OPTIMIZING BPR PLANT OPERATIONS FOR ACHIEVING SUSTAINABLE LOW EFFLUENT PHOSPHORUS

The radical PO43− is used by all life forms for storing energy in the form of high energy phosphate bonds and can thus not be destructed by bacteria in activated sludge. When effluent containing phosphorus is passed to a water body, algae blooms result through photo-synthesis. 1 kg of phosphorus as P has the potential to grow 138 kg COD in the form of algae that can rot and exert a high oxygen demand (Randall, 1992). Phosphorus can be removed only by either chemical precipitation or uptake in the cells of certain phosphorus accumulating organisms (PAO) occurring naturally in all activated sludge. Removal of the cells with the sludge in the final clarifiers will remove the phosphorus from the liquid stream. It is possible to reduce soluble (ortho) phosphorus to 0.03 mg/L by either chemical or biological means. The reliability of either process depends on the reliability of the mechanical plant and on the operational control. This paper will discuss operational needs for ensuring an effluent soluble phosphorus concentration of less than 0.1 mg/L. The removal of the soluble phosphorus to low levels must be accompanied by effective removal of the solids, which contain particulate phosphorus, in order to reduce the total phosphorus to the required levels of less than 0.1 mg/L.