AWWA ACE93151

Water quality studies were conducted on three storage reservoirs of varying geometry (diameter-to-height ratios) and operation (amount of volumetric change during a fill/drain cycle). Tank influent and effluent were monitored for free chlorine. Chlorine and temperature measurements were also conducted at various depths within the tank water column. In each of the tanks studied, chlorine decay appeared to occur. Tank geometry did not appear to have a significant effect on mixing characteristics. All tanks generally behaved more as completely mixed rather than plug flow reactors. As a consequence of mixing, chlorine loss during a single fill/drain cycle was more pronounced in tanks with the least volumetric change during the fill/drain cycle. The assumption of completely mixed behavior of storage tanks suggests that consideration in their design be given to maximizing volumetric change and minimizing average water age during fill/drain cycles.