AWWA water science最新文献

Communities are now turning to potable reuse to augment their water supply portfolios in response to increasing demand and climate uncertainty. One barrier to broader implementation is a lack of regulations for direct potable reuse (DPR) in some locations. An incomplete understanding of the foundation of existing DPR frameworks may be contributing to this barrier. The objective of this study was to use a publicly available quantitative microbial risk assessment (QMRA) tool—DPRisk—to explain the basis behind California's existing indirect potable reuse regulations, California's draft DPR regulations, and an Expert Panel's response to those draft regulations. Then, leveraging a robust raw wastewater pathogen dataset from the literature, DPRisk was used to justify two alternatives: one based on maximum simulated pathogen concentrations and the other based on 97.4th percentile concentrations. The latter represents an effort to seek equivalency between “raw wastewater” (i.e., California) and “treated effluent” (i.e., Texas) approaches. Using justified QMRA assumptions, the baseline log reduction value (LRV) targets were determined to be 15/11/11 (maximum) or 13/10/10 (97.4th percentile) for viruses, Giardia, and Cryptosporidium. Additionally, instead of augmenting the baseline LRVs to account for undetected treatment process failures, tolerances for off-specification conditions (e.g., up to 3 logs for 3–12 days per year) were characterized. With this foundational knowledge, stakeholders can better understand and adopt these frameworks or use DPRisk to establish a new framework that better addresses their unique constraints, including considerations for preferred treatment paradigms and capital and operational costs.

Changing source water quality namely through increasing natural organic matter (NOM) concentration challenges surface water treatment, especially direct filtration. We conducted a pilot-scale assessment of various adaptation strategies (e.g., clarification, granular activated carbon [GAC] filtration) for direct filtration facilities under the stress of rising NOM levels. Recognizing that changing source water can impact broader aspects of treatment, we considered the implications of Fe and Mn removal via KMnO₄ pre-oxidation. GAC media showed promise as an adaptation strategy, providing ~60% removal of dissolved organic carbon (DOC), and a significant reduction in disinfection by-product formation potential (DBPfp). However, KMnO₄ pretreatment showed limited Mn and Fe removal, and filters with GAC media released dissolved Mn at up to ~30% of prefilter levels. These data suggest that using GAC may come with the risk of poor Mn removal performance if Mn is not removed during pretreatment. This work highlights the complexities anticipated under emerging climate pressures and emphasizes the need for comprehensive treatment solutions that consider factors beyond NOM.

The U.S. Environmental Protection Agency (EPA) is considering a regulatory revision of the Disinfectant and Disinfection Byproduct Rule (DBPR) with a goal of limiting nationwide exposure to DBPs of emerging health concern. The occurrence of four brominated haloacetic acids (HAAs), which are generally more toxic in in vitro assays than the five currently regulated HAAs and are candidates for future regulation, were surveyed in 4924 public water systems under EPA's fourth unregulated contaminant monitoring rule (UCMR4). Using UCMR4 data, this study evaluated the nationwide occurrence of nine HAA species and the potential for two regulatory scenarios (the mass sum of all nine HAA species, HAA9, or just the six brominated HAA species, HAA6Br) to control nationwide exposure to the most toxic HAAs. Neither HAA9 nor HAA6Br approaches were effective for identifying water systems that exhibit high HAA exposure, assessed as additive cytotoxicity, because they are more specific to the HAA species that form at high concentrations rather than the species that are most toxic. However, the effectiveness of HAA6Br is highly sensitive to the relative toxicity of one HAA compound, monobromoacetic acid, which has the highest in vitro toxicity among HAAs but also the lowest occurrence and about which little is known regarding in vivo health risks. In contrast to HAA9, systems with high HAA-associated additive toxicity tend to share similar treatment and disinfectant characteristics as systems with high HAA6Br concentrations. Systems with high source water bromide and total organic carbon were far more likely to use chloramines as a disinfectant residual compared to other systems, but were no more likely to adopt organic precursor removal technologies (biofiltration, granular activated carbon, and ion exchange) than other systems, on average.

Year-round irrigation water restrictions can be effective water demand management tools if people adhere to them. Awareness and understanding of these regulations have important implications for compliance and long-term water supply goals. This study quantified irrigation restriction awareness-knowledge and how-to knowledge using survey data from residents with automated irrigation systems. Only half of those subject to irrigation restrictions were aware of these regulations; these irrigation restriction aware individuals reported varying perceived allowable watering frequency, implying that misunderstandings exist. Education, living in a homeowners association, hiring specific professionals, and information-seeking preferences distinguished irrigation restriction aware from unaware individuals. Binary logistic regression revealed that when considered together, race, education, income, hiring a professional for fertilizer application, and living in a homeowner association significantly influence awareness-knowledge. There are important opportunities to improve conservation outcomes by increasing both awareness and accuracy among target audience members.

The residence time of water in residential building water systems is a critical factor regarding water quality at end use. Published literature has highlighted the importance of water age in these systems and its relationship with pathogenic bacteria such as Legionella pneumophila. However, tools to measure water age in such plumbing systems are typically repurposed from other applications and include limitations that make them inappropriate for some plumbing systems. This work presents a novel means of estimating water age by assuming these systems operate without mixing. Data for this study was collected from a full-scale home equipped with an extensive array of flow meters to monitor water use. Further, 408 individual water quality samples were collected to ascertain water quality changes that take place in the plumbing. Model results show weak correlation with EPANET 2.2 (ρ = 0.666), a commonly used hydraulic modeling software. The results of the water age model were also evaluated with several variable selection tools. These analyses indicate that this method's water age results are a statistically significant (p < .05) predictor of Legionella concentrations. Model results from this approach could be used in plumbing design and/or operation to assist in managing Legionella risks.

Eight granular activated carbons (GACs) and one alternative adsorbent (AA) were evaluated using rapid small-scale column tests (RSSCTs) to remove low level per- and polyfluoroalkyl substances (PFAS) from several groundwaters. Results suggested variability among waters for adsorbents to reach breakthrough. Time to reach breakthrough appeared to be inversely proportional to the background dissolved organic carbon (DOC). Bituminous GACs (particularly F400 and UC1240LD) were more effective than non-bituminous. The elution order for PFAS was PFHxA (C6) > PFBS (C4) > PFOA (C8) > PFHxS (C6) > PFOS (C8). Multivariate regression predicted bed volumes at which F400 reached significant exhaustion (defined here as 60%) for PFOA using only two parameters (humic acid, DOC). This merits further study as these parameters could potentially be incorporated into models for predicting PFAS breakthrough. VOCs presence negatively impacted PFAS adsorption on GAC. Relative to GACs, the AA was not nearly as impacted by DOC and showed superior performance.