Optimised pH System for Coagulation/Flocculation Stages 

The most critical pH measurements and control are for the ‘Treated Raw Waters’. The pH of these waters is critical in order to optimise the addition of flocculent/coagulation chemicals.

These raw waters especially in winter months are cold (close to freezing) and often low ionic. With these 2 factors, using pH sensors with porous reference junctions, it’s impossible to achieve stable and accurate pH measurement. Porous electrodes all suffer diffusion potential errors (ca pH 0.3) and at low temperatures the impedance of the pH glass membrane increases by a full decade (RT 20 C impedance of 200 MOhm at zero this becomes 2000 MOhm). The net result is hit and miss pH correction and addition of coagulant/flocculent chemicals. This lack of pH control affects the effectiveness of the coagulation that adversely affects the filtration stages downstream.

The Refex pH sensor uses a unique and patented hard-non-porous ionically conductive material that has replaced the need for the unreliable and inaccurate porous reference junction. The polymeric Refex material acts as an immobilised KCl electrolyte and also as an interface/barrier that separates the raw waters from the electrode’s internal Ag/AgCl half cell – hence there is no liquid contact/exchange. With no diffusion potential errors and Rock-Solid mV stability (no drifting) this Refex arrangement is almost maintenance free (every 90 days is achievable).

Accurate pH calibrations using buffers with values close to the pH value of the waters being tested – it’s possible to achieve a pH resolution of pH 0.01. Only the Refex electrode can achieve such tight resolutions.

Savings: Chemical Savings  - Correcting / flocculation/coagulation > GBP 2000,--/month/WTW; Maintenance: Usually weekly or Bi-weekly calibrations can be extended to every 90 Days; Long Life – the Refex electrode lasts longer than all others (5-10 times longer life).

The Refex electrode has a higher impedance reference (< 1 MOhm), for this reason it is necessary to use a top quality pH transmitter that has duel high impedance inputs for both pH and reference electrodes. 2 x 10 x 12 Ohm is the best. This is very important.

Refex offers new customers a Free Try-It/Like-It/Buy-It opportunity, free for 90 days obligation free.