SEARCH · PubMed Health

Results for “Flocculation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 1,369 records · Page 76Linked to original sources

PubMed2004

Physical and chemical processes for removing suspended solids and phosphorus from liquid swine manure.

A physical/chemical treatment train, that included 24-hour preliminary settling followed by coagulation/flocculation and sedimentation, was tested at a laboratory bench scale to treat liquid swine manure for the removal of total suspended solids (TSS) and total phosphorus (TP). Preliminary (i.e., natural) settling time had an effect on TSS removal within only the first 24 hours. TSS removal efficiency reached 75% (TSS concentration was reduced from 5,800 to 1,450 mg 1(-1)) after 24 hours of preliminary settling. Also, as a result of the 24-hour preliminary settling, TP concentration was reduced from 533 to 318 mg 1(-1), thus leading to a TP removal efficiency of 40%. When compared to ferric chloride, alum was more effective in reducing both TSS and TP. At a 95% confidence interval, alum dose, coagulation Gt (coagulation velocity gradient * rapid-mixing time), and flocculation Gt (flocculation velocity gradient * slow-mixing time) were not significant for TSS removal while alum dose was the only significant factor for TP removal. For the 24-hour settled liquid manure that had a TP concentration in the range of 362 to 401 mg l(-1)and as alum dose increased up to 1,600 mg 1(-1), TP removal efficiency increased up to 70%. Then, the rate of increase in TP removal efficiency per increase in alum dose started to decrease and TP removal efficiency reached about 93% at an alum dose of 3,000 mg 1(-1). Sequential alum dosing improved the TSS removal efficiency while it had no effect on TP removal efficiency. The mass ratio of removed TSS/applied alum increased from about 0.38, during a one-step dosing of alum at a concentration of 1,600 mg l(-1), to about 0.58 during a two-step dosing of alum at a concentration of 1,600 mg l(-1) (i.e., 800 mg l(-1) followed by another 800 mg l(-1)).

Alum Compounds↗

PubMed2006

Bioaugmentation of activated sludge with two Pseudomonas putida strains for the degradation of 4-chlorophenol.

The augmentation of activated sludge with two strains of Pseudomonas putida, CP1 and A(a) was investigated. Both strains of bacteria degraded 1.56 mM 4-chlorophenol. P. putida CP1 degraded the chemical using a modified ortho-cleavage pathway while P. putida A(a) used the meta-cleavage pathway. When activated sludge incapable of 4-chlorophenol degradation was augmented with either strain, substrate degradation occurred and followed the same biochemical pathways as when the bacteria were grown in pure culture. Insertion, in tandem, of the genes for gentamycin resistance and green fluorescent protein into the chromosomes of the two strains, enabled the survival and spatial location of the bacteria in the mixed microbial population to be monitored. Labelling the bacteria did not alter their degradative capabilities. P. putida CP1::Tn7-gfp survived in higher numbers than P. putida A(a)::Tn7-gfp following addition to the activated sludge. This was attributed to the ability of this strain to flocculate and become integrated in the activated sludge floc. Addition of P. putida CP1::Tn7-gfp or A(a)::Tn7-gfp to activated sludge resulted in smaller decreases in total cell numbers indicating a protective effect of the introduced P. putida strains on the overall microbial population from the harmful effects of 4-chlorophenol. The non-flocculant strain A(a) did not survive as well as CP1 in the activated sludge system and required a higher inoculum size to effect substrate degradation.

Biodegradation, Environmental↗

PubMed2002

Polyelectrolyte conditioning for iron-hydroxide-containing sludge produced from electroflocculation of fermentation wastewater.

The purpose of this study is to investigate the application of chemical conditioning method for the post-electroflocculation wastewater sludge treatment with polyelectrolytes of varying ionic characters, namely anionic, cationic and nonionic flocculating agents. Electroflocculation, a combination of the processes of electroflotation and electroprecipitation, was found effective to remove the organic and color components in monosodium glutamate fermentation wastewater. The settleability and dewaterability of the separated sludge, containing 15-20% of iron hydroxides, increased 35% and 60% due to polymer conditioning through a jar-test apparatus. The influence of shear conditions and polymer dose on the floc size, zeta potential, filterability and dewatering performance, and shear resistance of sludges was investigated. Experimental results showed that the anionic polymer acts as a better flocculating agent than both cationic and nonionic polymers, and the optimal polymer doses fall between 4.0 and 10.0 mg/g Fe sludge under corresponding shear rates of 200 300 rpm. This study also indicated that both charge neutralization and polymer bridging mechanisms operate in the sludge conditioning process.

Electrochemistry↗

PubMed2004

Development of biological livestock wastewater treatment system combined with physical pretreatment and chemical posttreatment.

Lab-scale livestock wastewater treatment process was operated. Treatment process was composed of anaerobic reactor, aerobic reactor, anoxic reactor, settler, and microorganisms activation reactor. We divided this system into Systems 1-5 according to various conditions. In Systems 4 and 5, ammonia stripping was performed as pretreatment. And flocculation was performed as posttreatment. Average influent concentrations of COD, BOD, TKN, and TP were 21,894, 11,533, 2255, and 415 mg/L, respectively, and COD/N and BOD/N ratios in influent were 9.9 and 5.3, respectively. When ammonia stripping was performed as pretreatment, effluent BOD concentration was 44.4 mg/L and removal efficiency was 99.62%. TN removal efficiencies in Systems 4 and 5 were 84.1 and 95.2%, respectively, and effluent TN concentrations were 305.9 and 78.4 mg/L, respectively, which was because of with without pH control. In operation period of Systems 4 and 5, average SNR and SDNR were 18.6 and 17.4 g N/kg MLSS/d, respectively, which was rate as much as endogenous denitrification rate because of long SRT due to low F/M ratio. In Systems 3, 4, and 5, optimal doses of flocculation agent were 350, 100, and 100 mg Fe/L. This difference was caused by alkalinities of Systems 3, 4, and 5, which were 750, 284, and 162 mg/L as CaCO3.

Ammonia↗

PubMedDate not supplied

Protein binding to iothalamate ethyl ester.

A major problem in the development of a particulate hepatolienographic agent is the prevention of particle aggregation upon contact with blood. When iothalamate ethyl ester, a particulate suspension for potential use as an hepatolienographic agent, was mixed with human or animal plasmas, it resulted in moderate to severe flocculation. In a study conducted to define the binding of plasma proteins to the iothalamate ethyl ester particles, plasma was reversibly adsorbed to various particle preparations. Fractions obtained by incubation of the particle-plasma complexes in buffers of increased ionic strength and decreased pH were subjected to polyacrylamide disc gel electrophoresis. The fraction containing the specifically bound proteins produced three distinct bands corresponding to prealbumin, albumin, and fibrinogen. Since the particles flocculated only when mixed with plasma, it is postulated that the fibrinogen-particle interaction is a major factor leading to particle agglutination.

Blood Proteins↗

PubMed1998

Floc stability and adhesion of green-fluorescent-protein-marked bacteria to flocs in activated sludge.

Wastewater is often treated using the activated sludge process. Flocculation and subsequent sedimentation of flocs are vital steps in this process that have direct influence on the quality of the effluent water from wastewater treatment plants. Since cells that remain free-living will decrease the quality of the effluent water it is important to understand the mechanisms of bacterial adhesion to flocs. The green fluorescent protein (GFP) was used as a cellular marker to study bacterial adhesion to activated sludge flocs in situ in sludge liquor. Cell surface hydrophobicity (CSH) was shown to be an important factor that determined the relative bacterial adhesion potential. High CSH correlated with high numbers of attached cells. However, the absolute adhesion of two test bacteria to different sludge flocs varied and could not be explained by the floc characteristics. Confocal laser scanning microscopy of GFP-marked cells showed their position in the floc matrix in situ. Hydrophobic cells attached not only on the surface but also within the floc, whereas hydrophilic cells did not. This indicates that cells may penetrate the flocs through channels and pores and increase the effective surface, which in turn makes the clarification of the wastewater effluent more efficient. The addition of polymers is common practice in wastewater treatment and was shown to increase bacterial adhesion to the flocs. A decrease in surface tension caused by addition of DMSO decreased adhesion, indicating the detrimental effect of surfactants on flocculation. An understanding of basic bacterial adhesion and aggregation mechanisms is important for the management and control of biotechnological wastewater treatment.

Bacterial Adhesion↗

PubMed1999

Involvement of outer-membrane proteins in the aggregation of Azospirillum brasilense.

A bioassay was developed to investigate biological factors involved in the aggregation of Azospirillum brasilense strain Cd. Cells were grown for 24 h under aggregation-inducing and non-aggregation-inducing conditions (high and low C:N, respectively) and sonicated for 20 s. The cells were washed by centrifugation and resuspended in potassium phosphate buffer containing the two types of sonication extract. A greater extent of aggregation and higher flocculation were observed after 2-3 h incubation in the presence of sonicates from cells grown at high C:N (H-cells) compared to cells grown at low C:N. Flocculation did not occur after incubation of these cells in phosphate buffer. Boiled or proteinase K-treated sonicates originating from H-cells had lower aggregation-inducing capacity. After fractionation of the crude sonicate, both the outer-membrane protein (OMP) and the total membrane (mostly OMP) fractions possessed relatively high aggregation specific activities. The aggregation-inducing capacity of the OMP fraction strongly correlated with its protein concentration in the bioassay. Treatment of this fraction with proteinase K also decreased its aggregation-inducing activity. These findings suggest that OMPs are involved in the aggregation process of cells of A. brasilense.

Azospirillum brasilense↗

PubMed2006

Point-of-use water treatment and diarrhoea reduction in the emergency context: an effectiveness trial in Liberia.

Communicable diseases are of particular concern in conflict and disaster-affected populations that reside in camp settings. In the acute emergency phase, diarrhoeal diseases have accounted for more than 40% of deaths among camp residents. Clear limitations exist in current water treatment technologies, and few products are capable of treating turbid water. We describe the findings of a 12-week effectiveness study of point-of-use water treatment with a flocculant-disinfectant among 400 households in camps for displaced populations in Monrovia, Liberia. In intervention households, point-of-use water treatment with the flocculant-disinfectant plus improved storage reduced diarrhoea incidence by 90% and prevalence by 83%, when compared with control households with improved water storage alone. Among the intervention group, residual chlorine levels met or exceeded Sphere standards in 85% (95% CI: 83.1-86.8) of observations with a 95% compliance rate.

Child, Preschool↗

PubMed1996

Isolation and characterization of a mutant of Saccharomyces cerevisiae affected in the FLO1 locus.

A non-flocculent strain of Saccharomyces cerevisiae was selected after EMS mutation of a flocculent and heterozygous FLO1 locus diploid. The analysis of 25 asci from this diploid showed in all cases segregation 0F:4NF, thus confirming that it was probably affected in the desired gene. After sporulation and dissection of asci, three haploid strains were chosen, which were altered in the locus FLO1. Crossing these three strains with two other ones having markers for ADE1 and pho11::LEU2, we could map the mutation at ca. 4.3 cM and ca. 37.7 cM from the PHO11 and ADE1 loci respectively.

Chromosome Mapping↗

PubMed1977

Serological responses in experimental bovine tuberculosis.

Five two-year-old heifers were each inoculated intravenously with 0.02 mg M. bovis strain AN5. Clinical, haematological and microbiological observations were made during the course of the experiment and antibody levels were measured before and after infection by means of the indirect immunofluorescent antibody (IFA) and bentonite flocculation tests. All cattle developed M. bovis infection varying in severity from peracute tuberculous pneumonia resulting in death within 33 days to chronic progressive generalised tuberculosis. Only cattle developing peracute or acute forms of tuberculosis showed marked haematological changes characterised by leucopenia with lymphopenia. Bacteraemia was detected in the two cattle with peracute tuberculosis 22 days after infection. Anti-mycobacterial antibody was detected after infection in all cattle but fluctuated markedly during the course of the disease. Of a total of 61 serum samples examined from all cattle after inoculation with M. bovis, only 38 were positive to the IFA test and 30 to the bentonite flocculation test. Only 18 were positive to both tests at any one time. IgM was the predominant type of anti-mycobacterial antibody detected by the IFA test and this was found to cross-react with M. avium in almost every sample.

Animals↗

PubMed1983

Reduction of interfering cytotoxicity associated with wastewater sludge concentrates assayed for indigenous enteric viruses.

Washing, freon extraction, and cationic polyelectrolyte precipitation were compared for their ability to reduce cytotoxicity associated with virus concentrates derived from beef extract eluates of wastewater sludges. Eluates concentrated by hydroextraction were usually much more toxic than those concentrated by organic flocculation. This difference may be due entirely to nondialyzable material naturally present in the beef extract which did not precipitate during flocculation at pH 3.5. Washing inoculated cell monolayers with saline containing calf serum before the addition of agar overlay media was most effective in reducing cytotoxicity, although it resulted in a greater virus loss, as compared with freon extraction and cationic polyelectrolyte precipitation.

Cell Line↗

PubMed1996

An evaluation of methods for the simultaneous detection of Cryptosporidium oocysts and Giardia cysts from water.

Methods for the simultaneous detection of Cryptosporidium parvum oocysts and Giardia cysts from water are described and their relative recovery efficiencies are assessed for seeded samples of both tap and river water. Cartridge filtration, membrane filtration, and calcium carbonate flocculation were evaluated, and steps to optimize the concentration procedures were undertaken. Increasing centrifugation to 5,000 x g, coupled with staining in suspension, was found to increase the overall efficiency of recovery of both cysts and oocysts. Cartridge filtration for both cysts and oocysts was examined by use of 100-liter volumes of both tap and river water. Improvements in recovery were observed for Cryptosporidium oocysts after extra washes of the filters. Calcium carbonate flocculation gave the maximum recovery for both Cryptosporidium oocysts and Giardia cysts and for both water types. A variety of 142-mm membranes was examined by use of 10-liter seeded samples of tap and river water. Cellulose acetate with a 1.2-micron pore size provided the best results for Cryptosporidium oocysts, and cellulose nitrate with a 3.0-micron pore size did so for Giardia cysts.

Animals↗

PubMed1965

ISOLATION, IDENTIFICATION, AND METABOLIC ROLE OF THE SUDANOPHILIC GRANULES OF ZOOGLOEA RAMIGERA.

Organisms isolated from activated sludge and identified as Zoogloea ramigera accumulated large amounts of sudanophilic granules as the cultures flocculated. The granules were extracted by chloroform and precipitated with ether from acid-hydrolyzed cells. Identification of the sudanophilic granules as poly-beta-hydroxybutyric acid (PHB) was confirmed by physical, chemical, and infrared spectral analyses. The isolated polymer accounted for 12.0 to 50.5% of the dry weight of the cells. The polymer was not synthesized when the culture was grown in a growth-limiting concentration of organic substrate; it did accumulate when the culture was grown in medium enriched with carbon and energy sources. An increase in concentration of intracellular PHB was directly proportional to optical density and uptake of glucose. Aside from intracellular storage of PHB as endogenous metabolite, the accumulation of PHB is noted as a possible mechanism of flocculation.

Arginine↗

PubMed2005

Identification and characterization of an SKN7 homologue in Cryptococcus neoformans.

Cryptococcus neoformans is an encapsulated fungal pathogen that primarily infects the central nervous system of immunocompromised individuals, causing life-threatening meningoencephalitis. The capacity of C. neoformans to subvert host defenses and disseminate by intracellular parasitism of alveolar macrophages in the immune-compromised host has led to studies to evaluate genes associated with C. neoformans resistance to oxidative stress. In the present study, we identify and characterize a C. neoformans homologue to SKN7, a transcription factor in Saccharomyces cerevisiae that regulates the oxidative stress response, cell cycle, and cell wall biosynthesis. To examine the contribution of SKN7 in the pathogenesis of fungal infections, we created skn7 mutants via targeted disruption. The skn7 mutants were observed to be more susceptible to reactive oxygen species in vitro and were significantly less virulent than the wild-type strain and a reconstituted strain as measured by cumulative survival in the mouse inhalational model. The Skn7 protein was observed to be important for expression of thioredoxin reductase in response to oxidative challenge. Interestingly, skn7 mutants were also observed to flocculate following in vitro culture, a novel phenotype not observed in skn7 mutants derived from other fungi. These findings demonstrate that SKN7 contributes to the virulence composite but is not required for pathogenicity in C. neoformans. In addition, flocculation of C. neoformans skn7 mutants suggests a potentially unique function of SKN7 not previously observed in other cryptococcal strains or skn7 mutants.

Animals↗

PubMed1991

Biophysical alteration of lung surfactant by extracts of cotton dust.

Byssinosis, a lung disease that can affect cotton mill workers, may be caused in part by lipopolysaccharides (LPS) from Gram negative bacteria. In vitro, LPS complexes with sheep lung surfactant (SLS). To determine whether LPS in extracts of cotton dust alters the biophysical characteristics of lung surfactant, aqueous extracts (1.0% w:v) of sterile surgical cotton (SSC) and a bulk raw cotton dust (1182DB) were prepared. Aliquots of the soluble extracts were incubated with SLS and studied by sucrose gradient centrifugation, surface tension analysis, and high pressure liquid chromatography (HPLC). The chromatography was employed to analyse for 3-hydroxymyristate (3-HM), a fatty acid indicating LPS. Also, purified Enterobacter agglomerans LPS and 3-HM as controls and as mixtures with SLS, were studied by HPLC. Sucrose gradient centrifugation showed that SLS-SSC, SLS-1182DB, and the SLS control had similar densities that differed from the remaining controls. The SLS-1182DB exhibited a floccule absent in the other samples. Surface tension values of SLS-SSC and SLS-1182DB differed significantly from all controls but only slightly from one another. 3-Hydroxymyristate was detected by HPLC in the 3-HM control, EA-LPS, SLS-EA-LPS, and SLS-1182DB, but not in SLS-SSC or the remaining controls. Apparently, 3-HM was below the HPLC detection range in SSC. The data indicate that LPS in the 1182DB, SSC and EA-LPS samples complexed with SLS. Floccule development in SLS-1182DB but not in SLS-EA-LPS suggests a further component(s) present in the bulk raw cotton dust, as well as LPS, which complexes with SLS. The data suggest that biophysical alterations to lung surfactant may play a part in the pathogenesis of byssinosis.

Animals↗

PubMed1996

Involvement of a surface-active high molecular weight factor in degradation of polycyclic aromatic hydrocarbons by Pseudomonas marginalis.

A strain of Pseudomonas marginalis PD-14B, isolated from polycyclic aromatic hydrocarbon (PAH) contaminated soil, produced an extracellular surface-active factor of high molecular weight containing protein and lipopolysaccharide. A crude preparation of the factor, obtained from the culture both of cells grown in mineral salts (MS) medium with succinate and yeast extract, affected the extent of PAH degradation by the bacterial cells and prevented flocculation of PAHs in an aqueous suspension. A washed suspension of P. marginalis cells also prevented flocculation of PAH suspensions and emulsified liquid hydrocarbons. Incubation of the factor and the factor-producing strain in the presence of different PAHs resulted in gradual increase of turbidity of the PAH dispersions. The factor markedly stimulated rate and extent of turbidity generation by bacterial cells. The surface-active factor may promote infection of lettuce and other plants by this known pathogen and may also have application in bioremediation.

Biodegradation, Environmental↗

PubMed1978

Scanning electron microscopy of the spreading of barium sulfate suspensions on the gastric mucosa of the rat. Effect of wetting agents, bile salt and lecithine.

Scanning electron microscopy was performed on the rat stomach mucosa after application of BaSO4 and three barium-containing commercial contrast media. The degree of flocculation was assessed; flocculation could be prevented by using synthetic wetting agents and by physiologic, natural emulsifiers, sodium taurocholate and lecithine.

Animals↗

PubMed2005

Towards an understanding of adsorption behaviour in non-aqueous systems: adsorption of poly(vinyl pyrrolidone) and poly(ethylene glycol) onto silica from 2H, 3H-perfluoropentane.

The adsorption behaviour of low molecular weight poly(ethylene glycol) (PEG 600) and poly(vinyl pyrrolidone) (PVP K25) to silica particles has been investigated at room temperature (21 degrees C) in the partially fluorinated solvent 2H,3H-perfluoropentane (HPFP). PVP (absorbed amount, Gamma = 12 mg g(-1)) was found to adsorb more strongly than PEG (Gamma = 4 mg g(-1)). Both of these values were higher than observed in water. In a further distinction to the aqueous case, where PVP displaces PEG from the interface, no competitive adsorption effects were observed between these two polymers in HPFP, with the adsorbed amounts of each polymer being unchanged by the presence of the other. The stability of silica suspensions in HPFP was primarily dependent on the presence of PVP; PEG/silica systems were unstable, but PVP/silica and PEG/PVP/silica systems formed stable suspensions. All suspensions were destabilized by the addition of small (0.15 wt%) amounts of water. The observations made in this work would point to a flocculation phenomenon due to the addition of water, and not Ostwald ripening. The mechanism of this destabilization is likely to be water acting as a flocculation bridge between particles.

Adsorption↗