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\begin_body

\begin_layout Title
Turbulent Tube Flocculator 
\end_layout

\begin_layout Author
Felice Chan, Jonathan Christensen, Stephen Jacobs, Ana Oliveira
\end_layout

\begin_layout Date
May 17, 2014
\end_layout

\begin_layout Abstract
Since the Summer of 2013, the Turbulent Tube Flocculator team has been developin
g and optimizing a design for a lab scale turbulent tube flocculator to
 better mimic the processes that occur at full scale plants.
 From this, a vertical flocculator of approximately 1.5 m was constructed
 with 30 coils of flexible tubings connected with pieces of metal pipe.
 Currently, the team is working on the rest of the experimental setup, which
 involves pumps, turbidimeters, pinch valves, clay stock, temperature and
 pressure sensors, Settled Water Turbidity analyzer (SWaT), rapid mix, and
 Process Controller software.
 Clay will be added directly to the head tank to keep the suspension stable
 in absence of coagulant.
 The coagulant, injected immediately following rapid mix, is responsible
 for aggregation of suspended particles present in the solution.
 Experiments will measure turbidity reduction as a function of coagulant
 dosage.
 
\end_layout

\begin_layout Section
Introduction
\end_layout

\begin_layout Standard
The purpose of our research is to design, build, and test a lab scale turbulent
 tube flocculator.
 This is important because while the AguaClara plants in Honduras and India
 have turbulent flow flocculators, previous AguaClara research has only
 formed hypotheses from laminar flow flocculators.
 Thus, with the turbulent tube flocculator experimental apparatus, future
 AguaClara researchers will be able to more accurately conduct research
 to perfect the design of the full-scale plant.
 The prior literature that proved most relevant to this project related
 to either the materials needed for the building of the turbulent tube flocculat
or or to the size of eddies necessary for flocculation.
\end_layout

\begin_layout Standard
The 2013 Summer AguaClara team's design for the turbulent tube flocculator
 was a vertically-oriented, large coiled tube.
 The design used twelve pairs of pipes to constrict the tube to create turbulent
 eddies.
 The main goal of the Fall 2013 team was to perfect the initial design created
 in the summer of 2013 and then build the turbulent tube flocculator.
 
\end_layout

\begin_layout Section
Literature Review
\end_layout

\begin_layout Standard
Flocculation is a process that transforms a turbid suspension of tiny particles
 into a turbid suspension of larger particles.
 A gravity-driven hydraulic flocculator without mechanical agitation is
 an energy and cost efficient way to achieve flocculation.
 The flow through a hydraulic flocculator may include turbulent regions,
 which are caused by the expansion that results when the water changes direction
 as it flows around each baffle 
\begin_inset CommandInset citation
LatexCommand cite
key "key-1"

\end_inset

.
 A fractal description of flocs, estimates of floc separation distances,
 and estimates of relative velocities of floc particles dependent on the
 relevant flow regime, provide an overall prediction of the required reaction
 time for formation of settleable flocs based on influent turbidity, coagulant
 dose, and energy dissipation rate.
 Fluid viscosity is important for the beginning of flocculation where colloid
 sizes are smaller than the smallest fluid eddies.
 Turbulent eddies are shown to be significant for the final stage of flocculatio
n.
 In turbulent flow, the collision potential, defined as the product of the
 hydraulic residence time (
\begin_inset Formula $\theta$
\end_inset

) and the cube root of the energy dissipation rate (
\begin_inset Formula $\varepsilon$
\end_inset

), is expected to be a better predictor of flocculator performance than
 the commonly used product of hydraulic residence time and the velocity
 gradient G
\begin_inset Formula $\theta$
\end_inset

 
\begin_inset CommandInset citation
LatexCommand cite
key "key-2"

\end_inset

.
\end_layout

\begin_layout Standard
A high energy dissipation rate is expected to increase collision frequency,
 creating larger flocs more quickly, but can also break up large flocs in
 the process.
 Ideally, the flocs would be less than the maximum (terminal) size reached
 in the flocculator so that they can grow by capturing other colloidal particles
 in the water, but not too small as to increase the residual turbidity of
 the water.
 
\end_layout

\begin_layout Standard
For hydraulic flocculation systems, low turbidity water is produced with
 minimal fluid shear.
 Low energy dissipation rates produced the fastest settling flocs and the
 lowest turbidity water.
 Because the lowest turbidity water can be produced using large flocs, the
 flocculator and the sedimentation tank must be designed to not break up
 large flocs.
 However, these conclusions have been drawn from laminar flow tube flocculators.
 While it is likely that the eddies in turbulent flow break up flocs in
 ways similar to that of laminar fluid shear, this concept has not been
 tested.
 Therefore, more research is required to test the performance of adding
 zones with high energy dissipation rates to break apart and re-form flocs
 
\begin_inset CommandInset citation
LatexCommand cite
key "key-3"

\end_inset

.
 
\end_layout

\begin_layout Section
Methods
\end_layout

\begin_layout Subsection
Design from Summer 2013 Team
\end_layout

\begin_layout Standard
A design for the turbulent tube flocculator was created in Summer 2013 and
 executed in Fall 2013.
 The basic idea for the flocculator is to have a vertical coil of tubes
 and a series of constrictions created by metal or PVC tubes on the inside
 and outside of the coil that would be bolted together.
 Water would flow in from a head tank, flow up through the flocculator and
 exit to a settled water turbidity unit, an imaging system and the sink.
 The following dimensions for the flocculator were estimated (see table
 
\begin_inset CommandInset ref
LatexCommand ref
reference "tab:Calculated-Dimensions-Flocculator"

\end_inset

).
\end_layout

\begin_layout Standard
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Parameter
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Energy Dissipation Rate
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30 mW/kg
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Collision Potential
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100 m
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2/3
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Reynolds Number (Diameter)
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4000
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\begin_layout Plain Layout
Inner Diameter of Tubing
\end_layout

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0.0318 m (1.25 in)
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Length of Flocculator
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56.35 m
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Number of Coils
\end_layout

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30
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Diameter of Coil
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0.614 m
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1.125 m
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Constricted Height
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1.464 m
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Hydraulic Residence Time
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7.546 min
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\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Calculated Parameters of Flocculator
\begin_inset CommandInset label
LatexCommand label
name "tab:Calculated-Dimensions-Flocculator"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Assembly Process
\end_layout

\begin_layout Subsubsection
Assembly of Flocculator
\end_layout

\begin_layout Standard
After machining all necessary materials, the steel bars were set with pins
 inside the PVC pipes which were slotted into the plywood frame.
 Copper piping was used to connect the pieces of flexible tubing (figure
 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Flexible-tubing-connectors"

\end_inset

).
 The flexible tubing was wrapped around the PVC and the outer ring of PVC
 was bolted to the inner ring, creating the calculated constrictions in
 the flexible tubing.
 The final flocculator is shown below (figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Current-flocculator"

\end_inset

).
 After initial tests, the team faced an issue: the formation of air bubbles
 inside the flexible tubing (figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Air-bubbles-issue"

\end_inset

).
 Some kinks were maximizing the problem, so zip ties were applied to reduce
 the severity of the additional constrictions.
\end_layout

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\align center
\begin_inset Graphics
	filename connectors.jpg
	scale 50

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\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Flexible Tubing Connectors
\begin_inset CommandInset label
LatexCommand label
name "fig:Flexible-tubing-connectors"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\align center
\begin_inset Graphics
	filename flocculator.jpg
	scale 40

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Current Flocculator
\begin_inset CommandInset label
LatexCommand label
name "fig:Current-flocculator"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

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

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\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename Air bubbles.jpg

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Air bubbles issue 
\begin_inset CommandInset label
LatexCommand label
name "fig:Air-bubbles-issue"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Clay Stock Tank and Constant Head Tank
\end_layout

\begin_layout Standard
A frame supporting the clay stock tank and constant head tank has been assembled.
 Turbidity will be monitored in the head tank, and commensurate flow from
 the clay stock to the head tank will be controlled with a pinch valve.
 Temperature will also be monitored in the head tank, and commensurate flow
 of hot or cold water will be controlled with two solenoid valves.
 Finally, pressure will be monitored in the head tank to maintain the hydraulic
 grade line.
 
\end_layout

\begin_layout Standard
The setup is shown in figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Clay-Stock-Tank"

\end_inset

.
 The tank on the top is the clay stock tank and the one underneath is the
 constant head tank.
 The blue boxes on the side are the solenoid valves, which are connected
 to the constant head tank.
 
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placement H
wide false
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status open

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename head tanks.jpg
	scale 80

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Clay Stock Tank and Constant Head Tank
\begin_inset CommandInset label
LatexCommand label
name "fig:Clay-Stock-Tank"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
The required flow rate through the system is 100 mL/s, which can be adjusted
 by changing the height of the bucket and the height of the waste tube.
 The flow rate through the system was measured to be about 90 mL/s (by filling
 a graduated cylinder with water from the waste line over a certain amount
 of time and adding the SWaT flow rate of 1.00 mL/s.
 Therefore, the team raised the height of the constant head tank by putting
 a wooden board under the stand and then raising the stirrers and bucket,
 and lowering the waste line.
 The new flow rate through the system is approximately 100 mL/s.
\end_layout

\begin_layout Subsubsection
Rapid Mix and Drain Pump Module
\end_layout

\begin_layout Standard
After discussion, the team chose to change the rapid mix design, with a
 new module to house it and a pump connection to be used for draining.
 The rapid mix will be a small orifice with diameter 0.783 inches, which
 is set in the module to achieve a target energy dissipation rate of 1 W/kg.
 Coagulant will be dosed immediately following rapid mix via a needle interface
 built into the module.
 The pump connection will allow for the attachment of a centrifugal pump
 for draining the entire system when necessary.
 The design and completed module are shown in figures 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Rapid-mix-design"

\end_inset

 and 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Rapid-Mix-Module"

\end_inset

.
\end_layout

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\begin_inset Float figure
wide false
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status open

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename Rapid mix.jpg
	scale 80

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Rapid Mix Design and Drain Pump Position 
\begin_inset CommandInset label
LatexCommand label
name "fig:Rapid-mix-design"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\begin_inset Float figure
wide false
sideways false
status open

\begin_layout Plain Layout
\align center
\begin_inset Graphics
	filename rapid mix (2).JPG
	scale 40

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Rapid Mix and Drain Module
\begin_inset CommandInset label
LatexCommand label
name "fig:Rapid-Mix-Module"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Settled Water Turbidity Analyzer (SWaT)
\end_layout

\begin_layout Subsubsection
SWaT Calculations
\end_layout

\begin_layout Standard
Based on the AguaClara approach for plate settler design, the minimum spacing
 to prevent floc rollup is 2.5 cm (or 0.984 in), so the minimum diameter for
 the tube is 1 inch 
\begin_inset CommandInset citation
LatexCommand cite
key "key-4"

\end_inset

.
 With a target capture velocity, the length of the tube settler could be
 determined from equation 
\begin_inset CommandInset ref
LatexCommand ref
reference "eq:Vcapture"

\end_inset

, where S is the spacing or the diameter of the tube, L is the length of
 the tube, 
\begin_inset Formula $V{}_{Plate}$
\end_inset

 is the vertical velocity going through the tank and 
\family roman
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alpha is the plate angle (set at 60 degrees) to get solids to slide down
 the incline.
 We found that a length of 86 cm is required for the tube settler.
 
\end_layout

\begin_layout Standard
\begin_inset Formula 
\begin{equation}
V_{Capture}=\frac{S\text{·}V_{Plate}}{L·sin(\alpha)·cos(\alpha)+S}\label{eq:Vcapture}
\end{equation}

\end_inset


\end_layout

\begin_layout Standard
Equation 
\begin_inset CommandInset ref
LatexCommand ref
reference "eq:SWaT Flow Rate"

\end_inset

 was used to determine the flow rate.
 The minimum flow rate through the turbidimeter is 100 mL/min to prevent
 particles from settling in it.
 With a length of 86 cm, the flow rate through the tube settler will be
 100 mL/min.
 
\end_layout

\begin_layout Standard
\begin_inset Formula 
\begin{equation}
Q_{Tube}=A_{Tube}·\frac{V_{Capture}·(L_{Tube}sin(\alpha)·cos(\alpha)+D_{Tube}}{D_{Tube}}\label{eq:SWaT Flow Rate}
\end{equation}

\end_inset


\end_layout

\begin_layout Standard
A diagram showing the geometry of the tube settler with the appropriate
 labeled dimensions is shown in figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Tube-Settler-Geometry"

\end_inset

.
\end_layout

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

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename TubeSettler.jpg
	scale 80

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Tube Settler Geometry
\begin_inset CommandInset label
LatexCommand label
name "fig:Tube-Settler-Geometry"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Design
\end_layout

\begin_layout Standard
Based on the calculations, the settled water turbidity unit has been designed
 and fabricated to measure effluent turbidity.
 The SWaT system is located immediately following the flocculator and consists
 of a tube settler, turbidimeter and peristaltic pump.
 The specifications for the tube settler are given in the table 
\begin_inset CommandInset ref
LatexCommand ref
reference "tab:Tube-Settler"

\end_inset

 below.
 A diagram of the SWaT system is shown in figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:SWaT-Apparatus"

\end_inset

.
\end_layout

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Parameter
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Value
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Length
\end_layout

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86 cm
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Inner Diameter
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1.049 in
\end_layout

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Angle
\end_layout

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\begin_inset Text

\begin_layout Plain Layout
60 degrees
\end_layout

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\begin_inset Text

\begin_layout Plain Layout
Capture Velocity
\end_layout

\end_inset
</cell>
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\begin_inset Text

\begin_layout Plain Layout
0.174 mm/s
\end_layout

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Flow Rate
\end_layout

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</cell>
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\begin_inset Text

\begin_layout Plain Layout
100.7 mL/min
\end_layout

\end_inset
</cell>
</row>
</lyxtabular>

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
Calculated Parameters of Tube Settler 
\begin_inset CommandInset label
LatexCommand label
name "tab:Tube-Settler"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename SWaT.jpg
	scale 80

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
SWaT Apparatus
\begin_inset CommandInset label
LatexCommand label
name "fig:SWaT-Apparatus"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Process Controller
\end_layout

\begin_layout Standard
Process controller monitors and regulates the water level, temperature and
 turbidity in the constant head tank.
 The turbidity is measured by a turbidimeter loop, and the 
\begin_inset Quotes eld
\end_inset

on/off
\begin_inset Quotes erd
\end_inset

 controller vi (visual instrument) tells the clay pinch valve when to add
 more clay.
 States control the water level and the temperature.
 There are three states in total: off, filling, full, add hot water and
 add cold water.
 In the off state, everything is turned off.
 Filling adds both hot and cold water until the water level reaches a set
 minimum.
 The hot and cold water states add water of the appropriate temperature
 if the water level is too low.
 Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Process-Controller-Logic"

\end_inset

 shows when process controller transitions between different states.
 
\end_layout

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

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename Process Controller Map.jpg
	scale 65

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Process Controller Logic Map
\begin_inset CommandInset label
LatexCommand label
name "fig:Process-Controller-Logic"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Cleaning the Flocculator
\end_layout

\begin_layout Standard
The team has also been working on methods to clean out flocs that settle
 out in the flocculator.
 So far the team has tried simply flushing the system with a high flow,
 and then pumping all the water out of the system so that hopefully the
 flocs will get pulled out along with the water.
 However, this has only been mildly successful.
 
\end_layout

\begin_layout Standard
Other flocculation teams have run small pieces of sponge through the flocculator
 to remove the coagulant and clay that have adhered to the walls of the
 flocculator, but with the current apparatus the sponge would have too many
 opportunities to get stuck along the way, particularly through the rapid
 mix unit, and through each constriction in the flocculator.
 
\end_layout

\begin_layout Section
Analysis
\end_layout

\begin_layout Subsection
Experiments
\end_layout

\begin_layout Standard
The team performed a few tests with a target influent turidity of 50 NTU
 and a coagulant dose of 10 mg/L.
 The concentration of clay in the clay stock tank is 10 g/L (10 grams of
 clay to 1 liter of water) and the concentration of the coagulant stock
 is 5 g/L.
 Though this is a much higher coagulant stock concentration than what other
 teams have used in the past, the flow rate of the turbulent tube flocculator
 is also much higher than what other teams have had.
 To make this concentration, the team uses concentrated liquid PACl and
 dilutes it to the appropriate concentration using distilled water.
 The current lab stock concentration is 62.02 g/L so the volume of coagulant
 needed can be calculated in equation 
\begin_inset CommandInset ref
LatexCommand ref
reference "eq:VLab Stock"

\end_inset

, where 
\begin_inset Formula $C_{Stock}$
\end_inset

 is the desired stock concentration of 5 g/L and 
\begin_inset Formula $V{}_{Stock}$
\end_inset

 is the volume of the container holding the stock concentration.
 The volume of PACl needed is 0.242 L.
 Therefore, 2.758 L of distilled water is required to make the coagulant
 stock.
\end_layout

\begin_layout Standard
\begin_inset Formula 
\begin{equation}
V_{LabStock}=\frac{C_{Stock}V_{Stock}}{C_{LabStock}}\label{eq:VLab Stock}
\end{equation}

\end_inset


\end_layout

\begin_layout Standard
Because there is no floc blanket formation in this system, the main factor
 determining the length of experimentation is the hydraulic residence time
 which is 7.55 minutes.
 
\end_layout

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

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename experiment turbidity.jpg
	scale 60

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Graph of Influent and Effluent Turbidity
\begin_inset CommandInset label
LatexCommand label
name "fig:Influent-and-Effluent"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename pcstar.jpg
	scale 50

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Graph of pC*
\begin_inset CommandInset label
LatexCommand label
name "fig:Graph-of-pC*"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
Figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Influent-and-Effluent"

\end_inset

 shows the influent and effluent turbidities and figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Graph-of-pC*"

\end_inset

 is a graph of pC* (defined in equation 
\begin_inset CommandInset ref
LatexCommand ref
reference "eq:pc*"

\end_inset

).
 
\end_layout

\begin_layout Standard
\begin_inset Formula 
\begin{equation}
pC*=-log(\frac{Effluent(t+\theta)}{Influent(t)})\label{eq:pc*}
\end{equation}

\end_inset


\end_layout

\begin_layout Standard
Based on the results from preliminary experiments, there are a number of
 problems and potential modifications that should be addressed in order
 to improve the performance of the flocculator.
 First, the influent turbidity should be held constant at 50 NTU, but it
 fluctuates between 50 and 60 NTU.
 The team predicts that this is because of the long response time between
 the influent turbidimeter, process controller and the clay pinch valve.
 
\end_layout

\begin_layout Standard
The effluent turbidity for this experiment was also very large (and pC*
 was very low), which could be due to a problem with the coagulant dosing
 system so that the experiment was essentially running 50-60 NTU water through
 the flocculator without any coagulant.
 This is probably because the needle (steel tubing with inner diameter of
 0.394 mm) that was being used to inject coagulant became clogged, probably
 from solids forming at the tip of the needle.
 
\end_layout

\begin_layout Subsection
Air Bubbles
\end_layout

\begin_layout Standard
To remove as many air bubbles from the system as possible before running
 the experiment, the team has been folding over the end of the waste line
 to prevent any water from flowing through it, while simultaneously releasing
 the air release (figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Air-Release"

\end_inset

) right after the tube settler to allow the system to fill with was much
 water as possible instead of air.
 As figure 
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:Air-Release"

\end_inset

 shows, the part of the tubing where the air release is, is rigid and the
 tubing before and after it is flexible.
 When air is released from the system in this way, it creates a vacuum in
 the tubing right before and after the release which creates unintentional
 constrictions in the tubing.
 This may be unimportant since this part of the apparatus is located after
 SWaT, so all of that water is going to waste anyways.
 However, the danger of it is that it creates additional constrictions between
 the end of the flocculator and the beginning of SWaT, which would increase
 fluid velocities in the final coils of the flocculator that could break
 apart flocs.
 
\end_layout

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

\begin_layout Plain Layout
\begin_inset space \hfill{}
\end_inset


\begin_inset Graphics
	filename air release.jpg
	scale 80

\end_inset


\begin_inset space \hfill{}
\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Air Release
\begin_inset CommandInset label
LatexCommand label
name "fig:Air-Release"

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Section
Conclusions
\end_layout

\begin_layout Standard
The team will have to run a number of additional experiments in order to
 draw any conclusions about floc breakup theory with the turbulent tube
 flocculator.
 There are still a number of issues with the flocculator that will have
 to be addressed before the flocculator will yield a desirable effluent
 turbidity and pC*.
 
\end_layout

\begin_layout Section
Future Work
\end_layout

\begin_layout Subsection
Head Tank Restructuring
\end_layout

\begin_layout Standard
The team currently uses an air release plug at the end of the flocculator
 to release air from the system as described in Section 4.2.
 The constrictions this pressurization creates in the tubing are likely
 having a significant impact on floc stability, creating high fluid velocities
 that shear the flocs we have created.
 We have decided to leave the air pocket at that location, but the head
 tank must be raised to maintain a flow rate of 100 mL/s.
 We have already switched the clay stock tank and the constant head tank.
 This means that clay stock will now need to be pumped up to the head tank
 with a peristaltic pump.
 To achieve constant influent turbidity, the team should set up the clay
 pump to use a 
\begin_inset Quotes eld
\end_inset

PID
\begin_inset Quotes erd
\end_inset

 .vi file in process controller that changes the pump speed proportional
 to the deviation from target turbidity.
\end_layout

\begin_layout Subsection
Coagulant Injection Replacement
\end_layout

\begin_layout Standard
The needle that was injecting coagulant immediately following the rapid
 mix orifice was clogging and preventing coagulant from being added to our
 raw water.
 For the moment, it has simply been replaced with 1/4
\begin_inset Quotes erd
\end_inset

 tubing, however this does not inject the coagulant at the center of the
 rapid mix jet (at the centroid of the tube).
 A new injection device should be installed using thin tubing fed through
 a push-to-connect plug.
 This change should dramatically improve particle aggregation and dramatically
 decrease effluent turbidity.
\end_layout

\begin_layout Subsection
New Air Release Chamber
\end_layout

\begin_layout Standard
To solve the issue of air bubbles exiting the flocculator and entering SWaT,
 which disrupts effluent turbidity measurements, a new air release chamber
 should be installed in between the flocculator and SWaT.
 The rigid tubing from the current air release could be repurposed for this
 system (Tim in the shop helped us turn down the inner diameter of the PVC
 tee so that the non-standard rigid tubing would fit snugly inside the fittings).
 It should mimic SWaT, in that a vertical 1
\begin_inset Quotes erd
\end_inset

 PVC pipe (which does not need to be nearly as long as the SWaT tube settler)
 will divert some flow into a chamber which can be opened and closed (with
 a plug or a valve).
 This way, air bubbles that are pushed out of the flocculator will rise
 into this chamber and can be periodically released, rather than passing
 on into SWaT.
\end_layout

\begin_layout Subsection
Experimentation
\end_layout

\begin_layout Standard
The next goal is to start running tests to measure the effluent turbidity
 to evaluate the overall effectiveness of the flocculator.
 A major problem that the team has to address is that the stamp box experiences
 unexpected failures, of which the cause remains unknown.
 In the long run, tests will be performed to determine if there is a correlation
 between the amount of air gaps and the effectiveness of the turbulent flocculat
or.
 If there is, the team will have to find possible solutions to the issue.
 
\end_layout

\begin_layout Standard
The team is also working on the best way to clean the flocculator since
 an unexpected amount of clay is settling out in the flexible tubing between
 the head tank and the rapid mix.
 Further tests will be performed to determine other viable options for cleaning
 the flocculator.
 
\end_layout

\begin_layout Standard
Once these problems are addressed, the team will begin to compare the effluent
 and influent turbidities and how they are affected by coagulant levels.
 Eventually, the team will also run experiments at varying coagulant doses
 and test floc break-up theory.
 
\end_layout

\begin_layout Bibliography
\labelwidthstring References
\begin_inset CommandInset bibitem
LatexCommand bibitem
key "key-1"

\end_inset

Weber-Shirk, Monroe.
 Flocculation Model.
 N.d.
 PowerPoint notes from CEE 4540.
 Https://confluence.cornell.edu/display/cee4540/Syllabus.
\end_layout

\begin_layout Bibliography
\labelwidthstring References
\begin_inset CommandInset bibitem
LatexCommand bibitem
key "key-2"

\end_inset

Monroe L.
 Weber-Shirk, Leonard W.
 Lion, Flocculation model and collision potential for reactors with flows
 characterized by high Peclet numbers, Water Research, Volume 44, Issue
 18, October 2010, Pages 5180-5187, ISSN 0043-1354, http://dx.doi.org/10.1016/j.watr
es.2010.06.026.
 (http://www.sciencedirect.com/science/article/pii/S0043135410004136)
\end_layout

\begin_layout Bibliography
\labelwidthstring References
\begin_inset CommandInset bibitem
LatexCommand bibitem
key "key-3"

\end_inset

Tse, Ian C., Karen Swetland, Monroe L.
 Weber-Shirk, and Leonard W.
 Lion.
 "Fluid Shear Influences on the Performance of Hydraulic Flocculation Systems."
 Water Research 45.17 (2011): 5412-418.
\end_layout

\begin_layout Bibliography
\labelwidthstring References
\begin_inset CommandInset bibitem
LatexCommand bibitem
key "key-4"

\end_inset

Weber-Shirk, Monroe.
 Sedimentation.
 N.d.
 PowerPoint notes from CEE 4540.
 Https://confluence.cornell.edu/display/cee4540/Syllabus.
\end_layout

\end_body
\end_document
