AWWA water science最新文献

The feasibility of using a 2^6-1 fractional factorial design to screen the relative importance of six water quality and operational factors in the removal of microcystin-LR (MC-LR) by powdered activated carbon (PAC) was evaluated through jar testing. The factors were: PAC type, PAC dose, total organic carbon (TOC) concentration, turbidity, alum dose, and timing of PAC versus coagulant application. Follow-up tests were performed to examine the interaction of PAC dose and TOC concentrations. All MC-LR analyses were performed by enzyme linked immunosorbent assay (ELISA) and liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). The top three effect magnitudes were the same by ELISA and LC/MS/MS:PAC dose > PAC type > PAC application time. Correlation coefficients between removals estimated by ELISA and LC/MS/MS were >0.9 (p « .05). With both methods, the effects of PAC type and dose were found to be markedly larger than the other factors. The follow-up tests indicated a greater impact of PAC dose at higher natural organic matter concentrations. Factorial designs are not commonly used to plan drinking water jar test experiments. The results generated in this study were plausible with respect to the existing body of adsorption knowledge, thus helping to demonstrate the feasibility of the factorial approach.

Thirty-one drinking water storage tank sediment samples were collected in 13 states, 17 distribution systems, and 29 tanks over the course of 4 years. Sediment samples were characterized for elemental composition and physical properties, which were found to be inconsistent both between samples of the same distribution system and across geographical regions. Differences between samples from the same tank also indicated spatial differences in sediment composition within storage tanks. Color was found to qualitatively trend toward darker or lighter depending on the concentration of a few elements (iron, aluminum, calcium, and magnesium). Particle shape varied between samples though uniformity increased as the particle size decreased. The average sediment particle density in this study (1.99 g/cm³) was lower than the density of a widely used sediment resuspension model silica sand (2.65 g/cm³), possibly resulting in underestimation of resuspension in models. This study suggests that sediment properties are highly site and storage tank specific, necessitating individual characterization to achieve greatest accuracy in storage tank suspension and draining model inputs.

A protocol for responding to Legionella pneumophila detections in distribution system samples is presented and justified. The protocol was developed using existing protocols for building water systems, vetted in workshops, and provided to utilities participating in a research project. The protocol provides action levels and actions that utilities can take when L. pneumophila is detected in distribution system samples. Action levels are based on the best available science and expert judgment and are similar to those in protocols for assessing building water system monitoring results. Action levels should be reassessed as additional data and knowledge on the occurrence and growth potential of L. pneumophila in distribution systems become available. All positive detections trigger assessments that focus first on conditions local to the sample location and then extend further into the distribution system. Higher concentration or more frequent detections initiate more assertive responses and communication than lower concentration and frequency detections. The protocol provides a starting point for the development of protocols for purposes such as L. pneumophila operational surveillance or within an outbreak investigation.

While drinking water treatment plants (DWTPs) are not considered a source of per- and polyfluoroalkyl substances (PFAS), PFAS concentrate in treatment residuals relative to their source water concentrations. Regulatory actions considered for PFAS-impacted residuals could affect the cost and viability of conventional residual management practices. This study estimated the annual quantity of residuals generated in the United States and presents a framework for understanding how PFAS may concentrate in these residual streams. Findings of this work indicate that PFAS may substantially impact DWTP residuals management, especially coagulation and softening solids, at concentration factors greater than 100 and spent adsorbents at PFAS concentration factors greater than 10,000. If potential regulatory actions were to apply to coagulation and softening residuals, those regulations must consider impacts on disposal of more than 420,000,000 wet tons of at-risk DWTP residuals which are generated annually.

Interest is growing in potable reuse in response to water scarcity and the desire for sustainable supplies. While potable reuse systems must control a variety of physical, chemical, and microbiological contaminants, human enteric viruses are particularly concerning and drive process performance objectives due to their often-high occurrence in source waters, small size, potential resistance to treatment, and laborious methods to determine infectivity. This paper reviews the alignment of online monitoring practices with the mechanisms and time scales of the various barriers for enteric viruses. While there are numerous studies and reviews of individual barriers, no other review has been identified that covers operational monitoring of the entire potable reuse system. This paper also provides a critical assessment of the efficacy of current practices for operational and verification monitoring of the integrity of barriers to enteric viruses in potable reuse systems. The prevalence of human enteric viruses in wastewater and associated challenges of quantifying them through treatment are discussed within the risk management frameworks currently in use or under development for potable reuse systems. Monitoring approaches are then reviewed throughout the potable reuse water cycle. Current monitoring practices are compared with treatment process mechanisms and time scales, for the treatment barriers of biological wastewater treatment, membrane bioreactors, microfiltration/ultrafiltration, reverse osmosis, ultraviolet irradiation/advanced oxidation, ozonation, granular media/biologically active filtration, and chlorination. Monitoring and pathogen removal mechanisms are also reviewed for both environmental and engineered buffers. Implications are then discussed for future areas of research in potable reuse.

Scheduling pipe replacement is critical for water distribution systems (WDSs) when managing finances and water loss. WDS replacements are often delayed due to high immediate costs without considering long-term environmental consequences. This study is the first to examine a real-world WDS using a novel workflow transferrable to other WDSs that integrates GIS, hydraulic modeling, breakage prediction, and life cycle analysis to evaluate environmental impacts and water loss of five replacement schedules (25-, 50-, 75-, 100-, 150-year intervals). Environmental impacts were reduced by half when replacement interval changed from 25 year to 150 years, yet volume of water leaked from the system quadrupled. Benefits plateaued beyond 50–75-year replacement while water loss steadily increased. Lowering water loss through break management enabled one-sixth pipe replacement without exceeding original leakage at 25-year replacement. Results were robust to uncertainty parameters and assert the importance of equilibrating environmental impacts and water loss when designing pipe replacement frequency.

Bromide can promote monochloramine decomposition and disinfection byproduct (DBP) formation. Monochloramine and total chlorine stability as well as total trihalomethane and haloacetic acid formation were examined in groundwater with high bromide levels (300–1700 μg/L) following chlorine or KMnO₄ preoxidation. An N,N-Diethyl-p-phenylenediamine (DPD)-based total chlorine method detected chloramines and brominated amines (e.g., NH₂Br, NHBrCl). An indophenol-based monochloramine method showed minimal interference from brominated amines. Differences between these methods' measurements likely indicated brominated amine concentrations. Substantial total chlorine demands (up to ~3.5 mg/L in 4 days) following chlorine preoxidation were observed due to the presence of brominated amines. Total chlorine measurements were more stable and DBP formation was limited following KMnO₄ preoxidation because ammonia was dosed before chlorine, which inhibited brominated amine formation. A kinetic model developed elsewhere for dissolved organic matter (DOM)-free water generally tracked with experimental results but some deviations occurred possibly because DOM consumed bromochloramine or its reaction intermediates.

The interactions between dissolved silica and corrosion scale on lead pipes such as hydrocerussite (Pb₃(CO₃)₂(OH)₂) and aluminum containing amorphous phases can affect the rates of lead release from the pipes to drinking water. Batch experiments that were well mixed to fully suspend these materials complemented previous experiments that were performed with pipes with intact pipe scales. These experiments focused on chemical interactions between the corrosion scale materials and silicate by decreasing the effect of mass transfer processes associated with solute diffusion into and out of intact scales. The findings from the batch experiments help us understand that the benefits of silicate addition in controlling lead release observed in a previous pipe loop study with pipes with intact scale were primarily due to inhibited diffusion of lead through the scale as a result of silicate uptake and not due to chemical interactions between lead-containing solids and silicate.