STATE POINT ANALYSIS — A NEGLECTED OPERATIONAL TOOL FOR ACTIVATED SLUDGE SYSTEMS

The State Point Analysis (SPA) technique is a modified version of solids flux theory that offers significant advantages for evaluating solids interactions in activated sludge systems. In spite of this, its use has not permeated into the operations field; one of the reasons being the labor-intensive nature of the testing required to update flux curves to keep up with variations in sludge settleability. This paper suggests an alternative approach for generating plant-specific flux curves that could be extrapolated to cover a range of sludge settleabilities without requiring repetitive testing. One of the aims of this paper is to re-emphasize the potential benefits of the SPA and to encourage its use in treatment plants as a rational basis for making solids-inventory control decisions. Using examples from the 88-million gallon per day (mgd) Clark County Sanitation District (CCSD) wastewater treatment plant in Las Vegas, Nevada, the paper will illustrate how a computerized model of the SPA can be used to establish the operational limits of the activated sludge system under different scenarios and to investigate remedial options for different kinds of system failures. This paper will also show how the SPA model can be used to investigate the impact of operational changes on a desktop level before the changes are actually made to plant operation.