The real value of this control procedure is that is responds to pratically all loading, process balance and sludge quality characteristics to reveal the clarifier sludge flow rate that will best satisfy the net requirement of all these interacting variables. The calculated demand mixed liquor sludge concentrations and quality, sludge solids distribution between the aeration tanks and the final clarifiers, and the waste water flow rates. On a progressive long-term basis it also responds to changes in organic loadings and the interrelated sludge-wasting rates. This control procedure satisfies the dynamic requirements of the total process.