OPTIMIZING DISTRIBUTION STORAGE WATER-QUALITY - A HYDRODYNAMIC APPROACH

A rigorous three-dimensional hydrodynamic model of distribution reserv oir water quality is developed for use in simulating chemical mixing a nd internal patterns of flow exhibited within distribution storage res ervoirs. The model is predicated on the principles of computational fl uid dynamics and considers the basic forces and energy of the mixing f luid. In this approach, the three-dimensional time-averaged Navier-Sto kes fluid flow equations with a k-epsilon turbulence model are discret ized and ave solved over a finite-difference grid across the reservoir geometry. The motion of fluid particles throughout the reservoir can then be determined as a function of space and time. The resulting mode l is both accurate and robust, and it can be applied readily to all ty pes of storage reservoir configurations, characteristics, and hydrauli c conditions. The proposed numerical model was tested for a number of locations in the United States by comparing the results with both benc h-top and fill-scale test data. The applicability of the model is demo nstrated herein by application to a water plant clearwell. The effects of baffling on residence time distribution for disinfection effective ness were also investigated, and conclusions are stated The effective use of the proposed model can lead to improved designs, retrofitting p lans for existing facilities, or modified operational policies for new or existing reservoirs, and to aid in optimizing distribution water q uality and securing regulatory compliance and consumer satisfaction. ( C) 1997 by Elsevier Science Inc.