Measuring maximum specific growth rate and half saturation coefficient for activated sludge systems using a freeze concentration technique

Abstract

To measure the maximum specific growth rate (μ max) and the half saturation coefficient ( K s ), a simple respirometric technique was used, where differing volumes of concentrated wastewater were contacted with biomass in a respirometer and the response measured as a change in oxygen uptake rate (ΔOUR). The ΔOUR was then related to the growth rate, and a series of substrate concentration/growth rate relationships determined from which μ max and K s were calculated. A freeze concentration technique was developed to concentrate the wastewater. The concentration technique did not alter the response of the microorganisms to the wastewater. Maximum specific growth rates (μ max) and half saturation coefficients ( K s ) were found to vary between 1.3 and 1.9 d −1 and 1.5 and 3.2 mg l −1, respectively.