Nitritation performance and biofilm development of co- and counter-diffusion biofilm reactors: Modeling and experimental comparison

Department of Environmental Engineering, Technical University of Denmark, Miljoevej, Building 113, DK-2800 Kgs. Lyngby, Denmark.
Water Research (Impact Factor: 5.53). 03/2009; 43(10):2699-709. DOI: 10.1016/j.watres.2009.03.017
Source: PubMed


A comparative study was conducted on the start-up performance and biofilm development in two different biofilm reactors with aim of obtaining partial nitritation. The reactors were both operated under oxygen limited conditions, but differed in geometry. While substrates (O2, NH3) co-diffused in one geometry, they counter-diffused in the other. Mathematical simulations of these two geometries were implemented in two 1-D multispecies biofilm models using the AQUASIM software. Sensitivity analysis results showed that the oxygen mass transfer coefficient (Ki) and maximum specific growth rate of ammonia-oxidizing (AOB) and nitrite-oxidizing bacteria (NOB) were the determinant parameters in nitrogen conversion simulations. The modeling simulations demonstrated that Ki had stronger effects on nitrogen conversion at lower (0-10 m d(-1)) than at the higher values (>10 m d(-1)). The experimental results showed that the counter-diffusion biofilms developed faster and attained a larger maximum biofilm thickness than the co-diffusion biofilms. Under oxygen limited condition (DO<0.1 mg L(-1)) and high pH (8.0-8.3), nitrite accumulation was triggered more significantly in co-diffusion than counter-diffusion biofilms by increasing the applied ammonia loading from 0.21 to 0.78 g NH4+-NL(-1) d(-1). The co- and counter-diffusion biofilms displayed very different spatial structures and population distributions after 120 days of operation. AOB were dominant throughout the biofilm depth in co-diffusion biofilms, while the counter-diffusion biofilms presented a stratified structure with an abundance of AOB and NOB at the base and putative heterotrophs at the surface of the biofilm, respectively.

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    • "Biofilms in HfMBR are immobilized on the exterior (convex) surface of hollow polydimethylsiloxane (PDMS) membranes. For aerobic HfMBR, oxygen diffuses across the semi-permeable PDMS fiber wall to the biofilm from the attachment site, and also from the bulk liquid phase into the biofilm (known as counter-diffusion) (Wang et al., 2009). HfMBR have demonstrated improved gas transfer, high areal conversion rates (see Rector et al., 2006 for description of areal conversion rates), low energy demand, low maintenance, and reduced volatile stripping (Casey et al., 1999, 2000; Cote et al., 1989) relative to traditional co-diffusion biofilm reactors. "
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    Biotechnology and Bioengineering 02/2013; 110(2). DOI:10.1002/bit.24631 · 4.13 Impact Factor
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    • "They remain free of clogging or wetting problems and their diffusive resistance can be overcome by higher intramembrane pressures . The relatively high permeability of silicone has made it a popular dense membrane choice (Casey et al., 1999; McLamore et al., 2007; Wang et al., 2009), but silicone is only available in outer diameters on the order of millimeters, which limits the specific surface area. Membranes have been specifically designed for gas transfer applications, such as the degassing of water or the oxygenation of blood, but until of late, little research had been carried out on membranes tailored specifically to MBfR applications. "
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    • "In this reactor the biofilm is naturally immobilized on an substrate permeable membrane and counter-or (regarding the conventional biofilms where both the dissolved oxygen and substrates diffuse in the same direction) co-diffusion of oxygen and nutrients (organic component, ammonia, etc.) can take place. Several investigators have reported performance advantages of membraneaerated biofilm reactors for wastewater treatment (Aryal et al., 2009; Monthlagh et al., 2006) oxidation of organic components (Casey et al., 2000; Gross et al., 2007), nitrification (Rittman & Manem, 1992; Wang et al., 2009) etc. The structure of the biofilm can be homogeneous or heterogeneous depending on the substrate concentration (Piciorenau et al., 2001) because the growth rate of microorganisms depends strongly on the substrate concentration. "

    Mass Transfer in Multiphase Systems and its Applications, 02/2011; , ISBN: 978-953-307-215-9
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