Operator terms · Wastewater
What is dechlorination?
Dechlorination is removing chlorine from water before it is discharged, because chlorine that protects drinking water is toxic to fish and aquatic life. Wastewater plants that disinfect with chlorine often dechlorinate the effluent, using a chemical such as sulfur dioxide, so the discharge meets its permit.
Last reviewed 2026-08-03
Why remove chlorine
Chlorine disinfects the effluent, but the same chlorine harms fish and aquatic life in the stream it is discharged to, so the permit limits it.
How it is done
A dechlorinating chemical, commonly sulfur dioxide, is added after disinfection to neutralize the remaining chlorine before the water leaves the plant.
Common questions
- Why dechlorinate?
- Chlorine is toxic to aquatic life, so it is removed before discharge.
- What chemical is used?
- Commonly sulfur dioxide, added after disinfection.
- Do all plants do it?
- Plants that disinfect with chlorine and discharge to sensitive waters typically do.