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The photo was taken in the
Clarifier No 10 at a major WWTP
near Las Vegas.

Although the traditional EDI has
been installed, the strong
turbulence eddies entering clarifier
can be observed.  

It is interesting in noticing that the
plant operational staff had fully
opened the gates on the existing
EDI to lower the flow intensity and
turbulence. The operational
strategy should help to enhance
the clarifier hydraulic behavior
even if it introduces the inlet flow
along the radius rather than a
tangential direction, which was
expected by the original designers.
The flow intensity entering clarifiers through an gate on the existing EDI
can be determined by looking at the videos recorded during the plant
visiting. As shown in 3 figures below, the videos recorded consists of
13 image clips within a period of one second.

Figure 1 shows the first image clip taken at the time of 12.0 seconds.  A
floating mark right at the lip of the flow guide blade is selected at the
moment in this figure. The locations for the identical floating mark are
presented in Figures 2 and 3 with respect to  the 8th image clip of 12th
second and the first clap image clip of 13th second.  The distance
between the floating mark recorded the first image clip at 12th second
and one at the 13th second presents the traveling distance of the
floating mark within one second. This can be considered as an
averaged velocity (flow intensity) entering into clarifier through the
observed gate.

The traveling distance within a second can be estimated by referencing
it with the width of the flow guide blade.   In this case, the flow intensity
is approximately of 0.51 m/sec (1.7 ft/sec), which generates a fairly
strong turbulence under the typical clarifier flow conditions.

The field data illustrates the typical flow intensity entering a center-feed
clarifier equipped with a traditional EDI. Under the peak flow conditions,
the strong influent flow intensity and turbulence further increases. It is
one of the major reasons to bring up the dispersed sludge blanket
level and fail the clarifier operations when a large amount of bio-solids
sweeps over the effluent weir.
A best solution to eliminate the influent energy in the center-feed
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