Bates Engineering, Inc. Water Quality Modeling

A lot of attention has been focused on mixing in water storage facilities because of the increasing awareness of their impact on water quality. In the past, little has been understood about how flow actually passed through water storage facilities. As drinking water standards have become increasingly stringent, this has changed. Water utilities now want to know how water mixes in their facilities for some of the following reasons:

To obtain maximum disinfection credits by increasing the T10 / T time
To avoid stagnant zones that lead to water quality problems such as dbp's
To increase usable storage by improving hydraulic efficiency

The growing need for information on mixing in water storage facilities has resulted in two recent American Water Works Association publications. "Improving Clearwell Design for CT Compliance" (2000) focuses on developing plug flow in water treatment facility clearwells to maximize chlorine disinfection time. "Water Quality Monitoring of Distribution System Storage facilities" (2000) examines the unique flow problems of water tanks distant from the treatment facility. Bates Engineering was a contributing investigator in the latter Study. The information in both of these reports relies primarily on three investigation "tools"

Scale modeling
Computational Fluid Dynamics (CFD) modeling
Prototype monitoring

Bates Engineering believes each of these tools are invaluable in helping water utilities better understand mixing to make important physical and operational adjustments which improve water quality at a minimal cost. Each tool has its own special advantages and can be used to cross-calibrate the results of the other two. The most complete understanding of flow in water storage facilities can be gained by using as many of these tools as possible.

Bates Engineering is in a unique position in providing both scale and CFD models to our clients.

Examples of recently completed studies are:

City of Aurora, Colorado, 3 MG Zone 5 Reservoir, "Inlet Mixing Study"
Denver Water, Foothills 25 MG Reservoirs 1, 2 and 3, "Outlet Antivortex Study"
City of Fort Collins, Colorado Utilities, "East and West 15 MG Reservoirs Baffle Study"

The latter study won the 2000 Award of Excellence from the American Consulting Engineers Council of Colorado. The unique approach utilized by Bates Engineering allowed the City of Fort Collins to increase contact time in the two clearwells by 30% with minimal baffling and fraction of the cost of a traditional baffle system.