AWWA ACE65154

The objective of this project is to improve reservoir mixing while minimizing construction insidetwo reservoirs. The reservoirs, which are owned and operated by EPCOR Water Services Inc.in Edmonton, Alberta, Canada are arranged in parallel between the filters and the distribution pumpstation at the E.L. Smith Water Treatment Plant. Flow through the reservoirs is by gravity. Computational fluid dynamics(CFD) analysis has been used to identify stagnant regions and to develop a strategy to eliminatethem. The CFD software used in this analysis is Fluent. Mixing effectiveness can be evaluatedthrough examination of steady state velocity contours, but a more quantitative assessment hasbeen completed using Fluent's multi-species modelling capabilities. Time dependent solutionsproduced concentration contour plots that can be used individually, or compiled into ananimation sequence, to observe the mixing process. Also measurements of influentconcentration at the effluent can be used to compare reservoir performance over the full rangeof anticipated flow rates. These results could also be used to compare with tracer study results.Due to differences in their configuration, two different approaches to improve mixing have beenproposed, but not yet implemented. In one case, the reservoir is square with its influent andeffluent located at adjacent corners and there is a partial internal wall along the reservoircenterline prevented flow short-circuiting. Installation of nine short wall sections betweencolumns is sufficient to promote cross-channel mixing and eliminate regions of flow stagnationfor all flow conditions.In the second case, the reservoir is very long and narrow with the influent and effluent located atadjacent corners, leading to flow short-circuiting. Since the influent has very little kinetic energy,the ultimate solution involved constructing an internal wall with small openings to promote plugflow along the reservoir length and another to effectively relocate the effluent. Flow stagnation iseliminated, but there is greater uncertainty with the proposed solution because of the lowvelocities.CFD is an excellent prototyping tool to cost effectively examine various possibilities to improvereservoir mixing. The results can often be used to guide the development of innovative andcost-effective solutions, but sometimes uncertain results indicate that a conservative designapproach is appropriate. Includes 4 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

06/01/2007

Number of Pages:

16

File Size:

1 file , 5.2 MB