Phosphorus removal. A controllable process

A process for the efficient removal of phosphor- us from raw sewage has been developed. It consists of two treatment steps applied prior to primary clarification- conversion of soluble phosphate fraction to a suspended (insoluble) form, and coagulation of suspended phosphate and other solids. Laboratory and plant scale experience have indicated that the quantity of metals which must be added per unit of phosphorus removed from solution regresses as a function of the desired final ortho phosphate concentration. Automatic electronic process control instrumentation makes it possible to program the desired final concentration of phosphorus.