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PubMed2003

The influence of key chemical constituents in activated sludge on surface and flocculating properties.

This paper examines the influence of the chemical constituents of activated sludge and extracted extracellular polymeric substances (EPS) on the surface properties, hydrophobicity, surface charge (SC) and flocculating ability (FA) of activated sludge flocs. Activated sludge samples from 7 different full-scale wastewater treatment plants were examined. Protein and humic substances were found to be the dominant polymeric compounds in the activated sludges and the extracted EPS, and they significantly affected the FA and surface properties, hydrophobicity and SC, of the sludge flocs. The polymeric compounds proteins, humic substances and carbohydrates in the sludge flocs and the extracted EPS contributed to the negative SC, but correlated negatively to the hydrophobicity of sludge flocs. The quantity of protein and carbohydrate within the sludge and the extracted EPS was correlated positively to the FA of the sludge flocs, while increased amounts of humic substances resulted in lower FA. In contrast, increased amounts of total extracted EPS had a negative correlation to FA. The results reveal that the quality and quantity of the polymeric compounds within the sludge flocs is more informative, with respect to understanding the mechanisms involved in flocculation, than if only the extracted EPS are considered. This is an important finding as it indicates that extracting EPS may be insufficient to characterise the EPS. This is due to the low extraction efficiency and difficulties involved in the separation of EPS from other organic compounds. Correlations were observed between the surface properties and FA of the sludge flocs. This confirms that the surface properties of the sludge flocs play an important role in the bioflocculation process but that also other interactions like polymer entanglement are important.

Flocculation↗

PubMed2001

Interactions between organic flocculant PAN-DCD and dyes.

Organic flocculant polyacrylonitrile-dicyandiamide (PAN-DCD) was characterized by IR, 1H NMR and 13C NMR spectra. Polar groups, such as triazine, carboxyl, amidine, carbonamide and non-polar groups, such as methylene were identified in the macromolecular chain of PAN-DCD. The flocculant effectively decolorized the examined dyes in their aqueous solutions under acid condition. By comparing the IR spectra of dyes with that of PAN-DCD and that of flocs formed, weak chemical interactions between amino in PAN-DCD side chain and sulfonic acid group in the dye molecules were observed through the formation of -NH3+ SO3(-)-, NH2+ SO3(-)- or/and =NH+ SO3(-)-. By using equilibrium dialysis technique, the hydrophobic interactions between PAN-DCD and the dyes in the binding process were also observed from the experimental results. The binding extent of PAN-DCD to dye KN-R was greater than that of MO. The addition of urea into the binding system of KN-R by PAN-DCD reduced the first binding constant K from 12.2 x 10(5) (without urea) to 3.48 x 10(5) (with urea).

Acrylic Resins↗

PubMed2003

Coagulation-flocculation pretreatment of sanitary landfill leachates.

Sanitary landfill leachates are considered as heavily polluted industrial wastewaters, presenting significant time and spatial variations of their physical-chemical parameters. Special care is required for their efficient treatment and disposal. The main aim of this work was to examine the application of coagulation-flocculation for the treatment of raw and partially stabilized leachates. Jar-test experiments were employed in order to determine the optimum conditions for the removal of organic matter and color, i.e. coagulant-flocculant combination, effective dosage and pH control. Ferric chloride, aluminium sulphate and lime were tested as conventional coagulants, whereas four commercial polyelectrolytes were co-examined: one anionic, two cationic and a non-ionic polymer. High chemical oxygen demand (COD) removal capacities (about 80%) were obtained during the addition of ferric chloride to the partially stabilized leachates, whereas low COD reductions (i.e. lower than 35%) were measured during the addition of coagulants in the raw samples. The addition of polyelectrolytes and pH adjustment in the alkaline region were found to affect slightly the removal of pollutants. The physico-chemical process may be used as a useful pretreatment step, especially for fresh leachates, prior to biological treatment, or as a post-treatment (polishing) step for partially stabilized leachates.

Alum Compounds↗

PubMed2003

Solids, organic load and nutrient concentration reductions in swine waste slurry using a polyacrylamide (PAM)-aided solids flocculation treatment.

Increased swine production results in concentration of wastes generated within a limited geographical area, which may lead to land application rates exceeding the local or regional assimilatory capacity. This may result in pollutant transfer through surface water or soil-groundwater systems, environmental degradation, and/or odor concerns. Existing swine waste pit storage and lagoon treatment technologies may be inadequate to store or treat waste prior to land application without these concerns resulting. Efficient swine waste solids separation may reduce environmental health concerns and generate a value-added bioresource (solids). This study evaluated the efficiency of a polyacrylamide (PAM) flocculant-aided solids separation treatment to reduce pollution indicator concentrations in raw (untreated) swine waste slurry. Swine waste slurry solids separation efficiency through gravity settling (sedimentation) was evaluated before and after the addition of a proprietary polymeric (PAM) flocculant. Results indicated that polymer amendments at concentrations of 62.5-750 mg/l improved slurry solids separation efficiency and significantly reduced concentrations of other associated aquatic pollution indicators in a majority of analyses conducted (33 of 50 total analyses conducted). Results also suggested that PAM-aided solids separation from swine waste slurry might facilitate further treatment and/or disposal and therefore reduce associated environmental degradation potential.

Acrylic Resins↗

PubMedDate not supplied

Continuous recombinant bacterial fermentations utilizing selective flocculation and recycle.

Selective recycle has successfully been used to maintain an unstable plasmid-bearing bacterial strain as dominant in a continuous reactor, whereas the culture reverts to 100% segregant cells when selective recycle is not used. The plasmid-bearing strain is slower growing and flocculent; however, when the cells lose their plasmid, the resulting segregant cells are nonflocculent and grow at a faster rate due to their decreased metabolic burden. Both types of cells exit a chemostat and enter an inclined settler where the flocculent plasmid-bearing cells are separated from the nonflocculent segregant cells by differential sedimentation. The underflow from the cell separator, which is enriched with plasmid-bearing cells, is recycled back to the chemostat, while the segregant cells are withdrawn off the top of the settler and discarded. The experimental results agree well with selective recycle reactor theory. On the basis of the theory, a criterion is presented that has been shown to successfully predict whether or not a selective recycle reactor can maintain a plasmid-bearing strain.

Biotechnology↗

PubMedDate not supplied

Selective flocculation and precipitation for the improvement of virus-like particle recovery from yeast homogenate.

The purification of an intracellular product from a complex mixture of contaminants after cell disruption is a common problem in processes downstream of fermentation systems. This is particularly challenging for the recovery of particulate (80 nm in diameter) multimeric protein products, named virus-like particles (VLPs), from cell debris and other intracellular components. Selective flocculation for debris removal followed by selective precipitation of the target protein can be used as a preclarification step to aid purification. In this paper, selective borax flocculation of cell debris in yeast homogenate, followed by selective poly(ethylene glycol) precipitation of VLPs are defined with a view to demonstrating their potential in aiding the initial clarification stages of the purification sequence. The translation from laboratory scale to pilot scale operation is addressed, demonstrating the challenge of scale-up of solid-liquid separation stages for biological particle processing.

Borates↗

PubMedDate not supplied

Use of at-line spectrophotometry for the rapid definition of pilot-scale flocculation processes.

Traditionally most downstream bioprocesses have been operated without real-time knowledge of product and key contaminants, yielding little confidence in their operation and the impact on subsequent operations. A rapid UV-vis spectral prediction technique has been successfully demonstrated for the at-line characterization of a large scale continuous flocculation process in terms of RNA, key protein contaminants, and cell debris. A comparison was made between the spectral predictions and retrospective wet chemical assays, and a highly linear correlation was obtained. The spectral analysis technique allowed for real-time system information, which was applied to control the flocculation process to maintain satisfactory process performance, even when subjected to given possible process disturbances.

Alcohol Dehydrogenase↗

PubMed2003

Sugar-based gemini surfactant with a vesicle-to-micelle transition at acidic pH and a reversible vesicle flocculation near neutral pH.

A sugar-based (reduced glucose) gemini surfactant forms vesicles in dilute aqueous solution near neutral pH. At lower pH, there is a vesicle-to-micelle transition within a narrow pH region (pH 6.0-5.6). The vesicles are transformed into large cylindrical micelles that in turn are transformed into small globular micelles at even lower pH. In the vesicular pH region, the vesicles are positively charged at pH < 7 and exhibit a good colloidal stability. However, close to pH 7, the vesicles become unstable and rapidly flocculate and eventually sediment out from the solution. We find that the flocculation correlates with low vesicle zeta-potentials and the behavior is thus well predicted by the classical DLVO theory of colloidal stability. Surprisingly, we find that the vesicles are easily redispersed by increasing the pH to above pH 7.5. We show that this is due to a vesicle surface charge reversal resulting in negatively charged vesicles at pH > 7.1. Adsorption, or binding, of hydroxide ions to the vesicular surface is likely the cause for the charge reversal, and a hydroxide ion binding constant is calculated using a Poisson-Boltzmann model.

Cross-Linking Reagents↗

PubMed2002

Removal of dissolved organic matter from water by adsorption-flocculation using organobentonite.

Bentonite modified with short chain cationic surfactant might be the basis of a new approach to removing dissolved organic matter (DOM) from water. The treatment process involves dispersing bentonite to the DOM-containing water and then adding a small cationic surfactant to result in flocs which are agglomerates of organobentonite and bound DOM. The flocs are then removed from the solution by sedimentation. Experimental results indicate that Benzyltrimethylammonium bromide (BTMA)-bentonite displays a high affinity for DOM, most likely due to aromatic groups in the DOM molecule interacting with the benzene ring in the BTMA ion through increased pi-pi type interactions. Under appropriate operating conditions, 75% DOM removal and nearly 100% bentonite recovery could be achieved by the adsorption-flocculation process using BTMA-bentonite. Additionally, the rapid adsorption kinetics made adsorption-flocculation with BTMA-bentonite attractive for continuous treatment of large volumes of raw water. The bentonite may function as a recyclable surfactant medium for the adsorption and subsequent combustion of organic pollutants.

Adsorption↗

PubMed2004

Detection of Cryptosporidium oocysts and Giardia cysts in swimming pool filter backwash water concentrates by flocculation and immunomagnetic separation.

The purpose of the present study was to evaluate techniques for detection of Giardia cysts and Cryptosporidium oocysts in swimming pool filter backwash water. Calcium carbonate flocculation was used for water samples concentration of 1 l filter backwash water samples. Immunomagnetic separation (IMS) was used for separation of cysts and oocysts from detrital material. Cysts and oocysts were then detected using direct immunofluorescence. ColorSeed C&G was used as an internal standard. Recoveries were examined at several processing points. Highest recoveries (23% Cryptosporidium, 18% Giardia) were obtained using lower filter backwash volumes, greater IMS volumes, and addition of Tween20 to backwash samples prior to processing. The combination of CaCO3 flocculation, IMS and direct immunofluorescence was found to be an effective tool for the detection and quantification of Giardia spp. and Cryptosporidium spp. in filter backwash water samples.

Animals↗

PubMed1994

A surface lectin associated with flocculation in brewing strains of Saccharomyces cerevisiae.

A cell-wall-surface protein purified from the cells of Saccharomyces cerevisiae NCYC 227 was found to be involved in the non-sexual flocculation of this yeast. This 13 kDa protein was found to bind specifically to mannose. The protein bound to mannans isolated from yeast as well as in situ to intact cells, but only in the presence of calcium ions. The protein, a mannoprotein, formed aggregates as revealed in SDS-PAGE. Urea and higher temperatures prevented protein aggregation, suggesting that the flocculation of S. cerevisiae is primarily due to hydrogen bonding between mannan and protein.

Antibodies, Fungal↗

PubMed1999

Flocculation of hyphae is associated with a deletion in the putative CaHK1 two-component histidine kinase gene from Candida albicans.

In Candida albicans, three putative histidine kinase genes have been described thus far, including CaSLN1, CaNIK1/COS1 and CaHK1. The encoded proteins for C. albicans, CaSln1p and CaNik1p, which are similar to Sln1p from Saccharomyces cerevisiae and Nik-1 from Neurospora crassa, seem to function in osmoregulation and morphogenesis, respectively. Recently, the isolation of CaHK1, a putative histidine kinase gene from C. albicans has been reported. In addition to the histidine and aspartyl domains located at its C-terminus as previously described, it is shown here that the N-terminal domain of Cahk1p contains a P-loop motif and a sequence which shows significant homology with the seven C-terminal domains of serine/threonine kinases. The Ser/Thr-homologous domains of Cahk1p could, in fact, correspond to its sensor sequence. CaHK1 has been mapped to chromosome 2 and gene deletion studies were undertaken to understand its function. Deltacahk1 mutants are phenotypically different from any other histidine kinase mutants thus far described either in C. albicans or in any other yeast or filamentous fungus. This study demonstrates that deltacahk1 mutants flocculate extensively in a gene-dosage-dependent manner under conditions which induce germ-tube formation, such as growth in medium 199 (pH 7.5). The flocculation occurs by an interaction along the hyphal surfaces, probably because of the altered expression of one or more hyphal-cell-surface components in the deltacahk1 mutants. These results indicate that CaHK1 could be involved in regulating their expression.

Amino Acid Sequence↗

PubMedDate not supplied

Controlling harmful algal blooms through clay flocculation.

The potential use of clays to control harmful algal blooms (HABs) has been explored in East Asia, Australia, the United States, and Sweden. In Japan and South Korea, minerals such as montmorillonite, kaolinite, and yellow loess, have already been used in the field effectively, to protect fish mariculture from Cochlodinium spp. and other blooms. Cell removal occurs through the flocculation of algal and mineral particles, leading to the formation of larger aggregates (i.e. marine snow), which rapidly settle and further entrain cells during their descent. In the U.S., several clays and clay-rich sediments have shown high removal abilities (e.g. > 80% cell removal efficiency) against Karenia brevis, Heterosigma akashiwo, Pfiesteria piscicida and Aureococcus anophagefferens. In some cases, the removal ability of certain clays was further enhanced with chemical flocculants, such as polyaluminum chloride (PAC), to increase their adhesiveness. However, cell removal was also affected by bloom concentration, salinity, and mixing. Cell mortality was observed after clay addition, and increased with increasing clay concentration, and prolonged exposure to clays in the settled layer. Mesocosm, field enclosure, and flume experiments were also conducted to address cell removal with increasing scale and flow, water-column impacts, and the possible benthic effects from clay addition. Results from these studies will be presented, especially those in regards to water quality, seawater chemistry, bottom erodibility and faunal impacts in the benthos. At this time, clay dispersal continues to be a promising method for controlling HABs and mitigating their impacts based on existing information and experimental data.

Aluminum Hydroxide↗

PubMed2006

Control by sugar of Saccharomyces cerevisiae flocculation for industrial ethanol production.

The goal of this study was to develop conditional flocculant yeasts for use in the alcohol fermentation industry. Promoters were constructed to completely repress gene transcription in the presence of sugar and to support strong expression after the exhaustion of this compound. A fusion of regulatory regions of the ADH2 promoter with the FLO5 core promoter was constructed to regulate the FLO5 gene. This construct was inserted into multicopy plasmids and transformed into laboratory strains of Saccharomyces cerevisiae, whereby the transformed cells were selected by sedimentation from the bulk medium after sugar exhaustion, without decreasing ethanol production. The ADH2-FLO5 region was converted into an integrative cassette to disrupt the CAN1 gene in industrial yeast strains. Transformed cells became resistant to canavanine and demonstrated conditional flocculation. Although ethanol production was significantly decreased in the industrial transformants, this development reveals a promising technology for the substitution of centrifugation in industrial ethanol production.

Alcohol Dehydrogenase↗

PubMed2006

The mechanism by which overexpression of Gts1p induces flocculation in a FLO8-inactive strain of the yeast Saccharomyces cerevisiae.

GTS1 induces flocculation when overexpressed in the Saccharomyces cerevisiae strain W303-1A, which carries a mutant FLO8, the activator of flocculin genes. Herein, we report that the GTS1-induced flocculation was flocculin-dependent in nature and was caused by expression of the major flocculin Flo1p. Gts1p bound to the repressor Sfl1p, and their interaction at the transcriptional level was shown by reporter gene assays using the FLO1 promoter, suggesting that Gts1p induces the expression of FLO1 by inhibiting Sfl1p. Furthermore, the Q-rich domain with the preceding 18 amino acids of Gts1p bound mediators for RNA polymerase II.

Artificial Gene Fusion↗

PubMed2000

Phosphorylation of the GTS1 gene product of the yeast Saccharomyces cerevisiae and its effect on heat tolerance and flocculation.

The GTS1 gene from the yeast Saccharomyces cerevisiae showed pleiotropic effects on yeast phenotypes, including an increase of heat tolerance in stationary-phase cells and an induction of flocculation. Here, we found that the GTS1 product, Gts1p, was partially phosphorylated at some serine residue(s) in cells grown on glucose. Studies using mutants of protein kinase A (PKA) and CDC25, the Ras-GTP exchange activator, showed that PKA positively regulated the phosphorylation level of Gts1p. Overexpression of Gts1p in a mutant with attenuated PKA activity did not show any increase of heat tolerance and partially decreased flocculation inducibility, suggesting that phosphorylation of Gts1p is required for induction of these phenomena.

Cyclic AMP-Dependent Protein Kinases↗

PubMed1994

Continuous ethanol production by flocculating yeast in the fluidized bed bioreactor.

Continuous fermentation by a highly flocculant strain of the yeast Saccharomyces cerevisiae was carried out in a tower fluidized-bed bioreactor. The synthetic and molasses media with a total sugar concentration of 17% (w/v) were used for fermentation. Different dilution rates were tested. Stable cell densities of 50 kg m-3 (dry weight) were maintained for all dilution rates. The ethanol productivity was increasing linearly with dilution rates up to 15-20 kg m-3 h-1. Aeration of the culture stabilized flocculating activity and viability of yeast and also permitted long-term operation of the bioreactor.

Culture Media↗

PubMed1983

Mitochondrial flocculent densities in ischemia. Digestion experiments.

Flocculent densities appear in the mitochondrial matrix during ischemic damage. These densities were examined in kidneys after 2 hours of autolysis. The samples were embedded in water-miscible glycol methacrylate (GMA). Ultrathin sections on copper grids were digested with pronase, trypsin, ribonuclease T1, various phospholipases (A2, C, D), lipase, and desoxyribonuclease I. For statistical analysis the mean number (+/- SD) of densities per mitochondrion was determined in tubular epithelial cells. A statistically significant (p less than 0.001) decrease in the number of densities was apparent after treatment with pronase (75.5%) of the densities digested completely) and with trypsin (43.3% of the densities digested completely). Digestion with other enzymes did not significantly decrease the number of densities. This study provides quantitative support for the hypothesis that flocculent densities are composed of proteins, most probably mitochondrial membrane proteins or matrix proteins. The results do not support the hypothesis that RNA, neutral lipids, phospholipids or DNA are major constituents of these structures.

Animals↗