Initial-rate based method for estimating the maximum heterotrophic growth rate parameter (μHmax)

Currently, the method most used for measuring the maximum specific growth rate (μHmax) of heterotrophic biomass is by respirometry, using growth batch tests performed at high food/microorganism ratio. No other technique has been suggested, although the former approach was criticized for providing kinetic constants that could be unrepresentative of the original biomass. An alternative method (seed-increments) is proposed, which relies on measuring the initial rates of respiration (rO2_ini) at different seeding levels, in a single batch, and in the presence of excess readily biodegradable substrate (SS). The ASM1-based underlying equations were developed, which showed that μHmax could be estimated through the slope of the linear function of rO2_ini·(VWW + vML) vs vML (volume of mixed liquor inoculum); VWW represent the wastewater volume added. The procedure was tested, being easy to apply; the postulated linearity was constantly observed and the method is claimed to measure the characteristics of the biomass of interest.