Kinetics and Mechanisms of Low-Concentration - Multisubstrate Utilization by Biofilms (Soluble Microbial Products, Steady-State Secondary, Oligotrophic Bacteria, Biodegradation of Trace Organics, Modeling)
Two major studies employed laboratory-scale completely mixed biofilm reactors and naturally grown oligotrophs. The first study addressed formation of soluble microbial products (SMP) when the organic concentration was low and biofilms were the predominant form of biological activity. The experimental results indicated that the majority of effluents soluble organic carbon (SOC) was SMP, while only a small fraction of the effluent SOC was the residual original substrate. Intermediate microbial products (IMP), which were produced directly from substrate metabolism, were more important than metabolic end products (MEP), which were produced by basic metabolism. The steady-state concentrations of the effluent SMP and SOC were directly proportional to the influent substrate concentrations. An extended steady-state biofilm model was developed by incorporating into the existing steady-state biofilm model an SMP-formation model based on production of the two types of SMP (i.e., IMP and MEP). The model described successfully the experimental substrate utilization, SMP formation, and the removal of total soluble organic matter (SOC). Application of the model predicted that the best treatment efficiency in terms of effluent SOC can be achieved with an optimum biofilm thickness, which is controlled by the shear loss rate. The second part of the research investigated the kinetics of substrate utilization in a multisubstrate system. It was hypothesized that, when more than one energy and carbon source is present in the feed, an individual substrate is utilized not only by the biomass made by its own utilization, but also by the biomass made from other substrates. To test the hypothesis, three series of experiments were conducted using phenol and other organic materials to form multisubstrate systems. In each case, the utilization rate of a single organic compound was faster in a multisubstrate system than in a single substrate system. However, increases in utilization rate of the target compound was small when the other compounds were relatively refractory (e.g., humic substances) or when the biofilm already was deep with respect to the target compound. Steady-state secondary utilization modeling showed that satisfying a total S(,min) concentration for a multisubstrate system was the necessary condition for having biofilm growth and utilization of all the substrates present in the feed system.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign