Browsing by Author "Vargas, Ignacio T."

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    Empirical model for dissolved oxygen depletion during corrosion of drinking water copper pipes
    (PERGAMON-ELSEVIER SCIENCE LTD, 2010) Vargas, Ignacio T.; Pasten, Pablo A.; Pizarro, Gonzalo E.
    Predictive models characterizing the evolution and interaction of key parameters of water chemistry are needed to better understand corrosion events in drinking water pipes. We performed experiments with new copper pipes under combinations of pH, dissolved oxygen (DO), temperature, chlorine, and dissolved inorganic carbon. We found that DO consumption during 24 h of stagnation was not limited by diffusion, thus the DO consumption rate in the bulk water could be used to probe the processes occurring at the pipe surface. We propose a quantitative dependency of the DO consumption rate on a rather limited set of physicochemical parameters. (C) 2010 Elsevier Ltd. All rights reserved.
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    Enhanced copper release from pipes by alternating stagnation and flow events
    (AMER CHEMICAL SOC, 2007) Calle, Gustavo R.; Vargas, Ignacio T.; Alsina, Marco A.; Pasten, Pablo A.; Pizarro, Gonzalo E.
    Traditional studies of copper release in plumbing systems assume that the water extracted from a pipefollows a plug-type flow and that the pipe surface does not interact with the bulk water under flow conditions. We characterized actual stagnation-flushing cycles in a household pipe undergoing Corrosion in the presence of a microbial biofilm. The mass of copper released in 10 experiments was on average 8 times the value estimated by using the plug-flow assumption. The experimental copper release pattern was explained by an advection-diffusion model only if a high copper concentration occurs near the pipe surface after stagnation. Microscopic examination of the pipe surface showed a complex assemblage of biotic and abiotic features. X-ray diffraction analyses identified only malachite, while X-ray absorption spectroscopy also revealed cupric hydroxide and cuprite. These results indicate that the surface serves as a storage compartment of labile copper that may be released under flow conditions. Thus, the diffusive transport from the pipe surface to the bulk during stagnation is not the only control of the flux of copper to the tap water when porous reactive microstructures cover the pipe. Our results highlight the need for models that consider the interaction between the hydrodynamics, chemistry, and structure at the solid-water interface to predict the release of corrosion byproducts into drinking water.
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    Increase of the concentration of dissolved copper in drinking water systems due to flow-induced nanoparticle release from surface corrosion by-products
    (PERGAMON-ELSEVIER SCIENCE LTD, 2010) Vargas, Ignacio T.; Pavissich, Juan P.; Olivares, Tomas E.; Jeria, Gustavo A.; Cienfuegos, Rodrigo A.; Pasten, Pablo A.; Pizarro, Gonzalo E.
    Standard measurements of dissolved copper are made by filtering water samples through 0.45 mu m pore-size membranes. However, the surface of corroding metallic surfaces may be covered by topographic features < 0.2 mu m and structures that can be detached into the bulk water as nano-sized particles. A SEM, EDX, and AFM characterization of a corroding pipe after flow events revealed surface cavities, detached particles and attached particles with sizes between 0.05 and 0.2 mu m. Our findings show that the release of colloidal and nanoparticles of corrosion by-products into the water can result in an increase of the dissolved copper measurements. (C) 2010 Elsevier Ltd. All rights reserved.
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    Influence of solid corrosion by-products on the consumption of dissolved oxygen in copper pipes
    (PERGAMON-ELSEVIER SCIENCE LTD, 2009) Vargas, Ignacio T.; Alsina, Marco A.; Pasten, Pablo A.; Pizarro, Gonzalo E.
    Research on corrosion of copper pipes has given little consideration to the influence of solid corrosion by products on the processes occurring at the metal-liquid interface. Consequently, the effect of such solid phases on the rate of dissolved oxygen (DO) consumption remains poorly understood. In-situ experiments were performed in copper pipes under different carbonate concentrations and ageing times. Our results show that the amount of solid corrosion by-products and concentration of hydrogen ions affect the rate of DO consumption during stagnation. Furthermore, our findings support the existing hypothesis that the available concentration of hydrogen ions, rather than DO, is the limiting factor for copper release into drinking water. (C) 2009 Elsevier Ltd. All rights reserved.
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    Long-term evaluation of soil-based bioelectrochemical green roof systems for greywater treatment
    (2024) Tapia, Natalia; Gallardo-Bustos, Carlos; Rojas, Claudia; Vargas, Ignacio T.
    Water scarcity has generated the need to identify new sources. Due to its low organic contaminant load, greywater reuse has emerged as a potential alternative. Moreover, the search for decentralized treatment systems in urban areas has prompted research on using green roofs for greywater treatment. However, the performance of organic matter removal is limited by the type of substrate and height of the growing media. Bioelectrochemical systems (BESs) improve treatment performance by providing an additional electron acceptor (the electrode). In this study, nine reactors under three different conditions, i.e., open circuit (OC), microbial fuel cell (MFC), and microbial electrolysis cell (MEC), were built to evaluate the treatment of synthetic greywater in a substrategrowing medium composed of perlite and coconut fiber and operated in batch-cycle mode for 397 days. The results suggested that using BESs enables greywater treatment and the removal of pollutants to levels that allow their reuse for irrigation. Furthermore, electrical conductivity was reduced from 732.4 +/- 41.2 mu S/cm2 in OC to 637.32 +/- 22.73 mu S/cm2 and 543.15 +/- 19.69 mu S/cm2 in MEC and MFC, respectively. The soluble chemical oxygen demand in the latter treatments reached 76% removal, compared to levels above the OC, which only reached approximately 67%. Microbial community analysis revealed differences, mainly in the cathodes, showing a higher development of Flavobacterium, Azospirillum, and Zoogloea in MFCs, which could explain the higher levels of organic matter removal in the other conditions, suggesting that the BES could produce an enrichment of beneficial bacterial groups for treatment. Therefore, implementing BESs in green roofs enables sustainable longterm greywater treatment.