Evaluation of Different Methods for the Determination of Maximum Heterotrophic Growth Rates
Abstract:This work evaluated the most commonly used methods for determining maximum heterotrophic specific growth rates (μ m ) in batch reactors. Parallel batch experiments were conducted under various initial substrate-to-biomass (S 0/X 0) ratios and values of the solids retention time (c). The maximum specific growth rate, μ m , was determined simultaneously according to measurements of oxygen consumption (i.e., oxygen uptake rate, OUR) and volatile suspended solids (VSS) increase. The S 0/X 0 ratio was found to significantly influence μ m values. Under high S 0/X 0 ratios (= 20), fast-growing bacteria seemed to gain a competitive advantage resulting in higher μ m values than those obtained under low S 0/X 0 ratios (= 1.5). The OUR-based estimate of μ m (μ m (OUR)), under certain circumstances, is differentiated from μ m that is based on exponential bacterial growth (μ m(VSS)), and seems to be more a measure of substrate oxidation than a measure of bacterial growth. At high S 0/X 0 ratio and low c, μ m(OUR) was significantly higher than the μ m(VSS), indicating that considerable uncoupling between anabolism and catabolism was occurring under these conditions. Batch experiments conducted at high S 0/X 0 ratios seemed to be a more sensitive method for determining μ m values in the presence of an inhibitor than tests conducted at low S 0/X 0 ratios.
Document Type: Research Article
Publication date: November 1, 2003
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