Wastewater Lab · Chlorine Residual
What Is Chlorine Residual?
Chlorine residual describes chlorine remaining at a defined place and time; required values are facility specific.
What Residual Means
Chlorine residual is the measurable chlorine remaining after some chlorine has reacted with substances in the wastewater. Free, combined, and total residual are different terms; the required test identifies what is measured.
Why It Is Measured
Residual can provide operating evidence about chlorine disinfection and may also be monitored for permit or dechlorination requirements. Feed rate alone does not show what residual remains after demand and contact.
Time And Location Matter
Chlorine residual can change quickly. Use the required sampling point, timing, method, and immediate-analysis requirement where applicable. Do not apply one plant's target, contact time, or response to another facility.
Keep learning
Laboratory Fundamentals
This page comes from the free course. It follows a wastewater sample from collection to a result an operator can use, with short knowledge checks and a certificate of completion.
See the course