Laminar and turbulent regime changes in drinking water contact tanks

Transitions in flow regimes that can occur in drinking water contact tanks may significantly affect the disinfection efficiency of the system. To demonstrate these effects, the authors investigated the internal velocity fields and flow regime of a drinking water contact tank located in Jamestown, Colo. The baffling factor (BF) of the system fluctuated annually between 0.5 and 0.6 because of a shift in flow regime caused by changes in the flow rate of the system. The authors studied the effects of the regime change from laminar to turbulent flow (or vice versa) using computational fluid dynamics (CFD) models and physical tracer studies. Several inlet modifications were then investigated using CFD to determine which alteration would be most beneficial. Key findings showed that with proper inlet modification, the BF of the system could be stabilized at 0.6 during periods of high or low flow.