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Floc Size (floc + size)
Selected AbstractsIndustrial wastewater treatment in a membrane bioreactor: A reviewENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2004B. Marrot Abstract This paper provides a detailed literature review of wastewater treatment in a membrane bioreactor process (MBR) with special focus on industrial wastewater treatment. MBR systems are compared with conventional wastewater treatment systems. The characteristics of the bioreactor treatment process (biomass concentration and floc size, organic and mass loading rates, etc.) are examined. The membrane separation of microorganisms from the treated wastewater is discussed in detail. Problems of membrane fouling and membrane washing and regeneration, linked to activated sludge characteristics, are examined. © 2004 American Institute of Chemical Engineers Environ Prog, 23: 59,68, 2004 [source] Phenotypic diversity of Flo protein family-mediated adhesion in Saccharomyces cerevisiaeFEMS YEAST RESEARCH, Issue 2 2009Sebastiaan E. Van Mulders Abstract The Saccharomyces cerevisiae genome encodes a Flo (flocculin) adhesin family responsible for cell,cell and cell,surface adherence. In commonly used laboratory strains, these FLO genes are transcriptionally silent, because of a nonsense mutation in the transcriptional activator FLO8, concealing the potential phenotypic diversity of fungal adhesion. Here, we analyse the distinct adhesion characteristics conferred by each of the five FLO genes in the S288C strain and compare these phenotypes with a strain containing a functional copy of FLO8. Our results show that four FLO genes confer flocculation, but with divergent characteristics such as binding strength, carbohydrate recognition and floc size. Adhesion to agar surfaces, on the other hand, largely depended on two adhesins, Flo10 and Flo11. Expression of any FLO gene caused a significant increase in cell wall hydrophobicity. Nevertheless, the capacity to adhere to plastic surfaces, which is believed to depend on hydrophobic interactions, differed strongly between the adhesins. Restoring Flo8 yielded both flocculation and cell,surface adherence, such as invasive growth, a phenotype not observed when any of the single FLO genes was overexpressed. Taken together, this study reveals how S. cerevisiae carries a small reservoir of FLO genes that allows cells to display a wide variety of adhesive properties. [source] Effect of polymerization method on structure and properties of cationic polyacrylamideJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Yinghua Shen Abstract Acrylamide and 2-(methacryloyloxy)ethyltrimethylammonium chloride (AM/MADQUAT) copolymers were synthesized by solution and inverse microemulsion polymerization using (NH4)2S2O8/NaHSO3 as redox initiator at the same feed mole ratio, and their microstructure, such as sequence distribution and composition distribution, was calculated from monomer reactivity ratios of different polymerization methods. The results show that charge distribution is more uniform for copolymer prepared in inverse microemulsion than that in solution, and copolymer composition distribution is close to unity, and maintains approximately at the feed ratio. Furthermore, the influence of the two structures of cationic polyacrylamides on kaolinite floc size and effective floc density, reduction of Zeta potential and floc compressive yield stress had been investigated at pH 7. The results show that the kaolinite floc size and effective floc density are strongly dependent upon copolymer microstructure, with greater floc size and lower effective floc density being observed for copolymer prepared in inverse microemulsion than for that in solution. Copolymer microstructure has a marked effect on the Zeta potential, whose reduction in the magnitude was much greater in the presence of copolymer prepared in inverse microemulsion than that in solution. Greater compressive yield stress was achieved for the strong flocs produced by copolymer prepared in inverse microemulsion than for the weak flocs produced by that in solution. The difference in flocs compressive yield stress may be attributed to flocs structure. Therefore, in this article, a correlation between the cationic polyacrylamide structure and flocculation property for kaolinite suspension was established. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Palm oil mill effluent pretreatment using Moringa oleifera seeds as an environmentally friendly coagulant: laboratory and pilot plant studiesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2006Subhash Bhatia Abstract This research paper covers the suitability of the coagulation,flocculation process using Moringa oleifera seeds after oil extraction as a natural and environmentally friendly coagulant for palm oil mill effluent treatment. The performance of M. oleifera coagulant was studied along with the flocculant KP 9650 in removal of suspended solids, organic components and in increasing the floc size. The optimum values of the operating parameters obtained from the laboratory jar test were applied in a pilot-scale treatment plant comprised of coagulation,flocculation and filtration processes. Pilot-scale pretreatment resulted in 99.7% suspended solids removal, 71.5% COD reduction, 68.2% BOD reduction, 100% oil and grease removal and 91% TKN removal. In pilot plant pretreatment, the percentage recovery of water was 83.3%, and 99.7% sludge was recovered after dewatering in a filter press. Copyright © 2006 Society of Chemical Industry [source] Influence of Cationic Starch Adsorption on Fiber FlocculationCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2009N. Zakraj Abstract The adsorption of cationic starch on hardwood fibers and its influence on flocculation were studied in relation to the dosage of cationic starch, the effect of shear forces and the presence of different concentrations of inorganic salts in the paper stock. Flocculation was monitored by means of a focused beam reflectance measurement (FBRM) probe. It was established that floc size at low shear rates depends on adsorption efficiency. At high shear forces, flocs were irreversibly decomposed despite the presence of a higher amount of adsorbed cationic starch on the fibers. Therefore, flocculation was produced by a bridging mechanism. The results show a significant effect of inorganic salts on the adsorption of cationic starch on fibers. Low concentrations of inorganic salts usually improved the adsorption process while higher concentrations (> 0.01 mol/L) reduced the adsorption and limited the flocculation process. [source] Analysis of the Activated Sludge Process in an MBR under Starvation ConditionsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2006M. Vukovic Abstract An aerobic membrane bioreactor (MBR) at complete biomass retention was studied over a period of time under starvation conditions. Kinetic parameters were determined in a no-feed batch test. The decay rate of activated sludge, kd = 0.05,d,1, was determined by tracking the decrease of MLSS. The ratio of MLVSS/MLSS was in the range 0.76,0.85. The pH values were between 7.02 and 8.23. As a function of different initial concentrations of MLSS, specific nitrification rates qN, decreased from 4.23 to 0.02,mg-N/(g,MLVSS,d) and specific biodegradation rates qb increased from 0.23 to 1.90,mg-COD/(g,MLVSS,d). From experimental data the kinetic constants for respiration, which followed Monod kinetics, were determined as qO2max = 9.8,mg-O2/(g,MLVSS,h), Kx = 2.9,g/dm3. Additionally, a linear correlation between MLSS and mean floc size was found to exist during the biodegradation process. [source] Ultrasonic treatment of waste activated sludgeENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2006Raf Dewil Abstract Activated sludge processes are key technologies to treat wastewater. These biological processes produce huge amounts of waste activated sludge (WAS), now commonly called biosolids. Mechanical, thermal, and/or chemical WAS conditioning techniques have been proposed to reduce the sludge burden. The ultrasonic treatment of WAS is quite novel. The present paper reports on extensive investigations using an ultrasonic treatment of WAS, to study its potential to meet one or all of four objectives: (1) reduce WAS quantities; (2) achieve a better dewaterability; (3) provoke a release of soluble chemical oxygen demand (COD) from the biosolids, preferably transformed into biodegradable organics; and (4) possibly destroy the filamentous microorganisms responsible for sludge bulking. Although meeting these objectives would help to solve the problems cited, the energy consumption could be a considerable drawback: the paper will thus assess whether all or some objectives are met, and at what operational cost. A literature survey defines the occurring phenomena (cavitation) and the important operation parameters [such as frequency, duration, specific energy input (SE)]. The experiments are carried out in a batch reactor of volume up to 2.3 L. The ultrasonic equipment consisted of a generator, a converter, and a sonotrode, supplied by Alpha Ultrasonics under the brand name of Telsonic. Three different kinds of sludge were tested, with different concentrations of dry solids (DS) between approximately 3.5 and 14 g DS/L WAS. Ultrasonic energy was introduced in a continuous manner (against possible pulsed operation). The major operational parameters studied include duration of the ultrasonic treatment and specific energy input. The applied frequency was set at 20 kHz. The release of COD from the WAS phase into the filtrate phase is a function of the specific energy input with yields of nearly 30% achievable at SE values of 30,000 kJ/kg DS. A major fraction of the COD is transformed into biodegradable organics (BOD). The reduction in DS fraction of the sludge is proportional to the COD release rates. Although the DS content is reduced, the dewaterability of the sludge is not improved. This reflects itself in increased filtration times during vacuum filtration and in increased values of the capillary suction time (CST). This more difficult dewaterability is the result of considerably reduced floc sizes, offering an extended surface area: more surface water is bound (CST increases) and the filterability decreases as a result of clogging of the cake. To reach the same dryness as for the untreated cake, the required dosage of polyelectrolyte is nearly doubled when the SE of the ultrasound treatment is increased from 7500 to 20,000 kJ/kg DS. The ultrasonic reduction of filamentous WAS organisms is not conclusive and very little effect is seen at low intensities and short treatment durations. Microscopic analysis of the WAS identified the dominant presence of Actynomyces. The release of soluble COD and BOD certainly merit further research. © 2006 American Institute of Chemical Engineers Environ Prog, 2006 [source] | ||||||||||