Overview
Challenge
Accurate turbidity measurements are essential to drinking water treatment, and plants often face strict requirements to ensure finished water is safe for consumption. Monitoring turbidity before the release of treated water verifies the process is functioning as intended; turbidity values that exceed compliance limits may indicate equipment needs adjustment or maintenance.
Microbes, bacteria and other pollutants can attach to suspended solids, which makes turbidity an important parameter to watch as part of the disinfection process. And turbidity levels in water released into natural areas can influence the water quality of lakes, rivers, reservoirs and groundwater sources. If not monitored, high turbidity levels in effluent can have far-reaching implications for the ecosystems and communities that depend on them.
Municipal water companies in the U.K. take these responsibilities seriously, so it was important that, when the manufacturer of their current turbidity sensors announced end-of-life plans, this U.K. company found suitable replacements.
Knowing the transition would be a time-consuming and costly process, associates from the company were committed to thorough research and testing to make sure new equipment would meet their needs.
First, they needed equipment that would last. Their current system had been in place for over 20 years and they wanted to know they could count on this new investment for decades to come. Second, they needed replacement sensors that not only matched but exceeded the accuracy of their current sensors, to comply with strict water quality standards.
Third, they viewed the system update as an opportunity to improve efficiency by selecting equipment that would reduce maintenance duties for operators and simplify necessary steps like calibration. And finally, they knew that selecting a manufacturer with a commitment to customer service would prove invaluable during a total system overhaul.
Solution
The D-ISO checked all of the boxes. The sensor is capable of measuring changes in turbidity of less than .01 NTU and is highly sensitive to a wide range of particle sizes, making it ideal for meeting strict water quality standards.
A flow-through cell captures stray light to ensure a stable zero point, while a reference cell provides an easy, repeatable method of checking sensor performance, eliminating errors associated with chemical standards.
The sensor simplifies the calibration process by allowing operators to use either a wet turbidity standard or the dry calibration reference cell supplied with the sensor. And the sensor’s automatic self-cleaning mechanism reduces maintenance by preventing buildup of fouling in and around the flow-through chamber, increasing the durability of the device and giving operators valuable time to spend on other tasks.
For the initial test, the company bought 15 D-ISO units to test at one of their several treatment plants. In-Situ provided on-site assistance with the installation and offered operators guidance, support and expertise during the trial to smooth the transition to a new system.
Results
During the three months, engineers reported increased accuracy of results along with greater simplicity of calibration using the dry calibration reference cell. Now, the company has gradually replaced almost all of their aging units at each one of their many treatment facilities, between 50 and 60 units in all.
Anjie Stevens, a sales engineer for In-Situ who worked with the company, reports high customer satisfaction with the durability of the equipment and simplicity of use, but especially with the sensitivity of the sensors. Knowing the data is accurate brings operators peace of mind. “The measurements have to be right,” Stevens says. “It matters that they can have confidence in their system.”
