Practical outcomes of operating under ineffective mixing conditions in a treatment plant may lead to potential negative consequences such as poor floc formation, reliance on excess flocculant aid, decreased incorporation of dissolved organics in floc, and increased particle load to the filters. It was demonstrated through this study that the flocculation tanks were not adequately mixed for effective floc formation. These designs are based on a relatively older design approach and there is a need for evaluating the design in terms of local hydrodynamic parameters, which can be predicted effectively by CFD applications. Several plants across Canada have similar infrastructure. Kline Water Supply Plant in Halifax, Nova Scotia. This study used a numeric modeling technique-computational fluid dynamics (CFD)-to evaluate the existing flocculation facilities at the J.D. Optimization of mixing and coagulation is paramount in the effort to optimize removal of dissolved contaminants and particles in a full-scale treatment plant. Results were compared with experimental data obtained from real drinking water treatment plants located in the cities of Nuevo Laredo and Río Bravo, Tamaulipas and Piedras Negras, Coahuila, Mexico. The uniqueness of the solution is discussed, and comparison with simpler one and two-parameter models is provided. An optimization procedure, implemented in MS Excel, is then used to obtain the number of tanks, and the fractions of dead-space and bypassing minimizing the difference between tracer test data and unit's residence-time distribution function. Expressions for the first three moments of the proposed RTD function are derived. A three-parameter tank-in-series RTD model for interpretation of tracer tests is presented in this paper, where the parameters are the number of tanks, the portion of dead-space and the portion of bypassing.
Computational fluid dynamics (CFD) and residence-time distribution (RTD) based tracer test models may be used to identify such problems the RTD models are more appropriate for operating treatment units. Imperfect hydraulic behaviour of water treatment units, expressed by stagnation space and bypassing, may substantially reduce treatment efficiency.
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