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Query: UMLS:C0016382 (flushing)
 6,387 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A soil that had been historically contaminated with Aroclor 1242, 1248, 1254 and 1260 was decontaminated by two surfactant-mediated cleaning procedures that had been chosen to mimic ex-situ washing and in-situ soil flushing processes. A preliminary screening selected four surfactants (from 17 commercial formulations) for their ability to mobilise PCBs from the soil while suffering minimal losses to the supercritical carbon dioxide (scCO2) that was used in a separate back-extraction procedure. The mobilisation was enhanced, with minimal foam formation, by the presence of 17% (v/v) IBMK in the surfactant suspension. Each of the four surfactants, at 1, 3, or 5% (v/v) concentration, was evaluated by (i) 15 successive 10 min sonication-filtrations and (ii) continuous soil column flushing during 20 h. Each filtrate from (i) and samples, taken at hourly intervals, from (ii) were analysed for their PCB and surfactant content. Both extraction procedures mobilised PCBs efficiently when extended for longer periods and were modelled accurately as the sum of a constant and single-term exponential increase to a maximum. The predicted number of replicate stages required to mobilise 50% of the toxicants (t50) varied from 7 to 3 for sonication-washing of the soil (10 g) or from 6.8 to 2.8 h for column flushing of 30 g soil and decreased as the concentration of surfactant in the aqueous phase was increased. The combined PCB-laden aqueous suspensions were then back-extracted efficiently with scCO2 and the eluate was dechlorinated quantitatively as it traversed a short, heated column of silver-iron bimetallic mixture.
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PMID:Approaches to the remediation of a polychlorinated biphenyl (PCB) contaminated soil--a laboratory study. 1143 64

The salinity levels of wastewater and sludge are relatively high in some coastal cities as they may use saline water for toilet flushing, and as such,the sludge dewaterability can be affected by it. The salinity effect on sludge dewaterability was therefore investigated through experimental testing of specific resistance in filtration (SRF), time to filter (TTF), and final solid content of sludge. SRF and TTF were determined using Buchner funnel tests. The final solid content was estimated by centrifuging the sludge at four levels of rotational speed. Sludge with three salinity levels (5,000, 10,000 and 20,000 ppm) were considered in this study. Coagulants such as alum, iron(II) sulfate, and organic polyelectrolytes were added to the sludgetostudythe dewaterability of such sludge with chemical conditioning. Experimental results show that doubling the salinity level of the sludge from 10,000 to 20,000 ppm shows not much change in SRF and TTF. Compared with the sludge without chemical conditioning, the addition of the coagulants to the sludge at a salinity level of 5,000 ppm drastically reduces its SRF and TTF. However, sludge with and without chemical conditioning at a salinity of 20,000 ppm has similar SRF and TTF. The final solid content of sludge increases almost linearly with salinity. Among the coagulants used in this study, the cationic polyelectrolyte is found to be better in improving sludge dewaterability, while iron(II) sulfate performs slightly better in enhancing the final solid content of the sludge.
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PMID:Salinity effect on mechanical dewatering of sludge with and without chemical conditioning. 1177 Jul 73

This paper presents a modeling analysis of the geochemical evolution of a contaminated sandy aquifer at a uranium mill tailings site in the western United States. The tailings pond contains fluids having a pH of 1.5 to 3.5 and high levels of As, Be, Cd, Cr, Pb, Mo, Ni, Se, 226Ra, 228Ra, 230Th, 238U, and 234U. Seepage of tailings fluids into the aquifer has formed a low-pH ground water plume. The reclamation plan is to install a low-permeability cover on the tailings pond to stop the seepage and allow the plume to be attenuated by reactions with the aquifer matrix and flushed by uncontaminated upgradient ground water. To evaluate this reclamation scenario, ground water and sediment core samples were analyzed along one flowpath. Speciation-solubility and mass-transfer modeling revealed two sets of chemical reactions for acid seepage and flushing, respectively. The current concentrations and distribution of ground water constituents can be interpreted as being controlled by stepwise pH-buffer reactions with calcite, amorphous aluminum hydroxide, and amorphous iron hydroxides. These buffer reactions divide the aquifer into zones of near-constant pH, separated by interface zones. For the flushing stage, it is predicted that reactions with surface-bound species will dominate the reaction paths, and more pore volumes are required to neutralize the plume than predicted by models that do not consider surface reactions. Direct mineralogical and surface analysis is needed to substantiate this assertion.
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PMID:Natural attenuation reactions at a uranium mill tailings site, western U.S.A. 1179 46

Remediation of sites contaminated by chlorinated organic compounds is a significant priority in the environmental field. Subsequently, the addition of cosolvent solutions for in situ flushing of contaminated source zones has been successfully field tested. However, the treatment of effluent fluids in such cleanup efforts is an often overlooked component of this technology implementation. The purpose of this research was to evaluate the effectiveness of zero-valent iron (Fe(0)) in treating perchloroethylene (PCE) in an aqueous solution, and how the presence of a cosolvent (ethanol) and modification of the iron surface altered dechlorination. The modified iron surfaces included in this study were nickel-plated iron, acid-treated iron, and untreated iron surfaces. PCE dechlorination in the presence of each of the iron surfaces displayed pseudo first-order kinetics. The highest degradation rate of PCE occurred on the nickel-plated iron surface, 5.83 x 10(-3)h(-1), followed by the acid-treated iron, 4.92 x 10(-3)h(-1), and the untreated iron, 3.34 x 10(-3)h(-1). Dechlorination on each of the surfaces decreased with increasing cosolvent fractions. It was shown that as cosolvent fractions increased, PCE adsorption decreased and resulted in a concomitant decrease in PCE degradation rates.
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PMID:Degradation of perchloroethylene in cosolvent solutions by zero-valent iron. 1247 79

This research focused on providing guidelines for water utilities on the collection and handling of routine bacteriological samples and in developing scientifically-based approaches in selecting the most representative sampling locations. A laboratory-scale pilot distribution system was designed comprising two parallel loops, one using unlined cast-iron pipe and one using PVC pipe. Each loop contained six sampling ports, including (1) a distribution main dead end faucet, (2) one long (5.5 m; 18 feet) and (3) one short (0.3 m; 1 foot) household copper service line with threaded hose-bibb taps, (4) one hose-bibb with welded faucet, (5) one dedicated sampling port (modeled after a manufacturer's specifications) and (6) one laboratory-style (PVC) stop-cock sampling port. Residual chlorine concentrations were maintained at 0, 0.5, 1.5 and 2.0 mg/L stages during the course of the experiment. Bacterial samples were collected from the different sampling ports and assayed by membrane filtration and/or spread plate. Nutrient and R2A agars were used for heterotrophic plate counts (HPC), m-Endo agar for total coliform (TC) counts and Chromocult agar for injured bacterial analyses. Several methods of sample collection were tested using various combinations of flushing and tap disinfection, including "first flush" (no flushing, without tap disinfection), flushing only, tap disinfection only (using alcohol or hypochlorite solution) and flushing coupled with tap disinfection. The results indicated that the bacterial counts in samples drawn from dead ends were not significantly different from counts in samples from the other sample port configurations. First flush samples consistently produced the highest bacterial count results. Bacterial counts in samples from the long household copper service line were typically three orders of magnitude higher than in samples from the other sample ports. Thus, there is evidence that long copper household service connections may be unsuitable sample tap configurations for collecting samples intended to represent microbial quality in the distribution system.
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PMID:Laboratory testing protocol to identify critical factors in bacterial compliance monitoring. 1263 17

Deterioration in drinking water quality in distribution networks represents a problem in drinking water distribution. These can be an increase in microbial numbers, an elevated concentration of iron or increased turbidity, all of which affect taste, odor and color in the drinking water. We studied if pipe cleaning would improve the drinking water quality in pipelines. Cleaning was arranged by flushing the pipes with compressed air and water. The numbers of bacteria and the concentrations of iron and turbidity in drinking water were highest at 9 p.m., when the water consumption was highest. Soft deposits inside the pipeline were occasionally released to bulk water, increasing the concentrations of iron, bacteria, microbially available organic carbon and phosphorus in drinking water. The cleaning of the pipeline decreased the diurnal variation in drinking water quality. With respect to iron, only short-term positive effects were obtained. However, removing of the nutrient-rich soft deposits did decrease the microbial growth in the distribution system during summer when there were favorable warm temperatures for microbial growth. No Norwalk-like viruses or coliform bacteria were detected in the soft deposits, in contrast to the high numbers of heterotrophic bacteria.
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PMID:Removal of soft deposits from the distribution system improves the drinking water quality. 1472 29

Discoloured water is one of the main causes of customer complaints received by UK water suppliers. Flushing is recognised as a means of preventing red water events by mobilising material with the potential to cause discolouration. The understanding of the mechanisms and materials causing discolouration is limited. It is therefore necessary to characterise the materials mobilised by flushing, which are responsible for discolouration. The University of Sheffield and two UK water companies embarked on an in-depth programme of monitoring mains flushing. The programme involves collecting discrete samples during flushing of pipes of differing materials, diameters, age, source water and hydraulic regime. The results show iron to be the dominant material mobilised irrespective of pipe material. All samples indicate a direct correlation between turbidity, iron and manganese, and to a lesser extent with metals lead, copper, aluminium and zinc. Concentration of metals mobilised is independent of pipe material, diameter or age.
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PMID:Characterisation of materials causing discolouration in potable water systems. 1498 60

The application of extracting aqueous solutions with cyclodextrins in several soil remediation technologies has been increasingly studied but little is known about their removal capacities toward the inorganic species. Herein, the effectiveness of cyclodextrins (CDs) in extracting arsenic, copper, and iron from a mining soil is presented. In a preliminary test of four types of CD aqueous solutions, only the addition of carboxylmethyl-beta-cyclodextrin CMCD (a cyclodextrin derivative) led to a significant enhancement in arsenic removal. An increase in the concentration of copper and iron in the leachates was also observed with CMCD. Kinetic study of arsenic release was carried out at two temperatures (20 and 35 degrees C). The arsenic concentration in the leachates increases with increasing cyclodextrin concentration. At an 80 mM CMCD concentration, arsenic, copper, and iron released in filtrates were about 20-, 1,000-, and 4,000-fold greater, respectively, than that obtained using deionized water. In the soil system, the CMCD capacity removal was found to be higher for cations than for arsenic. Because the tetrachlorophenol can co-occur with arsenic and copper in several contaminated sites, its solubilization by CMCD was also investigated. Extraction experiments were performed to extract 2,3,4,6 tetrachlorophenol (TeCP) in spiked soil with CMCD. The results of batch experiments have shown that CMCD could significantly increase the TeCP extraction from soil. CD sorption on soils as quantified by a fluorescence technique was low, indicating no significant loss of CD during the leaching experiments. The use of CMCD as a flushing agent to enhance the removal of both inorganic and organic pollutants from mixed-contaminated soils appears as a promising remediation method.
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PMID:Enhanced solubilization of arsenic and 2,3,4,6 tetrachlorophenol from soils by a cyclodextrin derivative. 1531 36

The preferable route of iron delivery for most iron-deficient patients is oral. Parenteral iron therapy is used in patients who cannot tolerate oral iron or in cases in which oral iron is not sufficiently effective. The most frequent indications for parenteral iron therapy are unbearable gastrointestinal side effects induced by oral iron itself, worsening of inflammatory bowel disease symptoms, insufficient intestinal absorption, renal failure-caused anemia that is treated with erythropoietin, and unresolved ongoing bleeding, which would cause the acceptable oral doses of iron therapy to be exceeded. The serious adverse effects of iron dextran that was used in the past could explain the reluctance of medical personnel to prescribe this effective treatment. Patients with iron deficiency anemia were treated with intravenous iron in a primary care clinic. The iron gluconate was given in a dosage of 62.5 mg diluted in 150 mL of normal saline and was infused intravenously over 30 min, while iron sucrose was given in a dosage of 100 mg diluted in the same volume of normal saline and given at the same rate. In total, 724 infusions were administered to 57 patients. Iron sucrose was used in 628 infusions, and iron gluconate was used in the remaining 96. The frequency of the infusion treatments depended on the underlying disease and ranged from three times a week to once a month. Adverse effects were seldom observed and were minor in patients receiving iron gluconate, and were not registered at all in patients treated with iron sucrose. Two cases of flushing with paresthesias occurred. Slowing the infusion rate successfully eliminated these side effects. One case of hypotension was treated successfully with 500 cc of normal saline infusion. One case of dropout occurred, due to the patient's refusal to cooperate. No anaphylactic reactions were observed. Iron gluconate and iron sucrose are effective and safe for use in primary care clinics. The risk of adverse effects is low.
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PMID:Intravenous iron in a primary-care clinic. 1579 17

This study undertakes to examine, at laboratory scale, the technical feasibility, mechanisms and performances provided by coupling the enhanced flushing abilities of cyclodextrin solutions for pentachlorophenol (PCP) removal from contaminated soil with indirect electrochemical treatment for the final disposal of soil extract solutions containing high PCP loads (0.77mmolL(-1)). The hydroxypropyl-beta-cyclodextrin (HPCD) solution increased the aqueous concentration of PCP in soil extract effluents to as much as 3.5 times the concentrations obtained during the water flush of the soil. PCP was treated with electrochemically generated Fenton's reagent in an aqueous medium. The increase in PCP water solubility in the presence of HPCD is balanced by the corresponding decrease in PCP degradation rate under indirect electrochemical treatment. This is due to the high carbon content (HPCD and dissolved natural organic matter) in the soil extract solutions, which compete for the non-selective hydroxyl radical reaction to PCP. However, our results indicate that HPCD has a beneficial effect on the degradation rates of PCP. This relative improvement in PCP degradation could be explained by the formation of the ternary complex (PCP-cyclodextrin-iron) which may direct hydroxyl reaction to PCP and which would, in any case, justify the use of a Fenton -like process for the final treatment of soil extract solutions. Total disappearance of PCP and 90% abatement of the chemical oxygen demand were achieved within an 11h electrolysis treatment time. Elucidation of the PCP degradation pathway indicates that after successive PCP hydroxylations, oxidative opening of the PCP aromatic ring quickly occurred, leading to small unstable non-chlorinated or partially chlorinated short chain carboxylic acids, such as monochloroacetic and dichloromaleic acid. Determination of the concentration of these acids shows that indirect electrochemical treatment leads to oxalic acid accumulation in aqueous solutions treated. A decrease in toxicity was observed at the end of the treatment time.
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PMID:Coupling enhanced water solubilization with cyclodextrin to indirect electrochemical treatment for pentachlorophenol contaminated soil remediation. 1597 22


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