...
Spring
...
2008
...
Experiment
...
(Sara
...
Schwetschenau
...
,
...
Kevin
...
Borden,
...
T.
...
David
...
Mcevoy)
| Wiki Markup |
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{float:right|border=2px solid black|width=200px} {anchor:Sludge Judge}[!Pilot Plant- Sedimentation Tank^IMG_1085.jpg|width=200px!|Pilot Plant- Sedimentation Tank^IMG_1085.jpg] h5.Sludge Judge Results after one week - notice The thicker sludge seen at the bottom {float} |
The
...
first
...
sedimentation
...
tank
...
containing
...
the
...
floc
...
blanket
...
has
...
been
...
constructed.
...
Flocs
...
enter
...
the
...
tank
...
and
...
do
...
not
...
appear
...
to
...
be
...
breaking
...
up,
...
so
...
it
...
has
...
been
...
determined
...
that
...
our
...
entrance
...
pipe
...
was
...
large
...
enough.
...
The
...
hydraulics
...
are
...
working
...
correctly
...
and
...
the
...
water
...
levels
...
are
...
as
...
calculated.
...
We
...
also
...
measured
...
the
...
flow
...
rate
...
of
...
the
...
sedimentation
...
tank
...
and
...
the
...
sludge
...
hopper,
...
and
...
both
...
were
...
very
...
close
...
to
...
the
...
design
...
rates.
...
Over
...
the
...
past
...
week
...
we
...
have
...
been
...
observing
...
how
...
the
...
floc
...
blanket
...
has
...
been
...
forming.
...
Sludge
...
has
...
been
...
piling
...
up
...
slowly
...
and
...
a
...
suspension
...
of
...
flocs
...
has
...
begun
...
to
...
form.
...
By
...
the
...
end
...
of
...
the
...
first
...
week
...
it
...
was
...
very
...
clear
...
that
...
a
...
thin
...
floc
...
blanket
...
had
...
formed
...
in
...
the
...
tank.
...
Although
...
some
...
floc
...
were
...
noticed
...
to
...
still
...
be
...
making
...
it
...
up
...
to
...
the
...
effluent
...
manifold
...
a
...
large
...
number
...
of
...
flocs
...
were
...
being
...
captured
...
by
...
the
...
floc
...
blanket.
...
The
...
flocs
...
forming
...
the
...
blanket
...
were
...
relatively
...
large,
...
up
...
to
...
5
...
mm
...
in
...
diameter.
...
The
...
top
...
of
...
the
...
blanket
...
was
...
forming
...
around
...
the
...
level
...
of
...
the
...
sludge
...
hopper.
...
This
...
tells
...
us
...
that
...
the
...
hopper
...
is
...
successfully
...
controlling
...
the
...
level
...
of
...
flocs
...
in
...
the
...
tank.
...
Hopefully
...
with
...
more
...
time
...
for
...
development
...
the
...
floc
...
blanket
...
performance
...
will
...
improve
...
as
...
the
...
floc
...
blanket
...
thickens,
...
and
...
the
...
smaller
...
flocs
...
noticed
...
toward
...
the
...
top
...
of
...
the
...
tank
...
will
...
be
...
captured.
...
It
...
was
...
observed
...
that
...
upward
...
flow
...
through
...
the
...
tank
...
seemed
...
slightly
...
faster
...
in
...
the
...
front
...
corner
...
of
...
the
...
tank
...
by
...
the
...
effluent
...
manifold.
...
Upon
...
tank
...
draining,
...
it
...
was
...
observed
...
that
...
the
...
sludge
...
at
...
the
...
bottom
...
of
...
the
...
tank
...
formed
...
a
...
conical
...
shape.
...
The
...
evenness
...
of
...
the
...
conical
...
shape
...
demonstrates
...
that
...
flow
...
seems
...
to
...
be
...
flowing
...
uniformly
...
out
...
of
...
the
...
inlet
...
and
...
up
...
through
...
the
...
tank,
...
and
...
thus
...
the
...
slight
...
increase
...
in
...
flow
...
noticed
...
at
...
the
...
top
...
of
...
the
...
tank
...
is
...
not
...
significant,
...
and
...
it
...
is
...
not
...
leading
...
to
...
a
...
large
...
amount
...
of
...
scour
...
at
...
the
...
bottom
...
of
...
the
...
tank.
...
Flow
...
irregularity
...
is
...
a
...
concern
...
because
...
it
...
is
...
one
...
of
...
the
...
main
...
causes
...
of
...
blanket
...
instability
...
and
...
poor
...
blanket
...
formation.
Future Research
The goal of this project is to determine the most efficient method of sedimentation. The two technologies that have been considered are floc blankets and lamella. There are some concerns about building a sedimentation tank that relies solely on a floc blanket. It takes time to build up a floc blanket that works well, especially if the incoming water has a low initial NTU. Also if an improper alum dose if given to the flocculator for any amount of time the floc blanket may disappear, removing the only method of sedimentation. Having some addition settling mechanism such as lamella would help with with settling during the times when the floc blanket is not performing well. It is the goal of this project for this summer and the upcoming semester to determine the reliability of floc blankets and determine how difficult would be to maintain a floc blanket even during times when turbidity is low, if alum is not being dosed correctly, or if only small flocs are being produced.
Other research projects include developing methods that would encourage faster formation of floc blankets. Other ideas included adding a mesh fabric filter at the top of the tank just below the launder to capture an tinp floc that escape above the floc blanket. This mesh would also allow for higher V up values to be used the nesh would act a secondary capture for the smaller floc not captured in the blanket. Also given that φ floc is the major factor affecting sludge blanket formation, techniques to affect φ floc could also created stronger and better floc blankets.
Possible modifications of the floc blanket tank include: lowering the continuous flow sludge removal rate to minimize water waste, optimizing floc blanket performance by modifying the blanket height and installing a clay solution feed to increase inflow turbidity to better mimic conditions in Honduras.
After construction of the lamella sedimentation tank, research will be done to see if anything can be done to improve setting in this design. We also want to analyze the possibility of forming a floc blanket underneath the lamella. The combination of these technologies seems like a viable option.
Inline Turbidity meters can hopefully be procured to test the outgoing turbidity from each sedimentation tank. This will allow testing how well sedimentation tanks perform over time and during various conditions, such as performance of the flocculator and raw water turbidity.