Case Study: TN Class 1A Upgrade with Sodium Acetate Dosing System Retrofit

A WWTP upgraded from Class 1B to Class 1A, with TN limit tightened from 20mg/L to 15mg/L. The original system lacked carbon source; the retrofit added a sodium acetate dosing unit in the anoxic zone with electromagnetic flowmeter and controls, setting dosing rate by effluent TN.

After retrofit, TN met standard stably with controlled chemical use. This is a typical scenario overview, showing that upgrade is not only about biological tank expansion—carbon source supplement and metering matter equally.