A study of substrate removal in a microbial film reactor

An optimal operating strategy for fixed-bed bioreactors used in wastewater treatment

“…The Monod kinetic term, S/K S + S, represents the substrate limitation of a single substrate, S. Mass transfer limitations inside the biofilm result in decreasing microbial activity with increasing biofilm depth (Grasmick et al, 1979). It has been reported that the active biofilm length is on the order of 100 m (Harris and Hansford, 1976;Skowlund and Kirmse, 1989). The last term, B/K B + B, represents these diffusional limitations on the biomass growth and was used instead of complex calculation of an effectiveness factor.…”

Cold-climate nitrification on plastic media trickling filters

“…Flux-Limitation of Substrate Uptake Harris and Hansford (1976) demonstrated that the rate of sub strate uptake in trickling filters could be flux-limited by the sub strate, or by oxygen, or by both the substrate and oxygen simultane ously depending orl which reactant is depleted first within the biofilm depth as shown in Figure 15. Simultaneous substrate and oxygen flux limitation occurs over a narrow region of the normal range of bulk liquid substrate concentrations applied in fixed-film nitrification processes (Rittmann and Dovantzis, 1983).…”

“…Wastewater temperature effects Maier et al (1967), Harris and Hansford (1976), Benzie et al (1963), Antonie (1976), and others demonstrated that increasing the temperature of the wastewater feed causes greater substrate removal for the fixed-film process. This would be expected whether the process is flux-limited or metabolism-limited.…”

“…The substrate loading rate can be varied by changing either the hydraulic loading rate or the influent substrate concentration, or both. Harris and Hansford (1976), Sarner (1984), and Maier et al (1967 In addition, increasing the hydraulic loading rate increases the wetted surface area of the media providing more biofilm area for mass transport and utilization (Onda et al, 1968, andCrine, 1986). Crine (1986) predicted that an upper limit, less than complete wetting, exists for wetted area.…”

“…Typical oxygen and substrate concentration profiles in a biofilm. After Harris and Hansford (1976) Mass transfer in the liquid phase can be represented by Equation 6 when a single reactant is rate-limiting (Williamson and McCarty, 1976a). Parker and Merrill (1984) showed that BOD removal in a trickling filter plant at Mai mo followed zero-order kinetics in the upper zone and first-order kinetics in the lower zone, as predicted by the equa tions of Williamson and McCarty.…”