were fitted for 16 PFAS species and five commercial-activated carbons using an open-source pore and surface diffusion model that includes an automated parameter-fitting tool. The estimated model parameters are presented, and an uncertainty analysis was evaluated considering the expected temporal variability of influent concentrations. Expected treatment performance differed between two seasons in the pilot phase for the same carbon, which was not captured by modeled uncertainty. However, modeling results can support a utility's decision to choose activated carbon, and make design and operational decisions that can address changing water production rates and treatment goals. For the utility that undertook this pilot study and their desired treatment goals, granular activated carbon (GAC) was found to be an effective treatment technology for PFAS removal.

Informing remediation of benzene contamination in drinking water distribution systems through multi-criteria decision analysis.

When contamination incidents occur in drinking water distribution systems, utilities need to select the remediation technologies most suited to their system-specific conditions and the contaminants of concern. Technology selection often involves balancing competing priorities. Multi-Criteria Decision Analysis (MCDA) is a promising approach that has been used extensively in other industries but not yet in drinking water system remediation. This paper discusses development of a computer-based tool that allows practitioners to leverage the Analytical Hierarchy Process (AHP), a well-established method of MCDA, to select remediation technologies based on their effectiveness and their compatibility with the practitioner's project objectives. This paper focuses on benzene, a contaminant implicated for many years in contamination incidents following spills and, more recently, wildfires.

Functional categories of microbial toxicity resulting from three advanced oxidation process treatments during management and disposal of contaminated water.

Large volumes of contaminated water are produced via intentional and unintentional incidents, including terrorist attacks, natural disasters and accidental spills. Contaminated waters could contain harmful chemicals, which present management and disposal challenges. This study investigates three Advanced Oxidation Processes (AOPs) - UV/H2O2, O3/H2O2, and electrochemical oxidation using a boron-doped diamond (BDD) anode - to treat eleven contaminants including herbicides, pesticides, pharmaceuticals, and flame retardant compounds. To address treatment and toxicity concerns, this study focuses on the resulting microbial toxicity via Microtox® toxicity and Nitrification Inhibition tests. The results suggest four functional Microtox® toxicity categories upon AOP treatment, which are useful for streamlining AOP selection for specific applications. Except for one compound, the O3/H2O2 and UV/H2O2 AOPs achieved, within experimental error, 100% parent compound degradation during 2 h of treatment for all contaminants, as well as Microtox® toxicities that declined below 10% by the end of the treatment. In addition, anodic oxidation with a BDD electrode exhibited slower degradation and some increases in Microtox® toxicity. Only one compound exhibited above 50% Nitrification Inhibition, indicating the robustness of activated sludge to many contaminated and AOP-treated waters. These results indicate that AOP pre-treatment can be a viable strategy to facilitate drain disposal of contaminated waters, but that eco-toxicity may remain a concern.

High pressure decontamination of building materials during radiological incident recovery.

The release of radiological material from a nuclear incident has the potential to cause extensive radiological contamination requiring rapid decontamination. A promising method for rapid remediation is the use of pressure washers to decontaminate building and street surfaces. Pressure washers utilize both physical removal through surface ablation and chemical removal through desorption of bonded radionuclides. To understand the extent that each removal mechanism is present, overall removals, depth profiles, and wash water were analyzed from the pressure washing of various surfaces contaminated with cesium, strontium, and europium. Removals were dependent on surface type with over 80% of the radionuclides removed from concrete, 50-80% from asphalt, and only 20-25% from brick. Generally, the closer the radionuclide was to the surface of the material, the higher the removal, with europium being removed most readily followed by cesium then strontium, though some exceptions were evident. Comparing these removals and depth profiles of radionuclides in non-decontaminated coupons revealed that cesium and europium are mostly removed through surface ablation. Strontium, on the other hand, is desorbed from the surface, especially from brick and asphalt surfaces. Correspondingly, cesium and europium were attached to the particulates that were likely removed with the pressurized water. Strontium was primarily dissolved in the wash water, supporting the observation that the radionuclide is desorbed from each surface. Finally, the faster the surfaces were brought through the high pressure spray, the lower the removals, arising from decreases in both the physical and desorption mechanisms. Pressure washers were concluded to be a promising decontamination method during radiological incident relief. However, the surface and radionuclide identity must be considered when developing proper procedures.

Numerical Model for Decontamination of Organic Contaminants in Polyethylene Drinking Water Pipes in Premise Plumbing by Flushing.

Polymeric materials such as polyethylene are used extensively for indoor drinking water applications. These materials are subject to permeation by organic compounds such as those found in petroleum products and industrial chemicals, which can result in water quality issues with potential health effects. Although flushing is a common decontamination technique, disagreements and knowledge gaps in the scientific literature complicate prediction of how much flushing may be required to address organic contamination incidents. This paper utilizes a numerical solution to the diffusion equation to predict flushing decontamination times for toluene in cross-linked polyethylene tubing. Results suggest that for premise plumbing materials typically used for indoor drinking water applications, contaminated polyethylene tubing can be resistant to decontamination by flushing, possibly requiring days of continuous flushing to achieve contaminant removal to below regulatory levels.

Electrolyte selection and microbial toxicity for electrochemical oxidative water treatment using a boron-doped diamond anode to support site specific contamination incident response.

Intentional and unintentional contamination incidents, such as terrorist attacks, natural disasters, and accidental spills, can result in large volumes of contaminated water. These waters may require pre-treatment before disposal and assurances that treated waters will not adversely impact biological processes at wastewater treatment facilities, or receiving waters. Based on recommendations of an industrial workgroup, this study addresses such concerns by studying electrochemical advanced oxidation process (EAOP) pre-treatment for contaminated waters, using a boron-doped diamond (BDD) anode, prior to discharge to wastewater treatment facilities. Reaction conditions were investigated, and microbial toxicity was assessed using the Microtox® toxicity assay and the Nitrification Inhibition test. A range of contaminants were studied including herbicides, pesticides, pharmaceuticals and flame retardants. Resulting toxicities varied with supporting electrolyte from 5% to 92%, often increasing, indicating that microbial toxicity, in addition to parent compound degradation, should be monitored during treatment. These toxicity results are particularly novel because they systematically compare the microbial toxicity effects of a variety of supporting electrolytes, indicating some electrolytes may not be appropriate in certain applications. Further, these results are the first known report of the use of the Nitrification Inhibition test for this application. Overall, these results systematically demonstrate that anodic oxidation using the BDD anode is useful for addressing water contaminated with refractory organic contaminants, while minimizing impacts to wastewater plants or receiving waters accepting EAOP-treated effluent. The results of this study indicate nitrate can be a suitable electrolyte for incident response and, more importantly, serve as a baseline for site specific EAOP usage.

Integrated preservation and sample clean up procedures for studying water ingestion by recreational swimmers via urinary biomarker determination.

The use of cyanuric acid as a biomarker for ingestion of swimming pool water may lead to quantitative knowledge of the volume of water ingested during swimming, contributing to a better understanding of disease resulting from ingestion of environmental contaminants. When swimming pool water containing chlorinated cyanurates is inadvertently ingested, cyanuric acid is excreted quantitatively within 24 h as a urinary biomarker of ingestion. Because the volume of water ingested can be quantitatively estimated by calculation from the concentration of cyanuric acid in 24 h urine samples, a procedure for preservation, cleanup, and analysis of cyanuric acid was developed to meet the logistical demands of large scale studies. From a practical stand point, urine collected from swimmers cannot be analyzed immediately, given requirements of sample collection, shipping, handling, etc. Thus, to maintain quality control to allow confidence in the results, it is necessary to preserve the samples in a manner that ensures as quantitative analysis as possible. The preservation and clean-up of cyanuric acid in urine is complicated because typical approaches often are incompatible with the keto-enol tautomerization of cyanuric acid, interfering with cyanuric acid sample preparation, chromatography, and detection. Therefore, this paper presents a novel integration of sample preservation, clean-up, chromatography, and detection to determine cyanuric acid in 24 h urine samples. Fortification of urine with cyanuric acid (0.3-3.0 mg/L) demonstrated accuracy (86-93% recovery) and high reproducibility (RSD < 7%). Holding time studies in unpreserved urine suggested sufficient cyanuric acid stability for sample collection procedures, while longer holding times suggested instability of the unpreserved urine. Preserved urine exhibited a loss of around 0.5% after 22 days at refrigerated storage conditions of 4 °C.

Fate of malathion and a phosphonic acid in activated sludge with varying solids retention times.

This study examined the ability of activated sludge (AS) to sorb and biodegrade ethylmethylphosphonic acid (EMPA) and malathion, a degradation product and surrogate, respectively, for an organophosphate chemical warfare agent. Sorption equilibrium isotherm experiments indicate that sorption of EMPA and malathion to AS is negligible. EMPA at a concentration of 1 mg L(-1) degraded by approximately 30% with apparent first-order kinetics, possibly via co-metabolism from nitrification. Heterotrophic bacteria and abiotic mechanisms, however, are largely responsible for malathion degradation also with apparent first-order kinetics. EMPA did not inhibit chemical oxygen demand (COD) oxidation or nitrification activity, although malathion did appear to induce a stress response resulting in inhibition of COD oxidation. The study also included a 30-day experiment in which malathion, at a concentration of 5 mg L(-1), was repeatedly fed to AS in bench-scale sequencing batch reactors (SBRs) operating at different solids retention times (SRTs). Peak malathion concentrations occurred at day 4.5, with the longer SRTs yielding greater peak malathion concentrations. The AS reduced the malathion concentrations to nearly zero by day 10 for all SRTs, even when the malathion concentration in the influent increased to 20.8 mg L(-1). The data suggest a biodegradation pathway for malathion involving an oxygenase. Phylogenetic analyses revealed that all samples had an abundance of Zoogloea, though there was greater bacterial diversity in the SBR with the SRT of 50 days. The SBR with an SRT of 9.5 days had an apparent reduction in the diversity of the bacterial community.