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【In order to suggest the methodology for improving the equity of flow distribution in open channel with multiple outlet, CFD simulations were carried out for actual scale distribution channel being operated in domestic G_WTP(Water Treatment Plant). Also, before and after installing the longitudinal multi hole(diameter=250 mm, 116 holes) baffle suggested by this research, turbidity measurements data were collected for evaluating the effects of hydraulic modification for inlet flow equity. From the both results, total turbidity of settled water was lowered by 30 % and equity of flow distribution was improved about 60 % compared with before hydraulic structure modification.】

This study was conducted to qualify the equality of the flow distribution from open channel between rapid mixing basin and flocculation basins in a domestic S_ water treatment plant, and to suggest a remedy for improving the equality. In order to evaluate the feasibility of the suggested remedy, computational fluid dynamics (CFD) technique are used, and for verifying the CFD simulation results tracer tests were carried out. From the results of CFD simulation and tracer tests, it was investigated that the modification of hydraulic structure in the distribution channel, which is to install the longitudinal orifice baffle in flow direction, could improve the equality of the flow distribution over 75%.

In the case of S water treatment plant, it was designed to be mostly operated by direct filtration mode all the year round. To evaluate the conditions of such operation mode, in this study, we operated pilot plant by direct filtration process by making flocculation treatment water flow into anthracite filter and active carbon (Calgon, Norit) filter which is an assembly of deep bed filter paper, and studied to find out the principle in which turbidity is removed in filter paper by measuring turbidity and head loss by the depth of filter, and an appropriate operation method. Also we conducted comparison evaluation according to kinds of coagulant and evaluation according to the injection of a polymer coagulant, a filter aid, before letting filter flow into flocculation treatment water. On the basis of the optimum operation of direct filtration process using deep bed filtration, it is necessary to decide and inject the optimum injection volume of filter aids taking account for the quality of raw water and to operate anthracite filter, which will also contribute to lowering the operation expenses of a filtration plant and improving the quality of treatment water.

Dissolved air flotation (DAF) is a solid–liquid separation system that uses fine bubbles rising from the bottom to remove particles in water. In this study, we investigated the effect of L/W(L; length, W; width) on the hydrodynamic behavior in a DAF system using CFD (computational fluid dynamics) and ADV (acoustic Doppler velocimetry) technique. The factual full-scale DAF system, L/W ratio of 1:1, was selected and various L/W ratio conditions (2:1, 3:1, 4:1 and 5:1) were simulated with CFD. For modelling, 2-phase (gas–liquid) flow equations for the conservation of mass, momentum and turbulence quantities were solved using a Eulerian–Eulerian approach based on the assumption that a very small particle is applied in the DAF system. Also, for verification of CFD simulation results, we measured the actual velocity at some points in the full-scale DAF system with the ADV technique. Both the simulation and the measurement results were in good accordance with each other. We concluded that the L/W ratio and outlet geometry play an important role for flow pattern and fine bubble distribution in the flotation zone. In the ratio of 1:1, the dead zone is less than those in other cases. On the other hand, in the ratio of 5:1, the fine bubbles were more evenly distributed.