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\begin_layout Title
Sedimentation Tank Hydraulics Final Research Report
\end_layout

\begin_layout Author
Frances Ciolino, Hongyi Guo, Ethan Yen
\end_layout

\begin_layout Date
November 16, 2012
\end_layout

\begin_layout Abstract
The sedimentation tank hydraulics team this semester focused on optimizing
 the floc hopper.
 Our main goal was to learn more about the floc hopper geometry and reasons
 for floc blanket failure.
 We started the semester by looking at the vertical sedimentation velocity.
 This velocity is controlled by the flow into the tank and effects how fast
 the particles settle.
 If this velocity is too high or too low, the sedimentation tank will not
 form a proper floc blanket.
 
\end_layout

\begin_layout Abstract
We also looked into how the plan view area of the floc hopper would effect
 the floc blanket formation and performance.
 Changing the size of the floc hopper effects how much of the area allows
 for up-flow of the water and how much captures the flocs.
 In our current experiments we are trying different sizes at different wasting
 rates.
 We are looking for a size and rate that keeps the plant running efficiently,
 meaning the least amount of water wasted while keeping the water leaving
 the plant clean.
 
\end_layout

\begin_layout Abstract
One of the ideas we are working on is continuous wasting of the flocs.
 The idea behind this is to allow for constant removal of flocs instead
 of collecting the flocs and then manually opening a valve to let them leave
 the tank.
 When the wasting rate is optimal, the flocs will be allowed to compact
 before they are removed so that the least amount of water is lost in the
 process.
 Our last experiment looked at finding the proper wasting rate where the
 rate of particles flowing into the floc hopper is the same as the rate
 at which the particles are being removed.
\end_layout

\begin_layout Part
Literature Review
\end_layout

\begin_layout Standard
To prepare for our experiments the previous research done with sedimentation
 tank hydraulics was reviewed.
 Since we are repeating the hindered sedimentation velocity experiment from
 last semester, we read over that experiment in great detail.
 One of the conclusions made in that experiment was that the first 30 seconds
 was not long enough for finding the velocity because the computer program
 used to analyze the video was not sensitive enough to detect the small
 movement.
 We are therefore going to look at the sedimentation over a longer period
 of time.
 We decided on 10 minutes since the majority of the settling was completed
 by then.
 We are going to perform the experiment at the same 3 velocities previously
 used, .6mm/sec ,1.2mm/sec , and 1.6mm/sec.
 We are using a different insert so we will see if the other insert changes
 the outcome of the experiment.
 We also hope to study the behavior of the floc blanket as it settles to
 see if it gives any more insight into floc bed characteristics.
\end_layout

\begin_layout Standard
Previous AguaClara experiments conducted last spring looked at the idea
 of continuous wasting.
 In continuous wasting, sludge is continuously removed from the floc hopper.
 Since they are being continuously removed, the flocs are not given as much
 time to settle as in pulse wasting.
 Therefore suspended flocs were being removed instead of consolidated sludge.
 To minimize the wasting of clean water, the wasting rate should equal the
 rate at which flocs are flowing over the weir.
 This wasting rate is also a function of the influent rate and influent
 turbidity as well as the concentration of flocs in the floc blanket.
 
\end_layout

\begin_layout Standard
The previous team discovered that the overall problem with continuous wasting
 is that a high wasting rate will leave little time for flocs to condense
 and the waste pump will be drawing out clean water that could have been
 used for drinking.
 However, a low wasting rate can cause a floc blanket failure where flocs
 flow up into the tube settlers and eventually into the effluent.
 Therefore in our experiment testing different weir sizes, it will be important
 to find a balance where minimal water is being wasted and there is a high
 concentration of flocs in the weir, but not to the point where the floc
 blanket is in failure.
\end_layout

\begin_layout Part
Introduction 
\end_layout

\begin_layout Standard
The sedimentation tank is used to form a floc blanket in the bottom of the
 tank and allow clean water to flow out the plate settlers at the top.
 The floc blanket that forms is a dense area of particles and works like
 a filter to catch smaller particles that might not settle on their own.
 The jet reverser continuously re-suspends the flocs so they do not build
 up in the bottom of the tank.
 The floc blanket is continuously removed from the sedimentation tank so
 it does not build up and clog the tank.
 Removing the floc blanket is accomplished by installing a floc weir that
 allows the floc blanket to flow over the weir and out the sludge drain.
 
\end_layout

\begin_layout Standard
Optimizing the floc blanket and floc weir is an important part of reducing
 excess sludge and continuously allowing clean water to flow out of the
 tank.
 When optimized it also reduces the amount of water wasted by further concentrat
ing the flocs in the weir.
 We will be working on optimizing the floc hopper geometry for the best
 floc extraction.
 The best geometry will be one with the highest floc hopper concentration
 and the lowest optimal continuous wasting rate.
 
\end_layout

\begin_layout Standard
Another problem currently encountered in Aguaclara plants is detection of
 floc blanket failure before it occurs.
 Therefore we will be working on identifying floc blanket failure conditions
 so that a method can be constructed to avoid those failures in the future.
 This will allow the team to give operators the ability to recognize floc
 blanket failure before it occurs so operators can always be providing the
 best possible water to the community.
\end_layout

\begin_layout Standard
Another aspect of the sedimentation tank that is relevant to our current
 research is the buildup of sediment in the tank.
 Currently the flocs flow over the floc weir and settle for a while before
 being removed.
 This can cause the tank to have a buildup of condensed flocs over time.
 A buildup of flocs must be removed by shutting down the whole plant in
 order to clean the tank.
 Using continuous wasting instead of the current method could eliminate
 the buildup of flocs and therefore eliminate the necessity to shut down
 the plant to clean the tank.
 Our research will look into the possibility of continuous wasting as an
 option for future plants.
\end_layout

\begin_layout Part
Methods
\end_layout

\begin_layout Section*
Hindered Velocity Experiment
\end_layout

\begin_layout Standard
For the hindered velocity experiment we set the upflow velocities at 3 different
 rates to see how this would affect the settling velocity.
 The three upflow velocities we chose to test were 0.6mm/sec, 1.2 mm/sec,
 and 1.6mm./sec.
 We set the alum dose at 45mg/L and the influent turbidity at 100 NTU.
 The plant is allowed to run until an acceptable stable floc blanket is
 formed.
 At this point the influent pump is turned off and the floc blanket is allowed
 to settle.
 The settling is recorded using the LabVIEW program with the camera set
 at 5 sec/shot for eight minutes.
 The pictures are then compiled into a video which is used to analyze the
 settling velocity.
 LabVIEW measures the actual height of the floc blanket at each 5 sec interval
 which allows us to calculate the hindered sedimentation velocity.
\end_layout

\begin_layout Section*
Floc Hopper Geometry Experiment
\end_layout

\begin_layout Standard
We constructed three different floc wiers, each having a plan view area
 of 10%, 15% and 20% of the sedimentation tank plan view
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Floc Hoppers of Various Plan Views"

\end_inset

.
 The angle of the floc weir was kept constant among the three floc wiers,
 which results in varying volumes.
 The plant was run at 1.2 mm/sec, 45mg/L alum dosage and an influent turbidity
 at 100 NTU.
 A floc blanket is allowed to form and flocs are allowed to accumulate in
 the floc hopper.
 Once the floc hopper is filled, the wasting rate is set to 40 mL/min and
 is then decreased in incremental steps, allowing sufficient time for the
 floc bed to attain a steady state.
 Once the height of the floc bed and flocs in the hopper are constant, the
 wasting rate is recorded.
 After compiling all the data, the video analysis software is used to calculate
 the concentrations in the floc bed and floc hopper.
\end_layout

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\begin_inset Caption

\begin_layout Plain Layout
Floc Hoppers of Various Plan Views
\begin_inset CommandInset label
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name "fig:Floc Hoppers of Various Plan Views"

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\begin_inset Caption

\begin_layout Plain Layout
Sedimentation Tank
\begin_inset CommandInset label
LatexCommand label
name "Sedimentation Tank"

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\end_inset


\end_layout

\end_inset

A few changes were made to our setup.
 The first change is that we decreased our alum dose.
 After speaking with Monroe and looking at our flocs, he believed that our
 alum dose was too high.
 Our flocs looked larger than they should be, which suggests that the alum
 dose was too high.
 Monroe believed we could decrease our dose down to 15mg/L, so we have operated
 at this alum dose since.
 We have also decided to start running the tube settlers.
 This allows us to see how running those may affect the motion of the flocs
 in the sedimentation tank.
 It will also allow us to find the plant effluent turbidity.
 One discovery we made while running these experiments is that there was
 an area of the sedimentation tank that had a dead zone.
 In this area the flocs did not have a distinct upwards or downwards motion.
 The dead zone was right below the floc hopper.
 We got rid of this dead zone by attaching foam to the bottom of the floc
 hopper to block the flocs from entering that area 
\begin_inset CommandInset ref
LatexCommand ref
reference "Revised-Sedimentation-Tank"

\end_inset

.
 
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\begin_inset Caption

\begin_layout Plain Layout
Revised Sedimentation Tank with working Floc Blanket 
\begin_inset CommandInset label
LatexCommand label
name "Revised-Sedimentation-Tank"

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\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection*
Constant Wasting Rate
\end_layout

\begin_layout Standard
During this semester, we have run three different wasting rates (15ml/min,
 25ml/min and 30ml/min) for different plan view areas (10%, 15% and 20%).
 The floc hopper often goes empty within 30 to 60 seconds under these wasting
 rates.
 After the floc hopper empties, the wasting tube removes flocs right after
 flocs reach the bottom of the floc hopper which indicates the floc hopper
 is not compressing the flocs as intended.
 The concentration of the flocs sucked out by the wasting tube is the same
 as the concentration of flocs on the top of the floc blanket.
\end_layout

\begin_layout Standard
In order to make the floc hopper compress flocs and minimize the workload
 for the plant operator, we decided to run a low constant wasting rate experimen
t on the 10% plan view area floc hopper.
 The minimum flow rate we can get from the pump in our lab is 1.3ml/min,
 so we selected 1.5ml/min as our primary constant wasting rate.
 We then changed the wasting rate from 1.5ml/min to 15ml/min in small intervals.
 We also did experiments at wasting rates of 2.0ml/min and 2.5ml/min.
 
\end_layout

\begin_layout Part
Analysis
\end_layout

\begin_layout Section
Hindered Velocity Experiment
\end_layout

\begin_layout Standard
Based on the previous teams' results and hypotheses, we have a good idea
 of what we expect the data to show.
 Assuming that the height of the floc blanket remains constant, then the
 upward velocity should equal the sedimentation velocity of the flocs.
 Therefore, when the upward velocity goes to zero the downflow velocity
 should be the same as the upward velocity.
 The team from Spring 2012 actually discovered that the hindered sedimentation
 velocity was lower than this theoretical velocity, leading them to believe
 that wall effects were affecting the speed.
 Given this result, we expect that our data should fall close to the previous
 team's results, or at least be lower than the upflow velocity.
 
\end_layout

\begin_layout Standard
Unfortunately, when analyzing our images, we noticed that we could no longer
 locate our background images needed for analyzation.
 We took new background images, but because of possible camera movements,
 these may not provide the best images for analyzation.
 Therefore, our analysis will be different from what we originally expected,
 but we hope to be able to interpolate some sort of trend line from which
 to draw conclusions.
 The 0.6mm/sec experiment had images taken at 1 image/5 seconds while the
 other two experiments had images taken at 1 image/30 seconds.
 
\end_layout

\begin_layout Standard
Using rough interpolation we found that the the sedimentation velocity for
 0.6mm/sec upflow is around 0.086mm/sec, for 1.2mm/sec upflow is around 0.15mm/sec
 and for 1.6mm/sec upflow is of roughly 0.47mm/sec.
 While these numbers are significantly different from the previous semester's
 results (most likely because of our lack of background images), the relationshi
p between 0.6mm/sec and 1.2mm/sec upflow experiments are somewhat similar
 to the previous semester's results.
 
\end_layout

\begin_layout Subsection
0.6mm/sec
\end_layout

\begin_layout Standard
The following graph is a measurement of the height of the floc-water interface
 of our floc blanket compared to the frame number of the recorded video.
 The first half of the video appears to have a large range of values, but
 a trend can still be determined.
 
\end_layout

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	filename Floc-Water Interface.bmp
	lyxscale 50
	scale 50

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\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Floc-water interface for 0.6mm/sec upflow velocity 
\begin_inset CommandInset label
LatexCommand label
name "SedVel1"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection
1.2mm/sec
\end_layout

\begin_layout Standard
The data collected from this experiment appears to be the most chaotic.
 We are hoping that the basic trend of the first 50 images will be accurate
 enough data to use in our analysis.
 
\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
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	filename sed vel2flocwaterinterface.bmp
	lyxscale 50
	scale 50

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\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Floc-water interface for 1.2mm/sec upflow velocity 
\begin_inset CommandInset label
LatexCommand label
name "SedVel2"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection
1.6mm/sec
\end_layout

\begin_layout Standard
Similar to the 0.6mm/sec experiment, the first few frames of the video have
 a wide range of values, but a trend can still be determined.
 The end of the video has a more consistent trend.
\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
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	filename sedvel3 water interface+.bmp
	lyxscale 50
	scale 50

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\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Floc-water interface for 1.6mm/sec upflow velocity 
\begin_inset CommandInset label
LatexCommand label
name "SedVel3"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Section
Floc Hopper Geometry Experiment
\end_layout

\begin_layout Standard
We have discovered that continual wasting will significantly decrease the
 concentration of flocs in the wier and are currently devising possible
 experimental designs to increase floc concentration in wiers.
 Analysis was conducted using the imaging program.
 Note: Experiments were conducted in the following order, the 15% plan view
 experiments were conducted first, then 20% plan view, and finally 10% plan
 view.
 
\end_layout

\begin_layout Subsection
10% Plan View
\end_layout

\begin_layout Standard
At the 10% Plan View, we tested three different wasting rates at a 15 mg/L
 alum dosage.
 The rates we used were 15ml/min, 25ml/min, and 30ml/min.
 For the 25ml/min and 30ml/min tests, we attached the barrier strip under
 the floc hopper in order to keep flocs out of the dead zone.
 We noticed that for 15ml/min and 25ml/min, the flocs grew to a very high
 level in a short amount of time and the wasting rate had very little effect
 in lowering the floc blanket level.
 The 30ml/min experiment formed a very different floc blanket compared to
 the two pervious experiments.
 We are not quite sure why this was so, seeing as we did not change any
 of the setup before any of the experiments.
 The floc blanket for the 30ml/min started off slowly, maintaining a height
 far below the height of the floc hopper.
 However, after waiting for roughly two hours, the floc blanket rose to
 the height of the floc hopper and began functioning as theoretically expected.
 When the weir started wasting, the flocs in the hopper were quickly removed
 and the height of the floc blanket was maintained, although a lot of clean
 water was removed by the wasting tube as well.
 Nevertheless, this result is heartening, as we now know that floc blanket
 formation will occur, given a long enough time period for the blanket to
 form.
 We still are unaware as to why the two pervious wasting rates produced
 very different floc blanket characteristics.
 Below are the graphs of the concentrations of the floc blanket in relation
 to the height of the region of interest for a 10% plan view floc wier.
 0 cm signifies the bottom of the floc blanket.
 
\end_layout

\begin_layout Subsubsection
Wasting Rate 15 mL/min
\end_layout

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\begin_inset Caption

\begin_layout Plain Layout
Concentration vs.
 Height of ROI for 15 mL/min
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Wasting Rate 25 mL/min
\end_layout

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\begin_inset Caption

\begin_layout Plain Layout
Concentration vs.
 Height of ROI for 25 mL/min
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Wasting Rate 30 mL/min
\end_layout

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	filename cont. graphs/pva10/wasting30/wasting 30 concentration.bmp
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\begin_inset Caption

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Concentration vs.
 Height of ROI for 30 mL/min
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Analysis
\end_layout

\begin_layout Standard
After examining the concentration graphs, we have determined that due to
 eddies formed in the 25 mL/min experiment, the data from that experiment
 will be disregarded for our analysis.
 The height of the floc blanket is represented on the graph by a sharp decrease
 in concentration on the graphs.
 In the 15 mL/min experiment, this decrease began at roughtly 70 cm from
 the bottom of the ROI (Region of Interest: the area that the program studies).
 In the 30 mL/min experiment, the decrease began around 65 cm from the bottom.
 This may happen because the wasting rate is higher, and therefore, more
 flocs are removed from the top of the blanket.
 The concentration trend for both experiments are similar, with a high concentra
tion near the bottom of the ROI and a slight plateu of concentration at
 the middle representing the actual floc blanket and then a sharp decline
 that represents the end of the floc blanket.
 
\end_layout

\begin_layout Subsection
15% Plan View
\end_layout

\begin_layout Standard
We have tested the 15% plan view area at three different wasting rates.
 The rates we used were 15ml/min, 25ml/min, and 30ml/min.
 This shows a picture of the final floc blanket at these three wasting rates.
\end_layout

\begin_layout Standard
\begin_inset Float figure
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	filename floc blanket.gif
	lyxscale 50
	scale 25

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\begin_inset Caption

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Floc Blanket Formation (15ml/min, 25ml/min, 30ml/min)
\begin_inset CommandInset label
LatexCommand label
name "fig:Floc-Blanket-Formation"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset

From these pictures
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Floc-Blanket-Formation"

\end_inset

, we concluded that both the 15ml/min and the 25 ml/min wasting rates were
 not high enough.
 This conclusion was made based on the fact that the floc blanket takes
 up the entire sedimentation tank and flows up past the floc weir.
 For the 30 ml/min wasting rate we can see that the thick floc blanket is
 maintaining a height very close to the weir height.
 This shows that this wasting rate is very close to the correct rate.
 The main concern we have from the 30 ml/min rate is the formation of the
 eddy at the tip of the weir.
 We are not sure what implications the eddy formation has on the functioning
 of the rest of the floc blanket and weir.
 Below are the graphs of the concentrations of the floc blanket in relation
 to the height of the region of interest for a 15% plan view floc wier.
\end_layout

\begin_layout Subsubsection
Wasting Rate 15 mL/min
\end_layout

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\begin_inset Caption

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Concentration vs.
 Height of ROI 15 mL/min
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Wasting Rate 25 mL/min
\end_layout

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\begin_inset Caption

\begin_layout Plain Layout
Concentration vs.
 Height of ROI 25 mL/min
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Wasting Rate 30 mL/min
\end_layout

\begin_layout Standard
\begin_inset Float figure
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\begin_inset Caption

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Concetration vs.
 Height of ROI 30 mL/min
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Analysis
\end_layout

\begin_layout Standard
For the 15% Plan View experiments, we were running the experiments at a
 extremely high coagulant dose (45 mg/L) which prevented us from forming
 a proper floc blanket.
 A high coagulant dose increases the size of the flocs, but also increases
 the space in between the glued particles.
 This space is occupied by water, and therefore makes the larger flocs less
 dense, and more susceptible to the turbulent water.
 It is possible that higher wasting rates influenced the overall flow of
 the flocs which explains why the 15 mL/min experiment has a different concentra
tion profile than the other two experiments.
 The reason why the 25 mL/min and 20 mL/min concentrations have negative
 values is because the background image used as reference to the experimental
 images was darker.
 Since the analysis program measures concentration by the amount of light
 showing through the tank, if the experimental image is lighter than the
 background image, then the concentration is registered as negative.
 In the future, we will make sure to take background images before every
 experiment.
\end_layout

\begin_layout Subsection
20% Plan View
\end_layout

\begin_layout Standard
For 20 percent plan view we have collected data for the 25ml/min wasting
 rate.
 The following picture shows the sedimentation tank at the end of the experiment
:
\end_layout

\begin_layout Standard
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\end_inset


\end_layout

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\begin_layout Standard
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\begin_layout Standard
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\begin_layout Standard
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\begin_layout Standard
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\begin_layout Standard
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\begin_layout Standard
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\begin_layout Standard
\begin_inset space \space{}
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\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
sideways false
status open

\begin_layout Plain Layout
\begin_inset Graphics
	filename 20 percent.jpg
	scale 0.5
	rotateAngle 180

\end_inset


\begin_inset ERT
status open

\begin_layout Plain Layout


\backslash
centering
\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
20% Plan View at 25ml/min
\begin_inset CommandInset label
LatexCommand label
name "fig:20%-Plan-View"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
This picture (
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:20%-Plan-View"

\end_inset

) shows that floc blanket maintaining a height below the floc weir.
 We believe that the wasting rate was too high and caused this to happen.
 The wasting tube can be sucking up flocs from below the weir since this
 is not fully sealed and some flocs can flow up to the tube through the
 weir.
 One of the indications that this could be happening is that the water is
 significantly lighter right along the left edge of the weir where the wasting
 tube is.
\end_layout

\begin_layout Standard
At the 30 ml/min wasting rate, we changed the alum dosage from 45mg/L to
 15mg/L at Monroe's suggestion.
 We immediately noticed a denser floc blanket as well as smaller flocs.
 However, we still did not seem to be able to form a floc blanket.
 Below are the graphs of the concentrations of the floc blanket in relation
 to the height of the region of interest for a 20% plan view floc wier.
\end_layout

\begin_layout Subsubsection
Wasting Rate 15 mL/min
\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
sideways false
status collapsed

\begin_layout Plain Layout
\begin_inset Graphics
	filename cont. graphs/pva20/wasting15/wasting 15 concentration.bmp
	scale 50

\end_inset


\begin_inset ERT
status open

\begin_layout Plain Layout


\backslash
centering
\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Concentration vs.
 Height of ROI 15 mL/min
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Wasting Rate 25 mL/min
\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
sideways false
status collapsed

\begin_layout Plain Layout
\begin_inset Graphics
	filename cont. graphs/pva20/wasting25/wasting 25 cont..bmp
	scale 50

\end_inset


\begin_inset ERT
status open

\begin_layout Plain Layout


\backslash
centering
\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Concentration vs.
 Height of ROI 25 mL/min
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Wasting Rate 30 mL/min
\end_layout

\begin_layout Standard
\begin_inset Float figure
wide false
sideways false
status collapsed

\begin_layout Plain Layout
\begin_inset Graphics
	filename cont. graphs/pva20/wasting30/wasting 30 cont..bmp
	scale 50

\end_inset


\begin_inset ERT
status open

\begin_layout Plain Layout


\backslash
centering
\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Concetration vs.
 Height of ROI 30 mL/min
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Analysis
\end_layout

\begin_layout Standard
For these experiments, we were unable to form a floc blanket, but unlike
 the 15% plan view, we had a dense concentration of flocs at the bottom
 of the sedimentation tank.
 Also, for the first two experiments, the alum dosage was 45 mg/L while
 the last experiment was conducted with an alum dosage of 15 mg/L.
 All three concentration profiles have a spike in concentration at around
 50 cm from the bottom of the ROI.
 This could be because of an eddie located on the right hand side of the
 tank.
\end_layout

\begin_layout Section
Constant Wasting Rate
\end_layout

\begin_layout Standard
With 1.5ml/min as the wasting rate, the floc hopper remained full which indicates
 that the floc hopper compressed flocs.
 However, flocs were more likely to settle down in the wasting tube before
 reaching the turbidity meter.
 This explains why the reading of turbidity meter was about 70NTU, a turbidity
 lower than the influent turbidity.
 After we figured out that the flocs may be settling down in the wasting
 tube, we changed the wasting rate from 1.5ml/min to 15ml/min.
 Flocs settled in the wasting tube were resuspended and the reading of turbidity
 meter rose to 1100 NTU, the maximum reading range of the turbidity meter.
 This could indicate floc hopper does compress flocs like expected.
 At wasting rates of 2.0ml/min and 2.5ml/min, the height of flocs in the floc
 hopper began to decrease, indicating that the wasting rate was too high
 to keep the volume of flocs in the floc hopper constant.
 
\end_layout

\begin_layout Part
Conclusions
\end_layout

\begin_layout Section*
Hindered Velocity Experiment
\end_layout

\begin_layout Standard
We have finished compiling all the images recording our three up flow velocity
 (0.6mm/s, 1.2mm/s, 1.6mm/s) experiments into videos and we have to some extent
 figured out how to use post-analyze programs to analyze the data.
 From our data analysis, we are not quite sure about how concentration changes
 with distance, however, we can conclude that selection of Region of Interest
 and Background images may cause large variance in the result of analysis.
 We are expecting the same conclusion as was described in the literature
 review after we figure out how ROI and Background images affect the analysis.
\end_layout

\begin_layout Section*
Floc Hopper Geometry Experiment
\end_layout

\begin_layout Standard
We have finished all experiments regarding different plan view area (10%,
 15% and 20%) and different wasting rate (15ml/min, 25ml/min and 30ml/min).
 We also finished compiling all the images we now have into videos.
 Since it takes us several weeks to get all the experiments done, we changed
 some of the experiment conditions according to Dr.
 Weber-Shirk’s suggestion and our own new understandings, for example the
 coagulant dose was changed from 45mg/L to 15mg/L to make the floc blanket
 denser, the geometry of floc hoppers are also slightly changed.
 For our most recently done experiment, the plan view area of floc hopper
 is 10%, with a coagulant dose of 15mg/L and up flow velocity of 1.2mm/s,
 we could get a floc blanket with the same height of our floc weir about
 2 hours after we start the experiment and we could see flocs flowing into
 the floc hopper from the floc blanket.
\end_layout

\begin_layout Standard
Other Findings 
\end_layout

\begin_layout Enumerate
We have to clean up the turbidity meter each time before we run the experiment,
 for clay residues settled in the turbidity meter may cause the reading
 of the turbidity meter to be higher than what it should be, therefore,
 it could cause the actual inflow NTU to be lower than the reading of turbidity
 meter which affects the formation of floc blanket.
 
\end_layout

\begin_layout Enumerate
We should clear up the clay residues settled in the tubes and tube conjunctions
 regularly.
 Since clay is likely to settle down in the tubes, especially tube conjunctions
 when we have our apparatus stopped, it may add more head loss to our whole
 system.
 Therefore we need to decrease the inflow flow rate and the up flow velocity
 which inhibits the floc blanket going up.
 
\end_layout

\begin_layout Section*
Constant Wasting Rate
\end_layout

\begin_layout Standard
The results of the constant wasting rate experiment suggest that the floc
 hopper does help make flocs denser but it might be difficult to keep flocs
 from settling down in the wasting tube when the constant wasting rate is
 relatively low.
 Therefore, we may have to wash the wasting tube frequently to prevent flocs
 settling down in the wasting tube.
 This experiment suggests that there must be some optimal wasting rate that
 exists in a range that previous teams have not considered (somewhere between
 1.5mL/min and 2.0mL/min).
 
\end_layout

\begin_layout Part
Future Work
\end_layout

\begin_layout Enumerate
For the plan view area experiment, it seemed that the smaller plan view
 areas worked better than the large one.
 We believe this could also be due to the fact that when we increase the
 plan view area we are inadvertently increasing the vertical sedimentation
 velocity.
 Since increasing the plan view area decreases the space the water has to
 flow up, the velocity would increase if the flow is kept the same.
 Therefore the flow into the sedimentation tank should be adjusted so that
 the upflow velocity is the same for all three plan view areas.
 Since the variation in vertical sedimentation velocity would be eliminated,
 the relationship between the plan view areas would be clearer.
\end_layout

\begin_layout Enumerate
For our last experiment we used the 10% plan view area.
 We let a floc blanket form and filled up the floc hopper.
 We then slowly increased the wasting rate until we maintained a constant
 height in the floc hopper.
 This should be done for the other plan view areas.
 Then they can compare which plan view areas have the most concentrated
 waste while maintaining a clean effluent.
\end_layout

\begin_layout Enumerate
It would be helpful to better understand the relationship between coagulant
 does and particle size.
 Halfway through the semester we decreased our coagulant dose and had smaller
 particles and a more effective floc blanket.
 It would be interesting to see the difference between particle size and
 coagulant dose.
 At some point the coagulant dose will be too low and not remove particles
 efficiently, but we also suspect that at a high coagulant dose the particles
 will not form an effective floc blanket.
 By forming a floc blanket at different coagulant doses, we could find the
 optimal coagulant dose for maintaining a stable floc blanket and removing
 the most turbidity.
 Given enough time this could be run at various influent turbidity.
\end_layout

\begin_layout Enumerate
Understanding floc blanket failure modes would be helpful to plan operators.
 The relationship between coagulant does and floc blanket failure could
 be found from the previous experiments.
 With this information we should write a manual to help plant operators
 understand what is causing their floc blanket to fail and how to remedy
 it.
 It would also be interesting to see if the influent turbidity will also
 cause floc blanket failure.
 From the conclusions of the future semester's work a guide for the plant
 operators can be written.
\end_layout

\end_body
\end_document
