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Fort Worth, TX, United States

Hekman S.H.,Freese and Nichols Inc.
AWWA/AMTA Membrane Technology Conference and Exposition 2012 | Year: 2012

Brown County Water Improvement District No. 1 (BCWID) is a wholesale supplier of raw water used for irrigation and treated water used for municipal purposes in Brown and Coleman Counties of West Texas. Raw water is pumped from Lake Brownwood for treatment at BCWID's water treatment plants where it is then treated and delivered to wholesale customers. To meet increasing customer demand for water, BCWID hired Freese and Nichols to perform an evaluation of the District's existing water treatment plants in 2001. The need for at least 7.5 MGD additional treated water capacity was identified. The District's source water of Lake Brownwood historically has extremely good water quality: low turbidity averaging 5 NTUs and low organics of around 2 - 4 mg/l, which makes it ideal for membrane consideration. In the summer of 2003, a pressure type microfiltration (MF) system was selected for pilot testing to evaluate the feasibility of a membrane treatment system. The pilot test in winter 2003-2004 confirmed that no pre-treatment other than an oxidant was required, and the system was given one of the highest flux rates approved in Texas (80 gpd/sf). After construction and operation of the membrane plant, the design team performed a side-by-side comparison of membrane (7.5 MGD) and a conventional (7.5 MGD) treatment plant expansion, and determined that due to high water quality and reduced chemical costs; BCWID saved $3.6 million by selecting an integrated membrane treatment plant expansion over a conventional treatment plant expansion. Future expansion would save an estimated $1.6 Million per MGD. Since completion of the project, the plant has demonstrated a 23% reduced operational cost for the membrane plant when compared to the existing conventional plant. This paper highlights the unique advantages of the completed, integrated 7.5 MGD conventional and 7.5 MGD membrane plant and identifies some lessons learned with regard to approaching this type of project in the future. Specific topics include: 1. Flexibility of integrating the plant piping and hydraulics to function in a separate parallel conventional/membrane mode or with conventional as pre-treatment for the membrane plant, 2. Flexibility in having common components such as raw water terminal storage, clearwells, high service pumping, and chlorine and ammonia feed facilities, 3. Cross-training plant staff in both conventional and membrane operations and maintenance, and 4. Integration of regulatory reporting. © 2012 American Water Works Association. Source

Wurbs R.A.,Texas A&M University | Schnier S.T.,Urbana University | Olmos H.E.,Freese and Nichols Inc.
Journal of Water Resources Planning and Management | Year: 2012

The water rights analysis package (WRAP) is a generalized river/reservoir system simulation model that is routinely applied in Texas in regional and statewide planning studies and administration of the water right permit system. The WRAP modeling system was recently expanded by adding short-term storage frequency and supply reliability analysis capabilities. Individual reservoirs and multiplereservoir systems can be analyzed considering numerous water users and complex water management practices. The new modeling features are based on dividing the hydrologic period-of-analysis into many short-simulation sequences with each starting with the same storage conditions. Two alternative frequency/reliability analysis methodologies, called the equal-weight and probability-array options, are compared in this paper with a case-study application. The probability array option is designed toimprove the accuracy of storage frequency estimates by modeling hydrologic persistence as reflected in the preceding reservoir storage contents on the basis of a regression of natural streamflow versus preceding storage from a long-term simulation. © 2012 American Society of Civil Engineers. Source

Venkataraman K.,Tarleton State University | Tummuri S.,Freese and Nichols Inc. | Medina A.,Tarleton State University | Perry J.,Tarleton State University
Journal of Hydrology | Year: 2016

Management of water resources in Texas (United States) is a challenging endeavor due to rapid population growth in the recent past coupled with significant spatiotemporal variations in climate. While climate conditions impact the availability of water, over-usage and lack of efficient management further complicate the dynamics of supply availability. In this paper, we provide the first look at the impact of climate change projections from an ensemble of Coupled Model Intercomparison Project Phase 5 (CMIP5) on 21st century drought characteristics under three future emission trajectories: Representative Concentration Pathway (RCP) 2.6, RCP 4.5 and RCP 8.5, using the standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI). In addition, we evaluate the performance of the ensemble in simulating historical (1950-1999) observations from multiple climate divisions in Texas. Overall, the ensemble performs better in simulating historical temperature than precipitation. In semi-arid locations such as El Paso and Laredo, decreasing precipitation trends are projected even under the influence of climate policies represented by the RCP 4.5. There is little variability in the SPI across climate divisions and across RCPs. The SPEI, on the other hand, generally shows a decreasing trend toward the latter half of the 21st century, with multi-year droughts becoming the norm under the RCP 8.5, particularly in regions that are already dry, such as El Paso. Less severe droughts are projected for the sub-humid eastern edge of the state. Considering that state water planning agencies are already forecasting increased water shortages over the next 50 years, we recommend proactive approaches to risk management such as adjusting the planning tools for potential recurrence of multi-year droughts in regions that are already water-stressed. © 2016 Elsevier B.V. Source

Maughn S.,Freese and Nichols Inc.
Pipelines 2014: From Underground to the Forefront of Innovation and Sustainability - Proceedings of the Pipelines 2014 Conference | Year: 2014

Being a design engineer and project manager of more than 100 miles of large-diameter pipeline projects (greater than 36-in. diameter) and installation has led to the privilege of witnessing multiple contractors and different installation techniques of pipe joint protection sleeves. This also has led to the experience of seeing corrosion problems on polyurethane-coated steel pipelines at pipe joints that can many times be related to poorly installed joint protection shrink sleeves. It has also exposed how the installation techniques and knowledge varies from contractor to contractor and even from work crew to work crew. A growing experience and understanding led to the realization that the heat-shrink sleeves were an important key to protecting one of the most vulnerable areas of the pipe during the installation process, which also led to the need to try and provide owners with quality installation of these products. In gasketed and weld-after-backfill installation techniques, the heat-shrink sleeves provide a very important protection layer to the steel pipe at these crucial points along the pipeline. A majority of the leaks and failures on pipelines are at the joints no matter what material the pipeline happens to be, so the need to find a way to ensure a better quality installation of the heat-shrink sleeves on polyurethane-coated steel pipes became apparent. Therefore, after witnessing several projects where a field representative of the heat-shrink sleeve manufacturer came out on site and performed field testing and installation instruction with the contractor crew members, the need was apparent for design engineers and resident representatives to conduct testing on heat-shrink sleeves. This would provide the opportunity to catch errors or improper installation techniques early on in the pipeline construction to try and minimize future corrosion problems that could potentially cause leaks or damage on the line. This testing started being performed at the very beginning of pipeline installation to verify the sleeves are properly installed and performing as they are intended for the protection of the pipeline joints. Data and information will be presented on how and when to perform the testing, what to look for, how to follow up with the contractor's crew, and how to convey testing results with the manufacturer's representative if necessary. Addressing this testing in the specifications of each project will also be addressed. These tests have been very valuable and have positively corrected poorly installed heat-shrink sleeves on pipeline projects. These tests are simple, but very effective and when performed early in the construction process, can help protect multiple areas of vulnerability along many miles of large-diameter pipelines. © 2014 American Society of Civil Engineers. Source

Rao B.,Texas Tech University | Anderson T.A.,Texas Tech University | Redder A.,Freese and Nichols Inc. | Jackson W.A.,Texas Tech University
Environmental Science and Technology | Year: 2010

The environmental occurrence of perchlorate (ClO4) can be related to either natural or anthropogenic sources. Recent studies highlighted the ubiquitous occurrence of natural ClO4 in the environment including wet deposition in the United States. Limited studies have investigated potential mechanisms responsible for natural ClO4 production in the environment. These studies have neither addressed the influence of relevant reaction conditions nor have they evaluated the rates of ClO4 production. The purpose of this study was to determine the comparative yields and rates of ClO4 production from O3 mediated oxidation of Cl, OCl, ClO2, ClO3, and ClO2. The influence of reactant (O3 and ClOx) concentration and pH were evaluated. The comparative rate and efficiency of ClO4 production is generally greater for higher oxidation states of Cl (2.7 to 0.5% for ClO 2/ClO2 and 0.02 to 0.005% for OCl/HOCl oxidation) with the notable exception of ClO3 which does not react with O3. The very slow rate of ClO4 production from Cl (?20 - 109 mM min1) even at elevated O3 and Cl concentrations implies negligible potential for anthropogenic ClO4 formation in process units of water/wastewater systems that use O3 for treatment. Based on results of ClO4 formation from tested Cl species and available literature, we propose a potential formation pathway for ClO4 from Cl with emphasis on the role of ClO2 and higher oxy-chlorine radicals/intermediates (e.g., Cl2O6) in its formation. © 2010 American Chemical Society. Source

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