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Query: UMLS:C0033036 (APC)
 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The addition of a low concentration of PAC (0.5gL(-1) of sludge, i.e. a dose of 4mgL(-1) of wastewater), in combination with a relatively long SRT (50 days), to improve membrane filtration performance was investigated in two pilot-scale MBRs treating real municipal wastewater. Continuous filterability tests at high flux showed the possibility to run for 18h at 72Lm(-2)h(-1) and 180h at 50Lm(-2)h(-1), while significant fouling occurred without PAC. In addition, measurements of the critical flux showed an increase of 10% for this strategy. Low dosage and high retention time makes it feasible and cost effective. Further advantages with regard to permeate quality and possible micropollutants removal are currently under investigation.
Water Res 2009 Feb
PMID:Low dose powdered activated carbon addition at high sludge retention times to reduce fouling in membrane bioreactors. 1901 May 12

The influence of temperature on P release from sediment of Lake Dianchi was discussed. Two kinds of inactivation agent schemes (Al2SO4.18H2O and PAC-Polymeric Aluminum Chloride) were used. The results show that the P release amount from sediment increased as the environmental temperature increased. As temperature raised 10 degrees C, the TP release amount increased 1.22%-38.69%, the DTP release amount increased 4.79%-76.82%. From 25 degrees C to 35 degrees C, the sediment had the largest P release increment. When temperature rose, the oxygen demand in the overlying water increased. Then the transformation speed of Fe3+ to Fe2+ increased, and then the release of Fe-P in sediment accelerated. On the other hand, microbe activity made the release possible through the transformation from organic-phosphorus to inorganic-phosphorus. The inactivation agents used here have significant effect on restraining the phosphorus release from sediment and the capture of particles containing phosphorus in overlying water. PAC had better P inactivation effect than Al2SO4 at 25 degrees C. Inhibition rate of P release from sediment by PAC was about 0.49%, 1.32%, 1.03% higher than Al2SO4 at 5, 15 and 25 degrees C, respectively. As the temperature rose to 35 degrees C, the capacity that PAC restricted P was weakened, so the effect of P release inhibition was weakened. Inactivation rate of Al2SO4 was higher about 2.25% than PAC to P from sediment at 35 degrees C. Temperature of sediments in PAC sets is 2-3 degrees C lower than that of Al2SO4 sets.
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PMID:[Effect of inactivation agents on the phosphorus release from sediment of Lake Dianchi at different temperature]. 1906 27

The purpose of this study was to compare the shear bond strength of orthodontic metallic brackets photo-activated with two different light-curing sources at different exposure times: halogen light (XL 1500, 3M ESPE) and LED light (Ortholux, 3M Unitek). Sixty bovine permanent lower incisors were inserted into PVC tubes containing plaster. The buccal surfaces were cleaned with pumice and water, and then etched with 37% phosphoric acid gel. The XT Primer bonding agent (3M Unitek) was applied to the enamel surfaces and the metallic pre-coated brackets (Transbond APC II system, 3M Unitek) were attached to upper central incisors. The teeth were randomly divided into four groups (n=15). In Group I (Control), halogen light was used for 40 seconds, while in Groups II, III, and IV were light-cured with LED light unit for 40, 10, and 5 seconds, respectively. The teeth were stored in distilled water at 37 degrees C for 24 hours. The brackets were submitted to shear bond strength test in universal testing machine (Instron) at a crosshead speed of 0.5 mm/minute. Shear bond strength means (MPa) were 4.87 for Group I; 5.89 for Group II; 4.83 for Group III, and 4.39 for Group IV. Tukey's test detected no statistically significant differences among the groups regarding the shear bond strength (p>0.05). Neither of the types of light-curing sources or exposure times influenced the shear bond strength of metallic brackets.
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PMID:Shear bond strength of metallic brackets photo-activated with light-emitting diode (LED) at different exposure times. 1908 70

Based on two common coagulants-polyferric sulfate (PFS) and polyaluminum chloride (PACl), some measurements and processes in the background of Pb (II) concentration sudden increase in water were studied. The removal efficiency of Pb(II) was compared between PAC and diatomite absorption with coagulation. The effect of coagulant dosage, initial concentration of Pb(II), pH value and KMnO4 preoxidation on coagulation were investigated. The results showed that using PFS was better than PACl for the removal of Pb(II). The regulating pH value up to 9 could improve the removal efficiency of Pb(II) up to 95% by coagulation under the optimum dosage of coagulant PFS of 10 mg/L. KMnO4 preoxidation could improve the removal efficacy of Pb(II) by coagulation of PACl only. The Pb(II) removal efficiency of PAC and diatomite absorption with coagulation were almost equal. Pb(II) concentration could be lowered from 402 microg/L to below 10 microg/L under the condition that dosages of PAC or diatomite were 10 mg/L or 25 mg/L by using PFS. The same effect could be got under the condition that dosages of PAC or diatomite were 20 mg/L or 50 mg/L by using PACl. KMnO4 and diatomite are dosed at the same time would weaken their function each other. Therefore, diatomite adsorption coupled with coagulation is the simplest and most effective method for removing Pb(II).
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PMID:[Emergent treatment process for raw water polluted by heavy metal Pb (II)]. 1914 82

The present study investigates the efficacy of various oxidizing treatments (ClO(-), ClO(2), KMnO(4), O(3), O(3)/H(2)O(2), O(3)/activated carbon) to remove from waters sodium dodecylbenzenesulphonate (SDBS), considered as model surfactant. Results obtained show that the use of ClO(-) and ClO(2) does not cause appreciable SDBS degradation. Additionally, in the case of ClO(-), trihalomethanes are generated, increasing system toxicity. Because the reaction kinetics between SDBS and KMnO(4) is very slow, a decrease in contaminant concentration is not observed, even at very acid pH values. SDBS reactivity with ozone is very low, with a kinetic constant (k(O)(3)) of 3.68 M(-1)s(-1), but its reactivity with HO() radicals is very high (k(OH)=1.16 x 10(10)M(-1)s(-1)), therefore O(3)/H(2)O(2) and O(3)/activated carbon, which can also generate HO(), appear as promising advanced oxidation processes to remove this contaminant from waters. The method based on ozone and activated carbon was the only process studied that produced both an increase in SDBS removal rate (due to the generation of HO() radicals in the O(3)-PAC or O(3)-GAC interaction) and a considerable reduction in the concentration of dissolved organic carbon in the system due to the PAC adsorbent properties.
Water Res 2009 Apr
PMID:Effectiveness of different oxidizing agents for removing sodium dodecylbenzenesulphonate in aqueous systems. 1914 73

Alb species [Al12 AlO4 (OH)24(7+)] is multinuclear hydroxyl compound formed in PAC hydrolysis-polymerization process, with properties of small particle sizes, much positive charge, high aggregation degree and large molecular weight. Alb species was purified from PAC containing high concentration of Alb species using ethanol-acetone mixed precipitation method. The influence of dosage, pH and inorganic ions on humic acid removal from simulative water was studied by measuring zeta potential and UV254. The PDA output (FI curve) was analyzed and the relationship between the parameters (S1, S2, H1, H2) of FI curve and coagulation mechanism were studied at different Alb dosage and pH. When the dosage was 4.3 to 6.3 mg x L(-1) and pH was 3.0 to 6.0, the highest humic acid removal efficiency was obtained. The existence of NH4+, SiO3(2-) and H2PO(-) inhibits the coagulation performance. The results of coagulation kinetics and Zeta potential studies revealed that Alb acted mainly by charge neutralization as well as adsorption bridge building in water treatment.
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PMID:[Coagulation performance and mechanism of Alb species in polyaluminum chloride in removing humic acid]. 1918 3

A commercial fresh pack potato operation was used as a model to evaluate FIT fruit and vegetable wash effectiveness in reducing levels of microorganisms on potatoes and in flume water. Fresh potatoes were washed in flume water with or without FIT, or treated with a spray bar utilizing either FIT, 9 ppm chlorine dioxide (CIO2), or a water control. Both flume treatments were also evaluated for APC and Gram-negatives. There were no significant differences in reduction of these microorganisms on treated or control potatoes. However, levels of Gram-negative bacteria in FIT-amended flume water were reduced by 5.95 log CFU/g, and the APC was reduced by 1.43 log CFU/g. To validate plant trial findings, this test was repeated using solutions of sterile potato flume water from the fresh pack operation, containing a typical level of dissolved and suspended solids. Treatment solutions prepared with flume water or deionized water containing FIT, 9 ppm CIO2, or a water control were inoculated with E. coli O157:H7, Salmonella Typhimurium, or Pectobacterium carotovorumssp. carotovorum. FIT and ClO2 prepared with deionized water reduced levels of microorganisms by >6.1 to 6.6 log CFU/g to below the detection limit. FIT prepared with flume water reduced levels of all organisms by >6.0 to 6.4 log CFU/g to below the detection limit, whereas ClO2 prepared from flume water reduced bacterial levels of all organisms by only 0.7 to 1.4 log CFU/g. Neither FIT nor ClO2 was particularly efficacious against E. coli O157:H7, S. Typhimurium, APC, yeasts, or molds on potato surfaces.
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PMID:Efficacy of FIT produce wash and chlorine dioxide on pathogen control in fresh potatoes. 1924 58

The hydrolysis/precipitation behaviors of Al(3+), Al(13) and Al(30) under conditions typical for flocculation in water treatment were investigated by studying the particulates' size development, charge characteristics, chemical species and speciation transformation of coagulant hydrolysis precipitates. The optimal pH conditions for hydrolysis precipitates formation for AlCl(3), PAC(Al13) and PAC(Al30) were 6.5-7.5, 8.5-9.5, and 7.5-9.5, respectively. The precipitates' formation rate increased with the increase in dosage, and the relative rates were AlCl(3)>>PAC(Al30)>PAC(Al13). The precipitates' size increased when the dosage increased from 50 microM to 200 microM, but it decreased when the dosage increased to 800 microM. The Zeta potential of coagulant hydrolysis precipitates decreased with the increase in pH for the three coagulants. The iso-electric points of the freshly formed precipitates for AlCl(3), PAC(Al13) and PAC(Al30) were 7.3, 9.6 and 9.2, respectively. The Zeta potentials of AlCl(3) hydrolysis precipitates were lower than those of PAC(Al13) and PAC(Al30) when pH>5.0. The Zeta potential of PAC(Al30) hydrolysis precipitates was higher than that of PAC(Al13) at the acidic side, but lower at the alkaline side. The dosage had no obvious effect on the Zeta potential of hydrolysis precipitates under fixed pH conditions. The increase in Zeta potential with the increase in dosage under uncontrolled pH conditions was due to the pH depression caused by coagulant addition. Al-Ferron research indicated that the hydrolysis precipitates of AlCl(3) were composed of amorphous Al(OH)(3) precipitates, but those of PAC(Al13) and PAC(Al30) were composed of aggregates of Al(13) and Al(30), respectively. Al(3+) was the most un-stable species in coagulants, and its hydrolysis was remarkably influenced by solution pH. Al(13) and Al(30) species were very stable, and solution pH and aging had little effect on the chemical species of their hydrolysis products. The research method involving coagulant hydrolysis precipitates based on Al-Ferron reaction kinetics was studied in detail. The Al species classification based on complex reaction kinetic of hydrolysis precipitates and Ferron reagent was different from that measured in a conventional coagulant assay using the Al-Ferron method. The chemical composition of Al(a), Al(b) and Al(c) depended on coagulant and solution pH. The Al(b) measured in the current case was different from Keggin Al(13), and the high Al(b) content in the AlCl(3) hydrolysis precipitates could not used as testimony that most of the Al(3+) was converted to highly charged Al(13) species during AlCl(3) coagulation.
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PMID:Study on the hydrolysis/precipitation behavior of Keggin Al13 and Al30 polymers in polyaluminum solutions. 1940 89

This paper presents the results of bench-scale research into the efficiency of NOM removal by integrated processes-alum coagulation and PAC-adsorption. Experiments were conducted using riverine water samples (collected from the Odra River, Poland) and commercial powdered activated carbon. It has been shown that a PAC-enhanced coagulation process reduces the coagulant dose required and increases the process efficiency at the same time. For example, a coagulant dose of 2.0 mgAl/L and a PAC dose of 5 mg/L have produced results comparable to those of a coagulation process with no adsorbent aid but with a coagulant dose increased by 54%. The coagulation-adsorption tests were carried out at a pH of 6.0, which was lower than the pH(IEP) of the adsorbent. This procedure yielded a high extent of DOC and UV-254 removal, at 90% and 77%, respectively. The drop observed in the SUVA value after the process implied a decrease in reactive DOC forms and consequently a diminished risk that disinfection by-products might form. HPSEC analyses made it possible to describe the changes in the molecular weight distribution for the organic substances persisting in the water both after coagulation and after PAC-aided coagulation, and to evaluate their propensity to removal by the two methods. The coagulation process was effective as far as the removal of high-molecular-weight fractions is concerned. An increase in the removal of the low molecular weight NOM was achieved when the PAC-adsorption process had been combined with coagulation.
Water Sci Technol 2009
PMID:Effects of natural organic matter removal by integrated processes: alum coagulation and PAC-adsorption. 1947 89

Direct capillary nanofiltration was tested for reclamation of tertiary effluent from a municipal wastewater treatment plant. This process can be regarded as a promising treatment alternative for high quality water reuse applications when combined with powdered activated carbon for enhanced removal of organic compounds. The nanofiltration was operated at flux levels between 20 and 25 L/(m2 h) at a transmembrane pressure difference of 2-3 bar for approximately 4,000 operating hours. The study was conducted with PAC doses in the range from 0 to 50 mg/L. The plant removal for DOC ranged from 88-98%. The sulfate retention of the membrane filtration process was between 87 and 96%. The process provided a consistently high permeate quality with respect to organic and inorganic key parameters.
Water Sci Technol 2009
PMID:Capillary nanofiltration coupled with powdered activated carbon adsorption for high quality water reuse. 1958 22


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