Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Flocculation Tests”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed2002

Examination of three theories for mechanisms of cation-induced bioflocculation.

Research from different studies has been used to support three different theories pertaining to the role of cations in bioflocculation. These theories are the alginate theory. Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory, and divalent cation bridging (DCB) theory. The objectives of this research were to examine the role of cations in bioflocculation to determine which theory, if any, best describes cation induced bioflocculation. Experiments were performed using laboratory scale activated sludge systems with bactopeptone as a feed. The feed was supplemented with either calcium, magnesium, or sodium at increasing concentrations. Floc properties were analyzed in each reactor during steady state periods. The addition of calcium or magnesium to the feed individually resulted in improvements in SVI, CST, SRF, cake solids and floc strength and each of these divalent cations produced similar results. The addition of sodium to the feed resulted in a deterioration in floc properties relative to a control reactor. Analysis of these results suggest that the DCB theory best explains the role of cations. The discrepancies between different studies were examined and are thought to be a result of different experimental procedures in different studies and in particular the use of short-term batch tests versus continuous flow reactor studies. In addition, the implications of DCB theory suggests that activated sludge systems should attempt to lower the ratio of monovalent to divalent cations to improve floc properties and treatment performance.

Biodegradation, Environmental↗
PubMed2003

The vortex concentrator for suspended solids treatment.

The use of vortex concentrators is becoming increasingly popular for suspended solids reduction in combined sewer overflows and stormwater. This study is a laboratory investigation of the use of vortex concentrators to reduce the solids concentration of synthesized stormwater. The synthesized stormwater was made with water and addition of particles; sand, granular activated carbon, and sewer sediments. The vortex concentrator was made of acryl resin 300 mm in diameter. To determine the efficiency for various influent suspended solids (SS) concentrations, tests were performed with different SS concentrations. The samples were taken simultaneously at the influent storage tank and effluent tank, and measured SS concentrations. The range of surface loading rates were 120 to 850 m3/m2/day, and influent SS concentrations were varied from 300 to 5,000 mg/L. To determine the optimum coagulant dosage, jar tests were conducted with coagulants such as PAM and PAC. It was found that optimum coagulant and its dosage were PAM and 2 mg/L. The overall SS removal efficiency of the vortex concentrator for typical stormwater was estimated at about 65%. With an increase of SS concentration, the removal efficiency was increased. Since the SS concentration of stormwater was higher than 1,000 mg/L, the removal efficiency of the vortex concentrator for stormwater could be estimated to be 65-70%. The SS removal efficiency was increased with an increase of retention time, and the optimum retention time was 0.15-1.0 minutes. With an increase of the foul to overflow Q(F)/Q(o), a key parameter for vortex concentrator operation, the removal efficiency was increased. An alternative solution to improve treatment efficiency might be to set a follow-up retention basin. Based on a series of settling tests on the treated overflow water from the vortex concentrator, 5 to 10 minutes hydraulic retention time in a follow-up retention basin would substantially improve the results.

Carbon↗
PubMed2003

A review of the 1996-98 nonpathogenic H7N2 avian influenza outbreak in Pennsylvania.

The nonpathogenic avian influenza (AI) outbreak in Pennsylvania began in December 1996 when there was a trace back from a New York live bird market to a dealer's flock. A total of 18 commercial layer flocks, two commercial layer pullet flocks, and a commercial meat turkey flock were diagnosed with nonpathogenic AI (H7N2) viral infection with an economic loss estimated at between 3 and 4 million dollars. Clinical histories of flocks infected with the disease included respiratory disease, elevated morbidity and mortality throughout the house, egg production drops, depression, and lethargy. A unique gross lesion in the commercial layers was a severe, transmural oviduct edema with white to gray flocculent purulent material in the lumen. Layer flocks on two separate premises were quarantined but permitted to remain in the facilities until cessation of virus shed was determined through virus isolation. Several months later, clinical AI appeared again in these flocks. It is not known whether the recurrence of disease in these cases is due to persistence of the organism in the birds or the environment. In addition to serologic testing and virologic testing by chicken embryo inoculation, an antigen capture enzyme immunoassay was evaluated as a diagnostic tool for AI. Research projects related to disinfection, burial pits, and geographical system technology were developed because of questions raised concerning transmission, diagnosis, and control of nonpathogenic AI (H7N2).

Animals↗
PubMed2001

Quantification of the bond energy of bacteria attached to activated sludge floc surfaces.

The great majority of activated sludge bacteria exist incorporated in flocs. The increase in dispersed bacteria when exposed to increasing turbulent shear rates has been successfully modelled by a model assuming that the adhesion and erosion of cells may be considered in analogy to ordinary chemical phase transitions. By this adhesion-erosion model (AE-model), an "enthalpy" of cell adhesion can be estimated, and this value in turn determines the range of shear rates in which erosion of cells predominates. Application of the model has indicated that only a mass fraction less than ca. 6-17% may be released from activated sludge, even when exposed to a severe turbulent environment, i.e. only a small fraction of the flocs is dispersible by means of erosion by turbulence. The shear sensitivity and the dispersible floc fraction were found to depend on the floc composition. A net decrease in the floc EPS content during anaerobic sludge stabilisation causes a dramatic increase in the dispersed fraction, indicating the important role of EPS for the floc strength. It was found also that activated sludge cells do not reflocculate completely after exposure to high shear rates. This may be an indication that the cohesion energy of bacteria growing in colonies is greater than the energy of the more stochastic adhesion of dispersed cells to floc surfaces. It could also be another indicator of the importance of entanglement forces, which do not reform instantly, once broken. When the bond strength of cell attachment to sludge surfaces is altered by changes in the chemical environment, this may cause a change in the dispersible floc fraction as well as a change in the shear range of erosion. When the shear sensitivity constant kss is adopted for sludge characterisation, an increased degree of dispersion under standard test conditions will result in increased shear sensitivity estimates. The shear sensitivity may be used for the estimation of en equivalent change in the Gibb's energy of cell adhesion (delta (delta Gad/RT)).

Bacterial Adhesion↗
PubMedDate not supplied

Biogeochemistry of fluoride in a plant-solution system.

Fluoride (F-) pollutants can harm plants and the animals feeding on them. However, it is largely unknown how complexing and chelating agents affect F bioavailability. Two studies were conducted that measured F- bioavailability and uptake by rice (Oryza sativa L.). In the first study, rice was grown in solution culture (pH 5.0) with 0, 2, or 4 mM F- as KF to compare the interaction of F- with humic acid (HA) and with a conventional chelating agent, N-hydroxyethylenthylenediaminetriacetic acid (HEDTA). In the second study, F was supplied at 0, 0.5, 1.0, and 2.0 mM KF with an additional 2 mM F- treatment containing solution Ca at 2x (2 mM Ca) the level used in the first study, to test the effect added Ca had on F- availability and uptake. Total biomass was greatest with HEDTA and F- < 1 mM. Leaf and stem F concentrations increased exponentially as solution F- increased linearly, with nearly no F partitioning into the seed. Results suggest that F was taken up as HF0 while F- uptake was likely restricted. Additionally, F- competed with HA for Ca, thus preventing the formation of Ca-HA flocculents. The addition of soluble Ca resulted in the precipitation of CaF2 solids on the root surface, as determined by tissue analysis and energy dispersive X-ray spectroscopy.

Biological Availability↗
PubMed2001

Treatment of spent filter backwash water using dissolved air flotation.

There is increasing interest in treating recovered spent filter backwash water in the drinking water industry. In the USA the Filter Backwash Recycling Rule will come into effect in the near future. The purpose of the Rule is to prevent the concentrated pathogenic agents, potentially in the filter backwash water, from being returned to the head of the water treatment works without some form of treatment or dilution. By treating this flow both public health and financial liability can be better managed by the operating utility. Dissolved Air Flotation (DAF) was investigated as a possible technology alternative to simple or advanced sedimentation techniques. This application is not widespread but sits somewhere in between the two normal applications of DAF as a high solids sludge thickener and a low turbidity clarification system. Given this a pilot plant program, supported by jar testing, was undertaken to determine the process capability and the design parameters for this application. DAF proved to be very suitable for backwash water recovery. DAF effluent turbidities of < 1.0 NTU could be easily obtained, when raw water turbidities were in excess of 50 NTU. Chemical requirements were low with only a single low dose of polymer required to bind the floc particles to form a solids matrix suitable for flotation. Flocculation contact times ranged from 0-10 minutes depending on the nature of the raw water. Recycle rates as low as 5% performed satisfactorily with no significant improvement when increased to 20%. Sludge solids of 3.5-9.6% dry solids were found and very low volumes of sludge, < 0.1% of the incoming flow make the DAF solids handling system very compact.

Air↗
PubMed1999

Fine-needle aspiration biopsy of chromophobe renal cell carcinoma and oncocytoma: comparison of cytomorphologic features.

BACKGROUND: Chromophobe renal cell carcinoma (ChRCC) is a distinct tumor with a prognosis intermediate between renal oncocytoma (RO) and clear cell renal cell carcinoma. To our knowledge the cytologic features of only a limited number of ChRCC have been described to date. A retrospective review of the cytomorphologic features of ChRCC and a comparison with RO was performed. METHODS: Fine-needle aspiration biopsies (FNABs) of six cases of histopathologically proven ChRCC were reviewed. The material examined was comprised of smears, cytospins, Thin Prep Pap Test preparations, and cell block sections stained with Diff-Quik, Papanicolaou, and hematoxylin and eosin. Six FNABs of ROs were examined similarly. The cytomorphology of each tumor was studied and particular attention was paid to features differentiating the two entities. RESULTS: The characteristic cytomorphologic features of ChRCC (present in all cases) included round/oval, occasionally polygonal, moderately pleomorphic large cells present singly and in small clusters. The abundant cytoplasm was variegated, ranging from dense to flocculent to vacuolated, with prominent cytoplasmic membranes. The nuclei were large and hyperchromatic, with nuclear membrane irregularities and grooves present at least focally. Frequent binucleation was observed. Small nucleoli were present in many cells, but rarely prominent. In contrast, RO showed large cells with homogenous granular cytoplasm. The nuclei showed minimal to no nuclear membrane irregularities, tiny nucleoli, mild pleomorphism, and only an occasional large, more hyperchromatic nucleus was observed. CONCLUSIONS: ChRCC has a distinct combination of cytomorphologic features. Careful attention to cytoplasmic and nuclear features allows for the distinction between ChRCC and RO in cytologic preparations.

Adenoma, Oxyphilic↗
PubMedDate not supplied

Effects of chlorination on the adhesion strength and deflocculation of activated sludge flocs.

A side effect of the application of chlorine for controlling filamentous bulking is deflocculation of floc-forming bacteria, which may cause unacceptable effluent deterioration depending on dosing. It was assumed that chlorine may adversely affect the adhesion ability of floc bacteria, promoting their erosion in shear flow. The effect of chlorination on the strength of activated sludge flocs was investigated. The adhesion-erosion (AE) model developed by Mikkelsen and Keiding was used to interpret results from deflocculation tests with varying shear and solids concentration. The AE model yields the adhesion enthalpy (deltaHG/R) of cells in sludge flocs and parameters from the model were used to quantify the sludge in terms of floc strength. Two activated sludges with different initial characteristics were studied. The resulting model parameters showed that the AE model was suitable for quantifying the bond energy of particles to the activated sludge exposed to chlorine. For one activated sludge, adhesion of cells was largely unaffected by the applied chlorine doses. A second sludge showed reduced adhesion strength with chlorine, leading to increasing deflocculation. The simple batch test and AE model proved valuable for assessing the effect of chlorination on the flocs in activated sludge. By use of these procedures, it is possible to determine acceptable chlorine dosing to avoid excessive deflocculation and effluent deterioration.

Bacterial Adhesion↗
PubMed2002

Antimicrobial anionic peptide binds in vivo to Mannheimia (Pasteurella) haemolytica attached to ovine alveolar epithelium.

Endogenous antimicrobial peptide activity in vivo has rarely been demonstrated. To assess this, Mannheimia haemolytica (log(10) 10.20 cfu) was deposited into the lungs of adult sheep, which were killed at 0, 5, 10 and 20 min for necropsy. At 0 min, M. haemolytica appeared normal and monoclonal antibody to antimicrobial anionic peptide (AP) and Protein A-colloidal gold identified AP already bound to the bacterial surface. At 5-20 min, many organisms were distorted with flocculated intracellular constituents characteristic of AP cellular damage indicating that AP can bind to and presumably help inactivate organisms in vivo.

Animals↗
PubMed2004

Structural and functional modifications of sertoli cells in the testis of adult follicle-stimulating hormone receptor knockout mice.

Follicle stimulating hormone (FSH) plays important roles during testicular development and in the maintenance of spermatogenesis in the adult. However, the cellular events or pathways that FSH regulates to achieve these effects in Sertoli cells, where the FSH receptors (FSH-R) are located, is still not fully elucidated. The development of FSH-R knockout (FORKO) mice provides a model to examine alterations in testicular structure and function in its absence. To this end, light (LM) and electron microscopic (EM) analyses of perfusion-fixed testes of wild-type and FORKO mice of different ages were performed. Under the LM, a significant reduction was noted in the profile area of seminiferous tubules of FORKO mice compared with their wild-type counterparts at different ages. In addition, FORKO testes revealed large irregularly shaped spaces within the seminiferous epithelium, extending from the base to the lumen. Such spaces were often separated by anastomotic cords of spherical germ cells or completely surrounded elongating spermatids. This phenotype was restricted to half or less of the circumference of only some tubules, but was seen at all stages. EM analyses revealed that the spaces corresponded to an apparent accumulation of fluid in the Sertoli cell cytoplasm, coincident with an absence of the fine flocculent ground substance seen in wild-type mice. However, the Sertoli organelles, while less prominent, appeared intact and to be floating in the enlarged fluid-filled cytoplasm. Functionally, androgen-binding protein (ABP), a major secretory protein of Sertoli cells, was dramatically reduced in FORKO mice. These results suggest that FSH-R signaling normally maintains water balance in Sertoli cells in addition to regulating ABP production.

Animals↗
PubMed2006

Required minimum granule size in UASB reactor and characteristics variation with size.

The objective of this study was to define minimum size of bioparticles that could be classified as granules, to offer all advantages of granular sludge. Based on the theory of sedimentation, the minimum diameter bioparticles, which should be considered as granules was found out for specific gravity of sludge ranging between 1.01 and 1.05. For example, for specific gravity of 1.035 the minimum diameter of granules required for better sludge retention was 0.34 mm. The diameter based on this theory was evaluated by carrying out settling column analysis of a granular sludge obtained from lab-scale UASB reactor and verified with microscopic observation. To find out the effect of granules size on the nature of biodegradability, specific methanogenic activity (SMA) was carried out. It was observed that SMA increased with size of bioparticles tested in the range of 0.27-3.03 mm. The change in VSS/SS ratio and specific gravity was observed with size of granules. Consideration of variation in specific gravity with size of granules increased the degree of validation of sedimentation theory for the calculation of granules diameter.

Biodegradation, Environmental↗
PubMed2002

[Preparation of PSAS and its application in HAB prevention].

In order to obtain optimum PSAS (Polysilicate-aluminium sulfate) preparation conditions for removing HAB organisms, the 3-factor and 3-level orthogonal test was devised. Concentration of SiO2, Al3+/SiO2 molar ratio and pH were chosen as the three chief factors in PSAS preparation. The experimental results showed that the optimum preparation condition for various HAB organisms was different, and according to practical experimental operation, the appropriate preparation condition was considered as: concentration of SiO2 = 2%, molar ratio of Al3+/SiO2 = 1, and pH = 4. In addition, the coagulation efficiencies of PSAS on various HAB organisms were studied and compared with classical inorganic flocculant AS (Aluminium sulfate). The results indicated that the removal rates of PSAS were much higher than those of AS, and the dosages of PSAS were 30-40% lower than those of AS when they achieved the same removal rates. On the other hand, the anti-coagulation ability of HAB organisms varied with algal species, which was related to different physiological and ecological features of various algal cells.

Alum Compounds↗
PubMed2002

Occurrence of Cryptosporidium in agricultural surface waters during an annual farming cycle in lowland UK.

A 17-month survey based on weekly testing for Cryptosporidium oocysts in surface waters draining a livestock farm on a Warwickshire (UK) estate has shown that the parasite is present throughout the year, with the highest frequency of occurrence and maximum concentrations during the autumn and winter. The 190 ha farm is managed as an exemplar for a teaching institution. There were up to 800 livestock present at peak times of year in the catchment of the stream draining the estate. Oocysts were concentrated from grab samples by a flocculation procedure, stained with monoclonal antibody and detected by fluorescence microscopy. Overall, 274/418 (66%) of samples were positive for Cryptosporidium. Where the stream passed from the estate, the occurrence was 79%, with mean and median oocysts/l of 0.48 and 0.2, respectively. Highest oocyst levels coincided with calving and increased wild animal numbers following breeding. There was no correlation of oocyst levels with rainfall or slurry spreading. Cryptosporidium was also frequently found in a pond on arable land (no livestock) indicating that wild animals alone contributed oocysts to surface waters. These results from a well managed livestock farm may represent a typical natural baseline for levels of occurrence and concentration of Cryptosporidium oocysts in surface waters of the lowland agricultural environment of the UK.

Agriculture↗
PubMed2002

The use of waterworks sludge for the treatment of dye wastes.

Water treatment works using coagulation/flocculation in the process stream will generate a waste sludge. The works in Adana, Turkey uses ferric chloride. The potential for using this sludge for the treatment of reactive, direct, disperse, acidic, and basic dyestuffs by coagulation and sorption has been investigated. The sludge acted as a coagulant and removed colour with excellent removal efficiencies being obtained for basic, disperse and direct dyes. The optimum conditions were a pH value of 5 and a sludge dose of 2000 mg l(-1). Mediocre results were obtained for acidic and reactive dyes. The efficiency of the sludge was also compared with alum and ferric chloride for the same group of dyes. The sludge was also used as a coagulant to treat the wastewater from a textile factory. At doses of 2000-4000 mg l(-1), the sludge was as effective as ferric chloride and alum at removing COD. Sorption tests showed that the disperse and reactive dyes did not bind to the sludge. Langmuir and Freundlich constants were determined for the other three types of dye. Rate constants for the adsorption were determined using the Lagergren equation.

Adsorption↗
PubMed1998

Cloning and characterization of CAD1/AAF1, a gene from Candida albicans that induces adherence to endothelial cells after expression in Saccharomyces cerevisiae.

Adherence to the endothelial cell lining of the vasculature is probably a critical step in the egress of Candida albicans from the intravascular compartment. To identify potential adhesins that mediate the attachment of this organism to endothelial cells, a genomic library from C. albicans was used to transform a nonadherent strain of Saccharomyces cerevisiae. The population of transformed yeasts was enriched for highly adherent clones by repeated passages over endothelial cells. One clone which exhibited a fivefold increase in endothelial cell adherence, compared with S. cerevisiae transformed with vector alone, was identified. This organism also flocculated. The candidal DNA fragment within this adherent/flocculent organism was found to contain a single 1.8-kb open reading frame, which was designated CAD1. It was found to be identical to AAF1. The predicted protein encoded by CAD1/AAF1 contained features suggestive of a regulatory factor. Consistent with this finding, immunoelectron microscopy revealed that CAD1/AAF1 localized to the cytoplasm and nucleus but not the cell wall or plasma membrane of the transformed yeasts. Because yeasts transformed with CAD1/AAF1 both flocculated and exhibited increased endothelial cell adherence, the relationship between adherence and flocculation was examined. S. cerevisiae expressing either of two flocculation phenotypes, Flo1 or NewFlo, adhered to endothelial cells as avidly as did yeasts expressing CAD1/AAF1. Inhibition studies revealed that the flocculation phenotype induced by CAD1/AAF1 was similar to Flo1. Thus, CAD1/AAF1 probably encodes a regulatory protein that stimulates endothelial cell adherence in S. cerevisiae by inducing a flocculation phenotype. Whether CAD1/AAF1 contributes to the adherence of C. albicans to endothelial cells remains to be determined.

Adhesiveness↗
PubMed1997

A model for the kinetics of homotypic cellular aggregation under static conditions.

We present the formulation and testing of a mathematical model for the kinetics of homotypic cellular aggregation. The model considers cellular aggregation under no-flow conditions as a two-step process. Individual cells and cell aggregates 1) move on the tissue culture surface and 2) collide with other cells (or aggregates). These collisions lead to the formation of intercellular bonds. The aggregation kinetics are described by a system of coupled, nonlinear ordinary differential equations, and the collision frequency kernel is derived by extending Smoluchowski's colloidal flocculation theory to cell migration and aggregation on a two-dimensional surface. Our results indicate that aggregation rates strongly depend upon the motility of cells and cell aggregates, the frequency of cell-cell collisions, and the strength of intercellular bonds. Model predictions agree well with data from homotypic lymphocyte aggregation experiments using Jurkat cells activated by 33B6, an antibody to the beta 1 integrin. Since cell migration speeds and all the other model parameters can be independently measured, the aggregation model provides a quantitative methodology by which we can accurately evaluate the adhesivity and aggregation behavior of cells.

Antibodies↗
PubMed2002

Fate of coliphage in a wastewater treatment process.

The fate of coliphage in a wastewater treatment plant in the central part of Japan was investigated from March to December 2001. A relative abundance of coliphage, 1000-10,000 PFU/ml determined with three different Escherichia coli strains, was detected in the influent. But, no remarkable seasonal change in the phage concentration in the influent was observed during the ten-month test period. Almost ten times higher coliphage concentration was detected by the F+ E. coli strain than by the other two F- strains. The RNA phage was more stable than the DNA phage against aerobic treatment using activated sludge. Most of the phages in the influent and primary settling tank were detected as suspended forms. Anaerobic-aerobic treatment enhanced adsorption of the phage by the solid particles. Almost no phage was detected in the effluent. Aerobic treatment using activated sludge and/or the addition of flocculants such as PAC was effective for the removal of coliphage, an index of enteric viral pollution.

Journal Article↗
PubMed2004

Organic removals from highly proteinous wastewater from soya milk and tofu manufacturing plant.

Combined wastewater from soya milk and tofu manufacturing industry was treated by physico-chemical method using conventional coagulants such as lime, alum. ferric chloride, and ferrous sulphate in combination with synthetic cationic polyelectrolyte. The wastewater samples were analyzed as per the Standard Methods and the experiments were carried out using Jar test apparatus (Phipps & Birds). The ferric chloride in combination with synthetic cationic polymer (Oxyfloc-FL-11) in the ratio of 250:20 mg L(-1) resulted in very good removals of COD, BOD, and SS of 75.4, 79.8, and 96.0% respectively with complete removal of odor, color and turbidity.

Coagulants↗