Article

Side effects of flux enhancing chemicals in membrane bioreactors (MBRS): study on their biological toxicity and their residual fouling propensity

Department of Chemical Engineering, University of Technology Berlin, Strasse des 17. Juni 136, MA 5-7, 10623, Berlin, Germany.
Water Science & Technology (Impact Factor: 1.11). 02/2008; 57(1):117-23. DOI: 10.2166/wst.2008.660
Source: PubMed

ABSTRACT

Soluble and colloidal materials like soluble microbial products (SMP) or extracellular polymeric substances (EPS) are considered to be major foulants in membrane bioreactors (MBRs). Removing these fouling causing substances is thus thought to reduce the fouling of the membrane in general. In addition to traditional strategies for fouling prevention which mostly try to remedy the effects of fouling by air scour, etc., the new and promising method of adding chemicals is being investigated here. Previous tests with 30 different substances have shown that several of these reduce SMP concentration in the supernatant and enhance filtration. Nevertheless, additive dosing might have unknown side effects in filtration systems. Results presented in this study indicate that these additives may themselves cause severe fouling on different membranes if they remain unbound in the liquid phase. Therefore, the thorough control of the dosing rate of these chemicals will be of paramount importance in full scale applications. Biological toxicity of additives was measured in terms of respiration. OUR tests did not show inhibiting effects for most additives. Chitosan even showed an enhanced OUR due to biodegradability. Oxygen transfer could be enhanced for 25% with the addition of a polymer.

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    • "velocity of the fluid (m s −1 ) G external channel subdomain R i internal channel subdomain D thickness of the fluid envelope (m) K intrinsic permeability (m 2 ) w membrane or porous subdomain P pressure (bar) R ext external radius (m) R int internal radius (m) P transmembrane pressure (Pa or bar) interfacial tension (N m −1 ) r radius of cylindrical pore (m) ϕ packing density ∈ porosity of the porous medium eff effective viscosity (Pa s) dynamic fluid viscosity (Pa s) of biological activity, high quality effluent free of bacteria and pathogens, smaller plant size, and higher organic loading rates [5] [6] [7]. MBR combines both biological treatment of effluent and clarification by submerged low pressure polymeric ultrafiltration (UF) membranes. "
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    ABSTRACT: Submerged membrane bioreactor (SMBR) is a relatively advanced technology for waste water treatment that involves integrated aerobic and anaerobic biological processes with membrane filtration. In the present investigation, hydrophobic polyvinylidene fluoride (PVDF) and hydrophilic polyacrylonitrile (PAN) hollow fiber (HF) membranes were tested in an indigenously fabricated SMBR for dairy effluent treatment under aerobic conditions using mixed microbial consortia. Effect of operating parameters such as suction pressure, degree of aeration and trans-membrane pressure (TMP) on membrane performance in terms of flux, rejection of turbidity, BOD and COD besides fouling characteristics was investigated. The observed optimum permeabilities of PVDF and PAN HF membranes were approximately 108 and 115LMHbar(-1) with high extent of impurity removal. The rejection of COD was found to be 93% for PVDF and 91% for PAN HF membranes whereas corresponding rejection of BOD was observed to be 92% and 86%. A two-dimensional comprehensive model was developed to predict the hydrodynamic profile inside the module. Regression analysis revealed that the simulation results agreed well with experimental data.
    Full-text · Article · Apr 2014 · Journal of hazardous materials
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    • "velocity of the fluid (m s −1 ) G external channel subdomain R i internal channel subdomain D thickness of the fluid envelope (m) K intrinsic permeability (m 2 ) w membrane or porous subdomain P pressure (bar) R ext external radius (m) R int internal radius (m) P transmembrane pressure (Pa or bar) interfacial tension (N m −1 ) r radius of cylindrical pore (m) ϕ packing density ∈ porosity of the porous medium eff effective viscosity (Pa s) dynamic fluid viscosity (Pa s) of biological activity, high quality effluent free of bacteria and pathogens, smaller plant size, and higher organic loading rates [5] [6] [7]. MBR combines both biological treatment of effluent and clarification by submerged low pressure polymeric ultrafiltration (UF) membranes. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Submerged membrane bioreactor (SMBR) is a relatively advanced technology for waste water treatment that involves integrated aerobic and anaerobic biological processes with membrane filtration. In the present investigation, hydrophobic polyvinylidene fluoride (PVDF) and hydrophilic polyacrylonitrile (PAN) hollow fiber (HF) membranes were tested in an indigenously fabricated SMBR for dairy effluent treatment under aerobic conditions using mixed microbial consortia. Effect of operating parameters such as suction pressure, degree of aeration and trans-membrane pressure (TMP) on membrane performance in terms of flux, rejection of turbidity, BOD and COD besides fouling characteristics was investigated. The observed optimum permeabilities of PVDF and PAN HF membranes were approximately 108 and 115 LMH bar−1 with high extent of impurity removal. The rejection of COD was found to be 93% for PVDF and 91% for PAN HF membranes whereas corresponding rejection of BOD was observed to be 92% and 86%. A two-dimensional comprehensive model was developed to predict the hydrodynamic profile inside the module. Regression analysis revealed that the simulation results agreed well with experimental data.
    Full-text · Article · Jan 2014 · Journal of Hazardous Materials
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    • "Yoon et al., (2005) have reported that the addition of cationic polymer in a sludge was able to entrap macromolecular compounds within the flocs and to enhance the permeate flux. In a same way Lee et al. (2007), Hwang et al. (2007), Ji et al. (2008) and Iversen et al. (2008, 2009a,b) have demonstrated that the addition of cationic polymer or coagulant led to bigger and more porous flocs. Moreover as demonstrated by Lesage et al. (2005), Guo et al. (2006) and Ying and Ping (2006), the addition of adsorbent fine particles (activated carbon, zeolithe) in MBR allows to enhance filtration performances and to delay fouling (Remy et al., 2009; Kim and Lee, 2003; Fang et al., 2006; Park et al., 1999). "
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    ABSTRACT: For membrane bioreactors (MBR) applied to wastewater treatment membrane fouling is still the prevalent issue. The main limiting phenomena related to fouling is a sudden jump of the transmembrane pressure (TMP) often attributed to the collapse of the fouling layer. Among existing techniques to avoid or to delay this collapse, the addition of active particles membrane fouling reducers (polymer, resins, powdered activated carbon (PAC), zeolithe...) showed promising results. Thus the main objective of this work is to determine if fouling can be reduced by inclusion of inert particles (500 nm and inert compared to other fouling reducers) and which is the impact on filtration performances of the structuring of the fouling. Those particles were chosen for their different surface properties and their capability to form well structured layer. Results, obtained at constant pressure in dead end mode, show that the presence of particles changes foulant deposition and induces non-compressible fouling (in the range of 0.5-1 bar) and higher rejection values compared to filtration done on supernatant alone. Indeed dead end filtration tests show that whatever interactions between biofluid and particles, the addition of particles leads to better filtration performances (in terms of rejection, and fouling layer compressibility). Moreover results confirm the important role played by macromolecular compounds, during supernatant filtration, creating highly compressible and reversible fouling. In conclusion, this study done at lab-scale suggests the potential benefit to engineer fouling structure to control or to delay the collapse of the fouling layer. Finally this study offers the opportunities to enlarge the choice of membrane fouling reducers by taking into consideration their ability to form more consistent fouling (i.e. rigid, structured fouling).
    Full-text · Article · Feb 2011 · Water Research
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