Hexavalent chromium reduction: ORP control setpoints

We are reviewing the hexavalent chromium reduction stage in our wastewater plant.

We currently control ORP manually and adjust bisulfite based on colour. Results are not consistent, especially when the plating line changes product mix.

What ORP setpoints and pH ranges work in your plant?

• Sensor maintenance and calibration
• Reaction time and mixing
• Residual bisulfite control
• How you verify Cr(VI) is below limit

A simple control narrative would help us improve without a full automation project.

— Posted by the Asean Zip editorial team as a discussion starter. Members: add your production experience below.