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| The model shows how trihalomethanes rise to unacceptable levels with increasing water temperatures. |
By Hugh Monteith, Enviromega Inc.,
Robert C. Andrews
and Ronald Hofmann, University of Toronto, Dept. of Civil Engineering
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| The model shows how trihalomethanes rise to unacceptable levels with increasing water temperatures. |
In a recent innovative assignment, Civil Engineering students at the University of Toronto pooled their talents to address a growing drinking water issue. Teams of graduate students used computer simulation to determine how best to optimize a water treatment plant to meet tough new standards for disinfectant residual and disinfectant by-product (DBP) concentrations, while maintaining the mandatory reduction of indicator microbes.
The assignment marked a new approach by Dr. Robert Andrews and his research associate, Ron Hofmann, to address real-world problems in the classroom. According to Dr. Andrews, "the students were called upon to develop an optimal water treatment process train while taking into account both operational and regulatory constraints."
The students used a water treatment simulation program called WatPro (developed by Enviromega Inc.) for their assignment. The software allowed the students to easily modify the point of disinfectant addition, change the type of disinfectant or coagulant, and to add or modify unit processes in their assessment. Research on DBP formation completed by Dr. Andrews and his graduate students has been incorporated into the model, such that WatPro is state-of-the-art. For example, models for by-product formation when using chlorine dioxide as the primary disinfectant have just recently been added to the model. "WatPro represents a unique platform in which to integrate research that has been funded by many organizations, and completed by graduate students at the University of Toronto," said Prof. Andrews.
For the assignment, student teams assumed the role of consulting firms. The aspiring engineers were required to prepare a report addressing the concerns of a municipality faced with stringent new limits on total trihalomethanes (TTHMs) and haloacetic acids (HAAs). The criteria would be similar to those proposed in the USA for the Stage II Disinfectant/Disinfection By-Product Rule. The objective of the assignment was to evaluate potential treatment scenarios, and then recommend the modifications that would be required for process operations and in order to achieve the requirements, while still maintaining effective microbial control.
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