Nevada City, Nevada, United States
Nevada City, Nevada, United States

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David Holbrook R.,U.S. National Institute of Standards and Technology | Motabar D.,U.S. National Institute of Standards and Technology | Quinones O.,Southern Nevada Water Authority | Stanford B.,Southern Nevada Water Authority | And 2 more authors.
Environmental Pollution | Year: 2013

The increased use of titanium dioxide nanoparticles (nano-TiO2) in consumer products such as sunscreen has raised concerns about their possible risk to human and environmental health. In this work, we report the occurrence, size fractionation and behavior of titanium (Ti) in a children's swimming pool. Size-fractionated samples were analyzed for Ti using ICP-MS. Total titanium concentrations ([Ti]) in the pool water ranged between 21 μg/L and 60 μg/L and increased throughout the 101-day sampling period while [Ti] in tap water remained relatively constant. The majority of [Ti] was found in the dissolved phase (<1 kDa), with only a minor fraction of total [Ti] being considered either particulate or microparticulate. Simple models suggest that evaporation may account for the observed variation in [Ti], while sunscreen may be a relevant source of particulate and microparticule Ti. Compared to diet, incidental ingestion of nano-Ti from swimming pool water is minimal. © Published by Elsevier Ltd.


Rosario-Ortiz F.L.,Southern Nevada Water Authority | Wert E.C.,Southern Nevada Water Authority | Snyder S.A.,Southern Nevada Water Authority
Water Research | Year: 2010

Advanced oxidation treatment using low pressure UV light coupled with hydrogen peroxide (UV/H2O2) was evaluated for the oxidation of six pharmaceuticals in three wastewater effluents. The removal of these six pharmaceuticals (meprobamate, carbamazepine, dilantin, atenolol, primidone and trimethoprim) varied between no observed removal and >90%. The role of the water quality (i.e., alkalinity, nitrite, and specifically effluent organic matter (EfOM)) on hydroxyl radical ({radical dot}OH) exposure was evaluated and used to explain the differences in pharmaceutical removal between the three wastewaters. Results indicated that the efficacy of UV/H2O2 treatment for the removal of pharmaceuticals from wastewater was a function of not only the concentration of EfOM but also its inherent reactivity towards {radical dot}OH. The removal of pharmaceuticals also correlated with reductions in ultraviolet absorbance at 254 nm (UV254), which offers utilities a surrogate to assess pharmaceutical removal efficiency during UV/H2O2 treatment. © 2009 Elsevier Ltd. All rights reserved.


Hester G.A.,Southern Nevada Water Authority
43rd International Erosion Control Association Annual Conference 2012 | Year: 2012

Over the last several decades a number of the urban areas of the southwestern United States have experienced explosive population growth. With increasing populations and expanding urban sprawl, often come increased wastewater discharges, higher dry weather urban runoff and larger storm water discharges. Naturally formed receiving streams are now tasked with conveying increased urbangenerated volumes of flow. Often these outfall streams become de-stabilized with resulting increases in the rates of channel bed and bank erosion, higher volumes of sediment discharge, degradation in water quality and loss of valuable riparian lands. One of the largest single stream restoration programs currently underway in the western U.S. and an example of one community's successful efforts to combat stream zone erosion, to restore wetland and riparian habitat, to improve the quality of water discharging into Lake Mead, and to develop recreational opportunities, is Southern Nevada's $270 million dollar effort to stabilize and restore the non-federally owned portion of the 20 kilometer (12.5 mile) long outfall stream known as the Lower Las Vegas Wash. This paper describes how this massive effort, which is now nearing completion, was formulated and has become successful through many years of multi-agency cooperation, comprehensive, adaptive planning, and environmental sensitivity.


Hester G.A.,Southern Nevada Water Authority
43rd International Erosion Control Association Annual Conference 2012 | Year: 2012

The use of rock riprap for grade control structure design has become a popular method of stream channel stabilization and restoration. Understanding the hydraulics and forces involved with discharges over riprap gradient control structures is paramount to the long term success of most stream channel restoration projects. Considerable research has been previously devoted to developing rock-sizing methodologies and characterizing hydraulic stresses on rock riprap. However, stream restoration specialists are often confused as to the most appropriate methodologies to apply during the planning process and in many cases are left uncertain of the realistic capability of riprap gradient control facilities to sustain varying flow conditions over the long term. To give stream channel restoration professionals more confidence in channel stability design and application, the Southern Nevada Water Authority enlisted the assistance of Colorado State University's Engineering Research Center to conduct a wide range of large scale physical hydraulic modeling of rock riprap grade control structures to aid in determining the most appropriate design methodologies to apply for long term success. 1:6 Froude-scale rock riprap grade control models, containing varying D50 riprap sizes, were developed and subjected to a wide range of discharges during the study. This paper summarizes the results of the study and is supplemented with field observations of actual installations under high discharge conditions.


Woods G.C.,Southern Nevada Water Authority | Dickenson E.R.V.,Southern Nevada Water Authority
Journal - American Water Works Association | Year: 2015

The complete database of results from the second Unregulated Contaminant Monitoring Rule (UCMR2) was analyzed in depth for N-nitrosodimethylamine (NDMA) occurrence across the United States and analyzed for trends associated with factors reported. Disinfectant type, source waters, regional variability, population density, and seasonal variability were all examined for potential impacts on NDMA. Detectable levels of NDMA were found in 17% of samples and 25% of treatment plants. The other five listed nitrosamines were detected in less than 1% of samples. The strongest factor found positively associated with NDMA occurrence was chloramine use. Likewise, the use of surface waters was found to be linked to NDMA occurrence such that surface waters (even when decoupled from chloramine use) demonstrated elevated levels of NDMA over groundwater sources. No clear seasonal trends could be deciphered, but data supplied from utilities servicing fewer than 10,000 customers provide evidence that smaller utilities have some of the most extreme NDMA levels and subsequently may have a difficult time meeting any future NDMA regulation. © 2015 American Water Works Association.


Vanderford B.J.,Southern Nevada Water Authority | Mawhinney D.B.,Southern Nevada Water Authority | Trenholm R.A.,Southern Nevada Water Authority | Zeigler-Holady J.C.,Southern Nevada Water Authority | Snyder S.A.,University of Arizona
Analytical and Bioanalytical Chemistry | Year: 2011

Proper collection and preservation techniques are necessary to ensure sample integrity and maintain the stability of analytes until analysis. Data from improperly collected and preserved samples could lead to faulty conclusions and misinterpretation of the occurrence and fate of the compounds being studied. Because contaminants of emerging concern, such as pharmaceuticals and personal care products (PPCPs) and steroids, generally occur in surface and drinking water at ng/L levels, these compounds in particular require such protocols to accurately assess their concentrations. In this study, sample bottle types, residual oxidant quenching agents, preservation agents, and hold times were assessed for 21 PPCPs and steroids in surface water and finished drinking water. Amber glass bottles were found to have the least effect on target analyte concentrations, while high-density polyethylene bottles had the most impact. Ascorbic acid, sodium thiosulfate, and sodium sulfite were determined to be acceptable quenching agents and preservation with sodium azide at 4 °C led to the stability of the most target compounds. A combination of amber glass bottles, ascorbic acid, and sodium azide preserved analyte concentrations for 28 days in the tested matrices when held at 4 °C. Samples without a preservation agent were determined to be stable for all but two of the analytes when stored in amber glass bottles at 4 °C for 72 h. Results suggest that if improper protocols are utilized, reported concentrations of target PPCPs and steroids may be inaccurate. © Springer-Verlag 2011.


Pisarenko A.N.,Southern Nevada Water Authority | Stanford B.D.,Southern Nevada Water Authority | Yan D.,Southern Nevada Water Authority | Yan D.,University of Arizona | And 5 more authors.
Water Research | Year: 2012

An ozone and ozone/peroxide oxidation process was evaluated at pilot scale for trace organic contaminant (TOrC) mitigation and NDMA formation in both drinking water and water reuse applications. A reverse osmosis (RO) pilot was also evaluated as part of the water reuse treatment train. Ozone/peroxide showed lower electrical energy per order of removal (EEO) values for TOrCs in surface water treatment, but the addition of hydrogen peroxide increased EEO values during wastewater treatment. TOrC oxidation was correlated to changes in UV 254 absorbance and fluorescence offering a surrogate model for predicting contaminant removal. A decrease in N-nitrosodimethylamine (NDMA) formation potential (after chloramination) was observed after treatment with ozone and ozone/peroxide. However, during spiking experiments with surface water, ozone/peroxide achieved limited destruction of NDMA, while in wastewaters net direct formation of NDMA of 6-33 ng/L was observed after either ozone or ozone/peroxide treatment. Once formed during ozonation, NDMA passed through the subsequent RO membranes, which highlights the significance of the potential for direct NDMA formation during oxidation in reuse applications. © 2011 Elsevier Ltd.


Vidal-Dorsch D.E.,Southern California Coastal Water Research Project | Bay S.M.,Southern California Coastal Water Research Project | Maruya K.,Southern California Coastal Water Research Project | Snyder S.A.,Southern Nevada Water Authority | And 3 more authors.
Environmental Toxicology and Chemistry | Year: 2012

The occurrence and concentrations of contaminants of emerging concern (CECs) were investigated in municipal effluents and in marine receiving water. Final effluent from four large publicly owned treatment works (POTWs) and seawater collected near the respective POTW outfall discharges and a reference station were collected quarterly over one year and analyzed for 56 CECs. Several CECs were detected in effluents; naproxen, gemfibrozil, atenolol, and tris(1-chloro-2-propyl)phosphate were the compounds most frequently found and with the highest concentrations (>1μg/L). Gemfibrozil and naproxen had the highest seawater concentrations (0.0009 and 0.0007μg/L) and also were among the most frequently detected compounds. Effluent dilution factors ranged from >400 to approximately 1,000. Fewer CECs were detected and at lower concentrations in seawater collected from the reference station than at the outfall sites. Effluent concentrations for some CECs (e.g., pharmaceuticals) were inversely related to the degree of wastewater treatment. This trend was not found in seawater samples. Few temporal differences were observed in effluent or seawater samples. Effluent CEC concentrations were lower than those currently known for chronic toxicity thresholds. Nevertheless, the evaluation of potential chronic effects for CECs is uncertain because aquatic life toxicity thresholds have been developed for only a few CECs, and the effluent and seawater samples had compounds, such as nonylphenol, known to bioaccumulate in local fish. Additional data are needed to better understand the significance of CEC presence and concentrations in marine environments. © 2012 SETAC.


Marti E.J.,Southern Nevada Water Authority | Marti E.J.,University of Nevada, Las Vegas | Pisarenko A.N.,CA Technologies | Peller J.R.,Indiana University Northwest | Dickenson E.R.V.,Southern Nevada Water Authority
Water Research | Year: 2015

Nitrosamines are a class of toxic disinfection byproducts commonly associated with chloramination, of which several were included on the most recent U.S. EPA Contaminant Candidate List. Nitrosamine formation may be a significant barrier to ozonation in water reuse applications, particularly for direct or indirect potable reuse, since recent studies show direct formation during ozonation of natural water and treated wastewaters. Only a few studies have identified precursors which react with ozone to form N-nitrosodimethylamine (NDMA). In this study, several precursor compound solutions, prepared in ultrapure water and treated wastewater, were subjected to a 10M excess of ozone. In parallel experiments, the precursor solutions in ultrapure water were exposed to gamma radiation to determine NDMA formation as a byproduct of reactions of precursor compounds with hydroxyl radicals. The results show six new NDMA precursor compounds that have not been previously reported in the literature, including compounds with hydrazone and carbamate moieties. Molar yields in deionized water were 61-78% for 3 precursors, 12-23% for 5 precursors and <4% for 2 precursors. Bromide concentration was important for three compounds (1,1-dimethylhydrazine, acetone dimethylhydrazone and dimethylsulfamide), but did not enhance NDMA formation for the other precursors. NDMA formation due to chloramination was minimal compared to formation due to ozonation, suggesting distinct groups of precursor compounds for these two oxidants. Hydroxyl radical reactions with the precursors will produce NDMA, but formation is much greater in the presence of molecular ozone. Also, hydroxyl radical scavenging during ozonation leads to increased NDMA formation. Molar conversion yields were higher for several precursors in wastewater as compared to deionized water, which could be due to catalyzed reactions with constituents found in wastewater or hydroxyl radical scavenging. © 2014 Elsevier Ltd.


News Article | November 18, 2016
Site: marketersmedia.com

Paul Grant owns a Henderson landscaping company in Las Vegas, Nevada and he has issued a friendly reminder to all residents not to forget to switch their irrigation systems to the winter schedule. This is in light of the mandatory watering restrictions that limits landscape irrigation in southern Nevada to just one designated day per week. The restriction came into effect on November 1st and they will be enforced right up until February 28th. “These winter watering restrictions also apply to drip irrigation systems and residents that don’t comply could be hit with a water waste fine. As the restrictions came into effect on November 2nd, most people will already have taken action. However, while carrying out my weekly landscape maintenance jobs in Henderson, I’ve noticed that some residents still haven’t made the switch. Failure to comply leads to all kinds of problems considering the shortages of water in and around Las Vegas,” Paul noted. Grant says “Don’t water on days that are rainy and/or windy as water can be dispersed in the wrong direction, and soil can become over saturated on wet days. By simply turning off sprinklers during these weather conditions can result in a saving of about 500 gallons of water. Homeowners must check what watering group they fall into which will determine the day of the week that they’re permitted to run their systems. They can do this by checking their monthly water bill or by logging onto the Southern Nevada Water Authority (SNWA) website.” Landscaping in Henderson and the rest of Las Vegas has become all the more topical in recent months as the water crisis in this area becomes more of a concern. The state has experienced a very warm, dry summer again this year, which further increases the probability that there will be a water shortage in Lake Mead by as soon as 2018. This has sparked wide-spread concern, so switching irrigation systems to their winter schedules couldn’t be more important than it is now. For more information, please visit http://www.landscapinghendersonpro.com

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