Anode

Cathode

Reference electrode

Monitoring system

d.c. power source

+

-

2Cl⁻ → Cl₂ + 2e⁻

4(OH)⁻ → O₂ + 2H₂O + 4e⁻

2H₂O + O₂ + 4e⁻ → 4(OH)⁻

4(OH)⁻

Cl⁻