ABSTRACT
This chapter reports the field data which supports the theoretical development and definition of the Sludge Quality Index (SQI). Two traditional solids flux models along with an empirical Sludge Volume Index model will be investigated to obtain solids flux curves and the associated Sludge Quality Indexes. To develop a meaningful control algorithm for a step-feed process, a reliable method is needed to evaluate sludge settling characteristics. Solids flux analysis involves measuring sludge settleability which leads to a sludge settling constraint. Initial settling curves are obtained by conducting settleability tests on several concentrations of a waste activated sludge. This data can be used to construct the solids flux curve either graphically or with mathematical modeling. Calculating an SQI provides a single quantitative variable which describes the sludge settling character by combining the effects of the shape and position of the solids flux settling curve. A step-feed aeration system provides an additional control variable to the activated sludge process.
