WET Center Project:Methods to Assess Physical Water Treatment Efficacy

Project: Research project

Project Details


WET Center Project:Methods to Assess Physical Water Treatment Efficacy Development of Rapid Methods to Assess the Efficacy of Physical Water Treatment Introduction Physical water treatment processes have the ability to prevent scale formation without the addition of chemicals. The majority of physical water treatment devices result in the formation of sub-micron calcium carbonate crystals. As water flows to a more scale-inducing environment, the microscopic crystals are the most energetically favorable surface for crystalline growth instead of surfaces. The successful result is no scale formation on surfaces. Methods to assess the success of physical water treatment devices require large volumes of water and one month to complete. There is a need to rapidly assess physical water treatment devices to both determine their efficacy and provide quality control in real world applications. Conventional water quality measurements will show not effect from physical water treatment. This is because alkalinity measurements require acid addition that dissolves calcium carbonate crystals. Conventional analytical techniques for calcium measure all forms of calcium and do not differentiate between calcium in calcium carbonate crystals from free calcium ions. Therefore, a technique that can rapidly assess the efficacy of a physical water treatment device can also be used to monitor a physical water treatment device to ensure it is functioning correctly. Methods The most promising method to rapidly assess physical water treatment systems is the calcium ion selective electrode. Other methods include particle counting and sizing of particles. Calcium ion selective electrodes measure only free calcium and a decrease in free calcium concentration will occur with successful physical water treatment. These methods will be used to assess template assisted crystallization, electromagnetic water treatment and electrically induced precipitation. The proposed ANSI standard for evaluating the prevention of scale formation will be undergoing validation and the results with the calcium ion selective electrode will be compared to the validation results. Phase 1 Different physical water treatment devices will be tested as a function of flowrate through the device. The devices will be inserted into a inch PVC pipe and the flowrates will be varied by using increasing the friction losses with a ball valve inserted ahead of the treatment device. The apparatus used to complete the study entitled Evaluation of Alternatives to Domestic Ion Exchange Water Softeners will be used. For each test, a 350 gallon tank will be filled with tap water or ISTB 4 cooling water such that the same water source will be used for all testing with a particular physical water treatment device. The flowrates will be varied over the range of flowrates recommended by the manufacturer of each device. Physical water treatment devices that will be tested include template assisted crystallization, electrically induced precipitation and various electromagnetic technologies. Water samples will be taken from the water in the 350 gallon tank and samples will be taken after physical water treatment every 5 minutes for a 30 minute time period at each flowrate. The samples will be analyzed for total calcium, free calcium, total hardness, alkalinity and pH. Samples will be analyzed for free calcium using a calcium ion selective electrode immediately after sampling as the calcium carbonate crystals formed during physical water treatment are metastable and the free calcium ion concentration will change during storage. Total calcium and total hardness will be done by EDTA titration using a digital titrator using Hach methods. pH will be measured using a conventional pH probe. Alkalinity will be measured by titration with sulfuric acid in accordance with Standard Methods. Both the pH probe and the calcium ion selective electrode will be calibrated with certified standards. Data will be analyzed by comparing the water chemistry before and after physical water treatment. Of particular interest is the change in free calcium ion concentration as this implies that free calcium ions are being converted to calcium carbonate crystals. The Langelier Index (LI) will also be calculated before and after physical water treatment. The free calcium ion concentrations will be used after physical water treatment to correctly assess the scaling potential after physical water treatment. Also, the alkalinity measurement will be adjusting to include the carbonate that has combined with the free calcium. Therefore, physical water treatment both reduces free calcium ion concentrations and alkalinity in an effective manner and this can be captured by correctly calculating the Langelier Index. Phase 2 The second phase of this research will focus on characterization of the calcium carbonate crystals. This will be done by using the high performance liquid chromatography single particle analysis that was developed at Arizona State University to characterize nanoparticles. The calcium carbonate crystals are known to be 4-12 nanometers in size so the technique should be applicable. Samples of physically treated water will be analyzed as quickly as possible after treatment by the high performance liquid chromatographic method. Single crystals will be identified by their mass Spectra and their size and composition will be compared to those identified by Gebauer et al., (2008). Gebauer et al, (2008) used an analytical ultracentrifuge to characterize the nanoparticles combined with theoretical analysis of the possible crystal structure. Successful development of the high performance liquid chromatographic method will provide an additional tool that can rapidly assess the performance of physical water treatment device.
Effective start/end date5/1/1310/31/14


  • INDUSTRY: Various Consortium Members: $22,000.00


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