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\begin_body

\begin_layout Title
Tube Flocculator
\end_layout

\begin_layout Author
\begin_inset space ~
\end_inset

Primary Authors: Huifei Wu, Danhong Luo
\begin_inset Newline newline
\end_inset

Primary Editor: Karen Swetland
\end_layout

\begin_layout Date
Date Submitted: 12/02/2011
\end_layout

\begin_layout Abstract
In order to build a complete hypothesis to support our experiments, we read
 three papers about PACl.
 They showed the main mechanisms for PACl are electrostatic patch coagulation,
 bridge-aggregation and precipitation/charge neutralization, and revealed
 that the alkalinity and size of the coagulant aggregates could influence
 the flocculator performance.
 From these hypotheses, we began the tube flocculator residual turbidity
 test experiment, coagulant particle size measurement and coagulant absorbency
 measurement.
 We expect that the raw water treated by the vacuum filtered coagulant would
 have a lower residual turbidity compared with unfiltered coagulant.
\end_layout

\begin_layout Abstract
To gain a deeper understanding of how the ionic strength would influence
 the turbidity removal efficiency, some literature concerning about ionic
 strength and the effect of 
\begin_inset Formula $Ca^{2+}$
\end_inset

 and 
\begin_inset Formula $Na^{+}$
\end_inset

 have been reviewed.
 They showed that, competition of 
\begin_inset Formula $Na^{+}$
\end_inset

 delays effective shielding of the micelles by 
\begin_inset Formula $Al^{3+}$
\end_inset

 until higher 
\begin_inset Formula $Al^{3+}$
\end_inset

 is present, and adding Ca would increase the content of 
\begin_inset Formula $Al_{13}$
\end_inset

which could enhance the flocculation efficiency of PACl in water treatment.
 In the next experiments we hope to find out the particular ions that influence
 flocculation efficiency over a range of coagulant doses.
\end_layout

\begin_layout Abstract
We found out that decreased ionic strength in the raw water would have a
 negative effect on the coagulation performance, therefore we ran an ionic
 strength test experiment by comparing the turbidity removal efficiency
 of the distilled water and the tap water.
 From the recent work, we find there is a good linear relationship between
 theoretical ionic strength and conductivity and the turbidity and the PACl
 dosage do not influence this relationship.
 The research also reveals that distilled water which has the lowest ionic
 strength has a worse turbidity removal efficiency than tap water which
 has a higher ionic strength.
 One thing need to be noticed is that we assumed there is a linear relationship
 between PACl dosage and needed 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 to keep pH at 7.5.
 However, in this experiment, with the increasing of PACl dosage, the needed
 dosage of 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 decreased at first and then increased.
 Further experimentation is needed to reveal the relationship between 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 needed under different PACl dosage to maintain a constant pH at 7.5.
 
\begin_inset Newpage pagebreak
\end_inset


\end_layout

\begin_layout Section
Literature Review
\end_layout

\begin_layout Subsection
Alkalinity effect of coagulation with polyaluminum chlorides: Role of electrosta
tic patch
\begin_inset CommandInset citation
LatexCommand cite
key "key-1"

\end_inset


\end_layout

\begin_layout Standard
Mechanism of electrostatic patch coagulation
\end_layout

\begin_layout Standard
Because PACl was not well neutralized at the point of optimal dosage, EPC(electr
ostatic patch coagulation) was introduced to explain PACl's residual turbidity
 removal mechanism.
\end_layout

\begin_layout Standard
EPC mainly depends on the amount and sort of species in PACl.
 Due to a high percentage of 
\begin_inset Formula $Al_{a}$
\end_inset

(monomeric species of aluminum), 
\begin_inset Formula $PACl_{0}$
\end_inset

(The chosen B values, [OH]/[Al] molar ratio, of PACl were 0, and the resulting
 products was denoted as 
\begin_inset Formula $PACl_{0}$
\end_inset

) was not stable after dosing and would form colloidal or amorphous hydroxide
 precipitate via hydrolysis.
 This kind of precipitate functions as electrostatic patches because it
 was usually positively charged and able to neutralize the negative charges
 on the clay particles.
 
\begin_inset Formula $PACl_{10}$
\end_inset

, 
\begin_inset Formula $PACl_{22}$
\end_inset

 and 
\begin_inset Formula $PACl_{25}$
\end_inset

(The chosen B values of PACl were 1.0, 2.2 and 2.5 and their resulting products
 were denoted as 
\begin_inset Formula $PACl_{10}$
\end_inset

, 
\begin_inset Formula $PACl_{22}$
\end_inset

 and 
\begin_inset Formula $PACl_{25}$
\end_inset

) which contain a lot of 
\begin_inset Formula $Al_{b}$
\end_inset

 (polymeric species which can react with ferron rapidly) and 
\begin_inset Formula $Al_{c}$
\end_inset

 (high polymerized or colloidal species which cannot react with ferron)
 were very stable and cannot be further hydrolyzed and transformed into
 hydroxide precipitate.
 The electrostatic patches could be formed through its rapid adsorption
 onto clay particles and subsequent aggregation and rearrangement.
\begin_inset Newline newline
\end_inset


\begin_inset Float figure
placement H
wide false
sideways false
status collapsed

\begin_layout Plain Layout
\begin_inset Graphics
	filename 1.jpg
	scale 60

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
Schematic diagram of electrostatic patch coagulation
\end_layout

\end_inset


\end_layout

\end_inset

 This could be used to explain the mechanism of electrostatic patch coagulation.
\end_layout

\begin_layout Subsection
Distinct coagulation mechanism and model between alum and high 
\begin_inset Formula $Al_{13}-PAC$
\end_inset


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

\end_inset


\end_layout

\begin_layout Subsubsection
PACl working mechanism
\end_layout

\begin_layout Standard
Main mechanisms for PACl are electrostatic patch coagulation and bridge-aggregat
ion while charge neutralization also has some effects on the flocculation
 process.
 The residual turbidity declined sharply at very low aluminum concentrations
 and the lowest occurred far before the isoelectric point but then increased.
 The corresponding optimum coagulant dosages were 
\begin_inset Formula $10^{-6}$
\end_inset

mol/L.
 We can draw this result from Fig.2
\begin_inset Float figure
placement H
wide false
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status collapsed

\begin_layout Plain Layout
\begin_inset Graphics
	filename 2.JPG
	scale 60

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
The 
\begin_inset Formula $\xi$
\end_inset

-potential and residual turbidity curves as a function of aluminum dosage
 during coagulation of 0.5 g/L silica microsphere suspension by alum and
 PACl 2.2 (pH 6.5; 
\begin_inset Formula $NaNO_{3}$
\end_inset

: 0.01M; 
\begin_inset Formula $NaHCO_{3}$
\end_inset

: 0.001M)
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
The author thinks that the rapidly adsorbed species may aggregate, rearrange
 and finally form electrostatic patches over portions of particle surface.
 The positively charged patches could attract negative silica particle aggregati
on.
 As the dose of PACl increased further, re-stabilization appeared after
 the maximum turbidity removal.
 The author thinks this implied that particles repelled each other.
 However, with further addition of PACl, the residual turbidity declined
 again due to some amorphous precipitates formed giving sweep-flocculation.
 
\end_layout

\begin_layout Standard
This is the detailed information we could use for our hypothesis.
 Also the re-stabilization should be noted.
\end_layout

\begin_layout Subsubsection
Surface coverage and adsorption isotherm models
\end_layout

\begin_layout Standard
The results show that the maximum surface coverage of PACl was around 0.4.
 The optimum coagulation of silica suspension after PACl addition occurred
 when surface coverage was less than 0.1.
 The author says it is reasonable to suggest that for PACl, the electrostatic
 interaction is the main driving forces for the adsorption process.
 This opinion could be used to support our experiment and we also could
 try to make some effort to improve the utilization of surface.
\end_layout

\begin_layout Standard
Due to the stoichiometric relationship between coagulant dosage and surface
 concentration of dispersion(particle concentration), more precise control
 of dosage of PACl is required for efficient operation.
\end_layout

\begin_layout Subsection
Coagulation of silica microspheres with hydrolyzed Al(III) - Significance
 of 
\begin_inset Formula $Al_{13}$
\end_inset

 and 
\begin_inset Formula $Al_{13}$
\end_inset

 aggregates
\begin_inset CommandInset citation
LatexCommand cite
key "key-3"

\end_inset


\end_layout

\begin_layout Subsubsection
Coagulant size distribution and morphology
\end_layout

\begin_layout Standard
Colloidal aluminum species formed with increasing basicity.
 With increasing B values, particle size increases from about 10 to several
 dozen nm and the large size section becomes broader.
 We should pay attention to this conclusion because the basicity influences
 the coagulant size.
 Also, the author hypothesizes that 
\begin_inset Formula $Al_{13}$
\end_inset

 aggregates were formed by the individual 
\begin_inset Formula $Al_{13}$
\end_inset

 unit via out-sphere bridging and these structures maintain the identical
 tetrahedral environment under certain conditions.
\end_layout

\begin_layout Subsubsection
Zeta-potential of coagulants
\end_layout

\begin_layout Standard
Positive zeta values are stable in the pH range of 4-7 for coated silica
 particles.
 Since the zeta values of 
\begin_inset Formula $Al_{13}$
\end_inset

aggregates are higher than the pure 
\begin_inset Formula $Al_{13}$
\end_inset

 in the acidic range, the author assumes that 
\begin_inset Formula $Al_{13}$
\end_inset

aggregates might release 
\begin_inset Formula $Al_{13}$
\end_inset

units under pH shock.
 Here is a relationship between pH and the size of the coagulants.
\end_layout

\begin_layout Subsubsection
Floc size distribution
\end_layout

\begin_layout Standard
During the experiment, large flocs of ~500
\begin_inset Formula $\mu m$
\end_inset

 are formed at lower dosage.
 However, without enough positive polycations to destabilize negative silica
 particles, particle aggregation induced by B2.8 is retarded, resulting in
 a lower turbidity removal.
 In this part, we could conclude that if we only pay attention to the get
 the big size of the PACl, we might fail because we ignore the effect of
 the positive polycations.
\end_layout

\begin_layout Subsection
The effect of total hardness and ionic strength on the coagulation performance
 and kinetics of aluminum salts to remove humic acid
\begin_inset CommandInset citation
LatexCommand cite
key "key-5"

\end_inset


\end_layout

\begin_layout Subsubsection
The effect of ionic strength on removal efficiency
\end_layout

\begin_layout Standard
In this study, the removal efficiency of HA and HA-kaolin water decreased
 with increasing ionic strength for PACl and Nano-PACl.
 We can draw this conclusion from Fig.
 3 and Fig.
 4.
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename 3.JPG
	scale 60

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
Effect of ionic strength on coagulation performance in HA water treatment.
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename 4.JPG
	scale 60

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
Effect of ionic strength on coagulation performance in HA–kaolin water treatment.
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
The author thought this is because with increasing ionic strength of water,
 the activity of PACl's hydrolysis products decreases.
 We could use this to inform our expected results.
\end_layout

\begin_layout Subsubsection
The effect of ionic strength on PACl
\end_layout

\begin_layout Standard
As ionic strength only influences the activity of charged ion, for given
 ionic strength, PACl containing 
\begin_inset Formula $Al_{13}$
\end_inset

 with the highest charge would lose more activity than other aluminum species.
 As a result, the PACl's removal efficiency is lower than aluminum species
 (Fig.
 3).
\end_layout

\begin_layout Subsection
Effect of ionic strength and competitive adsorption of 
\begin_inset Formula $Na^{+}$
\end_inset

 on the flocculation of lauryl sulfate micelles with 
\begin_inset Formula $Al^{3+}$
\end_inset


\begin_inset CommandInset citation
LatexCommand cite
key "key-7"

\end_inset


\end_layout

\begin_layout Subsubsection
Effect of 
\begin_inset Formula $Na^{+}$
\end_inset

 on competitive adsorption of cations onto the micellar surfactant
\end_layout

\begin_layout Standard
The paper shows the effect of 
\begin_inset Formula $NaCl$
\end_inset

 concentration on the flocculation curves (Fig.
 5).
 An increase in 
\begin_inset Formula $[NaCl]$
\end_inset

 results in an increase in the residual surfactant concentration and a narrowing
 of the region of optimal flocculation.
 This is because when 
\begin_inset Formula $Na^{+}$
\end_inset

 concentration is much higher than 
\begin_inset Formula $Al^{3+}$
\end_inset

, 
\begin_inset Formula $Na^{+}$
\end_inset

 will has higher possibility to cover most of the micelles, a neutral bonding
 site where flocculation can occur.
 This is consistent with the binding factor (
\begin_inset Formula $\beta$
\end_inset

) result in Fig.
 6: with increasing in 
\begin_inset Formula $[NaCl]$
\end_inset

, 
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\begin_inset Formula $\beta$
\end_inset

 becomes smaller, which means
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\begin_inset Formula $Al^{3+}$
\end_inset

 is lower, and the neutralization is less effective.
 As 
\begin_inset Formula $Na^{+}$
\end_inset

 is not a powerful coagulant, high concentrations of 
\begin_inset Formula $Na^{+}$
\end_inset

 result in poor removal efficiency.
 The competition of 
\begin_inset Formula $Na^{+}$
\end_inset

 delays effective shielding of the micelles by 
\begin_inset Formula $Al^{3+}$
\end_inset

 until higher 
\begin_inset Formula $Al^{3+}$
\end_inset

 is present.
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename 8.JPG
	scale 60

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
SDS remaining in solution in the presence of a given free 
\begin_inset Formula $Al^{3+}$
\end_inset

 concentration for different overall 
\begin_inset Formula $[NaCl]$
\end_inset


\end_layout

\end_inset


\end_layout

\end_inset


\begin_inset Float figure
placement H
wide false
sideways false
status collapsed

\begin_layout Plain Layout
\begin_inset Graphics
	filename 9.JPG
	scale 60

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
Binding factor (defined as the ratio of Al to SDS ions in the flocculate)
 vs free 
\begin_inset Formula $Al^{3+}$
\end_inset

 concentration
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
The effect of ionic strength
\end_layout

\begin_layout Standard
In this paper, the author assumes the chemical activity constant above 
\begin_inset Formula $I=0.38$
\end_inset

 
\begin_inset Formula $mole/L$
\end_inset

, so Davies equation 
\begin_inset Formula $\log\gamma=-0.5z^{2}\left(\frac{\sqrt{I}}{1+\sqrt{I}}-0.2I\right)$
\end_inset

 is used here.
\end_layout

\begin_layout Standard
From Davies equation we could deduce that, with the addition of 
\begin_inset Formula $NaCl$
\end_inset

, the chemical activity 
\begin_inset Formula $\left(\gamma\right)$
\end_inset

 is reduced.
 But from the result show in Fig 7, the minimum solubility region loosely
 corresponds to the higher activities within each series, but the actual
 values of the activities corresponding to optimum flocculation or full
 solubility regions are quite different between series.
 So the author concludes a decrease in the ratio of flocculation is not
 a matter of the activity of 
\begin_inset Formula $Al^{3+}$
\end_inset

 dropping below a giving critical value to achieve the adequate binding
 of 
\begin_inset Formula $Al^{3+}$
\end_inset

 on the micelles.
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename 10.JPG
	scale 60

\end_inset


\end_layout

\begin_layout Plain Layout
\begin_inset Caption

\begin_layout Plain Layout
Residual SDS concentration remaining in solution (white symbols) and activities
 of 
\begin_inset Formula $Al^{3+}$
\end_inset

 (black symbols) against 
\begin_inset Formula $Al^{3+}$
\end_inset

 concentrations.
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Effects of Ca on the distribution, structure and morphology of aluminum
 species in polyaluminum chloride
\begin_inset CommandInset citation
LatexCommand cite
key "key-8"

\end_inset


\end_layout

\begin_layout Subsubsection
Effect of Ca on distribution of Al
\end_layout

\begin_layout Standard
The results from this study can be seen in Fig.8 below.
\end_layout

\begin_layout Standard
The results show that both 
\begin_inset Formula $Al_{m}$
\end_inset

 and 
\begin_inset Formula $Al_{13}$
\end_inset

 content increase after 
\begin_inset Formula $CaCl_{2}$
\end_inset

 is added and 
\begin_inset Formula $Al_{13}$
\end_inset

 is much higher if 
\begin_inset Formula $CaCl_{2}$
\end_inset

 is added before the basification.
 This is useful since 
\begin_inset Formula $Al_{13}$
\end_inset

is the optimal species in PAC for flocculation.
\end_layout

\begin_layout Standard
The 
\begin_inset Formula $\delta$
\end_inset

 and linewidth in NMR spectra of 
\begin_inset Formula $Al_{m}$
\end_inset

 and 
\begin_inset Formula $Al_{13}$
\end_inset

 decrease when the 
\begin_inset Formula $Ca/Al$
\end_inset

 molar ratio of the sample rises.
 The decrease of 
\begin_inset Formula $\delta$
\end_inset

and linewidth implies the structure and chemical environment of 
\begin_inset Formula $Al_{m}$
\end_inset

 and 
\begin_inset Formula $Al_{13}$
\end_inset

 are changed due to the shielding of the sixfold or fourfold coordinated
 
\begin_inset Formula $Al$
\end_inset

 in 
\begin_inset Formula $Al_{m}$
\end_inset

 or 
\begin_inset Formula $Al_{13}$
\end_inset

.
 The ability of PACl to self-aggregate is reduced due to the complex of
 
\begin_inset Formula $Ca^{2+}$
\end_inset

with the oxygen atom of 
\begin_inset Formula $Al$
\end_inset

 species to form the structure of 
\begin_inset Formula $Al-O-Ca$
\end_inset

.
 This is an explanation for the improved coagulation performance with higher
 ionic strength since it means the 
\begin_inset Formula $Al$
\end_inset

 species in PAC tend to be smaller after adding 
\begin_inset Formula $CaCl_{2}.$
\end_inset

 Also the Al species becomes scattered and its tendency to polymerization
 decreases due to the repulsion between the positive charges on 
\begin_inset Formula $Ca$
\end_inset

 or 
\begin_inset Formula $Al$
\end_inset

 species.
 This is good for our experiments because we need the relatively small Al
 aggregates rather than the large ones because the smaller one is more effective
 and would has high charge neutralization ability .
 
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Table Ca.PNG
	scale 60

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
Effect of Ca-adding on the content and chemical shift of Al species in PAC
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Effect of 
\begin_inset Formula $Ca$
\end_inset

 on structure and morphology of 
\begin_inset Formula $Al$
\end_inset

 species.
\end_layout

\begin_layout Standard
The results are shown in the Fig.9.
 We can see that the 
\begin_inset Formula $Al$
\end_inset

 species tend to scatter and the density of the aggregates decreases with
 the increasing of 
\begin_inset Formula $Ca/Al$
\end_inset

 molar ratio.
 The branch aggregates disappear gradually and are converted into granules
 whose diameter is diminished as function of the Ca/Al ratio.
 The images support the idea that we could get smaller 
\begin_inset Formula $Al$
\end_inset

 species by adding 
\begin_inset Formula $Ca.$
\end_inset


\end_layout

\begin_layout Standard
Also, adding 
\begin_inset Formula $Ca$
\end_inset

 could prevent the 
\begin_inset Formula $Al_{13}$
\end_inset

 species aggregated in solution and enhance the charge neutralization ability
 of PAC and improve its flocculation efficiency in water treatment.
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename Ca.PNG
	scale 50

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
AFM images of PAC with different Ca/Al molar ratio.(a)
\begin_inset Formula $Ca/Al$
\end_inset

=0; (b)
\begin_inset Formula $Ca/Al$
\end_inset

=0.2; (c)
\begin_inset Formula $Ca/Al$
\end_inset

=0.4; (d)
\begin_inset Formula $Ca/Al$
\end_inset

=0.6.
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Section
Materials and Methods 
\end_layout

\begin_layout Subsection
Particle Size Experiment
\end_layout

\begin_layout Subsubsection
Particles and coagulants
\end_layout

\begin_layout Standard
All chemicals used in this study were of analytical grade except those being
 specifically mentioned, and solutions were prepared with deionized water.
\end_layout

\begin_layout Enumerate
Clay particles
\begin_inset Newline newline
\end_inset

Kaolin clay was used as model particles in this study because of their strong
 negative charge in suspension, homogeneity and simple morphology.
 The raw water was prepared by mixing the clay solution with the water in
 tank.
\end_layout

\begin_layout Enumerate
Coagulants
\begin_inset Newline newline
\end_inset

Polyaluminum chloride (PACl) was used as the coagulant in this investigation.
 We used unfiltered and vacuum filtered coagulant to go through the tube
 flocculator, and test the RT respectively.
 Unfiltered coagulant was prepared by dissolving coagulant in deionized
 water.
 Vacuum filtered coagulant was prepared with unfiltered coagulant filtered
 with filter papers with pore size 0.70
\begin_inset Formula $\mu m$
\end_inset

, 0.45
\begin_inset Formula $\mu m$
\end_inset

 and 0.10
\begin_inset Formula $\mu m$
\end_inset

 in turn.
\begin_inset Newline newline
\end_inset

Our hypothesis is that the electrostatic patch is a major mechanism for
 PACl coagulation.
 We assume that with a big enough coagulant particle size, the patches could
 function efficiently.
 Because if the patch size was bigger than the optimal size, it was a waste
 of coagulant as the middle part of the patch did not contribute to successful
 flocculation; if the patch size was smaller than the optimal size, it was
 not strong enough to form electrostatic attraction between clay particles
 and precipitate.
 So, we try to use the vacuum filtered coagulant to find the optimal size
 of the coagulant to get a good and efficient coagulation.
\end_layout

\begin_layout Subsubsection
Tube Flocculator RT experiments
\end_layout

\begin_layout Standard
Coagulation experiments were conducted in a tube flocculator apparatus.
 
\end_layout

\begin_layout Standard
To initiate an experiment, a total amount of 5 mL/s working suspension was
 transferred to the tube flocculator plant.
 The suspensions went through several small radius loops in order to get
 rapidly mixing, and went through a 84m long and big radius loop to get
 slow mixing.
 The flocs were allowed to settle for 30 min before residual turbidity measureme
nts were taken.
 After sedimentation, supernatant samples were withdrawn for pH measurements.
 The RT and pH measurements were conducted using a turbidimeter (XX, XX,
 Co., USA) and a pH meter (XX, XX, XX), respectively.
\end_layout

\begin_layout Standard
This experiment was investigated to test the RT removal efficiency of the
 unfiltered and vacuum filtered coagulants.
\end_layout

\begin_layout Subsubsection
Coagulant particle size measurement
\end_layout

\begin_layout Standard
The coagulant particle size measurement were conducted using a Zetasizer
 analyzer (Malvern Co., UK).
\end_layout

\begin_layout Standard
This experiment was to test the particles size of the vacuum filtered coagulator
, and try to figure out the exact particle size after vacuum filtration.
\end_layout

\begin_layout Subsubsection
Coagulant absorbance measurement
\end_layout

\begin_layout Standard
The coagulant absorbance measurement were conducted using a spectrophotometer
 (XX,XX , Co., UK).
 The specific process can be found at Eriochrome Cyanine R Method
\begin_inset CommandInset citation
LatexCommand cite
key "key-6"

\end_inset

.
\end_layout

\begin_layout Standard
Before testing the coagulant absorbance, we first test the absorbance of
 standard solutions of known concentration, and use the absorbance results
 to draw a graph which shows the relationship between concentration and
 absorbance.
 Then we test the absorbance of the unfiltered and vacuum filtered coagulant.
 Use the absorbance and find the corresponding concentration to figure out
 the concentration of the coagulant.
\end_layout

\begin_layout Standard
This experiment was investigated to determine the concentration of the coagulant.
 Because although we knew the concentration of the coagulant, after filtering,
 the concentration of vacuum filtered coagulant decreased.
 And in this way, we can figure out the exact concentration of the vacuum
 coagulant.
\end_layout

\begin_layout Subsection
Ionic Strength Test Experiment
\end_layout

\begin_layout Subsubsection
Materials
\end_layout

\begin_layout Standard
All chemicals used in this study were of analytical grade except those being
 specifically mentioned, and solutions were prepared with distilled water.
 The coagulants and the clays are the same as the particle size experiment.
 
\end_layout

\begin_layout Subsubsection
Jar Test 1
\end_layout

\begin_layout Standard
The objective of the first jar test is to find the optimal dosage of the
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 which controls the chemical stock concentration when running the tube flocculat
or apparatus.
 The 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 is used to control the pH of the water because we need to maintain the
 pH at 7.5 throughout each experiment.
 This is a critical process to make sure our final results will be reliable.
 Firstly, we put 1.152 mg PACl into 1.0 L distilled water and then slowly
 add the 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 into the mixed water.
 At the same time, we stir the water to make the chemicals mix well.
 During the mixing period, pH is monitored using the pH probe.
 When the pH reaches 7.5, we stop adding 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 and record the concentration.
 The same processes are repeated to make sure we could get a reliable result.
 Then we could use a simple equation to calculate the concentration of 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

which we need for the stock solution.
 Also, through the jar test we found that adding some clay into the water
 does not change the pH of the distilled water.
 That means the mixing process of the coagulant and clay does not change
 the pH.
 The conductivity of the jar solution is recorded after the pH is adjusted.
 Then we use the relationship between the conductivity and the ionic strength
 to calculate the real ionic strength in the whole apparatus.
\end_layout

\begin_layout Subsubsection
Jar Test 2
\end_layout

\begin_layout Standard
The objective of the second jar test is to find the relationship between
 the experimental ionic strength and theoretical ionic strength, as these
 two ionic strengths do not equal in previous experiments.
 In this test, conductivity is used as the indicator of experimental ionic
 strength, because experimental ionic strength cannot be got from the conductivi
ty probe directly, and according to the Russell approximation: 
\begin_inset Formula $I=1.6\times10^{-5}\times Specific\; Conductance\;(in\; mmho/cm)$
\end_inset

, the experimental ionic strength can be estimated from the conductivity.
 It should be noted that the Russell approximation is only valid when ionic
 strength is less than
\begin_inset Formula $10\frac{mol}{m^{3}}$
\end_inset

.
\end_layout

\begin_layout Standard
Firstly, we added PACl (69.3g/L) (refer table 1 for the detailed dosage)
 into 1.0L distilled water and slowly added the 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 into the mixed water to make the pH approaching 7.5.
 Then we controlled the amount of clay (refer table 2 for the detailed dosage)
 added to control the turbidity of raw water.
 After adding clay, we recorded the pH and conductivity.
 As previous experiments showed that clay does not influence the conductivity
 and pH of water.The amount of PACl and 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 added could be used to calculate how much 
\begin_inset Formula $NaNO_{3}$
\end_inset

 is needed to reach ionic strength to 0.5, 5 and 10 (refer table 3 for the
 detailed dosage) using MathCAD.
 After dosing the 
\begin_inset Formula $NaNO_{3}$
\end_inset

, we recorded the final pH and conductivity.
\end_layout

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

\begin_layout Plain Layout
\begin_inset Tabular
<lyxtabular version="3" rows="3" columns="5">
<features tabularvalignment="middle">
<column alignment="center" valignment="top" width="0">
<column alignment="center" valignment="top" width="0">
<column alignment="center" valignment="top" width="0">
<column alignment="center" valignment="top" width="0">
<column alignment="center" valignment="top" width="0">
<row>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
Target Ionic Strength (
\begin_inset Formula $mole/m^{3}$
\end_inset

)
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
0.4
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
1
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
5
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
10
\end_layout

\end_inset
</cell>
</row>
<row>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
Influent Turbidity (NTU)
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
15
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
50
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
100
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
150
\end_layout

\end_inset
</cell>
</row>
<row>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
Coagulant Dose (mg/L)
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
1.00
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
2.01
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
3.01
\end_layout

\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Plain Layout
4.02
\end_layout

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

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
Experiment Condition
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Tube Flocculator RT test experiments
\end_layout

\begin_layout Standard
In this part, the whole process is the same as the particle size experiment
 except we use the distilled water instead of the tap water.
 Also, another stock tank of 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 is needed to maintain the pH at 7.5.
 During the experiment, we take some water from the output tube to test
 the conductivity of the treated water.
 
\end_layout

\begin_layout Section
Analysis
\end_layout

\begin_layout Subsection
Particle Size Experiment
\end_layout

\begin_layout Standard
Currently, we just ran some experiments and there are no final results.
 This is a description about our theory and expected results.
\end_layout

\begin_layout Standard
As electrostatic patch serves an important role in coagulation, we assume
 that some of the coagulant patches was not utilized efficiently.
 Because some coagulant in the middle part of the patch did not work actually,
 and this caused the waste of coagulation.
 So through filtration, we try to find out the optimal coagulant particle
 size range when the coagulant can be strong and big enough to form the
 electrostatic patches or bridges between flocs.
\end_layout

\begin_layout Standard
Based on the theory and our hypothesis, our expectation is that the raw
 water treated by the vacuum filtered coagulant would have a lower residual
 turbidity compared with unfiltered coagulant.
\end_layout

\begin_layout Subsection
Ionic Strength Experiment
\end_layout

\begin_layout Standard
Currently, we just ran some experiments and there are no final results.
 This is a description about our theory and expected results.
\end_layout

\begin_layout Standard
As clay particles have a negative charge, and we assume charge neutralization
 and electrostatic patches are the main mechanisms for clay particles moving
 from tap water.
 According to the Debye length calculation equation 
\begin_inset Formula $\frac{1}{\kappa}=\sqrt{\frac{\epsilon_{r}\epsilon_{0}k_{b}T}{2N_{A}e^{2}I}}$
\end_inset


\begin_inset CommandInset citation
LatexCommand cite
key "key-4"

\end_inset

, when decreasing the ionic strength, the Debye length of the clay particles
 gets bigger.
 Thus, the repulsion between clay particles is felt over larger distances.
 That means with the increasing ionic strength, it is easier for coagulant
 and clay particles collision and form precipitation.
\end_layout

\begin_layout Standard
Based on the theory and our hypothesis, our expectation is that distilled
 water which has the lowest ionic strength would have a worse turbidity
 removal efficiency than tap water which has a higher ionic strength.
\end_layout

\begin_layout Subsubsection
Relationship between PACl Dosage and 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset


\end_layout

\begin_layout Standard
From Figure 5, we found that with the increasing of PACl dosage, the needed
 dosage of 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 to maintain the pH at 7.5 displayed an increasing trend and reached the
 highest point when PACl dosage equaled to 4.0194gm/L.
 Based on the theory, there should be a linear relationship between PACl
 dosage and needed 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

.
 But in the experiment, when we linearize all scatter points, 
\begin_inset Formula $R^{2}$
\end_inset

 is around 0.44-0.81 which indicates a pool fit of the equation, so we cannot
 conclude the relationship by using the linearize equation.
 
\end_layout

\begin_layout Standard
It should be noticed that we assume clay has little influence on the pH
 of the system, however, the experiment reveals that raw water's turbidity
 has some impact on the needed dosage of 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

, especially the turbidity reached 150NTU.
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename 5.JPG
	scale 60

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
Dosage relationship between PACl and 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 to maintain pH=7.5
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Relationship between Ionic Strengthen and Conductivity
\end_layout

\begin_layout Standard
From the Figure 6 and 7, we found a good linear relationship between ionic
 strengthen and conductivity.
 It should be noticed that, when we linearize the scatter plots, the trendlines
 were forced through zero (y-intercept =0) because we know that if the ionic
 strength is zero, the conductivity must be zero.
 The linearization equation could be concluded as: 
\begin_inset Formula $Ionic\; Strength=0.0080\times Conductivity\:(in\; mmho/cm)$
\end_inset

, and this equation used to calibrate the relationship between Ionic strengthen
 and conductivity has an extremely good fit (
\begin_inset Formula $R^{2}=0.99$
\end_inset

).
 
\end_layout

\begin_layout Standard
Also, the turbidity and the PACl dosage do not influence the relationship
 between ionic strength and conductivity.
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename 6.JPG
	scale 60

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
Relationship between ionic strength and conductivity under different turbidities
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Standard
The linearization equation from the above graph that is : 
\begin_inset Formula $Ionic\; Strength=0.0079\times Conductivity\:(in\; mmho/cm)$
\end_inset


\end_layout

\begin_layout Standard
Since the relationship between ionic strength and conductivity is very similar
 as the turbidity and the PACl dose change, we could use this equation for
 various turbidities and PACl doses.
 
\end_layout

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

\begin_layout Plain Layout
\begin_inset Graphics
	filename 7.JPG
	scale 60

\end_inset


\begin_inset Caption

\begin_layout Plain Layout
Relationship between ionic strength and conductivity under different PACl
 dosages when turbidity=100NTU
\end_layout

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Section
Conclusions 
\end_layout

\begin_layout Subsubsection
Ionic Strength Experiment
\end_layout

\begin_layout Enumerate
Based on our experiments, the relationship between PACl dosage and needed
 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 dosage is nonlinear, and high turbidity of raw water would increase the
 needed dosage of 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

.
\end_layout

\begin_layout Enumerate
There is a strong linear relationship between theoretical ionic strengthen
 and experimental conductivity.
 The relationship is approximately 
\begin_inset Formula $Ionic\; Strength=0.0079\times Conductivity\:(in\; mmho/cm)$
\end_inset

.
\end_layout

\begin_layout Section
Future work
\end_layout

\begin_layout Subsection
Particle Size Experiment
\end_layout

\begin_layout Standard
In the future, more information is needed to build a complete hypothesis
 to explain our experimental results in this area.
 Future work includes reading papers about PACl that focus on the influence
 of the coagulant size on turbidity removal efficiency.
 Moreover, more experimentation is needed under controlled conditions to
 see if the results are consistent with the hypothesis we made.
\end_layout

\begin_layout Subsection
Ionic Strength Experiment
\end_layout

\begin_layout Enumerate
Read more literature about ionic strength and continue the research.
\end_layout

\begin_layout Enumerate
Experiment further to verify the relationship between needed dosage of 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

and PACl is needed.
 Since changing the concentration of 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 during the experiment may lead to a big change in the needed dosage of
 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

, we will try to use the same concentration of 
\begin_inset Formula $Na_{2}CO_{3}$
\end_inset

 to finish a set of experiment to minimize the error from the dosage concentrati
on.
\end_layout

\begin_layout Enumerate
Find out the particular ions which influence flocculation efficiency over
 a range of coagulant doses.
 Because experiments between tap water and distilled water shows that tap
 water has a wider flocculation range and higher removal efficiency, we
 want to find out which ions in the tap water are responsible.
\end_layout

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

\end_inset

Dongsheng Wang, Changqing Ye, Alkalinity effect of coagulation with polyaluminum
 chlorides: Role of electrostatic patch, Colloids and Surface A: Physicochem.
 Eng.
 Aspects.
 294 (2007) 163-173.
\end_layout

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

\end_inset

Xiaohong Wu, Xiaopeng Ge, Distinct coagulation mechanism and model between
 alum and high Al13-PACl, Colloids and Surface A: Physicochem.
 Eng.
 Aspects.
 305 (2007) 86-96.
\end_layout

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

\end_inset

Xiaohong Wu, Dongsheng Wang, Coagulation of silica microspheres with hydrolyzed
 Al(III) - Significance of Al
\begin_inset Formula $_{12}$
\end_inset

 and Al
\begin_inset Formula $_{13}$
\end_inset

 aggregates, Colloids and Surface A: Physicochem.
 Eng.
 Aspects.
 330 (2008) 72-79.
\end_layout

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

\end_inset

Debye length, http://en.wikipedia.org/wiki/Debye_length.
 9(2011).
\end_layout

\begin_layout Bibliography
\labelwidthstring References
\begin_inset CommandInset bibitem
LatexCommand bibitem
key "key-5"

\end_inset

Yan Wang, Bao Yu Gao, Xiu Ming Xue, Wei Ying Xu, The effect of total hardness
 and ionic strength on the coagulation performance and kinetics of aluminum
 salts to remove humic acid, A: Physicochem.
 Eng.
 Aspects.
 160(2010)150-156
\end_layout

\begin_layout Bibliography
\labelwidthstring References
\begin_inset CommandInset bibitem
LatexCommand bibitem
key "key-6"

\end_inset

Powder Pillows, 2010.
 Aluminum-Eriochrome Cyanine R Method (Edition 6).
 U.S.A., Hach Company, 1-9.
\end_layout

\begin_layout Bibliography
\labelwidthstring References
\begin_inset CommandInset bibitem
LatexCommand bibitem
key "key-7"

\end_inset

P.
 Paton-Morales and F.
 I.
 Talens-Alesson, Effect of ionic strength and competitive adsorption of
 
\begin_inset Formula $Na^{+}$
\end_inset

 on the flocculation of lauryl sulfate micelles with 
\begin_inset Formula $Al^{3+}$
\end_inset

.
 Langmuir 2001, 17, 6059-6064.
\end_layout

\begin_layout Bibliography
\labelwidthstring References
\begin_inset CommandInset bibitem
LatexCommand bibitem
key "key-8"

\end_inset

Zhao Huazhang, Ge Xiaopeng, Luan Zhaokun, Effects of Ca on the distribution,
 structure and morphology of aluminum species in polyaluminum chloride.
 Chinese Science Bulletin, 2004 Vol.
 49, No.
 12 1241-1244.
\end_layout

\end_body
\end_document
