Residual

Definition

The concentration of active biocide remaining in the system after demand has been satisfied.

Maintaining a residual ensures persistent lethality, and chlorine programs in alkaline systems depend heavily on residual persistence. Rapid biocide consumption despite adequate feed rates suggests chemistry is being consumed by EPS before it reaches organisms. Rising biocide demand without increased system loading signals that biology is establishing faster than treatment disrupts it.

Related concepts

Biocide demand · Contact time · Extracellular polymeric substances (EPS)

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Part of The Blueprint of Water · 📏 measurement