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\author 238565013 "monroe" 
\author 1000245830 "aguaclara" 
\end_header

\begin_body

\begin_layout Title

\change_deleted 238565013 1367680884

\series bold
Depth
\change_inserted 238565013 1367680885
Surface
\change_unchanged
 vs.
 
\change_inserted 238565013 1367680894
Sub
\change_unchanged
Surface 
\change_deleted 238565013 1367680931
Sand Filtration Progress Report
\change_inserted 238565013 1367680951
Inlet Systems for Sand Filtration
\change_unchanged

\end_layout

\begin_layout Standard

\series bold
\begin_inset Note Note
status open

\begin_layout Paragraph

\series bold
Excellent progress!
\change_inserted 238565013 1367681179
The data you are collecting is impressive and is instructive.
 It is remarkable how similar the filters are.
 The observation that the subsurface injection filter is easier to backwash
 is quite interesting.
 We don't use a surface wash system with our SRSF and your research suggests
 that we likely won't need a surface wash system.
\end_layout

\begin_layout Plain Layout

\change_inserted 238565013 1367681404
I'm most interested now in learning what happens when the coagulant dose
 is increased significantly.
 I'd like to know what failure looks like for the subsurface injection filter.
 Can you get it to clog very quickly with a high coagulant dose? What happens
 when it clogs quickly? If you have time to run a few more experiments at
 higher coagulant dosages that would be great.
 i also understand that the semester is over...
\change_unchanged

\end_layout

\begin_layout Plain Layout
The graphs are good image quality.
 Thanks.
\end_layout

\begin_layout Plain Layout
Graphs have captions and thus they don't have titles (small detail that
 you can fix if possible).
 Also the font size in the graph needs to be large enough so that it is
 the equivalent of 12 point when the image is scaled for the PDF.
\change_inserted 238565013 1367679089

\end_layout

\begin_layout Plain Layout

\change_inserted 238565013 1367679164
You have confused the labels and the captions.
 Labels are short descriptors used to allow cross referencing in the document
 so you don't ever have to keep track of figure numbers.
 Captions are the descriptions of the figure.
 The labels don't appear in the final document.
 
\change_unchanged

\end_layout

\begin_layout Plain Layout
Instead of referring to your columns as 
\change_inserted 238565013 1367680478
the control filter
\change_deleted 238565013 1367680478
column 1
\change_unchanged
 and 
\change_inserted 238565013 1367680564
the subsurface injection filter
\change_deleted 238565013 1367680564
column 2
\change_unchanged
, give them descriptive labels.
 I'd suggest subsurface and surface as the words that describe the two methods
 of injecting water into the filter beds.
 I see that you used subsurface injection and control.
 Those words are fine too.
 Go through the document and replace every instance of 
\begin_inset Quotes eld
\end_inset


\change_inserted 238565013 1367680478
the control filter
\change_deleted 238565013 1367680478
column 1
\change_unchanged

\begin_inset Quotes erd
\end_inset

 and 
\begin_inset Quotes eld
\end_inset


\change_inserted 238565013 1367680564
the subsurface injection filter
\change_deleted 238565013 1367680564
column 2
\change_unchanged

\begin_inset Quotes erd
\end_inset

 including in the figure legends.
\end_layout

\begin_layout Plain Layout
You had the figure images inserted in the caption box in several of the
 figure floats.
 I moved the images to be in the figure float and not in the caption box.
\end_layout

\begin_layout Plain Layout
See Help/embedded objects to learn how to embed figures side by side.
\end_layout

\begin_layout Plain Layout
I accepted changes.
 I didn't track changes when I moved many of your figures.
 Please track changes that you make so I can easily see what you change
 for the final report.
\change_inserted 238565013 1367679752

\end_layout

\begin_layout Plain Layout

\change_inserted 238565013 1367679797
Make sure to include experimental conditions for each graph (filtration
 velocity and coagulant dose).
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Date
May 
\change_inserted 1000245830 1368047969
8
\change_deleted 1000245830 1368047969
3
\change_unchanged
, 2013
\end_layout

\begin_layout Author

\series bold
Team Members: 
\series default
McKenzie Hubert, Hannah Stahl, Eric Grohn, Michelle Bowen
\end_layout

\begin_layout Section*
Abstract
\end_layout

\begin_layout Standard
Through experimental analysis and observation, this research compares a
 conventional rapid sand filter, in which the raw water flows into the sand
 bed from above, with a stacked rapid sand filter, in which raw water is
 injected below the surface of the sand bed .
 To evaluate how head loss and particle capture efficiency are influenced
 by the inlet boundary condition, the influent turbidity, 
\change_deleted 1000245830 1368034651
flow rate
\change_inserted 1000245830 1368034655
filter velocity
\change_unchanged
, coagulant dosage, size of sand grains, and depth of the sand bed are varied.One
 current hypothesis is that during depth filtration, particles are unable
 to collect in regions of high shear between the sand grains because of
 a high 
\change_deleted 1000245830 1368034668
flow rate
\change_inserted 1000245830 1368034671
filter velocity
\change_unchanged
 of the influent water which breaks up large flocs and pushes the particles
 deeper into the sand bed, essentially filling up the pores layer by layer
 from the top to the bottom of the bed.
 Consequently, we predict that head loss will increase linearly as a function
 of time when depth filtration occurs as opposed to an exponential increase
 when surface filtration occurs and the top of the filter bed becomes clogged
 with particles.
 
\end_layout

\begin_layout Section*
Literature Review
\end_layout

\begin_layout Standard
Contaminated water may enter sand filters from the top, from the bottom,
 or—as in AguaClara’s stacked rapid sand filter—from within the sand bed.
 Since AguaClara is the first to inject water directly into the middle of
 the sand bed, there exists little to no research about the advantages or
 disadvantages of this method versus the typical method of flow into the
 top surface of the sand bed; we therefore plan to compare these two methods
 through various experiments.
 After the water enters the system, from either the top of the sand bed
 or injected below the surface of the sand bed, it flows through the bed
 at a velocity set by the flow rate.
 
\end_layout

\begin_layout Standard
There are four ways the particles in the water can be filtered by the sand
 grains: (1) they may be bigger than the pore size between grains, causing
 them to get trapped (a process called sieving); (2) they may stick to a
 sand grain due to their coagulant coating applied earlier in the water
 treatment process; or (3) their charge may draw them to a sand grain, to
 which they then attach (a process called binding); (4) they may settle
 to a sand surface due to gravity.
 Filters need to be periodically cleaned due to the build-up of particles
 in the sand bed over time.
 Filters that run at a low velocity often need surface washing, since the
 particles tend to collect at the top.
 Higher velocity systems generally do not need surface washing but instead
 undergo a process called backwashing (Balasubramaniam).
 In this process, the direction of flow is reversed, causing the sand bed
 to fluidize and particles to detach from the sand grains.
 Detached particles are then suspended and can be transported out of the
 bed with the effluent.
 The frequency of backwashing necessary depends on the the rate at which
 the filter pores are filled with particles.
 This in turn depends on several factors, especially velocity.
 What is of particular interest to our research is not how frequently the
 pores fill up but the distribution of the particles in the filter bed—at
 the surface of the sand bed or throughout it.
 A variety of sources have suggested but not completely confirmed that the
 following factors are significant: velocity of the influent water, amount
 of coagulant applied to the influent water, concentration of influent suspended
 solids, and size and type of filter media.
 We will conduct experiments to evaluate these parameters and their effects
 on location of head loss build-up.
 Rapid sand filters can be designed to not require a backwash pump if six
 filters are placed side-by-side, and five valves may be shut off to create
 a combined water pressure strong enough to propel a backwash in one of
 the filters.
 In a SRSF, six filters are stacked vertically, and a single valve is used
 to backwash the system.
 One advantage of the SRSF is that it accomplishes the same goals as a conventio
nal rapid filter but reduces the number of filters required by a factor
 of 6; this translates into a large decrease in construction costs and makes
 the filter more practical for small communities, particularly in developing
 countries.
 If a single rapid sand filter is used as would be the case for small communitie
s, then an additional advantage is that SRSF are backwashed without a need
 for pumps or storage of filtered water.
 A possible disadvantage of the SRSF that Professor Bisogni presented is
 the impossibility of using more than one type of filter media.
 The other sand filtration technology that can be operated without electricity
 is slow sand filtration.
 However, such a filter is approximately 260 times larger than an SRSF and
 thus its capital cost is considerably higher.
\end_layout

\begin_layout Section*
Introduction
\end_layout

\begin_layout Standard
The filtration process in water treatment plants significantly reduces the
 turbidity in drinking water produced by the plants.
 Different types of filter models and methods are available, including those
 that use membranes and various filter media.
 AguaClara’s mission to produce energy efficient, low-cost treatment plants
 has led to the development of what is called a Stacked Rapid Sand Filter
 (SRSF).
 In this design, slotted pipes inject water into 6 different layers of the
 sand bed.
 Out of all of the AguaClara water treatment plants in current operation,
 only the Tamara plant has a SRSF installed.
 Turbidity measurements from this plant, compared to those from the other
 plants without filters, confirm that filtration substantially improves
 the quality of the effluent water.
 According to the data reported by monitor.wash4all.org for the month of March
 2013, the average turbidity of filtered water from the Tamara plant was
 0.14 NTU, while the average turbidity of the water after it passes through
 the sedimentation tank in this plant is 1.12 NTU.
 As this data suggests, filtration significantly improves the turbidity
 of the water.
 The goal of the Depth vs.
 Surface Sand Filtration research team is to learn what factors, such as
 
\change_deleted 1000245830 1368034713
flow rate
\change_inserted 1000245830 1368034716
filter velocity
\change_unchanged
, coagulant dosage, and initial turbidity, may affect the type of filtration
 (surface or depth) that occurs within the SRSF.
 This experiment will hopefully expose which type of filtration occurs in
 the SRSF (surface, depth, or a combination of both) and how the flow inlet
 boundary conditions affects the overall efficiency and head loss of the
 filter over time.
 We compared different inlet boundary conditions, both by subsurface injection
 (the slotted pipe method, which is tested with 
\change_inserted 238565013 1367680564
the subsurface injection filter
\change_deleted 238565013 1367680564
Column 2
\change_unchanged
) and by the conventional downflow method in which influent water enters
 through the top of the bed and exits from the bottom, which is tested with
 
\change_inserted 238565013 1367680478
the control filter
\change_deleted 238565013 1367680478
Column 1
\change_unchanged
.
 Evaluating the performance of both techniques led to a determination of
 which method to implement in future filter designs to reduce head loss
 and increase particle capture efficiency.
 This research will ultimately extend AguaClara’s knowledge about the filtration
 process and may be used to help diagnose and fix clogging problems within
 the SRSF in the future if we are able to pinpoint what factors and capacities
 of such parameters determine surface or depth filtration.

\color red
 
\color black
It is possible that a high coagulant dosage will cause large flocs to grow
 in the plant which could potentially clog the mesh used in the subsurface
 injection tube.
 If this phenomenon occurs, it would provide insight as to why there may
 be structural problems with the SRSF.
 Large flocs may accumulate on the ridges of the slotted pipes and potentially
 block the flow of water.

\color red
 
\color inherit
This information can be used by the design team to minimize the size of
 the SRSF without losing efficiency and reduce production costs of future
 water treatment plants.
\end_layout

\begin_layout Standard
Our overarching goal of this research is to understand what causes the switch
 between surface and depth filtration.
 Our aim is to potentially reduce surface filtration effects by injecting
 water into the filter bed.This is critically important because if surface
 filtration occurred in a slotted pipe in the SRSF, it would result in rapid
 clogging.
 We will be investigating if it is possible that perhaps high dose of coagulant
 could cause the SRSF to switch to surface filtration.
 If that happened, it could have serious ramifications for treatment plants.
 This would lead to questions such as what would physically occur in the
 plant, how would the operator realize what is happening, and what would
 be required to fix the problem? This problem falls under one of the major
 themes of our research, which is to try and determine under what conditions
 might the slotted pipes in the SRSF clog? We know that the filter at Tamara
 needs to be cleaned every few months, but we think that is due to the fact
 that the fabrication system for the slotted pipes is resulting in sand
 leaking into the pipes and we think that sand is causing the clogging.
 But it could be possible that the pipes would be clogging even if sand
 weren't leaking into the pipes.We hope our research will help us better
 understand how often and to what extent the plant operators will need to
 perform routine maintenance on SRSF to clean the slotted pipes.
 Successful operation of SRSF will require that conditions leading to clogging
 of the slotted pipes be avoided and that appropriate methods be developed
 to clean the slotted pipes if necessary.
\end_layout

\begin_layout Section*
Our Theory
\end_layout

\begin_layout Standard
The regions in the sand bed in which the shear forces are the greatest are
 the regions in which the area between the sand grains (size of the pore)
 is the smallest because the water is forced to travel at a faster velocity
 due to this decreased area.
 We believe that surface filtration occurs when the particles collect in
 these regions and are likely to fill and clog the pore, preventing water
 from flowing through it (Figure 1).
 Our theory is that particles tend to build up in these regions because
 the shear forces acting on the particles by the water flowing through the
 pore are not strong enough to overcome the forces that bind the particles
 to the sand grains.
 
\end_layout

\begin_layout Standard
Shear in a pore is given by
\end_layout

\begin_layout Standard
\begin_inset Formula 
\begin{equation}
\tau=\frac{4\mu\overline{V}}{r}\label{eq:shear in a pore}
\end{equation}

\end_inset


\end_layout

\begin_layout Standard
Where
\change_deleted 1000245830 1368034729
 
\change_unchanged

\begin_inset Formula $\tau$
\end_inset

is the shear,
\change_deleted 1000245830 1368034736
 
\change_unchanged

\begin_inset Formula $r$
\end_inset


\change_deleted 1000245830 1368034741
 
\change_unchanged
is the pore radius,
\change_deleted 1000245830 1368034744
 
\change_unchanged

\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\strikeout off
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\noun off
\color none

\begin_inset Formula $\overline{V}$
\end_inset


\change_deleted 1000245830 1368034758
 
\change_unchanged
is the average pore velocity,
\change_deleted 1000245830 1368034765
 
\change_unchanged

\begin_inset Formula $\mu$
\end_inset


\change_deleted 1000245830 1368034767
 
\change_unchanged
is the viscosity of the fluid.
 
\begin_inset CommandInset ref
LatexCommand ref
reference "eq:shear in a pore"

\end_inset

 assumes fully developed laminar flow.
 The velocity in a pore increases and the radius of the pore decreases as
 the pore fills with solids and thus the shear in the pore increases with
 solids loading.
 The attachment force is expected to be correlated with the surface coverage
 of the colloids with coagulant precipitate.
 Thus surface filtration is expected to occur at high coagulant dosages
 and low 
\change_deleted 1000245830 1368034788
flow rate
\change_inserted 1000245830 1368034794
filter velocitie
\change_unchanged
s.
\end_layout

\begin_layout Standard
In surface filtration the intraparticle forces are strong enough so that
 the particles are able to bridge across the pores.
 
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Life of a Floc - Surface Filtration without explanation.jpg
	lyxscale 75
	scale 50

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Our theory behind surface filtration is that particles stick to the sand
 grains in regions that are likely to clog the pore.
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
Our theory is that depth filtration occurs within the sand bed because the
 particles tend to collect in regions of lower shear, which is near the
 base or top of the sand grains where the area between sand grains is greater
 than that of the narrow channel.
 Again, we hypothesize that this must be due to the relative forces acting
 on the particles.
 We suspect that the shear forces prevent the particles from collecting
 in the middle of the pores, and thus the passage for water to flow into
 the depths of the sand bed is left open.
 A lower coagulant dosage and a higher velocity of influent water are expected
 to produce this type of filtration (Figure 2).
 
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Life of a Floc - Depth Filtration without explanation.jpg
	lyxscale 75
	scale 50

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Depth filtration most likely occurs when particles are captured in regions
 of low shear in between sand grains, leaving the pore mostly open for water
 to flow through.
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
We hypothesize that by injecting the water below the surface of the sand
 bed, we are forcing depth filtration to occur because of the higher velocity
 as a result of the smaller size of the inlet slots of the inlet pipe and
 the local higher velocity in the inlet region.
 In our initial experiement we will be recording head loss across the filter
 over time.
 We hypothesize that the head loss will increase at a linear rate over time,
 as this process continues throughout the depth of the sand bed as particles
 fill up successive layers of pores (though not completely clogging them)
 and the water is able to travel deeper within the bed and deposit their
 particles in these deeper pores.We also hypothesize that a higher coagulant
 dose will cause head loss to increase at a higher rate, as the filter will
 fill faster.
 Coagulant makes the particles stick to the sand grains, and shear forces
 attempt to remove the particles from these grains, so there is a critical
 interaction between these forces within the sand bed.
 These predictions are shown in Figure 3.
\end_layout

\begin_layout Standard
We believe that subsurface injection of the raw water into the sand bed
 will increase the particle capture efficiency
\begin_inset Note Note
status open

\begin_layout Plain Layout
I wouldn't expect subsurface injection to have higher particle capture efficienc
y.
 I would expect subsurface injection to have less head loss for the same
 amount of particle removal
\change_inserted 1000245830 1368050119
.
 This is true, but this paragraph was our initial hypothesis.
 We now realize it is incorrect, but we didn't feel like it was appropriate
 to change our initial hypothesis.
\change_unchanged

\end_layout

\end_inset

 and decrease the head loss 
\change_deleted 238565013 1367678560
required to run and backwash the
\change_inserted 238565013 1367678564
 during filtration
\change_deleted 238565013 1367678567
 filter
\change_unchanged
.
 
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Head loss v.s. time.jpg
	scale 70

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
\begin_inset CommandInset label
LatexCommand label
name "Expected changes in head loss with different coagulant dosages while keeping influent turbidity constant."

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
The two major differences between the two methods of filtering will be where
 the water is loaded in the filter and with what velocity the water enters
 the sand bed (refer to Figure 4).
 In the case of the model SRSF, the constriction will cause the water to
 enter the filter at a signifcantly higher velocity, though the two filters
 will filter the same volume of water in the same amount of time.
 We hypothesize that this higher velocity will prevent surface filtration.
 This could lengthen the filter run time if conditions are such that surface
 filtration occurs in the control.
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Velocity vs depth.jpg
	scale 70

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
\begin_inset CommandInset label
LatexCommand label
name "Velocity of the influent water in the SRSF as it enters and exits the sand column through small slots."

\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Section*
Methods
\end_layout

\begin_layout Standard
We have constructed an apparatus to perform various experiments on sand
 filtration.
 The test apparatus consists of two sand column filters.
 The first column filters water downward through the sand bed, consistent
 with a conventional rapid sand filter.
 The second column features a small fitting that injects water into the
 middle of the sand bed to create conditions of subsurface injection similar
 to those of the AguaClara SRSF.
 Tap water amended with clay and coagulant was run through the filters.
 The effluent turbidity and head loss of each column was measured and used
 to compare their overall performances.
 The influent turbidity, coagulant dosage, and 
\change_deleted 1000245830 1368034803
flow rate
\change_inserted 1000245830 1368034806
filter velocity
\change_unchanged
 were varied to determine the effect of each on the efficiency of filtration
 and the accumulation of head loss.
\end_layout

\begin_layout Subsection*
Description of Testing Setup
\end_layout

\begin_layout Standard
In summary, the components of the test setup fall into three catagories:
 input system, sand columns, and sensor system.
 The input system components determine the composition of the water that
 we need for a specific filtration test.
 It is able to vary 
\change_deleted 1000245830 1368034845
flow rate
\change_inserted 1000245830 1368034848
filter velocity
\change_unchanged
, coagulant dosage, and clay dosage (i.e.
 how dirty the water is before filtration).
 The two sand columns are where the sand filtration occurs.
 Dirty water flows down through the sand beds and clay flocs are filtered
 out.
 The sensor system allows us to measure influent and effluent trubidities,
 as well as headloss across the columns.
\end_layout

\begin_layout Standard
More specifically, the components of the test setup are described in the
 following two figures, the first of which is a labeled 
\change_deleted 1000245830 1368045679
circuit 
\change_unchanged
diagram, and the second is a labeled photo of the test bench.
 The purpose of each component is described in the following list:
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(a) Clean water is taken from the 
\change_inserted 238565013 1367678666
temperature controlled (Temperature set to 
\change_inserted 1000245830 1368036156
20
\change_deleted 1000245830 1368036155
??
\change_inserted 238565013 1367678666
 C) and aerated 
\change_unchanged
clean water supply tank in HLS 160.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(b) Water mixed with clay is stored in a stock tank.
 This stock is constantly being stirred by an electric mixer.
 The concentration of clay in this stock tank was varied according to the
 test we were currently running.
 We would vary the clay concentration and the clay pump (d) speed until
 we achieved the desired NTU on the influent turbidity.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(c) Water mixed with PAC coagulant is stored in a stock tank.
 When choosing the concentration of coagulant in the stock tank, the following
 relation was used: (Coagulant concentration in the stock tank)*(Flow rate
 out of the stock tank) = (Coagulant concentration in the sand filters)*(Total
 flow rate through the sand filters).
 Thus, keeping in mind that the maximum flow rate out of the stock tank
 using a 100 rpm peristalic pump and size 13 tubing is 6 mL/min, we varied
 the stock tank coagulant concentration to achieve the desired coagulant
 concentration in the sand filters.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(d) Two separate peristalic pumps were used to pump the clay stock solution
 and the coagulant stock solution from their stock containers to the influent
 water tubing.
 The speed of each could be varied to achieve the desired level of coagulant
 or clay concentration in the influent water solution.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(e) A rapid mix chamber was used to mix the coagulant solution with the
 clay water solution.
 This chamber created high turbulence water that mixed the two separate
 solutions into one uniform solution, most likely forming small clay flocs
 in the process.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(f) An influent turbidimeter measured the turbidity of the water/clay/coagulant
 solution before it passed through the sand filters.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(g) Two peristalic pumps pump water through the sand columns in the downward
 direction.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(h) Two flow accumulators are used to smooth out the water flow from the
 peristalic pumps.
 The flow accumulators are closed containers that are filled halfway with
 water.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(i) Pressure sensors are installed across the sand columns.
 These sensors measure the difference in head between the top and the bottom
 of the sand columns.
 These sensors are zeroed before each test, when the water is not flowing.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(j) A fitting with a small tube is used to inject water into the middle
 of the bed of sand.
 Due to the small diameter of the tube, the water velocity through it is
 very high.
 This subsurface injection fitting allows us to create conditions similar
 to the slotted pipes in the AguaClara SRSF.
 A diagram of water through each of the two sand columns is provided in
 a following figure.
 We have chosen the diamater of the tube so that the velocity of water exiting
 from the subsurface injection fitting into the sand bed is very close to
 that of the velocity of water exiting the slotted pipe in the AguaClara
 SRSF.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(k) Two solenoids control the flow out of the bottom of the columns.
 These solenoids are open during filtration, and closed during backwash.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(l) The effluent turbidity of both sand filters is measured.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(m) A peristalic pump is used to backwash both columns between tests.
 This pumps water up through the columns, fluidizes the sand beds, and flushes
 all the deposited clay from the previous test.
\end_layout

\begin_layout Labeling
\labelwidthstring 00.00.0000
(n) Two solenoids control the flow of water out of the top of the sand columns.
 These solenoids are open during backwash and closed during filtration.
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Computer_Schematic.png

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
A schematic of our current experimental apparatus.
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename lab_bench_(labeled).png
	scale 70

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Photo of the experimental apparatus in the lab.
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename flow_paths_visual_(surface_vs_subsurface).png
	scale 50

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Left: Water flow in conventional downflow filter; Right: Water flow using
 subsurface injection fitting.
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard

\series medium
We ran several tests.
 For each test, a value for 
\change_deleted 1000245830 1368034878
flow rate
\change_inserted 1000245830 1368034881

\series default
filter velocity
\change_unchanged

\series medium
, coagulant dosage, and influent turbidity was chosen.
 The test were run for a predetermined amount of time, measuring the effluent
 turbidities and head losses across the columns.
 The typical values for 
\change_deleted 1000245830 1368034902
flow rate
\change_inserted 1000245830 1368034904

\series default
filter velocity
\change_unchanged

\series medium
 (through a single column), coagulant dosage, and influent turbidity were
 
\change_inserted 1000245830 1368034917
2
\change_deleted 1000245830 1368034916
1
\change_unchanged
 
\change_deleted 1000245830 1368034923
mL/s
\change_inserted 1000245830 1368034924
mm/s
\change_inserted 238565013 1367678794

\begin_inset Note Note
status open

\begin_layout Plain Layout

\change_inserted 238565013 1367678822

\series medium
You can make these values independent of the size of the filter bed by reporting
 velocities instead of flow rates.
 
\change_unchanged

\end_layout

\end_inset


\change_unchanged
, 5 mg/L polyaluminum chloride, and 200 NTU respectively.
 However, values as low as 
\change_deleted 1000245830 1368034945
0.25 mL/s
\change_inserted 1000245830 1368034950
0.5 mm/s
\change_unchanged
 and as high as 
\change_deleted 1000245830 1368034954
2.5 mL/s
\change_inserted 1000245830 1368034956
5 mm/s
\change_unchanged
 will be used for 
\change_deleted 1000245830 1368034938
flow rate
\change_inserted 1000245830 1368034941
filter velocity
\change_unchanged
.
 Values between 0.5 mg/L and 15 mg/L will be used for coagulant dosage.
 Values between 80 NTU and 450 NTU will be used for influent turbidity.
 Our hypothesis is that head loss will increase over time (as the flocs
 collect in the filter).
 When the filter is backwashed, we expect head-loss to return to its original
 value (because the collected flocs are flushed out of the filter).
 By examing where the clay particles collect in the filter, we can see which
 cases produce surface filtration and which cases produce depth filtration.
\end_layout

\begin_layout Standard
It is important to note that 
\change_inserted 238565013 1367680564
the subsurface injection filter
\change_deleted 238565013 1367680564
column 2
\change_unchanged
 has a fitting that simulates the conditions for subsurface injection.
 Thus, since all other conditions are the same, we can compare subsurface
 injection to surface injection by comparing the turbidities and head loss
 between the two columns.
\end_layout

\begin_layout Subsection*
Process Controller Method Files and Software Setup 
\end_layout

\begin_layout Standard
In our Process Controller method file we have the following states: 
\end_layout

\begin_layout Itemize
Off: All pumps are off; all solenoids are closed
\end_layout

\begin_layout Itemize
Filter: Coagulant pump, clay pump, and the two filter pumps (one for each
 column) are on; the two solenoid valves near effluent turbidimeters are
 open, the other two solenoids are closed
\end_layout

\begin_layout Itemize
Backwash: Backwash pump is on (pumping water up through both columns); the
 two solenoid valves near effluent turbidimeters are closed, the other two
 solenoids are open
\end_layout

\begin_layout Itemize
Test: A disposable state to test different pieces of equipment in the apparatus
 before making any changes to the other states
\end_layout

\begin_layout Standard
Each of the states includes a series of set points, some of which include:
\end_layout

\begin_layout Itemize
Off/On: Correspond to boolean 0/1 respectively.
 Can be used to turn pumps off/on.
\end_layout

\begin_layout Itemize
Turbidimeters: Includes an ID number (necessary for sorting the information
 gathered from each one)
\end_layout

\begin_layout Itemize
Pumps: Fractions and Flow Rates to dictate the speed at which each pump
 is run
\end_layout

\begin_layout Itemize
Run Time: Determines the length of time to run an experiment in the filter
 state before switching to the off state (this set point is only used when
 in automatic mode)
\end_layout

\begin_layout Section*
Qualitative Observations
\end_layout

\begin_layout Standard
There was a consistent difference in the location of particular capture
 between the two filters.
 The clay water that we ran through the system was a milky white color,
 and when particles got trapped in the sand, they appeared as little white
 specks between the sand grains that were observable with the naked eye.
 After running dirty water through the system for a period of time, a layer
 of flocs accumulated on the top of the sand band in 
\change_inserted 238565013 1367680478
the control filter
\change_deleted 238565013 1367680478
column 1
\change_unchanged
 (conventional downflow).
 A majority of the particles were trapped near the surface, as shown by
 the whiteness of this region of the sand bed.
 The lower depths of the filter did not show as much as a color difference,
 indicating that fewer particles were captured there.
 In 
\change_inserted 238565013 1367680564
the subsurface injection filter
\change_deleted 238565013 1367680564
column 2
\change_unchanged
 (subsurface injection), particles were trapped in the sand both above and
 below the injection site.
 because the water coming into the filter entered at such a high velocity,
 the clay and water particles collided with the sand grains and the opposite
 wall of the column, dispersing in all directions.
 Particles in the control column were filtered from top to bottom of the
 sand bed.
 Particles in the subsurface injection column were also captured in a similar
 
\begin_inset Quotes eld
\end_inset

top to bottom
\begin_inset Quotes erd
\end_inset

 manner, but in the beginning of the experiment, the capturing of the flocs
 also spread in the upwards direction above the injection site as well as
 below it.
 
\end_layout

\begin_layout Standard
As noted above, thin layer of visible flocs formed on the top surface of
 
\change_inserted 238565013 1367680478
the control filter
\change_deleted 238565013 1367680478
column 1
\change_unchanged
 (control), including some very large flocs that were similar in size to
 (or larger than) the sand grains.
 These larger, heavier flocs were difficult to remove with our standard
 backwash method, even when operating the backwash pump at a higher speed.
 No such large and heavy flocs were observed in 
\change_inserted 238565013 1367680564
the subsurface injection filter
\change_deleted 238565013 1367680564
column 2
\change_unchanged
 (subsurface injection), which may imply that subsurface injection prevents
 large flocs from forming during filtration, as opposed to surface filtration
\change_inserted 238565013 1367678984

\begin_inset Note Note
status open

\begin_layout Plain Layout

\change_inserted 238565013 1367678991
This is a very interesting observation.
\change_unchanged

\end_layout

\end_inset


\change_unchanged
.
 Because of this difference, 
\change_inserted 238565013 1367680564
the subsurface injection filter
\change_deleted 238565013 1367680564
column 2
\change_unchanged
 could be backwashed at a lower backwash pump speed than 
\change_inserted 238565013 1367680478
the control filter
\change_deleted 238565013 1367680478
column 1
\change_unchanged
, without large flocs remaining in the column afterwards.
 Because of the floc build-up observed on the surface of 
\change_inserted 238565013 1367680478
the control filter
\change_deleted 238565013 1367680478
column 1
\change_unchanged
, the subsurface injection tube was also checked for similar build-up which
 could cause clogging.
 Before backwashing the system, 
\change_inserted 238565013 1367680564
the subsurface injection filter
\change_deleted 238565013 1367680564
column 2
\change_unchanged
 was drained and the influent tubing removed so that the metal tubing and
 mesh could be properly inspected.
 Both the tubing and the mesh were clear of any particles, which supports
 the idea that surface filtration does not occur during subsurface injection,
 even with very high turbidity.
 (Note: This inspection and these observations were made after filtering
 400 NTU water (influent turbidity) for 2 hours (See Figure 8).)
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename 400 NTU photo-e2.jpg
	scale 30

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_inserted 1000245830 1368048647
After filtering 400 NTU water for 2 hours.
 Notice how the sand bed is tinted white where the particles collected in
 both columns and the layer of build-up on the control column.
\change_unchanged

\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Section*
Quantitative Analysis
\end_layout

\begin_layout Standard
Figures 8-14 show the measured headloss over time for different variables,
 including coagulant dosages, 
\change_deleted 1000245830 1368034993
flow rate
\change_inserted 1000245830 1368034998

\series medium
filter velocitie
\change_unchanged

\series default
s, and influent turbidities.
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Turbidity 90 NTU 8 hour headloss graph.pdf
	scale 40

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_deleted 1000245830 1368027784
Head loss as a funtion of time for the two filters given 90 NTU influent
 and a coagulant dose of ??
\change_inserted 1000245830 1368033677
Influent Turbidity: 90 NTU; Filter Velocity: 2 mm/s; Coagulant Dosage: 5
 mg/L
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\align center

\change_deleted 1000245830 1368027794
\begin_inset CommandInset label
LatexCommand label
name "Low Influent Turbidity"

\end_inset


\change_unchanged

\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Turbidity 400 NTU 2 hour headloss graph.pdf
	scale 40

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_deleted 1000245830 1368027753
Type caption here!
\change_inserted 1000245830 1368033724
Influent Turbidity: 400 NTU; Filter Velocity: 2 mm/s; Coagulant Dosage:
 5 mg/L
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\align center

\change_deleted 1000245830 1368027761
\begin_inset CommandInset label
LatexCommand label
name "High Influent Turbidity"

\end_inset


\change_unchanged

\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Coagulant Dosage 0.5 mgL headloss graph.pdf
	scale 40

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_deleted 1000245830 1368027743
Type caption here!
\change_inserted 1000245830 1368033844
Influent Turbidity: 165 NTU; Filter Velocity: 2 mm/s; Coagulant Dosage:
 0.5 mg/L
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\align center

\change_deleted 1000245830 1368027749
\begin_inset CommandInset label
LatexCommand label
name "Low Coagulant Dosage"

\end_inset


\change_unchanged

\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Coagulant Dosage 15 mgL headloss graph.pdf
	scale 40

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_inserted 1000245830 1368033883
Influent Turbidity: 200 NTU; Filter Velocity: 2 mm/s; Coagulant Dosage:
 15 mg/L
\change_deleted 1000245830 1368027732
Type caption here!
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\align center
\begin_inset CommandInset label
LatexCommand label
name "High Coagulant Dosage"

\end_inset


\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Flow Rate 0.25 mLs headloss graph.pdf
	scale 40

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_deleted 1000245830 1368027718
Type caption here
\change_inserted 1000245830 1368034108
Influent Turbidity: 400 NTU; Filter Velocity: 0.5 mm/s; Coagulant Dosage:
 5 mg/L
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\align center

\change_deleted 1000245830 1368027727
\begin_inset CommandInset label
LatexCommand label
name "Low Flow Rate"

\end_inset


\change_unchanged

\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Flow Rate 2.5 mLs headloss graph.pdf
	scale 40

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_inserted 1000245830 1368034213
Influent Turbidity: 240 NTU; Filter Velocity: 5 mm/s; Coagulant Dosage:
 5 mg/L
\change_deleted 1000245830 1368027671
Type caption here!
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\align center

\change_deleted 1000245830 1368027677
\begin_inset CommandInset label
LatexCommand label
name "High Flow Rate"

\end_inset


\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Standard
Figures 15-19 display both the influent and effluent turbidities of each
 experiment which tested similar independent variables (coagulant dosage,
 
\change_deleted 1000245830 1368035005
flow rate
\change_inserted 1000245830 1368035007

\series medium
filter velocity
\change_unchanged

\series default
, and influent turbidity).
 The influent turbidity is measured on the primary axis, while the effluent
 turbidities of columns 1 and 2 is shown on the right hand secondary axis.
\end_layout

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

\begin_layout Plain Layout
\align center

\change_inserted 1000245830 1368031492
]
\change_unchanged

\begin_inset Graphics
	filename about 130 NTU turbidity graph.pdf
	scale 40

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_inserted 1000245830 1368034289
Influent Turbidity: 130 NTU; Filter Velocity: 2 mm/s; Coagulant Dosage:
 5 mg/L
\change_deleted 1000245830 1368027684
Type caption here
\change_unchanged

\end_layout

\end_inset


\change_deleted 1000245830 1368027708

\begin_inset CommandInset label
LatexCommand label
name "Mid-range Influent Turbidity (approximately 130 NTU)."

\end_inset


\change_unchanged

\end_layout

\end_inset


\change_deleted 1000245830 1368031498

\end_layout

\begin_layout Standard

\change_inserted 1000245830 1368030033

\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Coagulant Dosage 0.5 mgL turbidity graph.pdf
	scale 40

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_deleted 1000245830 1368027611
Type caption here
\change_inserted 1000245830 1368034345
Influent Turbidity: 165 NTU; Filter Velocity: 2 mm/s; Coagulant Dosage:
 0.5 mg/L
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\align center

\change_deleted 1000245830 1368029521
\begin_inset CommandInset label
LatexCommand label
name "Low Coagulant Dosage."

\end_inset


\change_unchanged

\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Coagulant Dosage 15 mgL turbidity graph.pdf
	scale 40

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_deleted 1000245830 1368027621
Type caption here
\change_inserted 1000245830 1368034387
Influent Turbidity: 200 NTU; Filter Velocity: 2mm/s; Coagulant Dosage: 15
 mg/L
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\align center
\begin_inset CommandInset label
LatexCommand label
name "High Coagulant Dosage."

\end_inset


\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Flow Rate 0.25 mLs turbidity graph.pdf
	scale 40

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_deleted 1000245830 1368027630
Type caption here!
\change_inserted 1000245830 1368034444
Influent Turbidity: 400 NTU; Filter Velocity: 0.5 mm/s; Coagulant Dosage:
 5 mg/L
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\align center
\begin_inset CommandInset label
LatexCommand label
name "Low Flow Rate."

\end_inset


\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Flow Rate 2.5 mLs turbidity graph.pdf
	scale 40

\end_inset


\begin_inset Note Note
status open

\begin_layout Plain Layout
Adding a secondary axis that is almost the same as the primary axis makes
 this confusing.
 Use the same axis for both influent and effluent to facilitate comparison.

\change_inserted 238565013 1367679697
 An alternative to the two axis approach is to use a log scale on the y
 axis.
 That way you can clearly see the performance improvment of each of the
 filters.
\change_unchanged

\end_layout

\end_inset


\begin_inset Caption

\begin_layout Plain Layout

\change_deleted 1000245830 1368027639
Type caption here
\change_inserted 1000245830 1368034492
Influent Turbidity: 240 NTU; Filter Velocity: 5 mm/s; Coagulant Dosage:
 5mg/L 
\change_unchanged

\end_layout

\end_inset


\end_layout

\begin_layout Plain Layout
\align center
\begin_inset CommandInset label
LatexCommand label
name "High Flow Rate."

\end_inset


\end_layout

\end_inset

Note for Figures 13 and 18: If this test had been run for a longer period
 of time, we expect that the turbidities would have leveled out to become
 very close to one another as shown in the other experiments.
 Even though it may not be as clearly represented on this particular graph,
 it still shows that the headloss increases at a higher rate over time for
 
\change_inserted 238565013 1367680479
the control filter
\change_deleted 238565013 1367680479
column 1
\change_unchanged
.
\end_layout

\begin_layout Section*
Conclusions
\change_inserted 238565013 1367679970

\begin_inset Note Note
status open

\begin_layout Plain Layout

\change_inserted 238565013 1367680564
It is hard to keep track of the control filter and the subsurface injection
 filter.
 Eliminate the code notation.
 By the way using codes instead of descriptive language is a common practice
 in technical writing that many authors use.
 
\change_unchanged

\end_layout

\end_inset


\change_unchanged

\end_layout

\begin_layout Standard
From the data we collected at different influent turbidity level
\change_inserted 238565013 1367679897
,
\change_unchanged
s 
\change_deleted 238565013 1367679908
and different flow
\change_inserted 238565013 1367679909
filtration
\change_unchanged
 rates 
\change_deleted 238565013 1367679916
through the columns
\change_inserted 238565013 1367679918
and coagulant dosages
\change_unchanged
, we observed a consistent trend that the headloss in both columns increased
 linearly over time.
 However, the rate of increase in headloss over time in 
\change_inserted 238565013 1367680479
the control filter
\change_deleted 238565013 1367680479
column 1
\change_unchanged
 was greater than that of 
\change_inserted 238565013 1367680564
the subsurface injection filter
\change_deleted 238565013 1367680564
column 2
\change_unchanged
.
 The only exception to this trend was when the 
\change_deleted 1000245830 1368035019
flow rate
\change_inserted 1000245830 1368035021

\series medium
filter velocity
\change_unchanged

\series default
 for each column was at a high value of 
\change_deleted 1000245830 1368035027
2.5 mL/s
\change_inserted 1000245830 1368035028
5 mm/s
\change_unchanged
.
 In this case, there appeared to be little difference between the rate of
 increase in headloss over time between the columns.
 
\end_layout

\begin_layout Standard
We believe there may be a connection between the influent velocity to the
 sand bed and the rate of increase in headloss over time.
 One clear connection that we found was that water entering the sand bed
 at a high 
\change_deleted 1000245830 1368035036
flow rate
\change_inserted 1000245830 1368035039
filter velocity
\change_unchanged
 deposited smaller flocs 
\change_deleted 1000245830 1368032746
and there appeared to be less floc build-up
\change_unchanged
 on the surface of 
\change_inserted 238565013 1367680628

\begin_inset Note Note
status open

\begin_layout Plain Layout

\change_inserted 238565013 1367680641
I think you got confused too with the coded notation.

\change_inserted 1000245830 1368032774
 We did mean the control filter, there was noticeably less build-up at the
 higher flow rate.
\change_unchanged

\end_layout

\end_inset

the control filter
\change_deleted 238565013 1367680479
column 1
\change_unchanged
.
 This suggests that influent velocity substantially affects whether depth
 or surface filtration occurs within the filter.
 It appeared that at higher 
\change_deleted 1000245830 1368035058
flow rate
\change_inserted 1000245830 1368035062
filter velocitie
\change_unchanged
s, that depth filtration occured in 
\change_inserted 238565013 1367680479
the control filter
\change_deleted 238565013 1367680479
column 1
\change_unchanged
 because a top film of particles did not form, even at high influent turbidity
 values of 240 NTU.
 In 
\change_inserted 238565013 1367680564
the subsurface injection filter
\change_deleted 238565013 1367680564
column 2
\change_unchanged
, because of the small diameter of the injection tube, the velocity is always
 relatively high, which would also explain why there was no floc build-up
 on the mesh of the tube.
 This supports that the SRSF design is better than a traditional downflow
 filter because the headloss builds up more slowyly over time, meaning that
 the filter can be run for a longer period of time before backwashing without
 needing to resort to surface washing the filter to properly clean it.
\end_layout

\begin_layout Standard
The effluent turbidities of each column were consistently similar to each
 other despite changes in influent turbidity and the difference in method
 of water injection.
 Minor discrepancies of about 1-2 NTU between the measured effluent turbidities
 of the columns is likely due to differences in calibration between the
 turbidimeters, which is an observation we made while testing the accuracy
 of the turbidimeters before running any experiments.
 
\begin_inset Note Note
status open

\begin_layout Plain Layout
rewrite the next sentence
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This leads us to believe that flow rate and coagulant dosage, while they
 may the overall effluent turbidity, the relative differences between the
 columns is not substantial.
 
\change_inserted 1000245830 1368035085
After varying the coagulant dosage and filter velocity through the columns,
 the effluent turbidity was similar for both columns.
 
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So then it would appear as if 
\change_inserted 238565013 1367680564
the subsurface injection filter
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column 2
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 was not noticeably better at capturing or removing particles from the water
 than 
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the control filter
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column 1
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 and there is no advantage to the SRSF design in this respect.
 The only advantage we can interpret from our gathered data is that the
 SRSF design has a slower increase in headloss over time.
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Future Work
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My immediate goal would be to learn what conditions cause surface filtration
 to occur in the subsurface injection filter.
 What would happen if the coagulant dose were increased significantly? Would
 the screen clog?
\change_inserted 1000245830 1368045327
 - We tried to run one last experiment but no significant results that were
 worth reporting here.
 But we included this task as future work and a possible challenge for future
 semesters.
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After analyzing the results of our initial experiments, we believe that
 further investigation into the effects of high 
\change_deleted 1000245830 1368035145
flow rate
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filter velocitie
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s on each of the two types of filters may be beneficial to support our claim
 that at high 
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flow rate
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filter velocitie
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s, depth filtration occurs to a certain degree even in the conventional
 RSF.
 
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Also, it would be interesting to try to run an experiment for the sole purpose
 of clogging the injection site of the subsurface filter.
 By determining what kinds of parameters may cause this (probably low flow
 rate and high turbidity) and recording these values, we may be better able
 to predict under what conditions the actual SRSF will clog.
 The head loss and effluent turbidity could continue to be monitored during
 this test as well to see what kinds of changes occur.
 By forcing the subsurface filter to fail we could simulate what kinds of
 physical implications this would have on the filter itself and on other
 components of the test apparatus connected to the filter.
 This information could inform plant operators of what signs to look for
 and could provide insight as to how to respond in situations in which it
 appears as the SRSF is clogging.
 
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Other factors that were not tested but could also affect the headloss and
 effluent turbidities are different filter media or sand sizes.
 It would be interesting to see how changing this parameter would function
 in the SRSF and affect the headloss and effluent turbidities.
 Another idea to improve the particle capture efficiency of the SRSF design
 might be to filter the influent water twice through the filter to see if
 turbidity improves.
 It is possible that the remaining particles in the water after the initial
 filtering would be so small that they would not be captured during the
 second filtering, but we believe further investigation could possibly help
 improve the current SRSF model.
 Finally, the team may consider treating the water before and/or after the
 filtration process by .
 adding more coagulant to the raw water just before it enters the filter
 or installing a foam filter after the SRSF to potentially capture even
 more particles that were not removed in the filter.
 This plan would take some significant design changes to the apparatus used
 in the first round of experiments, and time does not permit us to test
 these new ideas.
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\begin_layout Section*
References
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\begin_layout Address
“Basics of Filtration.” Wyckomar UV Water Purification.
 Wyckomar Inc.
 Web.
 16 Feb.
 2013.
 http://www.wyckomaruv.com/PDFs/Basics%20of%20Filtration.pdfBalasubramaniam,
 Vigneswaran.
 "Effect of particle size in depth filtration: Measurements and modeling."
 Electronic Doctoral Dissertations for UMass Amherst.
 (January 1, 1997).
 Paper AAI9737593.
 Web.
 20 Feb.
 2013.
 <http://scholarworks.umass.edu/dissertations/AAI9737593>
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\begin_layout Address
Benth, Bryant et al.
 “Evaluation of Wastewater Filtration.” Utah Water Research Laboratory.
 Utah State University (1981).
 Web.
 20 Feb.
 2013.
 
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\begin_layout Address
Farizoglu, Burhanettin.
 “The performance of pumice as a filter bed material under rapid filtration
 conditions.” Filtration & Separation 40.3 (April 2003): 41-47.
 Web.
 13 Feb.
 2013.
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\begin_layout Address
“Fundamentals of Particle Removal by Depth Filtration.” Culligan.
 Web.
 13 Feb.
 2013.
 <www.culliganmiami.com/pf4.html>
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\begin_layout Address
“Head Loss.” Water/Wastewater Distance Learning Website.
 Mountain Empire Community College.
 Web.
 20 Feb.
 2013.
 <http://water.me.vccs.edu/courses/CIV240/lesson7.htm>
\end_layout

\begin_layout Address
Jusoh, Ahmad.
 “Effective depth, initial head loss and backwashing criteria as the key
 factors of burned oil palm shell (BOPS) granular filtration.” Desalination
 and Water Treatment 10.1-3 (2009): 80-86.
 Web.
 13 Feb.
 2013.
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\begin_layout Address
Lau, Boris L T.
 “Physicochemical aspects of Cryptosporidium surrogate removal in carbon
 block filtration.” American Water Works Association Journal 97.2 (Feb.
 2005): 12, 92-101.
 Web.
 13 Feb.
 2013.
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\begin_layout Address
“Principles of Filtration.” Sterlitech Corporation.
 Web.
 13 Feb.
 2013.
 <www.sterlitech.com/principles-of-filtration>
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\begin_layout Address
Pourrezaei, Parastoo.
 “Physico-Chemical Processes: Water Environment Research, 2010 Literature
 Review.” Water Environment Federation.
 Web.
 13 Feb.
 2013.
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Sutherland, Ken.
 “Depth filtration: Efficient separation processes through depth filtration.”
 Filtration & Separation 48.5 (Sept.-Oct.
 2011): 12-15.
 Web.
 13 Feb.
 2013.
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Monroe, can you help us out with Lyx sometime? This looks really unprofessional,
 and we want to make it look better, but none of us have experience with
 Lyx.

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 Do an initial check with the help files.
 That is how I learned what I know.
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Also, we tracked all of our changes but we weren't sure if you still wanted
 us to...
 Should we also track them when we revise it for the final time?
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 Yes, track changes again.
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