Getting smart with water quality monitoring

Located 350 km north of Sydney, Kempsey Shire Council uses monitoring stations to ensure water quality standards are being maintained. One such legacy system was equipped with sensors for measuring pH and chlorine. The sensors used reagents to establish measurements; however, it was becoming unreliable and required time-consuming upkeep.

Chlorine sensors are traditionally a high-maintenance monitoring solution, generally requiring a constant routine of replacing parts (membrane caps), upkeep of electrolytes, increased labour and equipment costs. Additionally, the presence of chloramines, either intentional or unintentional, can also have a strong influence on readings, creating errors in free chlorine analysis.

Of greatest concern for the council was the fall-off in accuracy and the need for frequent recalibration.

As a result, the council decided to update its time-consuming water quality monitoring with a smarter ‘plug-and-play’ solution for its water and wastewater services.

The council compared a number of alternative systems and decided on the Bürkert Online Analysis System. The compact modular design has an integrated HMI display; I/O modules; a range of available sensor cubes including pH, chlorine (Cl₂) or chlorine dioxide (ClO₂), conductivity, oxidation reduction potential (ORP/redox) and turbidity; as well as a cleaning system. All of which can be wall or panel mounted, or built into an existing cabinet, which is the solution the council used.

The solution reduced the maintenance requirement, diminishing drift and the need to recalibrate — which were all regarded by the council as essential advantages for its application. The zero effects from chloramines was an added bonus.

Bürkert’s Cl₂ and ClO₂ sensor cubes contain a high-precision membrane-covered amperometric sensor, but the difference is they are based on MEMS (microelectromechanical systems) technology. This microchip allows for precision measurements, with little to no drift as its readings are not influenced by chloramines. These cubes only require small samples for measurements and have a fast response time (t90) of less than 30 s.

Once installed, the individual sensor modules or ‘cubes’ are essentially plug-and-play. It’s a simple process to create alarm parameters for each sensor cube, ensuring that any anomaly in the process is identified quickly.

“We are very pleased with the new system,” said Greg Morrow, Instrument Technician at the Kempsey Shire Council’s South West Rocks plant. “Since it was installed, there has been no need to recalibrate the chlorine or the pH sensor cubes. Their performance has been verified using portable laboratory equipment (a DPD1 photometer reference test) for free chlorine. Furthermore, the sensors’ response time has been virtually instant, far exceeding the performance of the alternatives we looked at.”

Bürkert’s Online Analysis System communicates with existing control protocols and with personnel, both on and off site. Any deviation from the set criteria is notified immediately. This integration helps reduce time between a deviation from process parameters and remedial action required to correct the situation.

“After 10 months in operation, the accuracy has been excellent; there’s no drift in either the chlorine or the pH measurements,” said Tristan Nowland, Instrument Technician. “Additionally, the amperometric chlorine MEMS sensor chip isn’t affected by chloramines, providing true chlorine analysis. Another major benefit is the cubes are not reagent-based, and so the maintenance requirement for this system is greatly reduced.”

The performance and ease of installation of these systems has prompted the council to install the Bürkert Online Analysis System at several other reservoirs and water treatment plants.

These systems are designed to provide all the analysis data required for most applications — as well as acting as a data logger to provide necessary evidence for maintaining water quality standards.

Top image credit: ©stock.adobe.com/au/Vasily Merkushev