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Wastewater affordability is a pressing concern in the US as the cost of collecting and treating wastewater continues to rise rapidly, and reports have revealed that millions of residents are experiencing a lack of equitable access to affordable wastewater management. The USEPA has established an affordability metric based on 2.5% of median household income (MHI) and affordability is typically interpreted as the monthly utility bill. However, this approach is not applicable to the 25% of US households that are not connected to networked sewer. This study developed the first statewide methodology for mapping wastewater affordability for users of both networked and onsite wastewater treatment systems (OWTS) based on USEPA guidelines. The methodology used local data from the Alabama Department of Environmental Management (ADEM), utilities, and the US Census Bureau. This article presents a novel methodology for quantifying water and wastewater affordability challenges for large geographical areas while maintaining the accuracy of small-spatial scale analysis. This study also incorporated income inequalities by using census tract-level household income data to estimate the number of households in Alabama with unaffordable wastewater access. This study revealed that wastewater access affordability challenges are more widespread than indicated by traditional MHI-based analysis and are likely affecting approximately 445,000 households in Alabama (23.7%). This study also showed that expansions in the available funding and types of eligible applicants for grant programs that subsidize OWTS capital costs could reduce OWTS affordability challenges eightfold. We propose using this methodology to quantify affordability challenges alongside a suite of approaches to address wastewater affordability in the US at the utility and household levels to preserve the human right to affordable sanitation. Practical Applications: Wastewater affordability is a key aspect of providing sustainable wastewater collection and treatment for US residents. The ongoing discussions about wastewater access affordability are often centered around customers of sewer utilities and neglect to consider the affordability challenges of residents with OWTS (commonly known as septic tank systems). This study develops a methodology for analyzing statewide wastewater access affordability for both residents with sewer bills and users of OWTS based on annual household incomes at the census tract level. This study reveals that wastewater affordability challenges affect both users of centralized sewer networks and OWTS including approximately 445,000 households in Alabama (23.7%). [ABSTRACT FROM AUTHOR]

The reactive transport of metal and radionuclide contaminants in the subsurface often significantly influences their long-term fate and effect in the environment. Typically, predictions of contaminant migration at a site involve the measurement of a distribution coefficient ([K.sub.D]), which is used to describe the interactions between the contaminant and the subsurface. The typical implicit assumption is that the adsorption isotherm (e.g., [K.sub.D]) is independent of the solid/solution ratio. Many geochemical factors, however, play a significant role in the reactive transport of contaminants in groundwater. The adsorption and transport of U(VI), for example, is strongly influenced by the presence of Fe oxyhydroxides and the carbonate system. However, these solutes or adsorbates and adsorbent interact with one another in a complex and highly nonlinear manner. Modeling of U(VI) adsorption has shown that under certain conditions, the solid/solution ratio can theoretically have a significant impact on the U(VI) adsorption isotherm. In particular, combining strongly interacting solutes [U(VI) and carbonate] and adsorbents [Fe(III) oxyhydroxides] that have monocomponent solute or adsorbate adsorption isotherms that are independent of the solid/solution ratio results in a multicomponent system where adsorption isotherms become dependent on the solid/solution ratio. The solid/solution ratio can therefore be critical when extrapolating the results of batch experiments, generally conducted at low solid/solution ratios, to column experiments and then to the field. These results have implications for modeling, scaling, and predicting the reactive transport of U(VI) and other strongly interacting solutes (e.g., metals and dissolved organic C) in subsurface environments.

ABSTRACT Methyl tertiary hexyl ether (MtHxE) and methyl tertiary octyl ether (MtOcE) are currently being developed as replacement oxygenates for methyl tertiary butyl ether (MtBE) in gasoline. As was the [...]

A mechanistic understanding of U sorption in natural soils and sediments is useful for determining its transport and bioavailability in the environment. X-ray absorption spectroscopy (XAS) was used to determine the mechanisms by which U(VI) sorbs to three heterogeneous subsurface media reacted under static and dynamic flow conditions. Regardless of the media chosen, ternary surface complexes were the dominant type of sorption complex. Uranyl phosphate complexes were formed in subsurface media from more acidic environments. In contrast, uranyl carbonate ternary surface complexes formed in media from more neutral conditions. The complexes are predominantly inner-sphere, although some outer-sphere complexes may also be present, and appear to be on iron (hydr)oxides and possibly aluminosilicates. Additionally, the uranyl phosphate and carbonate complexes are highly disordered, which contributes to their reversible sorption properties.

The observation that mercuric sulfide forms in mercury-contaminated soils located in flood plain areas may have an impact on the remediation efforts of such soils. A study of mercury-contaminated soils in Oak Ridge, TN, determined that the soil redox conditions that occur during flooding and the presence of metal sulfides or sulfhydryl groups in the analyzed soil provided the means by which metacinnabar, a form of mercuric sulfide, forms.