The effect of pH adjustment on the internal corrosion rate of cast iron and copper water distribution pipes

Two experimental sessions were conducted to examine to effects of pH adjustment on internal corrosion of cast iron and copper water distribution pipes. The Greater Vancouver Regional District uses surface lakes as its potable water source. As confirmed by chemical water characteristics monitoring, the supplied tap water has several of the attributes of an aggressive water: low pH (4.9 to 5.7), low alkalinity (10 to 15 mg/L as CaCO₃), low hardness (6 to 7 mg/L as CaCO₃), and dissolved oxygen consistently near saturation. Because of this aggressive nature, the tap water has a tendency to dissolve water distribution pipes, and in particular domestic copper pipes (municipal cast iron mains are cement lined for corrosion protection). This accelerated corrosion of copper pipes not only increases the maintenance costs for home owners, it also encourages high levels of copper in their tap water. This last finding was confirmed by a preliminary tap water metal concentration survey wherein, after a month of sampling of six dwellings, it was found that the recommended maximum copper level of 1.0 mg/L was exceeded in 67% of the cold water morning first flush samples. The investigated corrosion control measure consisted of pH adjustment to target values of 6, 7 and 8, through the addition of hydrated lime (Ca(OH)₂). Cast iron and copper pipe samples were exposed to pH adjusted water for durations ranging from one to twelve weeks. For the most part, the adjusted pH experimental flow-through units were gravity-fed; however, to examine the effects of the much higher normal distribution system pressure, another set of control units were maintained at system pressure. Although it was found that the absolute winter corrosion rates were higher than the summer rates, analysis of the relative coupon weight loss variations, with reference to the gravity control unit, lead to two major findings. The corrosion rates of cast iron were ten times those of copper and the increased pH acted to enhance these cast iron corrosion rates by approximately 15%. However, pH adjustment successfully decreased copper corrosion by 68%. The effects of the increased pressure on corrosion were different for both metals. The corrosion rates of cast iron coupons in the control pressurized cells were twice the rates of the coupons in the gravity control units. The effect of the increased pressure on copper was not as marked, but the rates were found to be slightly lower than expected from the pressurized water lower pH.Applied Science, Faculty ofCivil Engineering, Department ofGraduat

Intégration du développement durable par les principes et la démarche de conception dans un cours projet

Le cours ING4901 - Projet intégrateur en développement durable est un cours projet pluridisciplinaire offert aux étudiants de tous les programmes de génie de la dernière année du baccalauréat à l’école Polytechnique de Montréal. Depuis le trimestre d’automne 2009, des étudiants inscrits au cours ARC3012-B - Atelier forme et technique sont intégrés aux équipes d’étudiants en génie et un enseignant en architecture a joint l’équipe professorale pour encadrer les étudiants en architecture. Le cours ING4901 vise à intégrer le développement durable dans la formation et démontre que tous les ingénieurs et architectes sont concernés par le développement durable, peu importe leur domaine de pratique. Au-delà de l’intégration des notions techniques acquises au cours du baccalauréat et l’intégration du développement durable, le cours initie les étudiants à la conception intégrée, pratique de plus en plus courante dans la conception de bâtiments verts, et au travail d’équipe pluridisciplinaire. Un des fondements du développement durable est la transversalité, concept difficile à mettre en application, mais qui assure le succès d’un projet parce que les contraintes et objectifs de toutes les disciplines sont pris en considération dès le début du projet. Les enseignants tentent par l’encadrement et les activités de faire travailler les étudiants ensemble et éviter le travail en silo, malgré le langage technique différent des membres de l’équipe. Les enseignants encadrent la démarche de conception des étudiants, proposent des activités impliquant des professionnels de différents domaines pour les soutenir techniquement et les guident pour l’intégration du développement durable.The course ING4901 - Sustainable Development Capstone Project is a pluridisciplinary, last-year undergraduate project course offered to engineering students from all programs at École Polytechnique de Montréal. Since the term fall 2009, students in architecture who had registered for final-year undergraduate course ARC3012B – Workshop form and technique were integrated into the teams of engineering students. A teacher from the School of Architecture joined the teaching team to supervise the architecture students. The course ING4901 aims to integrate sustainable development into the educational background and demonstrate that all engineers and architects should be concerned with sustainable development no matter what their field of practice. In addition to incorporating technical concepts learned during the bachelor’s program the course introduces students to integrated process design, a practice that is increasingly common in the design of green buildings. A foundation of sustainable development, integrated process design may be difficult to apply but can ensure a project’s success, as the constraints and goals of all disciplines involved are considered from the beginning of the project. Through course activities and support, teachers encourage students to work together and avoid working in silo despite the different technical languages of team members. Teachers supervise the students’ design process, organize activities involving professionals from different fields to provide students with technical support, and guide students in addressing all aspects of sustainable development

Intégration du développement durable par les principes et la démarche de conception dans un cours projet

The course ING4901 - Sustainable Development Capstone Project is a pluridisciplinary, last-year undergraduate project course offered to engineering students from all programs at École Polytechnique de Montréal. Since the term fall 2009, students in architecture who had registered for final-year undergraduate course ARC3012B – Workshop form and technique were integrated into the teams of engineering students. A teacher from the School of Architecture joined the teaching team to supervise the architecture students. The course ING4901 aims to integrate sustainable development into the educational background and demonstrate that all engineers and architects should be concerned with sustainable development no matter what their field of practice. In addition to incorporating technical concepts learned during the bachelor’s program the course introduces students to integrated process design, a practice that is increasingly common in the design of green buildings. A foundation of sustainable development, integrated process design may be difficult to apply but can ensure a project’s success, as the constraints and goals of all disciplines involved are considered from the beginning of the project. Through course activities and support, teachers encourage students to work together and avoid working in silo despite the different technical languages of team members. Teachers supervise the students’ design process, organize activities involving professionals from different fields to provide students with technical support, and guide students in addressing all aspects of sustainable development

Modelling Nitrification of a Lagoon Effluent in Moving-Bed Biofilm Reactors

Abstract A pilot study was performed at the Sainte-Julie wastewater treatment plant to evaluate the potential of using the Moving-Bed biofilm reactor (MBBR) process for removing BOD5 (5-day biochemical oxygen demand) and ammonia nitrogen in a two-stage process at the exit of the first lagoon. Nitrification was observed in the first reactor at rates similar to those reported in the literature for a similar biomass carrier when bulk liquid dissolved oxygen (DO) concentrations were 6 g of O2 per m3. Nitrification rates were significantly reduced when DO was reduced to 3 g of O2 per m3. DO concentrations were maintained at 6 g of O2 per m3 in the second reactor, and nitrification rates comparable to those reported in the literature were observed for a temperature range of 3 to 16°C. An empirical DO-limited model was validated for the first reactor while in the second reactor nitrification was found to be either DO limited or total-ammonia-nitrogen limited, depending on nitrification rates in the upstream reactor. The DO-limited model predicts that the MBBR process is more sensitive to organic load than it is to temperature. A commercially available numerical model was calibrated to the results of the pilot study. Model results indicate that detachment and attachment rates play an important role in determining nitrification rates in the biofilm. Similar nitrification rates in an MBBR system installed upstream and downstream from an aerated lagoon in winter conditions were predicted using the empirical DO-limited model.</jats:p