Browsing by Author "Lagos, GE"

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    Aging of copper pipes by drinking water
    (AMER WATER WORKS ASSOC, 2001) Lagos, GE; Cuadrado, CA; Letelier, MV
    Thermodynamic models were used to correlate experimental and field data for the concentrations of copper (Cu), anions, and cations in drinking water with Cu-containing scales on the inner walls of pipes. This study focused special attention on the aging processes of these scales. Precipitation and dissolution were predicted to be the main aging causes for Cu scales present on the inner walls of pipes. When data were grouped by the solid that controls solubility, the average 8-h stagnant Cu concentration in drinking water was found to decrease linearly with average pipe age. For these average values, langite was the most soluble and youngest film, followed in both solubility and age by cupric hydroxide, azurite, brochantite, malachite, and tenorite. The more stable solids-malachite and tenorite-were 8 and 16 times less soluble, respectively, than the most soluble solid, langite. Scales usually contained more than one compound, a finding that was attributed to temperature changes, variability of water composition, long stagnation periods, and aging. During the aging process, parts of a young scale surface area may be covered and blocked for further reaction by a precipitate. During long stagnation periods, such factors as changes in pH, oxygen, and carbon dioxide concentrations and precipitation of calcium solids may induce a different Cu compound precipitate.
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    Model for estimation of human exposure to copper in drinking water
    (1999) Lagos, GE; Maggi, LC; Peters, D; Reveco, F
    A model denominated Consumption Habit Exposure Model, (CHEM), was developed for the calculation of human individual acute and chronic exposure to copper in drinking water. The model can estimate daily exposure of individuals as well as the maximum concentration of copper which individuals ingest during a 24-h period. The CHEM model requires carrying out a water consumption habit questionnaire and measuring the minimum and maximum concentration of copper in homes, as well as minimum and random copper concentration at work and study places. The case study employed was a representative sample of the population of Santiago, Chile. The validation of the model was established with reference to the application in a limited number of homes of the composite proportional method, (CPS), used to measure human chronic ingestion of contaminants from drinking water. It was found that 4.5% of the sampled population is exposed daily to one cup of water or more at the maximum copper concentration available at the tap. The probabilities that the different age groups are exposed to one cup or more of water at c(MAX) during 1 day are greater for the 20-64-year-old group, followed by the 64-year-old group, and then by the younger age groups in descending order. Ingestion of copper from drinking water by the population of Santiago is on average 9.0% of the World Health Organization recommendations for minimum total ingestion of copper for adults, assuming that 100% of the copper contained in drinking water is absorbed. (C) 1999 Elsevier Science B.V. All rights reserved.
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