The Ag/AgCl reference in your SAGD produced water loop is already poisoned.
Not “maybe degraded.” Poisoned. H₂S reacts with the silver chloride coating to form Ag₂S — a sulfide film that blocks ion exchange and shifts your reference potential in one direction, permanently.
In Athabasca bitumen operations, produced water H₂S concentrations routinely exceed 50 ppm. At those levels, a standard single-junction Ag/AgCl reference loses 0.04–0.06 pH units per week. After 30 days, your sensor reads 0.2 pH low. Your AEPA discharge report says the water is more acidic than it is.
That is not a calibration error. That is a reportable measurement failure.
The fix is not recalibrating more often. Frequent calibration masks drift — it does not eliminate the root cause.
The fix is architecture:
Double-junction reference: the outer chamber creates a buffer zone using a non-contaminating electrolyte (KNO₃ or KCl saturated with AgCl-free gel). H₂S never reaches the Ag/AgCl element.
PTFE diaphragm: standard ceramic junctions clog with sulfide precipitate within weeks. PTFE is chemically inert to H₂S and maintains stable junction potential under high-fouling loads.
Pressurized reference: in high-flow SAGD loops, electrolyte bleed-out reverses direction under process pressure. A pressurized reference maintains positive outward flow.
All Schrödinger process electrodes for SAGD applications ship with double-junction PTFE architecture as standard — not as an upgrade.
If your current sensor did not come with that, your data is not reliable.
schrodinger.ca