The empirical parameters for the sludge settling velocity (Vo, m/hr) and sludge settling rate constant (k, m3/kg) in a secondary clarifier are developed using large column settling tests performed at a range of initial solid concentrations. The procedure used to develop these parameters requires specialized equipment, is time consuming, and not very practical for a daily operations of a treatment facility. Consequently the relationship between these parameters and a simple sludge volume index (SVI) test have been developed, including Daigger and Roper (1985) and Wahlberg and Keinath (1988). These correlations were developed for municipal facilities with varied industrial contributions. These correlations have equipped operators with a tool to optimize secondary clarifier operations with minimal effort. The purpose of this paper is to develop a similar relationship for refinery activated sludge wastewater treatment facilities. Such a tool would allow refinery treatment plant operators to optimize secondary clarifier operations and, in some cases forgo the capital expense of additional clarifiers.