An Accurate and Low Maintenance pH Measurement System is Developed

REFEX and Northern Ireland Water (NIW) together developed an accurate and low maintenance pH measurement and control system for optimising coagulation in cold, low ionic raw water feeding into the 23 Water Treatment Plants operated by NIW and Kelda (Yorkshire Water) in Northern Ireland.

After six months of evaluation, it was determined that REFEX sensors paired with either Knick or Yokogawa pH transmitters provided the best performance overall. It is important to note that both the Knick and Yokogawa transmitters have galvanically separated dual high impedance inputs (2 x 1012Ω) for their pH and reference connections. This high impedance characteristic protects the electrodes well from potentially damaging ground loops and noise.

The NIW/Kelda engineers that carried out this project were Alan Jackson (now retired) and Roy McAlonon (now telemetry). Both Alan and Roy have recommended and approved REFEX pH sensors with Knick or Yokogawa transmitters for use in the WTW’s in Northern Ireland and have provided testimonials endorsing these 2 pH arrangements and their performance.

As a result of the testing, REFEX/Knick combination was chosen by NIW/Kelda water as their corporate standard for measuring pH. The RFEEX/Knick arrangement was found to provide the best accuracy, the fastest response to pH change and had the lowest maintenance cost.

REFEX sensors are deployed in a variety of applications throughout the system: Incoming raw water pH measurement for correction/coagulation optimisation, Primary filter pH measurement, Secondary filter pH measurement, Manganese filter pH measurement, Final water pH measurement and correction.

Savings in excess of £1.0MM in total have resulted from standardising on the REFEX/Knick pH arrangement at NIW/Kelda Water.

Using the REFEX solution, it was clear that the quality of water received by each WTW was significantly improved. The ability to continuously optimise coagulation in the raw water had significant benefit for downstream filtration. Overall, treatment and production efficiency was increased with an improvement in consistency of final water quality while driving down direct costs.

Our electrodes come with a 5 year warranty.