This chemical feed method of dechlorination has the best reproducible results.

• A. Batch reactor
• B. Chemical metering pump
• C. Pass-through mixer
• D. Chlorine gas scrubber

Answer: (B)

Precise, consistent dosing of the dechlorinating chemical is what yields repeatable results. When you dechlorinate, you must match the amount of chemical (like sodium thiosulfate or sodium sulfite) to the residual chlorine and the water flow, so every batch or stream gets the same treatment. A chemical metering pump provides accurate, continuous dosing that can be adjusted for flow rate and residual chlorine, delivering a stable dose every time and reducing variability due to human error or batch-by-batch differences.

A batch reactor introduces variability because each batch can differ in contact time, mixing efficiency, and starting chlorine levels. A pass-through mixer helps mix streams but does not control how much chemical is added. A chlorine gas scrubber removes chlorine from air, not dissolved chlorine in water, so it doesn’t achieve dechlorination of the water stream.