RIO
SRT Calculator
Sludge age & wasting
Today
Target sludge age
days
Set your WAS pumps to
gpm
Rounded to the nearest 25 gpm. Move toward it gradually — don't chase it in one big jump.
Sludge age status
as of
7-day average
d
trust this for control
Today's SRT
d
one day bounces around
·target d
Readings for
Advanced — count clarifier blanket solids (MCRT)
Off = SRT (aeration only). Most operators leave this off for daily control.
14-day sludge age trend
SRT target
Recent days
DateSRTWAS gpm
Method: M. Gaugler, "Determining the Proper Wasting Rate of Activated Sludge," OWEA 2024. · Numbers are only as good as the readings behind them — eyeball odd samples before acting.