Water Online

June 2012

Water Online the Magazine gives Water & Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.

Issue link: http://wateronline.epubxp.com/i/66306

Contents of this Issue

Navigation

Page 32 of 45

Tutorial solids with a high level of accuracy. A TDS instrument uses compensated conductivity mea- surements, taking into account solution type to determine the actual amount of dissolved solids in solution or Total Dissolved Solids (TDS). The measurement is reported as parts per million or parts per thousand, generally. Proper solution modeling is critical to accurate TDS readings, as well as the accuracy of the original conductivity reading. Again, this is because each kind of chemical constituent conducts electricity to varying degrees and will affect the total con- ductivity disproportionately with variations in temperature. Select and calibrate a TDS meter by the solution standard that most closely matches the application in which the TDS measurement will be made. A meter that has a conductivity- to-TDS conversion algorithm that accounts for critical points in changes of the behavior of the solution based on actual testing is more accurate. Ask the manufacturer about the conversion algorithms if you are unsure. A TDS meter that allows you to specify a custom solution TDS conversion based on your own testing will yield the greatest accuracy in situations where the characteristics of the sample are known. Some manufacturers will make calibration solutions to order. Calibrate with a solution in the upper two-thirds of the range of concentrations that will be mea- sured. Routine Calibration And Maintenance Choose an instrument that can stand up to the conditions to which it will be subjected. Familiarize yourself with the oper- ation and maintenance of your instrument. Clean your conductiv- ity cell and calibrate conductivity, resistivity, and TDS parameters to the proper standard solutions per your operation manual. Inspect the instrument for wear and tear and store it properly to prevent unnecessary damage. Finally, an instrument is only as good as its user. The dissolved solids meter is designed to tell you how much of a known sub- stance is in the water, not what is in the water. A dissolved solids meter will not identify specific ions, only the concentration of ions, generally. You must know what chemical constituents exist in what concentrations in the solution to be tested and choose an instrument standardized to that solution type with accuracy specs that match the range of possible measurements. This means that, ultimately, the accuracy of the instrument depends on you. Saving Time And Money The more accurate your process control measurements are, the fewer chemicals and solutions you'll have to use generally. And, using fewer chemicals means reduced costs in chemical removal. When optimizing cycles of concentration, accurate monitoring could mean increasing the number of cycles until the solution has to be dumped, drastically reducing water consumption. Imprecisely cali- brating and spot checking/monitoring with cheap instru- mentation is going to cost you in increased chemicals, cycles, and downtime or even eventual equimpment fail- ure. So, purchasing a quality instrument up front will pay for itself almost immediately, whereas getting that cheap low quality one may cost you for a long time. Heather Rekalske is a technical writer for the Myron L Company, a provider of a broad spectrum of water quality instrumentation, including monitor/controllers as well as precision digital and analog handheld meters. Don't settle for metal. Food Service On-site Sodium Hypochlorite Generation Water Softening Bryneer brine maker Plas-Tanks Industries, Inc. 39 Standen Drive | Hamilton, OH 45015 | (513) 942-3800 | www.plastanks.com wateronline.com ■ Water Online The Magazine, Cleanwater Edition 31

Articles in this issue

Links on this page

Archives of this issue

view archives of Water Online - June 2012