AWWA water science最新文献

Enhancing drinking water resilience has become increasingly important. However, a comprehensive analysis of drinking water emergency countermeasures is lacking. This study evaluated eight countermeasures including monitoring, local alternatives, reclaimed water, interconnection, bulk water, pre-packaged water, emergency treatment, and isolation valves from resilience and sustainability (i.e., life cycle cost) perspectives. While countermeasures such as interconnections perform relatively well from both perspectives, there is a clear trade-off between resilience and cost. Local alternatives and emergency treatment respond quickly and provide sustained supply during emergencies but may incur higher costs. Bulk water and pre-packaged water are typically inexpensive but have limited supply capacity and take time to distribute. As future threats are likely to become more frequent and prolonged, it is prudent for service providers to invest in countermeasures that perform well in both resilience and cost and use an integrated approach that combines high capital projects with bulk/pre-packaged water contracts.

Correction to https://doi.org/10.1002/aws2.1153.

Since publication of the article, a production error was identified in Table 1, where the last two column headings were swapped. The error had no effect on the analyses or conclusions reported in the study.

Correction to Table 1.

Existing heterotrophic denitrification reactors rely on microorganisms to consume dissolved oxygen (DO) and create conditions suitable for denitrification, but this practice leads to excessive microbial growth and increased organic carbon doses. An innovative reactor that uses nitrogen gas sparging through a contactor to strip DO was developed and tested in the lab. It reduced influent nitrate from 15 to <1 mg/L as N with nitrite accumulation <1 mg/L as N. It maintained a consistent flow rate and developed minimal headloss, making it easier to operate than the denitrifying dual-media filter that was operated in parallel. Gravel, polyvinyl chloride pieces, and no packing media were assessed as options for the nitrogen-sparged contactor, and gravel was found to support denitrification at the highest loading rate and was resilient to nitrogen-sparging shutoffs and intermittent operation. This innovative reactor appears promising for small drinking water systems.

Exposure to lead through drinking water is of concern for children, particularly at schools and early education and care facilities (EECFs), where they spend much of their time. We use lead and copper data from monitoring in schools and EECFs in Massachusetts (USA) and create risk indices based on the percentage of fixtures in a school above three water lead level (WLL) thresholds (15, 5, and 1 ppb) to model which building characteristics, water source, and water treatment practices are associated with a school exceeding these thresholds. Local building characteristics had larger effects than information about the public water supplier (PWS), and buildings built from 1950 to 1980 were most at risk. Daily flushing and fixture replacement often decreased elevated WLLs, and water coolers had lower WLLs than other fixtures. These findings highlight the value of WLL monitoring programs and can be used to prioritize future investment in monitoring and remediation.

Granular media filtration remains a critical treatment process and regulatory requirement for managing pathogenic protozoa in drinking water. It is a dynamic process in which performance inherently varies. While research has focused on characterizing or maximizing (oo)cyst removal in individual filters, the risk implications of combinations of filters moving through different phases of the filter cycle (leading to temporal variation in plant-scale performance) have not been described. Increasing threats from climate-change-exacerbated landscape disturbances leading to more variable source water quality emphasize the need for such evaluations. Here, a modeling framework was developed to investigate the impacts of individual filter performance variation on plant-scale performance. It is shown that improving maximal removal during stable operation does not necessarily improve average performance. The effect of other design and operational strategies like increasing the number of filters or implementing proactive operations (e.g., avoiding breakthrough) are analyzed, thereby providing guidance for increasing treatment resilience.

Biological treatment is gaining ground as a means to enhance removal of total organic carbon (TOC) as part of a multi-barrier treatment train for water reuse. Here we applied biodegradable dissolved organic carbon (BDOC) analysis to evaluate the extent of removal of various TOC fractions through a pilot-scale water reuse train employing flocculation/sedimentation, ozone, biologically active carbon (BAC), and granular activated carbon (GAC). BDOC analysis highlighted GAC and ozone treatments as critical to non-biodegradable dissolved organic carbon removal and the need to optimize BAC performance to maximize GAC adsorption capacity. BDOC analysis was further applied to benchmark process performance to operational conditions, such as empty bed contact time (EBCT), occurrence of nitrification, and operational upsets. The lower EBCT proved to be less resilient to nonideal conditions. Overall, BDOC analysis proved an asset for understanding and improving operation of ozone/BAC/GAC treatments for water reuse.

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.