Spanish Water Utility Tackles Disinfection with Measurement and Control Solutions

In an optimally controlled disinfection process, analyzers continually measure the presence of chemical compounds such as disinfectants in the water in accordance with local regulations.

The equipment installed for this purpose had a small peristaltic pump adding sufficient chemical to correct the pH value for an accurate measurement. Subsequently, the reagent for measuring free chlorine was added. However, these chemicals were kept in separate plastic containers located in a box with the rest of the mechanisms necessary for measurement and control. The chemicals—both the corrector and the reagent—were affected by the heat, jeopardizing the reliability of the measurement.

Through a mutual agreement, Grundfos and Badger Meter (supplying s::can sensors and controller) commenced robust research and development work to design a very low maintenance disinfection dosing solution, with minimal calibration required. These efforts culminated in a versatile set up, which includes a CU 382 control panel (con::lyte controller), and three PID control outputs for Digital Instrument Dosing (DID).

Available as pre-assembled systems with bypass flow cell or as kits for applications with tank-immersed sensors, DID systems are intended for monitoring and control of disinfectants, pH, ORP, conductivity, turbidity, organics and temperature. The water flow through the cell is kept at an appropriate level by a flow restrictor. Lack of water is detected by a flow switch, which signals an alarm. With the DID solution, measurement of water parameters directly in the tank or basin without the need for a bypass line and flow cell is possible, simplifying measurement and control without complex maintenance requirements.

The solution supplied—a DID system with chlori::lyser, condu::lyser and ph::lyser—is easy to install and simplifies maintenance as each sensor is practically maintenance-free for a very long time. The probe provides accurate and continuous measurement of free chlorine without the need for pH correction or the addition of any other chemicals as was the case with the previous system.

“Once commissioned, the equipment hasn’t caused any problems. It’s a big improvement compared to the previous situation. The installation of the equipment is very simple. When the configuration was done and the probe was polarized, which usually takes about 20-30 minutes, the equipment has worked flawlessly,” the maintenance manager states.

The technology of the DID system offers uninterrupted measurement, allowing for constant monitoring of the disinfection treatment and offering an improved responsiveness on the part of the operator in case of failure. This is unlike other systems which measure free chlorine at intervals of several minutes. Today, after many years in operation, the system is working correctly and remains easy to maintain.

“[The equipment] does not require pH correction and has a high-quality chlorine probe. It is only necessary to change the very small quantities of electrolyte, and in most cases, it is not even necessary to calibrate. In the case of this plant, the electrolyte is changed approximately once a year. Its analogue, digital and PID outputs make it fully compatible with existing data logging and real-time monitoring equipment in the plant,” says the maintenance manager.

This Spanish drinking water pumping station not only benefitted from the ease of installation and full connectivity with existing control and monitoring systems, but they were also able to reduce costs and the level of maintenance without sacrificing measurement accuracy.