AWWA WQTC62514

Chemical reagents mixing within raw water appears at several stages of the drinking water process. In particular, in the clarification step, coagulant and flocculant (or polymer aids) dosage and mixing within raw water have to be efficient to avoid over-dosage, reducing expenses and limiting residual reagent leakage. Computational Fluid Dynamics (CFD) modeling allows to assess the corresponding mixing device efficacy before implementing it on site. Full-scale data can be used to reproduce the phenomena involved inside the process. In this study, three applications of mixing assessment through CFD are considered: two designs of flash mixing for coagulant dispersion are compared, residence time distribution is studied for a potential extra mixing chamber and injection system location and efficacy for coagulant-aid are studied on full-scale data. Optimum operating conditions, optimum device location and predictive behavior can be derived from CFD, to support the operator in its technical optimization of mixing devices. Includes 6 references, tables, figures.