AWWA water science最新文献

Water characteristic impacts on granular activated carbon (Filtrasorb 400) adsorption of nine per- and polyfluoroalkyl substances (PFAS) were studied. Multispecies competitive isotherms had lower effective solid phase capacities ($��q_e�$) than single species isotherms. pH 9 q_es were somewhat reduced (max 19%) compared to pH 7.7–8.1. Decreasing ionic strength (10 to 2 mM) substantially (79%–146%) increased PFAS q_es. Divalent ion (calcium and sulfate) presence without changing ionic strength increased q_es (43%–140%). Natural organic matter (NOM) presence reduced PFAS q_es with the reduction somewhat offset by calcium and sulfate presence. This reduced capacity suggested both direct competition with NOM and pore-blockage hindered PFAS adsorption. Ideal adsorbed solution theory poorly predicted the competition, likely due to nonideal behaviors of adsorbed species and GAC surface heterogeneity. Findings provide insights into the complex interactions between different water constituents and the adsorptive surface to help optimize PFAS treatment efficacy and minimize operational costs.

An assessment of the public health risk posed by Legionella pneumophila in public drinking water was performed on a dataset of 9181 samples collected by 57 water utilities. Overall, 109 (1.19%) samples were positive for L. pneumophila, and only 5 (0.054%) were greater than 1 MPN/mL. When detected, 73% of the positive results were < 10 MPN/100 mL, indicating that L. pneumophila levels in drinking water distribution systems are typically very low. Applying a Quantitative Microbial Risk Assessment model to the six utilities with the highest frequency of L. pneumophila revealed that the annual risk of infection was below the 10⁻⁴ level used for controlling microbial contaminants under the Safe Drinking Water Act. Overall, a national estimate of risk for exposure to L. pneumophila from drinking water distribution systems would be exceedingly small (< 1 × 10⁻⁷ annual risk of infection). Even the sample with the highest detected concentration of L. pneumophila (267 MPN/100 mL) was less than a 1 × 10⁻⁴ risk of infection for a single exposure (from a faucet). Despite the low risk levels, the results should encourage water utility managers to continue to monitor for L. pneumophila and implement corrective measures so as to maintain levels below public health thresholds. The results of this study should not promote complacency among water utilities but encourage them to apply best management practices for Legionella control. The USEPA should consider including L. pneumophila testing in the next Unregulated Contaminant Monitoring Rule program so that a more complete assessment can be obtained for L. pneumophila in drinking water.

Total organic carbon (TOC) and permanganate chemical oxygen demand (COD_Mn) are the most commonly employed methods to determine the amount of natural organic matter (NOM) in raw and drinking water. However, the usage of COD_Mn is questionable due to its variable degrees of oxidation for different types of organics. Our study investigates the ratio of COD_Mn to TOC in source waters with diverse NOM compositions characterized by specific UV absorbance (SUVA) and total organic nitrogen (TON). Herein, mountainous water sources with high amounts of humic substances (high SUVA, low TON) exhibit approximately 1.8–2.5 times higher COD_Mn values than lowland algae-laden sources (low SUVA, high TON) despite having the same TOC values. The determination of COD_Mn, therefore, can give misleading information about the amount of organics in waters with different NOM character and underestimate the NOM concentration in lowland algae-laden water sources, which could have implications for drinking water quality.

Austin Water (AW) is the municipal water utility for Austin, Texas, and performs future water supply planning through an integrated water resource planning process known as Water Forward. This article details Austin Water's methodology for incorporating climate projections from Global Circulation Models (GCMs) into their water supply planning process and offers a framework for other water utilities and planning organizations to incorporate similar analyses, enhancing their ability to address future uncertainties.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) accumulation near the water surface was measured within a wastewater treatment plant (WWTP) aeration basin. Three different sampling methods targeted near-surface samples (centimeters below the water surface), surface microlayer samples (millimeters below the water surface), and PFAS flux meters (centimeters above the water surface to capture aerosols) were used to interrogate PFAS enrichment as a function of proximity to the water surface. Sampling of stable foams was also employed in this investigation. Results showed that, for long-chained PFAS, substantial PFAS enrichment occurred only within millimeters of the surface, in aerosols, and in foams. Deployed PFAS flux meters showed increasing capture with decreasing height above the wastewater surface and with increasing PFAS surface activity. Using a screening-level model to extrapolate results of the field test, substantial (64%–92%) removal of long-chained PFAS from the bulk wastewater could be attained if near-surface (within centimeters of the water surface) aerosol capture to prevent redeposition of the PFAS-rich aerosols into the bulk wastewater was extended to the entire aeration basin.

Geochemical solubility modeling is a cost-effective method to estimate equilibrium lead (Pb) concentrations in drinking water under specific environmental conditions. Laboratory Pb-solubility studies (sometimes called coupon studies) are also economical and can generate comparative Pb solubility data for different water qualities. Both methods are widely used by utilities in screening corrosion control treatment, and both methods are assumed to provide insights on CCT for Pb without the influence of years of built-up scale. No research has compared the two methods to see if they give similar results for the same water. While these techniques have limitations and do not always represent Pb levels in service lines and premise plumbing, they are valuable for predicting Pb solubility trends under controlled conditions. In this study, Pb coupons immersed in chemically diverse waters provided experimental data on Pb solubility, which was then compared to predictions from two widely used geochemical models, MINEQL+ and LEADSOL. In tests without orthophosphate (PO₄³⁻), experimental Pb concentrations increased as pH decreased, consistent with model predictions. Between pH 7.5 and 8.5, Pb levels slightly declined as predicted by the model but were less dependent on dissolved inorganic carbon (DIC) than model predictions. However, at pH 8.5–10, Pb concentrations remained constant experimentally, whereas the model predicted significant reductions in Pb. Neither MINEQL+ nor LEADSOL models and experimental data were statistically the same using the built-in constants. Adjusting Log K_sp for hydrocerussite allowed the data and models to be statistically the same. In waters with PO₄³⁻, high DIC (50 mg/L as C) experimental results matched model predictions. At low DIC (3 mg/L as C), Pb concentrations varied less than modeled, and higher PO₄³⁻ doses were needed to reduce Pb levels compared to low-DIC waters. Overall, geochemical modeling and Pb solubility studies provide critical insights into Pb control strategies, and either or both methods can help screen the impact of possible water quality changes on Pb levels. Solubility testing is preferred, as site-specific solubility constants are generally unknown. Using the solubility models' adjustments to Log K_sp described in this paper is recommended if the site-specific Log K_sp is unknown.

The Environmental Protection Agency has finalized regulations to require water systems to replace millions of lead pipes with safer alternatives for carrying drinking water into U.S. homes. Before replacing them, water systems must identify where these lead service lines are located due to incomplete inventories. We conducted a randomized controlled trial to evaluate an intervention that targeted properties with unknown pipe material in Trenton, New Jersey—a community with older housing stock and a high concentration of people of color, renters, and households experiencing poverty. The intervention included two treatments: door hangers with information about a self-inspection process that allowed residents to submit a photo of their service line, and similar door hangers offering gift card incentives upon submission of a self-inspection. These treatments had null or small effects on residents' participation in self-inspection. Under 1% of treated addresses participated in a self-inspection, including those offered the highest incentive of $100.