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DEGREE PROJECT, IN ANALYTICAL CHEMISTRY, SECOND LEVEL
STEHAG, SWEDEN 2015
Calcium Chloride as a Co-Coagulant
WATER TREATMENT
KRISTOFER HÄGG
KTH ROYAL INSTITUTE OF TECHNOLOGY
RINGSJÖVERKET
www.kth.se
i
Acknowledgements
I would like to express my gratitude to everyone who assisted me during this project. There were
many who showed great interest in this work, which made the study that much more interesting to
do.
First, I would like to thank my main supervisor, Kenneth Persson, at Lund Universitet and research
manager at Sydvatten, who gave me the opportunity to work on this thesis and who supported me
during this study.
Thanks to my second supervisor, Britt-Marie Pott, process engineer at Sydvatten, for helping me a
great deal during the experiments conducted at the water treatment facility.
Thanks to everyone at TETRA Chemicals for showing me around the CaCl2 manufacturing facilities
and for supporting this project. A special thanks to Fabrice Dutiel and Olof Norrlöw at TETRA
Chemicals for showing great interest and for all the positive feedback.
I would also want to thank everyone at Ringsjöverket for all the help I received and making my daily
work easier. In particular, Agneta Jönsson for helping me in the laboratory. Also, thanks to Marianne
Franke, laboratory manager for making sure I had everything I needed to conduct the experiments
and for laughing with me when things went wrong.
ii
Preface
This thesis is a result of a collaboration between Sydvatten AB, a municipal drinking water producer,
TETRA Chemicals, a CaCl2 producer and distributor and Lund Universitet. The hypotheses was
formulated by TETRA Chemicals, based on pre-studies they conducted in June 2013.
The studies were conducted at Ringsjöverket, a water treatment facility in Stehag, Sweden. The work
was financed by Sydvatten AB, Lund Universitet and TETRA Chemicals.
The work focused on CaCl2 as an adjunct in iron and aluminum assisted coagulation and flocculation.
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Abstract
As populations continue to grow, the demand for fresh drinking water is increasing. This puts a lot of
pressure on drinking water producers to strive for more efficient solutions and techniques. Many
producers worldwide use surface water as a raw water source, which they often treat through
coagulation and flocculation techniques. This is done by adding coagulant (e.g. metal coagulants),
creating instability in the suspension, causing flocculation. In this work, PIX-311 (a FeCl3 coagulant
produced by Kemira) and Al2(SO4)3 (ALG) were used as primary coagulants and CaCl2 (produced by
TETRA Chemicals) as an adjunct in a coagulation and flocculation study.
The goal of this work was to study the effects of CaCl2 additions to Fe(III) and Al(III) flocculation. The
experiments were conducted at Ringsjöverket (a water treatment facility), using jar tests to simulate
the treatment process on a laboratory scale. The raw water samples used in this study, were taken
from Bolmen, a lake in southern Sweden. A spectrophotometer was used to monitor the efficiency of
flocculation by UV-VIS absorption.
In the first experiments, various CaCl2 additions were added to Fe(III) flocculation, with FeCl3 as a
primary coagulant. To see if FeCl3 could be substituted with CaCl2, the amount of primary coagulant
was reduced to about 80% of the optimal dosage (the dose used daily by the water treatment plant).
In the next series of experiments, various amounts of CaCl2 were added with an optimal dose of
FeCl3. After that, the effects of CaCl2 additions to Al(III) flocculation were conducted, using Al2(SO4)3
as a primary coagulant. The experiments followed the previous scheme used in Fe(III) flocculation.
The UV-VIS results showed that no CaCl2 additions were effective enough to replace the primary
coagulant. However, reduced amount of primary coagulant benefited slightly from small CaCl2
additions. A likely explanation for this is the ability of Ca2+ to aid in charge neutralization and reduce
the repulsive forces between particles in suspension, aiding coagulation. Furthermore, CaCl2
additions, with reasonable certainty, did not increase the efficiency of Fe(III) flocculation. When the
CaCl2 dose was increased (from about 13µl to 820 µl per liter raw water), the effect became negative.
In other words, high doses of CaCl2 inhibited flocculation by, most likely, occupying adsorption sites
for the primary coagulant. This was observed for an optimal FeCl3 dose, reduced FeCl3 dose and an
optimal dose of Al2(SO4)3. In the more brief study on Al(III) flocculation, low CaCl2 doses did not
appear to have any effect on flocculation at first. However, when a reduced amount of Al2(SO4)3 was
used, the samples with CaCl2 gave better UV-VIS results once the pH was increased from 6 to about
6.15. One explanation for this could be that the shift in flocculation mechanism at higher pH, causes
CaCl2 to have an increased positive effect.
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Abstrakt
Rent färskvatten är nödvändigt för nästintill all mänsklig aktivitet. Detta gäller allt från dricksvatten
och sanitet till industri och agrikultur. I takt med befolkningsökningen, ökar färskvattenbehovet och
vikten av att kunna försörja befolkningen med rent vatten. Det finns många olika tekniker och
metoder att rena vatten som dricksvattenproducenter har till sitt förfogande. En av de vanligaste
reningsmetoderna, som kommer ligga i fokus i detta arbete, inkluderar rening genom koagulering
och flockbildning. Detta åstadkoms genom att ett koaguleringsmedel, vanligen metallkomplex,
tillsätts råvattnet vilket skapar instabilitet i suspensionen och resulterar i flockbildning. I det här
arbetet studeras CaCl2 (producerat av TETRA Chemicals) påverkan på denna process med PIX-311
(FeCl3 ett koaguleringsmedel producerat av Kemira) och Al2(SO4)3 (ALG) som primära
koaguleringsmedel.
Målet med denna studie var att utröna eventuella positiva påverkan av CaCl2 på
koaguleringsprocessen när FeCl3 respektive Al2(SO4)3 användes som primära koaguleringsmedel. För
att simulera processen på liten skala användes en flockulator med 6 stycken enliters bägare med var
sin programmerbar omrörare. Experimenten utfördes på Ringsjöverket och råvattenproven togs från
Bolmen, i Skåne. Efter experimenten undersöktes effektiviteten av koaguleringsprocessen genom att
prov analyserades i en spektrofotometer, där UV-VIS absorptionen mättes.
De första experimenten utfördes på råvattenprov där en reducerad mängd PIX-311 användes
tillsammans med CaCl2, för att testa om det primära koaguleringsmedlet delvis kunde ersättas med
CaCl2. En reducerad respektive optimal mängd koaguleringsmedel är baserat på vad verket använder
i den dagliga driften. I senare experiment användes en optimal mängd PIX-311 tillsammans med en
varierande mängd CaCl2, för att se om CaCl2 hade någon effekt på den optimala driften. Efter det
fortsattes experimenten med Al2(SO4)3 som primärt koaguleringsmedel, där effekten av CaCl2
studerades på samma vis.
Från UV-VIS resultaten visade det sig att det primära koaguleringsmedlet inte kunde ersättas med
någon mängd CaCl2 (varken för PIX-311 eller ALG), däremot hade CaCl2 en positiv effekt vid små
koncentrationer då en reducerad mängd PIX-311 användes. Anledning till dessa effekter kan förklaras
med att Ca2+ har förmågan att bistå med laddningsneutraliseringen och reducera de repulsiva
krafterna mellan partiklar i suspensionen. För en optimal dos PIX-311 hade, med stor säkerhet, en
liten dos CaCl2 ingen effekt på UV-VIS resultaten. När dosen CaCl2 ökade (från ca 13 µl till 820 µl) var
effekten negativ när både PIX-311 och ALG användes (både med reducerad och optimal mängd). En
trolig förklaring är att när dosen Ca2+ ökar börjar adsorptionssäten på partiklar att blockeras från
koaguleringsmedlet och en negativ effekt observeras. För experimenten med ALG upplevdes samma
resultat som för PIX-311, när en reducerad mängd ALG däremot användes tillsammans med CaCl2
observerades en oväntad trend. När pH ökades för dessa prover från 6 till ca 6,15, blev resultaten
gradvis sämre för alla prover tills pH nådde ca 6,15, där prover med CaCl2 uppvisade en plötslig
förbättring i UV-VIS resultat. En möjlig förklaring till detta fenomen är att
flockbildningsmekanismerna förändras med en ökad koncentration av negativa arter i suspension
och att den positiva effekten av CaCl2 därav ökar.
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Abbreviations
ALG Aluminumsulphate, Al2(SO4)3
DLVO Derjaguin, Landau, Verwey and Overbeek theory
DOC Dissolved oxygen content
EDL Electric double layer
HA Humic acid
NOM Natural organic matter
PACl Polyaluminumchloride
PIX, PIX-311 Ferric chloride, FeCl3
TOC Total organic carbon
UV-VIS Ultraviolet-Visible
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Content
1. Introduction .........................................................................................................................................1
1.1 Hypothesis ..........................................................................................................................................2
2. Water treatment ..................................................................................................................................3
2.1 Contaminants in surface water ..........................................................................................................3
2.1.1 Absorption and transmittance spectroscopy ..................................................................................3
2.1.2 Turbidity ..........................................................................................................................................4
2.1.3 Color ................................................................................................................................................5
2.2 Particles in suspension .......................................................................................................................5
2.2.1 Plain sedimentation .........................................................................................................................5
2.2.2 Particle surface charge ....................................................................................................................6
2.2.3 Electric double layer ........................................................................................................................7
2.3 Coagulation and flocculation ..............................................................................................................8
2.3.1 Coagulation and destabilization ......................................................................................................8
2.3.2 Iron and aluminum coagulants ..................................................................................................... 10
2.3.3 Ca2+ as a co-coagulant .................................................................................................................. 11
2.3.4 Jar tests ......................................................................................................................................... 12
2.3.5 Flocculation .................................................................................................................................. 13
3. Experimental ..................................................................................................................................... 15
3.1 Raw water ........................................................................................................................................ 15
3.2 Coagulants and additives................................................................................................................. 15
3.3 Preparation before jar test .............................................................................................................. 15
3.4 Jar tests ............................................................................................................................................ 16
3.5 Ultraviolet-Visible Spectroscopy ..................................................................................................... 16
4. Results and discussion ...................................................................................................................... 17
4.1 Effects of various CaCl2 additions on Fe(III) flocculation ................................................................. 17
4.1.1 Addition of 20 mol% CaCl2 ............................................................................................................ 17
4.1.2 Addition of 40 mol% CaCl2 ............................................................................................................ 18
4.1.3 Addition of 80 mol% CaCl2 ............................................................................................................ 20
4.1.4 Summary of experiments with reduced amount of PIX-311 ........................................................ 20
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4.2 Effects of CaCl2 with an optimal Fe(III) dose .................................................................................... 23
4.2.1 Addition of 20 and 40 mol% CaCl2 ................................................................................................ 23
4.2.2 Addition of 40 and 80 mol% CaCl2 ................................................................................................ 24
4.2.3 Summary of experiments with an optimal PIX-311 dose ............................................................. 24
4.3 Effects of CaCl2 additions on Al(III) flocculation .............................................................................. 27
5. Conclusion ......................................................................................................................................... 29
6. Further work ..................................................................................................................................... 30
References............................................................................................................................................. 31
Appendix ............................................................................................................................................... 33
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1. Introduction
Clean, fresh water is essential in our daily lives, for everything from drinking water and sanitation to industry and agriculture. Less than 0.02% of all water, is fresh liquid surface water, on which we all depend (Cunningham and Cunningham, 2013). Water is a part of a natural cycle, constantly renewed. However, renewal takes time and as the population continues to grow, so does the demand for fresh drinking water. As a consequence, the natural replenishing process isn’t enough to support our current and future needs. To be able to meet this demand, it is important to have a sustainable and a well developed fresh water production. Because ground water is not always enough to support everyone, it is common to use surface water as a fresh water source. Surface water does not undergo the natural infiltration, where a lot of the common contaminant gets reduced, as in ground water. This means that a few extra steps are needed to ensure high quality drinking water. Common contaminants in surface water include, natural organic matter (NOM), humic acid (HA), bacteria, viruses, silt, clay and various inorganic compounds (Trussel and Hand, 2012). One way to reduce these compounds, is through coagulation and flocculation by adding a coagulant. These coagulants are readily available and come in different forms. Often, different iron and aluminum complexes are used as coagulants because of their efficiencies and relatively low cost (Bratby, 1980). However, it is common that adjuncts are used to aid or improve the coagulation and flocculation process. Adjuncts can assist this process in many different ways (e.g. charge neutralization and bridge building) depending on their properties. In beer brewing industry it is well known that Ca2+ is a factor in yeast flocculation and beer clarification. Commonly, it is said that at least 50 ppm (mg/l) Ca2+ is needed in the wort, mainly for yeast to aggregate at the end of fermentation. Studies have shown that flocculation of yeast is improved with a Ca2+ concentrations up to 1 mol/m3 and that yeast cells depend on calcium to flocculate (Amory, Rouxhet and Dufour, 1988). This is because Ca2+ reduces the negative charge on yeast cells, causing them to adsorb onto each other and flocculate over time. This process is similar to what happens when a metal coagulant (FeCl3 or Al2(SO4)3) is added to raw water, which leads us to the focus of this study; can CaCl2 assist in FeCl3 and Al2(SO4)3 flocculation? CaCl2 could potently have several positive effects including, reducing the amount of FeCl3 or Al2(SO4)3 needed for coagulation, which would allow for a more sustainable way to treat water. Also, a reduction of primary coagulant would potentially reduce the cost of producing drinking water.
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1.1 Hypothesis
Hypothesis:
“Raw water treatment through coagulation and flocculation using FeCl3 is more effective if the water
sample is pre-treated with CaCl2.”
The hypothesis is based on studies done by TETRA Chemicals in June 23 2013 at Sydvatten AB’s water
treatment facilities in Stehag, Sweden.
The aim of this thesis is to study the effects on coagulation and flocculation of CaCl2 additions to
conventional raw water treatment using FeCl3 and Al2(SO4)3.
The objectives are as follows:
Is it possible to replace FeCl3 or Al2(SO4)3 with any given amount of CaCl2, without
compromising the results?
Determine the effect on water treatment using FeCl3 and Al2(SO4)3 with various CaCl2
concentrations.
Finally, summarize the result of the study taking cost into consideration. Which alternative
gives the best result in comparison with the total cost?
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2. Water treatment
This chapter will discuss common contaminants in natural water sources and give an introduction in
industrial water treatment techniques used today. The focus will be parameters of water quality,
suspension stability and water treatment through coagulation and flocculation.
2.1 Contaminants in surface water
Natural surface water sources (i.e. lakes) contain a variety of different organic and inorganic
contaminants. Organic contaminants consist of dissolved organic elements (proteins, humic acid),
colloids, bacteria, viruses, parasites and amoebas, while inorganic contaminants include silt, clay and
mineral oxides caused by natural erosion. Particles in water will effect water clarity, color and can be
infectious (i.e. bacteria and viruses). So to achieve high quality drinking water, removal of
containments is required. A common way to remove most of the contaminants in surface water is to
treat the raw water by coagulation and flocculation followed by filtration or sedimentation which will
be described later on. (Trussel and Hand, 2012) The following section will describe what unwanted
physical characteristics contaminants cause and common techniques to assess water quality used
today.
2.1.1 Absorption and transmittance spectroscopy
Spectrophotometers are used to test water samples for iron, organic compounds (e.g. Humic acid
and aromatic compounds) and small colloidal particles (0.45 µm). Iron and organic compounds
(containing double bonds) absorbing UV light, which is a reason why absorbance is often measured
at 254 nm. Different organic and inorganic compounds absorb light at different wavelengths, so the
wavelength used varies with the source water contaminants.
Figure 2.1.1 Schematic of a UV-VIS spectrophotometer (adapted from: Trussell and Hand, 2012).
The intensity of absorption is determined by passing a beam of light through a water sample of
known thickness and measuring the intensity (I) of transmitted light relative to the intensity (I0) that
4
would have been if no absorption occurred. A schematic picture of a UV-VIS spectrophotometer can
be seen in figure 2.1.1. The ratio of the intensity I to the intensity I0 is called transmittance (I/I0) and
can be determined at different wavelengths. Lambert developed an equation for the attenuation of
light as a function of the thickness of a homogenous medium and Beer developed the equation to
take concentration in consideration. According to the Beer-Lambert law, the probability that a
photon will be absorbed is directly proportional to the concentration of absorbing molecules and the
thickness of the sample (Alberty and Silbey, 2000). When analyzing water samples, distilled water is
used as a reference due to the fact that pure water will absorb light. Absorbance is defined as
followed:
𝑙𝑜𝑔 (𝐼
𝐼0) = −𝜀(𝜆)𝐶𝑥 = −𝑘𝐴(𝜆)𝑥 = −𝐴(𝜆) (1)
where
𝐼 - intensity of light after passing through a solution [mW/cm2]
𝐼0 - intensity of light after passing through distilled water [mW/cm2]
𝜆 - wavelength [nm]
𝜀(𝜆) - molar absorptivity of light –absorbing solute at a wavelength 𝜆, [l/mol, cm]
𝐶 - concentration of light-absorbing solute [mol/l]
𝑥- cuvette length [cm]
𝑘𝐴(𝜆) - absorptivity at wavelength 𝜆 [cm-1]
𝐴(𝜆) - absorptivity at wavelength 𝜆, dimensionless
A relationship of absorbance and transmittance can be derived and is as follows:
Transmittance, 𝑇,% = (𝐼
𝐼0) ∗ 100 (2)
𝑇 = 10−𝐴(𝜆) (3)
2.1.2 Turbidity
Turbidity is an indication of water clarity and is caused by suspended matter such as, silt, bacteria,
viruses and macromolecules. Turbidity is defined by optical properties that cause light to be
scattered and absorbed (Standard Methods, 2005). The technique for analyzing turbidity is called
nephelometry and is measured in nephelometric turbidity units (NTU). As seen in figure 2.1.1, a light
beem is directed into the water sample and a detector that is positioned at a 90o angle measures the
scattered light. Turbidity measurements are influenced by the suspended particles size, shape and
refractive index, which means that there is no direct correlation between the turbidity of the sample
5
and amount of suspended matter in the sample (Bratby, 1980). Furthermore, the size of the particles
in relationship to the incoming lights’ wavelength will have an impact on the intensity of the
scattered light. For small particles (one-tenth of the incoming lights wavelength) the light scattered is
fairly symmetrical. However, when the size of the particle increases it causes the light to be scattered
more in a forward direction. As a consequence, turbidity measurements are more sensitive to
particles in the size range of the used wavelength. Turbidity measurements are very useful in quality
control and is often used as an indicator in process control for increased concentrations of
containments, such as bacteria. (Trussell and Hand, 2012)
2.1.3 Color
Color can derive from different sources and is therefore described in two different ways, as apparent
color and true color. Like turbidity, apparent color is caused by suspended matter and is measured
on unfiltered samples, while true color is caused by dissolved species and is measured on filtered
samples. Water color is a good indication of organic content (such as humic acid), iron content and
turbidity. Color in water is assessed by visually comparing samples to a standard platinum-cobolt
solution and presented in an arbitrary color scale in color units (c.u.). The platinum-cobolt standard
used is yellow in color and resembles the color found in natural water. (Trussell and Hand, 2012 and
Bratby, 1980)
Color in water is an indication of contamination of some form and steps are therefore taken to
remove color from waters during treatment.
2.2 Particles in suspension
The following section will discuss the stability of particles in natural water.
2.2.1 Plain sedimentation
In plain sedimentation, clarification is achieved purely through the help of gravity without any added clarification aids. Given enough time eventually most particles will settle, however the time required wouldn’t be practical on a large scale drinking water production (Cheremisinoff, 2001). The technique is however utilized for primary treatment of raw water from fast flowing rivers, in order to minimize the amount of suspended material passing into the system (Ratnayaka, et. al., 2009). The time it takes for a particle to settle by its own depends on several different parameters. The settling characteristics include weight, shape and size of the particle and temperature of the medium (which affects the viscosity and/or frictional resistance of the water) (Cheremisinoff, 2001). A list of various particles and the settling times can be seen in table 2.2.1. Table 2.2.1 Particle settling time based on size and type (Source: Cheremisinoff, 2001).
Particle diameter (mm) Particle Type Time to settle one foot
10 Gravel 0.3 sec.
1.0 Coarse sand 3.0 sec.
0.1 Fine sand 38.0 sec.
0.01 Silt 33.0 minutes
6
0.001 Bacteria 35.0 hours
0.0001 Clay particles 230 days
0.00001 Colloidal particles 65 years
The velocity V (mm/s) with which a particle in water falls can be calculated through:
𝑉𝐶 =𝑔
1.8∗104(𝑟 − 1)
𝑑2
𝛾 (4)
where
𝑔 – gravitation, 9,82 [m/s2]
𝑟 – density of the particle [g/cm3, kg/m3]
𝑑 – diameter of particle [mm]
𝛾 – kinematic viscosity [m2/s]
Equation (4) is valid for slowly moving water (Reynolds number Re < 0,5) and kinematic viscosity 𝛾 is equivalent to absolute viscosity [Ns/m2] divided by the mediums’ density [kg/m3] (Ratnayaka, et. al., 2009). The kinematic viscosity varies with temperature, which can be seen in table 2.2.2. Table 2.2.2 Viscosity of water at various temperatures (Source: Camp, 1946).
Temperture (oC) 0 5 10 15 20 25
Value ϕ (m2/s) 10-6 1.79 1.52 1.31 1.15 1.01 0.90
2.2.2 Particle surface charge
Particles in water are classified as hydrophobic or hydrophilic. Hydrophobic particles in solution are
inherently unstable and will aggregate irreversibly over time. Hydrophilic particles, on the other hand
have polar or ionized functional groups, which allows them to stay in suspension. These particles
include proteins, humic acid (organic particles) and metal oxides (inorganic particles). Suspended
hydrophilic particles stability is caused by their surface charge. However, given enough time
hydrophilic particles will also settle (Trussell and Hand, 2012).
The surface charge of particles have different sources and their properties may change depending on
the environment. Humic acid for instance, has negatively charged surfaces which they acquire from
their functional groups (e.g. carboxylic acid groups). However, the surface charge of humic acid will
change if the pH of the surrounding solution drops below 3. The pH corresponding to the point in
which the surface charge of any given particle changes from negative to positive is defined as the
zero point of charge (ZPC) or isoelectric point (IEP) if no adsorption occurs. In natural surface water
particle-particle adsorption is a common occurrence, which makes pHzpc more applicable in these
systems (Trussell and Hand, 2012). An example of this are particles adsorbing humic acid causing
them to have a negative surface charge for pH values greater than 5 (Stumm and Morgan, 1996). In
the table below some common particles in surface water can be seen with their corresponding pHzpc
values.
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Table 2.2.3 Zero point charge of various particles found in natural waters (adapted from: Parks, 1967 and
Stumm and Morgan, 1981).
Type of Particle Zero Point of Charge, pHzpc
Algae 3–5
Bacteria 2–4
Humic acid 3
Oil droplets 2–5
Al2O3 9.1
CuO3 9.5
MgO 12.4
2.2.3 Electric double layer (EDL)
When negatively charged particles are in suspension in water, they are surrounded by an electric
double layer. As a result of the variation of electrical potential near the surface of the particle,
counterions accumulate around the particle forming two layers. Near the surface a fixed layer of
cations are adsorbed and forms a layer known as the Stern layer (previously known as Helmholtz
layer). This gives rise to another layer with a net charge of zero called the diffuse layer, which
consists of both cations and anions (figure 2.2.1).
Figure 2.2.1 Schematic overview of negative particle in suspension, illustrating the electric double layer
(Adapted from: Trussell and Hand, 2012).
8
In a situation where two negatively charged particles approach each other, the double layers overlap
and the electrostatic forces cause them to repel each other and the system is considered stable. The
zeta potential seen in figure 2.2.1, is an indication of the colloidal system stability. The zeta potential
is measured by applying an electric field between two electrodes forcing the negatively charge
particle to migrate. This movement (known as electrophoresis) causes adjacent water molecules to
follow the particle creating a shear plane. The potential between the bulk solution and the shear
planes is the measured zeta potential. So for small particles, a high zeta potential creates an energy
barrier that prevents flocculation. However, if the repulsive forces are reduced so that the attractive
forces can overcome the energy barrier, the system will be destabilized and rapid flocculation will
occur (Trussell and Hand, 2012). The interaction of attractive and repulsive forces between particles approaching each other is described by the DLVO theory. The theory is named after the scientist who developed it, Derjaguin and Landau, 1941 followed by Verwey and Overbeek, 1948.
2.3 Coagulation and flocculation
The emphasis in this chapter is the physical and chemical phenomena in the coagulation and flocculation process. Because the terms coagulation and flocculation are used in different manners in literature it is important to address these definitions. The term coagulation comes from Latin meaning drive together, which La Mer believed to be an appropriate term as he defined coagulation as the process of reducing the electric repulsion between particles with the addition of neutral salts (La Mer, 1964). More recent definitions of coagulation and flocculation will be used and are as follows (Bratby, 1980): “Coagulation is the process whereby destabilization of a given suspension or solution is effected. That
is, the function of coagulation is to overcome those factors which promote the stability of a given system.”
“Flocculation is the process whereby destabilized particles, or particles formed as a result of
destabilization, are induced to come together, make contact and thereby form large(r) agglomerates.”
2.3.1 Coagulation and destabilization
The coagulation process, as described by Bratby, is the destabilizing process of a suspension. This can be achieved by different means. Often in water treatment several mechanism are utilized including, compression of electric double layer, adsorption and charge neutralization, adsorption and particle bridging and sweep coagulation. Compression of electric double layer: One way to promote coagulation is to add ions (with no specific attraction for colloid surfaces) to increase the ionic strength of the solution and forcing the counter-ions closer to the surface of the particle. This compresses the electric double layer which allows the van der Waals forces to overcome the repulsive forces and flocculation will occur. However, this technique is not practiced in water treatment. (Trussell and Hand, 2012)
9
Adsorption and charge neutralization: Charged ions or polymers can be used to destabilize particles by adsorption and charge neutralization, while in adsorption and bridge building techniques, polymer is used as a primary coagulant. As discussed before, most particles in natural raw water are negatively charged (e.g. humic acid), as a result hydrolyzed metal salts and cationic organic polymers are often used for destabilization and charge neutralization. Cationic organic polymers are used for charge neutralization. However, they are more often used in combination with an inorganic coagulant in bridge building techniques. An optimal coagulant dose in adsorption and charge neutralization tends to be when the particles are only partially covered and if exceeded, the charge will change and stability will remain. (Trussell and Hand, 2012) Adsorption and particle bridging: In particle bridging, nonionic polymers are partially adsorbed to surfaces of particles leaving a part of the polymer free to be adsorbed onto a second particle. This mechanism is a result of intermolecular forces, e.g. dipole interactions and hydrogen bonding (Hunter, 2001), and allows adsorption to occur at several sites along the polymer chain. For flocculation to take place an adequate amount of polymer needs to be added. If an excessive dose is added, all the adsorption sites will be occupied and flocculation won’t occur (O’Melia, 1972). Sweep Coagulation/flocculation: Metal coagulant (e.g. FeCl3) in aqueous solution can form metal hydroxide precipitates if under the right conditions. This usually occurs when the contamination concentration is low and pH ranges between 6 and 8 (Trussell and Hand, 2012). When a polymetalion is adsorbed to a particle surface hydroxide accumulate and starts to enmesh surrounding particles. As the insoluble precipitate descends the remaining particles will be swept with the hydroxide, hence sweep coagulation/flocculation (Gillberg et. al., 2003). A comparison of the effects of, different colloid concentrations in water and coagulant doses, have on the type of coagulation that occurs can be seen below (figure 2.3.1).
Figure 2.3.1 Residual turbidity after jar tests as a function of particle and coagulant concentration of metal salts at constant pH. Section S1 to S4 indicates colloidal concentration in increasing order in the water samples. S1-low to S4-very high colloid concentration (Adapted from: Trussel and Hand, 2012, and Bratby, 1980).
10
For the lowest concentration levels of colloids (S1), the particles are removed with sweep coagulation (zone 4) once the coagulant dose is high enough. When the colloid concentration is increased (S2), the particles are at first removed by adsorption and charge neutralization (zone 2). As the coagulant dose is increased, the particles stabilize (zone 3) with a reverse charge (from negative to positive), followed by an increase in particle remove by sweep coagulation as the coagulant dose increases. At high colloid concentrations (S3), all zones are clearly defined. Removal of particles, can be seen through charge neutralization in zone 2 and through sweep coagulation in zone 4. Finally, at very high colloid concentration (S4), particle removal from charge neutralization and sweep flocculation merge to form one zone. This is possible because the concentration required for charge neutralization coincides with precipitation of metal hydroxide (Trussel and Hand, 2012).
2.3.2 Iron and aluminum coagulants
Aluminum and iron based coagulants are the most common metal coagulants used today because of their effectiveness and their relatively low cost. These coagulants however, are often produced using ore and hydrochloric acid (e.g. to produce FeCl3), which raises some concern about their sustainability. Iron and aluminum form multi-charged polynuclear complexes, through a series of hydrolytic reactions, which gives them their high efficiency. (Bratby, 1980) When aluminum and iron coagulants are introduced into water, they immediately dissociate and form water-coordinated complexes, Al(H2O)6
3+ and Fe(H2O)63+ (Bratby, 1980). What follows next is a
series ligand substitution, the ligand of interest being OH-. The first step for Al(H2O)63+ could be
described as (Bratby, 1980, Stumm and Morgan, 1962):
Al(𝐻2𝑂)63+
↔ Al(OH)(𝐻2𝑂)5
2+ +𝐻+ (5) Followed by,
Al(OH)(𝐻2𝑂)52+
→𝑂𝐻−
→ → 𝐴𝑙6(OH)15
3+ →𝑂𝐻−
→ →
𝐴𝑙8(OH)20 4+ →𝑂𝐻−
→ → 𝐴𝑙(𝑂𝐻)3(𝑠)
𝑂𝐻−
→ 𝐴𝑙(𝑂𝐻)4− (6)
The OH- ligand can act as bridges between metal atoms forming polynuclear complexes. Both iron and aluminum has the ability to form such complexes, the simplest being bi-nuclear complexes. (Bratby, 1980) Bi-nuclear species are the first step, as seen below, of the formation of polynuclear complexes (Trussell and Hand, 2012).
2(𝐴𝑙(𝐻2𝑂)5(𝑂𝐻)) 2+
−2𝐻2𝑂 → (7)
11
All species of iron and aluminum (mono or polynuclear) interact with the surrounding particles in different ways. Because of the difficulty of controlling which species of metal complexes that form, prehydralyzed metal salts as coagulants have been developed. These coagulants are prepared by reacting the metal with water and various salts. By doing this, control is gained over the species formed during the coagulation process and other benefits such as, lower dosage required and stronger floc-formation are achieved (Trussel and Hand, 2012).
Because Al2SO4 (ALG) and FeCl3 (PIX-311) are exclusively used as primary coagulants in this thesis, it is important to mention the operational requirement when using these coagulants. Iron and aluminum complexes react readily with different species in natural water. These reactions include ligand substitution with natural occurring phosphates and sulphates, which will impact the overall success of coagulation. This is a reason why it is important to use the right coagulant dose and why the dose varies with different natural waters. Also, as seen in (5), adding metal coagulants to water will lower pH and will have an impact on the waters alkalinity. (Trussel and Hand, 2012) An example of FeCl3 added to natural water can be described as (Bratby, 1980): 2𝐹𝑒𝐶𝑙3 + 3𝐶𝑎(𝐻𝐶𝑂3)2
↔ 2𝐹𝑒(𝑂𝐻)3 + 3𝐶𝑎𝐶𝑙2 + 6𝐶𝑂2 (8)
2𝐹𝑒𝐶𝑙3 + 3𝐶𝑎(𝑂𝐻)2
↔ 2𝐹𝑒(𝑂𝐻)3 + 3𝐶𝑎𝐶𝑙2 (9)
The reactions that metal coagulants participate in (e.g. hydration and stepwise substitution) are very rapid, which makes initial mixing of coagulant in raw water very important (Bratby, 1980). This will be discussed in more detail later on.
2.3.3 Ca2+ as a co-coagulant
The focus of this thesis is the effects that CaCl2 might have as a co-coagulant. It is unclear if CaCl2 has any effects on coagulation and flocculation when using commercially available coagulants such as FeCl3 (PIX-311) and Al2SO4 (ALG). There are however studies that indicate that calcium does have a positive effect on flocculation in some cases. R. H. Smellie, Jr., and V. K. La Mer discovered that phosphyrol esters, found in potato starch, rapidly flocculated colloidal dispersions of fine clay in presence of calcium. This was achieved by calcium (or other phosphate binding ions) crosslinking particles that already had adsorbed starch molecules. However, no flocculation occurred with non-phosphate binding ions like Na, K. (La Mer, 1964) In recent studies it has been shown that alkali-earth metal ions can assist in coagulant-humic acid (HA) adsorption by reducing the repulsive forces (Wang et. al., 2010). It was argued that the Ca2+ and Mg2+ ions would assist in charge neutralization of humic acid. At the same time, high concentration of alkali-earth metals would reduce adsorption by blocking adsorption sites for the coagulant, in this case bi-functional resin JN-10 (figure 2.3.2).
12
Figure 2.3.2 The action mechanism of the influence of high concentration of the alkaline-earth metal 258 ions on JN-10’s adsorption capacity for the HA (adapted from: Wang et al., 2010)
In another study, positive effects of calcium on polyaluminumclhloride (PACl) flocculation were observed. In the study, HA samples were pretreated with calcium and flocculated using PACl with different basicities (OH/Al ratios). The results indicated that calcium could enhance the size and strength of the flocs by reducing the zeta potential of HA. Furthermore, when studying floc breakage and re-growth, the floc size was larger for HA-calcium water than HA water, suggesting that calcium could neutralize the negatively charged HA chain and form bridges between adjacent molecules, and thereby promoting the aggregation of HA. (Dong, 2012)
2.3.4 Jar tests
Conducting jar tests is a good way of testing different procedures on a laboratory scale before tests are conducted on pilot scale. It can be used for testing coagulant dosage, optimal pH range and kinetic studies (e.g. initial mixing conditions). The jar test is supposed to simulate the conditions in the coagulation and flocculation process of the large scale plant. The flocculators utilized have programmable kinetic programs, this includes mixing speeds and duration. Usually, the kinetic program is set to simulate different phases by starting an initial rapid mixing phase (coagulation phase), slow mixing (flocculation phase) followed by no mixing (sedimentation phase). Once the program is finished, many different parameters can be tested to see the efficiency of the process. This might include, dissolved organic carbon (DOC), residual metal content and UV-VIS absorbance (indication of removed organic matter). All results are tied to the raw water in the jar test, which means that the results can’t always be applied to different waters. However, some trends seen in a series of tests can give an indication of, for example, new coagulant efficiencies (Trussel and Hand, 2012). A photo of a flocculator can be seen below (figure 2.3.3):
13
Figure 2.3.3 Photo of Kemira Flocculator 2000 used during this thesis project.
As discussed in section 2.3.2, the initial mixing speed is very important for a successful coagulation process. The time it takes to form mononuclear complexes such as AlOH2+ is in the order of 10-10 s, while polynuclear complexes could take up to 1 s to form (Bratby, 1980). Adsorption to particle of these complexes is very rapid (order of 10-10 s) (O’Melia, 1969) and time needed for the structural adjustments to the double layer is of the order 10-10 (Bratby, 1980). As a result, there is no benefit of having the rapid mixing exceeding 5 s in jar tests (Griffith and Williams, 1972). It is possible that longer mixing time will impair coagulation and flocculation results (Letterman, Quan and Gemmell, 1973).
2.3.5 Flocculation
(Essentially from Bratby, 1980, Trussell and Hand, 2012)
The process of flocculation is the stage where particles approach each other, adsorb and form larger agglomerates. Flocculation is divided into two stages, perikinetic flocculation and orthokinetic flocculation. Perikinetic flocculation is a naturally random process that comes from Brownian movement (random motion of particles suspended in fluid), which start immediately after destabilization and is complete within seconds. As the small particles (<0.1 µ) progressively become larger, the energy barrier proportionally increases with the floc area. Once the flocs reach a size of 1 to 100 µm the Brownian motion has little to no effect. The second stage, orthokinetic flocculation, continues with forced convection for particles larger than 1 µm. The mixing causes collisions between particles, however this also erodes and causes flocs to break up. If the forced convection is constant, a steady state of floc breakup and formation will occur given enough time (Parker et al., 1972). Another factor in flocculation is the differences in floc growth, which causes flocs to settle at different times. The difference in size and density also cause flocs to settle at different velocity. As a result, flocs collide promoting additional flocculation. This mechanism is called differential settling and will have an impact on sedimentation, assuming enough time is given.
14
The rate of flocculation is determined by particle collision and breakup in all three mechanisms mentioned above. In other words, the total rate of flocculation is a function of all three rates of flocculation. The rate of flocculation rij, is defined as:
𝑟𝑖𝑗 = 𝛼𝛽𝑖𝑗𝑛𝑖𝑛𝑗 (10)
Where, α – collision efficiency β – collision frequency factor (particles of size i and j) n – particle concentration (i and j particles)
The collision efficiency α, depends on the destabilization factor. So if particles are completely destabilized, the collision efficiency will be 1 (α ranges from 0 to 1). The collision frequency factor βij, depends on all collision frequencies of the different flocculation mechanisms and is as followed:
𝛽𝑖𝑗 = 𝛽𝑃𝑒𝑟𝑖𝑘𝑖𝑛𝑒𝑡𝑖𝑐 + 𝛽𝑂𝑟𝑡ℎ𝑜𝑘𝑖𝑛𝑒𝑡𝑖𝑐 + 𝛽𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑡𝑖𝑎𝑙 𝑠𝑒𝑡𝑡𝑙𝑖𝑛𝑔 (11)
There are three different models describing the flocculation process: spherical particles in a linear flow field, spherical particles in a nonlinear flow field, and fractal-based models. The floc growth prediction is what differentiates these models from each other. They are all based on different assumptions about particle-particle interactions, particle geometry and so on. The spherical particles in a linear flow field model assumes that particles are spherical and that the total floc volume is constant. The model doesn’t account for collision efficiency and van der Waals forces, which neglects the importance of perikinetic flocculation to some degree. These forces and interactions are more accurately described in the nonlinear model developed by Han and Lawler (1992). Flocculation theory was later developed in the fractal flocculation model. In this model the floc volume isn’t considered to be constant over time, which results in a more accurate depiction of the flocculation rate.
15
3. Experimental
3.1 Raw water
The raw water samples used in this study were taken from a lake, Bolmen in southern Sweden. The
water is transported through an 80 km long underground tunnel followed by a 25 km long raw water
pipeline to the municipal water treatment plant in Stehag southern Sweden. The incoming water
consists of up to 10% stormwater that was filtered through the soil into the tunnel. The raw water
quality used varied daily depending on previous conditions at the water source. The variation of the
water quality also depends on the current season. The experiments in this study were conducted
from January to April 2015 and during this time the water quality was as followed:
Table 3.1.0 Average raw water quality from January to April 2015. The temperature ranged from 2 oC to 5oC
during this period.
Date 20150113 to 20150212 20150212 to 20150314 20150314 to 20150413
Min Max Average Min Max Average Min Max Average
Turbidity 3.11 3.75 3.26 3.05 3.40 3.30 3.37 3.50 3.43
NO3-Neq 1.11 1.21 1.15 1.12 1.24 1.20 1.22 1.25 1.23
TOCeq 9.26 10.75 9.82 9.78 10.88 10.47 10.78 11.17 10.93
DOCeq 13.40 14.39 13.81 13.23 14.62 14.29 14.50 14.83 14.66
UV 40.2 43.8 41.6 40.0 44.1 43.1 43.9 44.8 44.2
3.2 Coagulants and additives
All coagulants used in the study were of food grade quality and were used directly without further
preparation with the exception of Al2(SO4)3 (Kemira ALG, Sweden). A 0.36% NaOH (Akzo Nobel,
Sweden) solution was used to control the resulting pH due to the decrease in pH caused by PIX-311
and ALG. The 36% by weight CaCl2 solution used was produced and provided by TETRA chemicals
(Helsingborg, Sweden). The first primary coagulant used was PIX-311, a 40% by weight FeCL3 solution
produced by Kemira (Helsingborg, Sweden) and provided by Sydvatten AB (municipal drinking water
producer). In later experiments, ALG was used as a primary coagulant, that was provided by
Sydvatten AB in pellet form. In the experiments, the primary coagulants and CaCl2 dose was
presented in percent. For PIX-311 and ALG, the percent was be based on the daily optimal dose (see
Appendix) used by Ringsjöverket, and for CaCl2 the percent was based on an optimal coagulant dose
of 61mg/l.
3.3 Preparation before jar test
Samples of raw water with added coagulant were pH-tested (using a WTW pH-197, pH meter) before
jar tests were conducted to ensure that the resulting pH would be within the optimal (or targeted)
range. NaOH (0.36% by weight) solution was added accordingly. In the experiments when PIX-311
was used no preparations were required. When Al2(SO4)3 was used as the primary coagulant
16
granulates of Al2(SO4)3 were dissolved in distilled water under rapid mixing to create a 200g/l
solution.
3.4 Jar tests
Jar tests were conducted in the water treatment plant in Stehag, Sweden using a program-controlled
flocculator (Flocculator 2000, Kemira; Helsingborg, Sweden). The setup consisted of six 1 liter glass
beakers and the jar test procedure was as follows:
1. The flocculator was programmed to 30 seconds rapid mixing (400 rpm), 20 min slow mixing
(50 rpm) and 30 min sedimentation (0 rpm). Each beaker was filled with one liter raw water.
2. Before the program was started CaCl2 and 0.36% NaOH were added to the beakers while
mixing (50 rpm).
3. The program was started and when 3 seconds remained of the rapid mixing, coagulant was
added. Once the rapid mixing was finished and slow mixing had started, the samples were
pH-tested.
4. When sedimentation was finished samples were taken with a 50 ml syringe 3 cm below the
surface.
The program was altered to its current method above after results indicated that brief rapid mixing
after the addition of FeCl3 gave better UV-VIS results (see Appendix).
3.5 Ultraviolet-Visible Spectroscopy
All samples were tested for residual natural organic matter (NOM) in a spectrophotometer (Hach
Lange, DR 5000) using a 5 cm cuvette. The absorption was measured at λ=245 nm and λ=436nm.
These wavelength were used by the water treatment plant for daily process control. In table 3.5.1
seen below, the average UV-VIS results are displayed, measured by the water treatment plant. The
measurements taken after the filters, are samples that have already gone through the process of
flocculation.
Table 3.5.1 Measured UV-VIS absorption results from 010215 to 100415, conducted by the water treatment
facility (Ringsjöverket). Samples were taken after quick filter 1 and 7 (after flocculation).
UV-VIS measurements Quick filter 1 Quick filter 7 Incoming raw water
Average UV-abs (λ=254 nm) 4.97 4.83 43.89
Average VIS-abs (λ=436 nm) - - 3.13
17
4. Results & Discussions
4.1 Effects of various CaCl2 additions on Fe(III) flocculation
During these experiments two samples acted as a control group with 100% PIX, two samples had 80%
PIX and two samples had 80% PIX and various amounts of CaCl2. The convections program was as
follows: 30s rapid mixing (400 rpm), 20min slow mixing (50 rpm) and 30 min sedimentation (0 rpm).
CaCl2 and NaOH were added before the program during slow mixing (50 rpm). PIX was added when 3
seconds of rapid mixing remained. Explanation for this can be seen in Appendix (Experiment 1 and 2).
4.1.1 Addition of 20 mol% CaCl2
The Aim of these experiments was to see if a low dose of CaCl2 (20 mol% of the optimal PIX dose)
would have any effect on flocculation when using a reduced amount of PIX (in this case 83 to 86%
PIX). As seen in figure 3.1, the effects of 103 to 107% PIX, 83- 86% PIX and 83- 86% PIX with added
CaCl2 were studied. These early results show that an addition of CaCl2 seem to have a positive effect
on UV-VIS results in some cases when comparing with samples without CaCl2 and the same amount
of PIX. However, it is not clear from these results if PIX can be substituted with CaCl2.
Figure 3.1 Results from Experiment 3 (2015-02-03, 2015-02-04 and 2015-02-05).
8
9
10
11
12
13
14
15
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
4,7 4,8 4,9 5 5,1 5,2 5,3
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
103 to 107% PIX VIS
83 to 86% PIX VIS
83 to 86% PIX with CaCl2 VIS
103 to 107% PIX UV
83 to 86% PIX UV
83 to 86% PIX with CaCl2 UV
18
4.1.2 Addition of 40 mol% CaCl2
In the following experiments the setup was the same however the CaCl2 dose was increased to 40
mol%. Results seen in figure 4.1 show that a reduced amount of PIX with CaCl2 gave better results at
pH below 4.9 compared with 108% PIX at the same approximate pH. This was also true for samples
with a reduced amount of PIX without CaCl2 (figure 4.2). At the same time samples with 108% PIX
produce better results when pH was above 5 in both cases (figure 4.1 and 4.2). The explanation for
this is that the optimal pH-range is altered based on the coagulant dose. If pH is reduced, the amount
of negative species in suspension will be reduced, and organic contaminants (e.g. humic acid and
protein) will obtain fewer negative charges on the surface. As a result, the optimal coagulant dose
will also be reduced. In other words, a reduced amount of PIX will transfer the optimal pH to a lower
range. (Gillberg et al., 2003)
Figure 4.1 Results from Experiment 4 A and B (2015-02-06 and 2015-02-09).
Figure 4.2 Results from Experiment 4 C to E (2015-02-10 and 2015-02-11).
8
9
10
11
12
13
14
15
16
17
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
1,6
4,7 4,8 4,9 5 5,1 5,2 5,3 5,4
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
108% PIX VIS
87% PIX VIS
87% PIX with CaCl2 VIS
108% PIX UV
87% PIX UV
87% PIX with CaCl2 UV
8
9
10
11
12
13
14
15
16
17
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
1,6
4,8 4,9 5 5,1 5,2 5,3 5,4
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
108% PIX VIS
86% PIX VIS
86% PIX with CaCl2 VIS
108% PIX UV
86% PIX UV
86% PIX with CaCl2 UV
19
At this point the used PIX dose was changed to match the optimal dose used by the water treatment
plant. The results of this can be seen in figure 5.1.
Figure 5.1 Results from Experiment 5 (2015-02-12, 2015-02-13 and 2015-02-17).
From these results it is quite clear that a 40 mol% addition of CaCl2 does not match the results from
samples with 100% PIX at pH around 5.1. However, as seen in figure 4.1, 4.2 and figure 5.1, a
reduced amount of PIX gave better UV-VIS results at pH below 4.9.
8
10
12
14
16
18
20
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
1,6
4,7 4,9 5,1 5,3 5,5U
V-a
bs
(λ=2
54
nm
/m)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
100 to 101% PIX VIS
80 to 81% PIX VIS
80 to 81% PIX with CaCl2 VIS
100 to 101% PIX UV
80 to 81% PIX UV
80 to 81% PIX with CaCl2 UV
20
4.1.3 Addition of 80 mol% CaCl2
During these experiments the CaCl2 dose was doubled to 80 mol%, which gave similar results (figure
6.1). At the optimal pH-range for 100% PIX, the reduced amount of PIX (with and without CaCl2)
produced poorer UV-VIS results. This can also be seen in table 6.8 below, where the average UV-VIS
results are clearly better for 100% PIX than 81% PIX with CaCl2. When comparing results from
samples with 81% PIX, the samples with CaCl2 does give better results. However, they don’t match
the results for 100% PIX.
Table 6.8 Average UV-VIS results for experiment 6.
Experiment 6 pH Range Average pH Average VIS-abs Average UV-abs
81% PIX without CaCl2 4.81-5.26 5.22 1.37 17.35
81% PIX with 80 mol% CaCl2 4.98-5.27 5.22 1.28 16.20
100% PIX 5.00-5.57 5.17 0.79 10.61
CaCl2 Effect 6.6% 6,6%
Figure 6.1 Results from Experiment 6 2015-02-18, 2015-02-19 and 2015-02-23.
4.1.4 Summary of experiments with reduced amount of PIX-311
When combining all results from experiment 5 to 11 (see Appendix) the effects of PIX dose and CaCl2
dose becomes clear (figure 6.2 and 6.3). The optimal pH for 100% PIX ranges from approximately 4.9
to 5.2 while the optimal pH range for 80% PIX is slightly lower. Lowering pH might cause corrosion
issues for drinking water producers and as a result it is more advantageous to keep pH above 5. As
seen in figure 6.2 and 6.3, the samples with reduced amount of PIX (with or without CaCl2) do not
share comparable results with samples of 100% PIX in that pH range. When the CaCl2 dose is
increased to 0.4g/l (over 64 times increase) the results appear to get worse. However, there are
8
10
12
14
16
18
20
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
1,6
4,7 4,9 5,1 5,3 5,5
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
100% PIX VIS
81% PIX VIS
81% PIX with CaCl2 VIS
100% PIX UV
81% PIX UV
81% PIX with CaCl2 UV
21
positive effects when a lower CaCl2 dose (40 to 80 mol%, or 13.72 resp. 27.4µl 36% CaCl2 (aq) per liter
raw water) is combined with 80% PIX. Based on literature data (Wang et al., 2010) Ca2+ does lend
support in coagulation by reducing repulsion forces between humus in solution and humus adsorbed
to coagulant. Also, when Ca2+ concentration reaches a certain point, the Ca2+ ions block the primary
coagulants’ (in this case FeCl3) adsorption sites and poorer results are observed.
Figure 6.2 The combined VIS-absorption results from experiment 5 to 11.
Figure 6.3 The combined UV-absorption results from experiment 5 to 11.
0,5
0,7
0,9
1,1
1,3
1,5
4,7 4,8 4,9 5 5,1 5,2 5,3 5,4 5,5 5,6
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
VIS
100% PIX VIS 80 to 81% PIX VIS
80 to 81% PIX with 40% CaCl2 VIS 80 to 81% PIX with 80% CaCl2 VIS
80% PIX with 0,4g/l CaCl2 VIS 100% PIX UV
Poly. (100% PIX VIS) Poly. (80 to 81% PIX VIS)
Poly. (80 to 81% PIX with 80% CaCl2 VIS)
8
10
12
14
16
18
20
4,7 4,8 4,9 5 5,1 5,2 5,3 5,4 5,5 5,6
UV
-ab
s (λ
=25
4 n
m/m
)
pH
UV
100% PIX VIS 100% PIX UV80 to 81% PIX UV 80 to 81% PIX with 40% CaCl2 UV80 to 81% PIX with 80% CaCl2 UV 80% PIX with 0,4g/l CaCl2 UVPoly. (100% PIX VIS) Poly. (100% PIX UV)Poly. (80 to 81% PIX UV) Poly. (80 to 81% PIX with 80% CaCl2 UV)
22
At the same time, when comparing results from experiment 4 (table 4.6), that same benefit doesn’t
appear. This could be explained by the increase of PIX in that experiment (from 80 to 87%) and/or
that the slight benefit of adding CaCl2 to 80% PIX is within the margin of error. It is important to
mention that the average results seen in table 4.6, are based on all the results within that specific pH
range and the distribution is not accounted for.
Table 4.0 Summary of Experiment 4 showing pH range, average pH, average UV-VIS results.
Experiment 4 pH Range Average pH Average VIS-abs Average UV-abs
86 to 87% PIX without CaCl2 4.86-5.04 4.95 0.783 10.4
86 to 87% PIX with 40 mol% CaCl2 4.88-5.03 4.95 0.785 10.5
CaCl2 Effect -0.3% -0.4%
A reason why the benefits are not observed in experiment 4, could also be that the pH only ranges to
5.04. As seen in table 6.8 and figure 6.2 and 6.3, where the pH is higher, a benefit of adding CaCl2 is
observed. This can also be seen in table 5.0 below, where a 40 mol% CaCl2 dose appear to improve
the UV-VIS results by 2.6 resp. 3.1%. So a benefit of adding CaCl2 could be that the optimum pH range
is shifted to higher pH or that the optimal pH range is broadened. As discussed previously, when pH
is increased, the negative species in the suspension increase and coagulation by charge neutralization
is reduced. As a result, when pH increases, the positive Ca2+ ions assist in charge neutralization, and
the UV-VIS results are improved. (Gillberg et al., 2003)
Table 5.0 Summary of Experiment 5 showing pH range, average pH, average UV-VIS results.
Experiment 5 pH Range Average pH Average VIS-abs Average UV-abs
81% PIX without CaCl2 5.01-5.15 5.07 1.03 13.67
81% PIX with 40 mol% CaCl2 4.98-5.13 5.07 1.00 13.31
CaCl2 Effect 3.1% 2.6%
In table 6.0, the standard deviation was considered for experiment 5 and 6, showing that the
observed positive effects of adding CaCl2 to a reduced amount of PIX, were reasonable.
Table 6.0 Summary of the standard deviations of Experiment 5 and 6. The standard deviation was calculated,
taking pH in consideration for each individual data point.
Experiment 5 Standard deviation VIS Standard deviation UV
81% PIX without CaCl2 0.02 0.29
81% PIX with 40 mol% CaCl2 0.02 0.28
Experiment 6 Standard deviation VIS Standard deviation UV
81% PIX without CaCl2 0.04 0.43
81% PIX with 80 mol% CaCl2 0.03 0.27
23
4.2 Effects of CaCl2 additions with an optimal Fe(III) dose
In these experiments CaCl2 was added to samples with 100% PIX. Similar to the previous section, one control group was used with only 100% PIX and the other samples with various amounts of CaCl2. The CaCl2 doses are presented in percent (20, 40 and 80 mol%) based on a 56.5g/m3 PIX dose. The setup varied throughout these experiments.
4.2.1 Addition of 20 and 40 mol% CaCl2
In this set of experiments 20 and 40 mol% CaCl2 were added to 100% PIX. The results in figure 7.3
appear to follow the same trend as previously observed, where a decrease in pH below 4.95
drastically degrades the UV-VIS-results. When comparing the different results it doesn’t seem like
CaCl2 has any impact. Again, there are individual samples with CaCl2 that give better results but it
isn’t systematic.
Figure 7.3 Results from Experiment 7A to N (2015-03-10, 2015-03-11 and 2015-03-12).
8
9
10
11
12
13
14
0,6
0,7
0,8
0,9
1
1,1
1,2
4,7 4,8 4,9 5 5,1 5,2 5,3
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV -VIS
100% PIX VIS
100% PIX with 20% CaCl2 VIS
100% PIX with 40% CaCl2 VIS
100% PIX UV
100% PIX with 20% CaCl2 UV
100% PIX with 40% CaCl2 UV
24
4.2.2 Addition of 40 and 80 mol% CaCl2
In the following experiments the CaCl2 dose was doubled to 40 and 80 mol%. The results from these experiments can be seen in Figure 8.1. An increase in CaCl2 dose appears to have very limited effects on UV-VIS absorption results. One thing to keep in mind is that the raw water quality varies day to day and these experiments are conducted over a period of days. Nonetheless, if CaCl2 had any impact (positive or negative), the results should show a trend to that effect.
Figure 8.1 Results from Experiment 8A to G (2015-03-17, 2015-03-18, 2015-03-19 and 2015-03-20).
4.2.3 Summary of experiments with optimal PIX-311 dose
When combining all the results from experiment 5 to 11 there appears to be a slight benefit by adding CaCl2 (figure 9.2). However, as mentioned before, the raw water quality changes over time (table 3.0). The early experiments were conducted in February and the later in March, which makes it difficult to be certain that the CaCl2 additions had any positive effects. In figure 9.3, the UV results appear to be independent of calcium dose. An interesting observation is that the inclinations of the trend lines in figure 10.2 seem to be similar and that they reveal a pH optimum around 5.2-5.25, while the UV results in figure 9.3 indicate that the pH optimum is lower. Based on that, average UV-results are slightly improved at a lower pH and average VIS-results are slightly improved at higher pH. In any case, a benefit of adding calcium could come from electric double layer compression described earlier (Trussell and Hand, 2012, Wang et al., 2010) or due to calcium’s ability to neutralize the HA’s negative charge and/or calcium’s bridged building abilities (Dong, 2012). As seen in the earlier experiments, a high calcium dose (0.4g/l 36% CaCl2 (aq)) gives worse UV-VIS results, however not to the same degree (figure 9.2 and figure 9.3).
8
9
10
11
12
13
14
0,5
0,55
0,6
0,65
0,7
0,75
0,8
0,85
0,9
0,95
1
4,7 4,8 4,9 5 5,1 5,2 5,3
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
100% PIX VIS
100% PIX with 40% CaCl2 VIS
100% PIX with 80% CaCl2 VIS
100% PIX UV
100% PIX with 40% CaCl2 UV
100% PIX with 80% CaCl2 UV
25
Figure 9.2 VIS Results from experiment 5 to 11. Trend lines are generated from samples between pH 4.9 and 5.2 resp. pH 5.2 and 5.6.
Figure 9.3 UV Results from experiment 5 to 11. Trend lines are generated from samples between pH 4.9 and 5.2 resp. pH 5.2 and 5.6.
R² = 0,0706 y = 1,5801x - 7,6152R² = 0,9387
y = 1,5736x - 7,5514R² = 0,8648
R² = 0,0768
0,4
0,6
0,8
1
1,2
1,4
1,6
4,7 4,8 4,9 5 5,1 5,2 5,3 5,4 5,5 5,6
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
VIS
100% PIX VIS 100% PIX with 40% CaCl2 VIS 100% PIX with 0,4g/l CaCl2 VIS
8
10
12
14
16
18
20
4,7 4,8 4,9 5 5,1 5,2 5,3 5,4 5,5 5,6
UV
-ab
s (λ
=25
4 n
m/m
)
pH
UV
100% PIX UV 100% PIX with 40% CaCl2 UV 100% PIX with 0,4g/l CaCl2 UV
26
Table 9.7 shows the results from experiments 7, 8 and 9, where a positive effect can be seen from CaCl2 additions (3% for average VIS and 1% for average UV). The positive effect could be, as discussed earlier, that the optimal pH range is broadened. However, the standard deviations displayed in table 9.7, suggest that these results are not significant. Table 9.7 Average UV-VIS absorption results from experiment 7 to 9. The standard deviation for data points from 4.9 to 5.2 pH are also displayed.
100% PIX
Experiment pH Range Average pH Average VIS-abs Average UV-abs
9 4.93-5.26 5.14 0.618 9.30
8 4.89-5.12 4.96 0.656 9.16
7 4.79-5.24 4.98 0.819 10.27
Total average 5.02 0.697 9.58
Standard deviation 4.9-5.2 0.087 0.53
100% PIX with 40 mol% CaCl2
Experiment pH Range Average pH Average VIS-abs Average UV-abs
9 5.01-5.26 5.18 0.631 9.50
8 4.9-5.16 4.99 0.636 9.08
7 4.75-5.2 5.01 0.761 9.93
Total average 5.06 0.676 9.50
Standard deviation 4.9-5.2 0.075 0.49
CaCl2 effect 3% 1%
The confidence level was tested for experiment 7 to 9 and the results can be seen in table 9.8. It is safe to say that the results from these experiments are significant and not generated by chance. Table 9.8 Regression analysis from experiment 7 to 9. States the confidence level (95%) of observed results.
Statistics Confidence VIS Confidence UV
100% PIX 3.97E-08 9.35E-06
100% PIX with 40 mol% CaCl2 1.68E-07 2.63E-04
One thing to reflect on, is that all the observed UV-VIS results compared to the UV-VIS results
received from the water treatment plant (table 3.5.1), are significantly poorer. Granted, the samples
from the water treatment plant were taken after the quick filters, however it serves well as an
indication of the observed results. With this in mind, if the experiments would be applied to the pilot
scale, the slightly positive effect of adding CaCl2 might be insignificant.
27
4.3 Effects of CaCl2 additions on Al(III) flocculation
In these experiments (experiment 12 and 13, see Appendix), 40% by weight CaCl2 (35.4 µl/l raw
water) and 0.4g/l CaCl2 (820µl/l raw water) was added to Al2(SO4)3 (ALG) flocculation. The percent
calcium was based on a 43g/m3 ALG dose. Only two sets of experiments were done with ALG, which
will make it difficult to draw any definite conclusions, however the experiments gave some
interesting results. As seen in figure 12.1, a high CaCl2 dose (0.4g/l) provides worse results and a low
CaCl2 dose (40%) does not appear to have any impact at all. As pH increases, the results start
wavering greatly. One possible explanation could be, that when pH increases, a predominance of
negative hydrolysis species occur. Furthermore, this could result in a gradual increase of flocculation
due to precipitate enmeshment or sweep flocculation (Bratby, 1980).
Figure 12.1 Results from Experiment 12A to L (2015-04-14, 2015-04-15, 2015-04-16, 2015-04-17, 2015-04-20,
2015-04-22 and 2015-04-23).
Table 12.13 shows the effect of CaCl2 additions and the average UV-VIS results. A high calcium dose
(0.4g/l) gave a -29% VIS result and a -13% UV result. At the same time, a low dose (40%) did not have
any significant impact on the results. These results are comparable with previous results, a high
calcium dose giving worse results and a low calcium dose having little to no effect on the results.
Table 12.13 Average UV-VIS absorption results from Experiment 12.
Experiment 12 pH Range Average pH Average VIS-abs Average UV-abs
ALG 5.93-6.50 6.21 0.790 13.22
ALG w 40% Ca 5.97-6.47 6.20 0.807 13.19
ALG w 0.4g/l Ca 5.97-6.46 6.22 1.022 14.91
CaCl2 effect VIS UV
ALG w 40% Ca -2% 0%
ALG w 0.4g/l Ca -29% -13%
10
11
12
13
14
15
16
17
18
19
20
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
5,9 6 6,1 6,2 6,3 6,4 6,5 6,6
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
ALG VIS
ALG with 40% CaCl2 VIS
ALG with 0,4g/l CaCl2 VIS
ALG UV
ALG with 40% CaCl2 UV
ALG with 0,4g/l CaCl2 UV
28
In the next experiment, the ALG dose was reduced to 79% (34g/m3) and the calcium additions were
40 and 80% by weight, based on 43g/m3 ALG dose. The results can be seen in figure 13.1. The
calcium addition does not have any effect until pH reaches about 6.15, where the sample with added
calcium suddenly improve the results significantly. According to Trussell and Hand, 2012, sweep
coagulation is one of the mechanisms that are possible at a pH range of 6 to 8 (due to metal
hydroxide formation in this range). As pH increases, the negative species increases and the
flocculation due to enmeshment increases. Once that happens CaCl2 might act as an adjunct in
sweep flocculation or aiding by bridge building (Dong, 2012).
Figure 13.1 Results from Experiment 13A to G (2015-04-28, 2015-04-29, 2015-04-30 and 2015-05-04).
The average UV-VIS result was calculated for all data points from pH 6.14 and 6.18, the results can be seen in
table 13.0 below. The samples with 80% CaCl2 appear to improve the average UV-VIS results the most, when
compared to samples with only reduced amount of ALG. These results are very interesting because they might
allow for water treatment at higher pH however, these experiments were limited and further studies need to
be conducted.
Table 13.0 Average UV-VIS results from Experiment 13. Results range from pH 6.14 to pH 6.18.
Experiment 13 pH Range Average pH Average VIS Average UV
79% ALG with 40% CaCl2 6.15-6.17 6.16 1.35 18.8
79% ALG with 80% CaCl2 6.14-6.17 6.16 1.16 17.3
79% ALG 6.16-6.18 6.17 1.43 19.8
CaCl2 Effect VIS UV
79% ALG with 40% CaCl2 5.7% 5.1%
79% ALG with 80% CaCl2 18.6% 12.7%
10
12
14
16
18
20
22
0,6
0,8
1
1,2
1,4
1,6
1,8
5,9 5,95 6 6,05 6,1 6,15 6,2 6,25 6,3
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
79% ALG VIS 79% ALG with 40% CaCl2 VIS 79% ALG with 80% CaCl2 VIS
79% ALG UV 79% ALG with 40% CaCl2 UV 79% ALG with 80% CaCl2 UV
29
5. Conclusions
When using a less than optimal PIX-311 dose, CaCl2 additions do not assist enough in coagulation and
flocculation to replace the effect of the reduced PIX-311 dose. From the results it was possible to see
that CaCl2 had a positive effect on flocculation when pH was above 5 at low dosage (40 to 80 mol%)
however, the UV-VIS results were inadequate and would not insure acceptable water quality . When
the CaCl2 dose was increased from 80 mol% to 0.4g/l (an equivalent of increasing the CaCl2 dose from
about 25µl to 820µl per liter raw water), a clear negative effect was observed due to coagulant-HA
hindrance, caused by hydrates formed by calcium.
The addition of 12.7µl CaCl2 per liter raw water (40 mol%) to an optimal amount of PIX-311 had an
3% positive VIS result and 1% positive UV result, based on those numbers. If that is correct, the water
treatment plant would need to add 19ml of 36% by weight CaCl2 per second (based on a water
production of 1500l/s) in order to improve the UV-VIS results by 1 and 3%. Which adds up to 1640 l
CaCl2 per 24 h. If cost is taken in consideration, the improved results would cost 2214 SEK per 24h
(based on a CaCl2 cost of 1000 SEK per 1000 kg and ρcalicum=1.35g/cm3). However, because of the
deviation in the results, the observed positive effects are within the margin of error, and hence, CaCl2
might not have any positive effect on the water quality.
When it comes to CaCl2 additions in Al(III) flocculation it appears that the results are, in some cases,
comparable with those of PIX-311. A high dose of CaCl2 (0.4g/l), seem to effect flocculation in the
same way. However, a low calcium dose (40% by weight), did not appear to be of any significant
impact on the results. If anything, it had a slightly negative effect.
When a non-optimal dose ALG was used with two different CaCl2 doses (40 and 80%), there did not
appear to be any impact except when pH was increased to about 6.15. At this point, the UV-VIS
results improved and the samples with CaCl2 gave better results than the sample without CaCl2
(figure 13.1). The most likely explanation is the increase of pH causing a shift in flocculation
mechanism. The result of this could be that the coagulation process could be conducted at higher pH
without compromising the results. At full scale, this would be very advantages due to the reduced
potential of concrete corrosion. That in mind, there could be a good reason to extend these studies.
30
6. Further work
In this thesis, coagulation and flocculation studies were conducted using FeCl3 and Al2(SO4)3 as
coagulants and CaCl2 as a co-coagulant. However, there are other coagulant such as, PACl that could
benefit from calcium additions, as seen in other experiments (Dong, 2012).
Even though calcium did not have much effect on NOM reduction, there are reasons to suspect that
CaCl2 could aid in enhancing floc strength and thereby reducing sludge (Peeters et al., 2011 and Yu et
al., 2014). Also, it might be interesting to see if calcium is effective at reducing specific
contaminations, such as bacteria or viruses.
Finally, because of the limited experiments done in this thesis, more studies could be conducted on
Al2(SO4)3. A more extensive study on this, might reveal if CaCl2 has any positive effects on aluminum
flocculation or if the result are comparable with FeCl3.
31
References
Alberty R. A., Silbey R. J., 2000. Physical Chemistry. 3rd edition. New York: John Wiley & Sons, inc. ISBN: 0-471-
38311-2
Amory, D. E., Rouxhet, P. G. and Dufour, J. P., 1988. Journal of the Institute of Brewing, 94(2), 79. Bache, D. H., Gregory, R. 2007 Flocs in water Treatment. IWA Publishing 2007, ISBN: 1843390639,
9781843390633
Bratby, J. 1980. Coagulation and flocculation, Uplands Press Ltd, Croydon, UK, pp 5
Camp, T. R. 1946. Sedimentation and the Design of Settling Tanks. Trans ASCE, III.
Cheremisinoff, N. P. 2001. Handbook of water and wastewater treatment technologies. Butterworth
Heinemann, ISBN: 978-0-7506-7498-0
Derjaguin, B. V., and Landau, L. D. 1941 ‘‘Theory of Stability of Strongly Charged Lyophobic Soles and Coalesance of Strongly Charged Particles in Solutions of Electrolytes,’’ Acta Physicochim. URSS, 14, 733–762. Dong M., Gao B., Xu W., Wang Y., Mao R. 2012 Effect of calcium on floc properties and membrane foulings in coagulation–ultrafiltration process by polyaluminum chloride (PACl) of different OH/Al3+ values, Desalination, Volume 294, 15 May 2012, Pages 30-35, ISSN 0011-9164 Gillberg L., Hansen B., Karlsson I. 2003. Konsten att rena vatten. Kemira Kemwater. Helsingborg, Sverige. ISBN: 91-631-4353-4 Griffith J.D., Williams R.G. 1972 Application of Jar Teat Analysis at Phoenix, Ariz., Jour. AWWA, 64, 12, Dec. , 825-830. Han, M., and Lawler, D. 1992 ‘‘The (Relative) Insignificance ofGin Flocculation,’’ J. AWWA, 84, 10, 79–91. Hunter, R. J. 2001 Foundations of Colloid Science, Vos. 1 and 2, Oxford University Press, Oxford, UK La Mer, V. K. 1964. La Mer VK. J Colloid Interface Science New York Academic Press, 1964:19:291
Letterman R.D., Quon J.E., Gemmell R.S. 1973. Influence of Rapid Mix Parameters on Floaculation, Jour. AWWA, Nov., 716-722. O'Melia C.R. 1969 A Review of the Coagulation Process, Public Wks., 100, May, 87 O’Melia, C. R. 1972 Coagulation and Flocculation, in W. J. Weber, Jr. (ed.), Physicochemical Processes for Water Quality Control, Wiley-Interscience, New York. O’Melia, C. R. 1978 Coagulation in Wastewater Treatment, in K. J. Ives (ed.), Scientific Basis of Flocculation, Noordhoff International, Leyden, Netherlands. Parker, D. S., Kaufmann, W. J., and Jenkins, D. 1972 Floc Breakup in Turbulent Flocculation Processes, J. Sanit. Eng. Div., 98, 79–99. Parks, G. A. 1967 Aqueous Surface Chemistry of Oxides and Complex Oxide Minerals; Isolectric Point and Zero Point of Charge, in Equilibrium Concepts in Natural Water Systems, Advances in Chemistry Series, No. 67, American Chemical Society, Washington, DC. Peeters B., Dewil R., Lechat D. & Smets I. Y. 2011. Quantification of the exchangeable calcium in activated sludge flocs and its implication to sludge settleability. Separation And Purification Technology, 83, pp. 1-8.
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Ratnayaka, D. D., Brandt, M. J. and Johnson K. M. 2009. Chapter 7 - Storage, Clarification and Chemical Treatment, In Water Supply (Sixth Edition), edited by Don D. Ratnayaka, Malcolm J. Brandt, K. Michael Johnson, Butterworth-Heinemann, Boston, Pages 267-314, ISBN: 9780750668439 Standard Methods 2005 Standard Methods for the Examination of Water and Waste Water, 21st ed., American
Public Health Association (APHA), American Water Works Association (AWWA), and Water Environment
Federation (WEF), Washington, DC.
Stumm, W., and Morgan J.J. 1962 Chemical Aspects of Coagulation, Jour.AWWA, 5A_, 8, Aug., 971-991. Stumm, W., and Morgan, J. J. 1981 Aquatic Chemistry, 2nd ed., Wiley-Interscience, New York. Stumm, W., and Morgan, J. J. 1996 Aquatic Chemistry, 3rd ed., Wiley, New York.
Trussell, R. R. and Hand, D. W. 2012, MWH's Water Treatment Principles and Design (3rd Edition), John Wiley &
Sons, Hoboken, NJ, USA.
Verwey, E. J. W. and Overbeek, J. T. G. 1948 Theory of the Stability of Lyophobic Colloids, Elsevier, Amsterdam. Wang J., Zhou Y., Li A., Xu L. 2010, Adsorption of humic acid by bi-functional resin JN-10 and the effect of alkali-earth metal ions on the adsorption, Journal of Hazardous Materials, Volume 176, Issues 1–3, 15 April 2010, Pages 1018-1026, ISSN 0304-3894. Yu J., Guo M., Xu X., Guan B., 2014 The role of temperature and CaCl2 in activated sludge dewatering under hydrothermal treatment, Water Research, Volume 50, 1 March 2014, Pages 10-17, ISSN 0043-1354
33
Appendix
Experiment 1 - 20mol% CaCl2-addition
Setup: Optimum PIX dosage: 58.67g, m-3 (2015-01-30). Used PIX dosage: 61g, m-3. 20mol% CaCl2 based on
61g/m3 PIX dose. Addition of PIX with 20 seconds remaining of rapid mixing. However PIX was added
to beaker 6 when 7 seconds remained.
Table 1.1 Results from Experiment 1 (2015-01-30).
Beaker 1 2 3 4 5 6
104% PIX (µl) 43 43 - - - -
83% PIX (µl) - - 34.4 34.4 34.4 34.4
NaOH 0.36% (µl) 950 950 220 220 220 220
CaCl2 (µl) - - - - 6.86 6.86
pH 4.98 4.98 5.08 5.10 4.97 4.95
VIS 13.3 11.5 18.5 14.4 16.5 9.60
UV 1.22 1.02 1.66 1.24 1.64 0.705
Figure 1.1 Results from Experiment 1 (2015-01-30).
As seen in Table 1.1 and Figure 1.1, the best results were observed from beaker 6. This is almost
certainly the result of a shorter rapid mixing time. This becomes especially clear if these results are
compared with the results from beaker 5 with the same CaCl2 and PIX additions. This lead to further
experiments with PIX added at different times.
0,6
2,6
4,6
6,6
8,6
10,6
12,6
14,6
16,6
18,6
20,6
0,6
0,8
1
1,2
1,4
1,6
1,8
4,9 4,95 5 5,05 5,1 5,15
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
104% PIX VIS
83% PIX VIS
83% PIX with CaCl2 VIS
104% PIX UV
83% PIX UV
83% PIX with CaCl2 UV
34
Experiment 2 – Effects of PIX additions at various time
Setup: Optimum PIX dosage: 58.67g, m-3 (2015-02-02) and 58.5g, m-3 (2015-02-03). Used PIX dosage: 61g,
m-3. No addition of CaCl2.
a) Addition of PIX when 20, 10, 5s remaining of rapid mixing.
Figure 2.1 Results from Experiment 2A (2015-02-02).
It is difficult to draw any conclusions when comparing the results from the samples because of the
variation of pH. However, it is clear that the samples from the 10 second additions resulted in a
better outcome compared with the samples from the 20 second additions.
Table 2.1 Results from Experiment 2A (2015-02-02).
Beaker 1 2 3 4 5 6
104% PIX (µl) 43 43 43 43 43 43
NaOH 0.36% (µl) 950 950 950 950 950 950
Time remaining (s) 20 20 10 10 5 5
pH 4.81 4.83 4.82 4.85 4.98 4.98
VIS 1.66 1.51 1.29 1.17 0.886 1.02
UV 15.8 15.4 13.8 12.8 10.7 11.7
9,5
10,5
11,5
12,5
13,5
14,5
15,5
16,5
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
1,6
1,7
1,8
4,8 4,85 4,9 4,95 5
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
PIX addition at 20s VIS
PIX addition at 10s VIS
PIX addition at 5s VIS
PIX addition at 20s UV
PIX addition at 10s UV
PIX addition at 5s UV
35
b) Addition of PIX when 7, 5, 3s remaining of rapid mixing.
Figure 2.2 Results from Experiment 2B, 2015-02-03.
The results seen in figure 2.2 show little variation in UV-absorption and VIS-absorption when
comparing the 7 seconds addition and 3 seconds addition. The results from the 5 second additions
seem to be slightly poorer. This can be explained by the lower corresponding pH-values for the
samples. Based on these results, the PIX addition was added when 3 seconds remained of the rapid
mixing in following experiments. The results also agree with Griffith and Williams, 1972, that stated
that rapid mixing times above 5 seconds may not improve flocculation efficiencies.
Table 2.2 Results from Experiment 2B (2015-02-03).
Beaker 1 2 3 4 5 6
104% PIX (µl) 43 43 43 43 43 43
NaOH 0.36% (µl) 950 950 950 950 950 950
Time remaining (s) 7 7 5 5 3 3
pH 4.95 4.95 4.9 4.89 5.02 4.97
VIS 0.804 0.902 1.02 0.877 0.799 0.894
UV 9.82 10.7 11.6 10.3 9.85 10.6
9,5
10
10,5
11
11,5
12
0,75
0,8
0,85
0,9
0,95
1
1,05
4,85 4,9 4,95 5 5,05
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
PIX addition at 7s VIS
PIX addition at 5s VIS
PIX addition at 3s VIS
PIX addition at 7s UV
PIX addition at 5s UV
PIX addition at 3s UV
36
4.1.3. Experiment 3 – Using 20mol% CaCl2
Setup: Optimum PIX dosage: 58.5 g, m-3 (2015-02-03), 59 g, m-3 (2015-02-04) and 57 g, m-3 (2015-02-05).
Used PIX dosage: 61g, m-3. 20mol% CaCl2 based on 61g/m3 PIX dose. Addition of PIX when 3 seconds
remaining of rapid mixing.
Figure 3.1 Results from Experiment 3 (2015-02-03, 2015-02-04 and 2015-02-05).
Table 3.1 Results from Experiment 3A (2015-02-03).
Beaker 1 2 3 4 5 6
104%PIX (µl) 43 43 - - - -
83%PIX (µl) - - 34.4 34.4 34.4 34.4
NaOH 0.36% (µl) 950 950 220 220 220 220
CaCl2 (µl) - - - - 6.86 6.86
pH 4.86 4.93 5.04 4.97 4.99 4.97
VIS 0.77 0.85 0.722 0.691 0.709 0.819
UV 9.37 10.1 9.93 9.42 9.69 10.1
Table 3.2 Results from Experiment 3B (2015-02-04).
Beaker 1 2 3 4 5 6
103%PIX (µl) 43 - - - -
83%PIX (µl) - - 34.4 34.4 34.4 34.4
NaOH 0.36% (µl) 950 950 220 220 220 220
CaCl2 (µl) - - - - 6.86 6.86
pH 5.02 5.04 4.77 4.92 4.95 4.97
8,4
9,4
10,4
11,4
12,4
13,4
14,4
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
4,7 4,8 4,9 5 5,1 5,2 5,3
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
103 to 107% PIX VIS
83 to 86% PIX VIS
83 to 86% PIX with CaCl2 VIS
103 to 107% PIX UV
83 to 86% PIX UV
83 to 86% PIX with CaCl2 UV
37
VIS 0.657 0.684 0.814 0.886 0.727 0.709
UV 8.81 8.9 9.97 10.8 9.91 9.62
Table 3.3 Results from Experiment 3C (2015-02-05).
Beaker 1 2 3 4 5 6
107%PIX (µl) 43 - - - -
86%PIX (µl) - - 34.4 34.4 34.4 34.4
NaOH 0.36% (µl) 950 950 220 220 220 220
CaCl2 (µl) - - - - 6.86 6.86
pH 4.77 4.83 4.97 4.85 4.94 5
VIS 1.15 1.2 0.768 0.788 0.765 0.711
UV 12.6 12.9 10.3 10.8 9.84 10
Table 3.5 Results from Experiment 3D (2015-02-05).
Beaker 1 2 3 4 5 6
107% PIX (µl) 43 - - - -
86%PIX (µl) - - 34.4 34.4 34.4 34.4
NaOH 0.36% (µl) 950 950 220 220 220 220
CaCl2 (µl) - - - - 6.86 6.86
pH 4.77 5 5.05 4.76 4.9 4.91
VIS 1.32 0.667 0.699 0.78 0.773 0.747
UV 14.1 8.96 10 9.85 9.91 9.94
38
4.1.3. Experiment 4 – 40mol% CaCl2
Setup: Optimum PIX dosage: 56.3 g, m-3 (2015-02-06 and 2015-02-09) and 56.5 g, m-3 (2015-02-10 and
2015-02-11). Used PIX dosage: 61g, m-3. 40mol% CaCl2 based on 61g/m3 PIX dose. Addition of PIX
when 3 seconds remaining of rapid mixing.
Figure 4.1 Results from Experiment 4 (2015-02-06 and 2015-02-09).
9
10
11
12
13
14
15
16
17
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
1,6
4,7 4,8 4,9 5 5,1 5,2 5,3 5,4
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
108% PIX VIS
87% PIX VIS
87% PIX with CaCl2 VIS
108% PIX UV
87% PIX UV
87% PIX with CaCl2 UV
39
Figure 4.2 Results from Experiment 4 (2015-02-10 and 2015-02-11).
Table 4.1 Results from Experiment 4A (2015-02-06).
Beaker 1 2 3 4 5 6
108% PIX (µl) 43 43 - - - -
87% PIX (µl) - - 34.4 34.4 34.4 34.4
NaOH 0.36% (µl) 950 950 220 220 220 220
CaCl2 (µl) - - - - 13.72 13.72
pH 4.88 4.79 5.04 4.97 4.88 4.89
VIS 1.1 1.49 0.779 0.769 0.724 0.83
UV 12.6 16.3 10.9 10.3 9.77 10.7
Table 4.2 Results from Experiment 4B (2015-02-09).
Beaker 1 2 3 4 5 6
108% PIX (µl) 43 43 - - - -
87% PIX (µl) - - 34.4 34.4 34.4 34.4
NaOH 0.36% (µl) 960 960 220 220 230 230
CaCl2 - - - - 13.72 13.72
pH 5.35 5.03 4.97 5.18 4.88 4.95
VIS 0.611 0.724 0.753 0.962 0.755 0.775
UV 9.3 9.22 10.2 13.1 9.95 10.4
Table 4.3 Results from Experiment 4C (2015-02-10).
Beaker 1 2 3 4 5 6
108% PIX (µl) 43 43 - - - -
8,5
9,5
10,5
11,5
12,5
13,5
14,5
15,5
16,5
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
1,6
4,8 4,9 5 5,1 5,2 5,3 5,4
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
108% PIX VIS
86% PIX VIS
86% PIX with CaCl2 VIS
108% PIX UV
86% PIX UV
86% PIX with CaCl2 UV
40
86% PIX (µl) - - 34.4 34.4 34.4 34.4
NaOH 0.36% (µl) 960 960 220 220 230 230
CaCl2 (µl) - - - - 13.72 13.72
pH 4.84 4.84 4.97 4.86 5.03 4.97
VIS 1.44 1.46 0.831 0.837 0.886 0.841
UV 15.5 15.8 10.9 10.6 11.6 11
Table 4.4 Results from Experiment 4D (2015-02-10).
Beaker 1 2 3 4 5 6
108% PIX (µl) 43 43 - - - -
86% PIX (µl) - - 34.4 34.4 34.4 34.4
NaOH 0.36% (µl) 965 965 220 220 230 230
CaCl2 (µl) - - - - 13.72 13.72
pH 5.2 5.32 4.9 5.25 4.9 4.98
VIS 0.709 0.613 0.785 1.08 0.746 0.778
UV 9.55 9.21 10.3 14.5 9.98 10.5
Table 4.5 Results from Experiment 4E (2015-02-11).
Beaker 1 2 3 4 5 6
108% PIX (µl) 43 43 - - - -
86% PIX (µl) - - 34.4 34.4 34.4 34.4
NaOH 0.36% (µl) 965 965 220 220 230 230
CaCl2 (µl) - - - - 13.72 13.72
pH 5.05 4.98 4.94 4.92 5.01 5.01
VIS 0.726 0.921 0.76 0.746 0.738 0.777
UV 9.36 11 10.2 10 10.3 10.5
Experiment 5- 40 mol% CaCl2
Setup: Optimum PIX dosage: 56.5 g, m-3 (2015-02-12 and 2015-02-17) and 56 g, m-3 (2015-02-13). Used PIX
dosage: 56.5 g, m-3. 40mol% CaCl2 based on 61g/m3 PIX dose. Addition of PIX with 3 seconds
remaining of rapid mixing.
41
Figure 5.1 Results from Experiment 5 (2015-02-12, 2015-02-13 and 2015-02-17).
Table 5.1 Results from Experiment 5A (2015-02-12).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 0 0 0 0
80% PIX (µl) 0 0 31.8 31.8 31.8 31.8
NaOH 0.36% (µl) 700 700 0 0 10 10
CaCl2 (µl) 0 0 0 0 13.72 13.72
pH 5.14 5.05 5.13 4.83 5.05 4.98
VIS 0.745 0.799 1.16 0.865 0.922 0.86
UV 10 10.2 15.1 11.1 12.5 11.6
Table 5.2 Results from Experiment 5B (2015-02-13).
Beaker 1 2 3 4 5 6
101% PIX (µl) 39.8 39.8 0 0 0 0
81% PIX (µl) 0 0 31.8 31.8 31.8 31.8
NaOH 0.36% (µl) 700 700 0 0 10 10
CaCl2 (µl) 0 0 0 0 13.72 13.72
pH 5.07 5.05 4.94 4.86 5.12 5.12
VIS 0.627 0.715 0.89 0.834 1.07 1.04
UV 8.76 9.43 11.7 10.9 14.1 13.8
8
10
12
14
16
18
20
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
1,6
4,7 4,9 5,1 5,3 5,5
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
100 to 101% PIX VIS
80 to 81% PIX VIS
80 to 81% PIX with CaCl2 VIS
100 to 101% PIX UV
80 to 81% PIX UV
80 to 81% PIX with CaCl2 UV
42
Table 5.3 Results from Experiment 5C (2015-02-13).
Beaker 1 2 3 4 5 6
101% PIX (µl) 39.8 39.8 0 0 0 0
81% PIX (µl) 0 0 31.8 31.8 31.8 31.8
NaOH 0.36% (µl) 700 700 0 0 10 10
CaCl2 (µl) 0 0 0 0 13.72 13.72
pH 5.16 4.9 5.05 5.01 5.13 5.11
VIS 0.666 0.989 0.99 0.892 1.13 1.07
UV 9.29 11.4 13.2 11.8 14.8 14.1
Table 5.4 Results from Experiment 5D (2015-02-17).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 0 0 0 0
81% PIX (µl) 0 0 32.2 32.2 32.2 32.2
NaOH 0.36% (µl) 700 700 0 0 10 10
CaCl2 (µl) 0 0 0 0 13.72 13.72
pH 5.1 5.07 5.15 5.03 5.09 5.21
VIS 0.689 0.744 1.27 0.894 1.03 1.36
UV 9.4 9.76 16.4 12.3 13.7 17.6
Table 5.5 Results from Experiment 5E (2015-02-17).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 0 0 0 0
81% PIX (µl) 0 0 32.2 32.2 32.2 32.2
NaOH 0.36% (µl) 700 700 0 0 10 10
CaCl2 (µl) 0 0 0 0 13.72 13.72
pH 4.98 5 4.92 5.07 5.03 4.98
VIS 0.763 0.771 0.858 0.976 0.91 0.952
UV 9.85 9.78 11.5 13.2 12.5 12.7
4.1.3. Experiment 6- 80 mol% CaCl2
Setup: Optimum PIX dosage: 56.5 g, m-3 (2015-02-18, 2015-02-19 and 2015-02-23). Used PIX dosage: 56.5 g,
m-3. 80mol% CaCl2 based on 61g/m3 PIX dose. Addition of PIX with 3 seconds remaining of rapid
mixing.
43
Figure 6.1 Results from Experiment 6 2015-02-18, 2015-02-19 and 2015-02-23.
Figure 6.3 Results from experiment 5 and 6.
Table 6.1 Results from Experiment 6A (2015-02-18).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 0 0 0 0
81% PIX (µl) 0 0 32.2 32.2 32.2 32.2
8
10
12
14
16
18
20
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
1,6
4,7 4,9 5,1 5,3 5,5
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
100% PIX VIS
81% PIX VIS
81% PIX with CaCl2 VIS
100% PIX UV
81% PIX UV
81% PIX with CaCl2 UV
8
10
12
14
16
18
20
0,5
0,7
0,9
1,1
1,3
1,5
4,7 4,9 5,1 5,3 5,5
UV
VIS
pH
UV-VIS
80 to 81% PIX VIS
80 to 81% PIX with 40% CaCl2 VIS
80 to 81% PIX with 80% CaCl2 VIS
80% PIX with 0,4g/l CaCl2 VIS
80 to 81% PIX UV
80 to 81% PIX with 40% CaCl2 UV
80 to 81% PIX with 80% CaCl2 UV
80% PIX with 0,4g/l CaCl2 UV
44
NaOH 0.36% (µl) 715 715 0 0 12 12
CaCl2 (µl) 0 0 0 0 27.4 27.4
pH 5.22 5.57 4.94 4.95 5.06 5
VIS 0.698 1.17 0.842 0.929 1.07 0.968
UV 9.71 15.9 11.4 12.3 13.9 12.8
Table 6.2 Results from Experiment 6B (2015-02-18).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 0 0 0 0
81% PIX (µl) 0 0 32.2 32.2 32.2 32.2
NaOH 0.36% (µl) 680 680 0 0 12 12
CaCl2 (µl) 0 0 0 0 27.4 27.4
pH 5.37 5.25 5.18 4.99 5.09 5.05
VIS 0.735 0.705 1.39 0.887 1.07 0.965
UV 10.8 10.1 17.7 12.1 14.2 13.1
Table 6.3 Results from Experiment 6C (2015-02-19).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 0 0 0 0
81% PIX (µl) 0 0 32.2 32.2 32.2 32.2
NaOH 0.36% (µl) 560 560 0 0 12 12
CaCl2 (µl) 0 0 0 0 27.4 27.4
pH 5 4.92 4.81 4.85 5.05 5
VIS 1.03 1.03 0.871 0.863 0.981 0.959
UV 12.1 12.1 11.3 11.3 13.1 12.7
Table 6.4 Results from Experiment 6D (2015-02-19).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 0 0 0 0
81% PIX (µl) 0 0 32.2 32.2 32.2 32.2
NaOH 0.36% (µl) 560 560 8 8 12 12
CaCl2 (µl) 0 0 0 0 27.4 27.4
pH 5.1 5.25 5.06 5.05 4.98 5.06
VIS 0.685 0.718 0.978 0.955 0.838 0.928
UV 9.26 10.3 13.2 12.9 11.5 12.6
Table 6.5 Results from Experiment 6E (2015-02-23).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 0 0 0 0
45
81% PIX (µl) 0 0 32.2 32.2 32.2 32.2
NaOH 0.36% (µl) 560 560 8 8 12 12
CaCl2 (µl) 0 0 0 0 27.4 27.4
pH 5 5.08 5.02 5.17 5.08 5
VIS 0.743 0.71 0.885 1.13 0.908 0.848
UV 9.74 9.68 12.2 15.1 12.5 11.6
Table 6.6 Results from Experiment 6F (2015-02-23).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 0 0 0 0
81% PIX (µl) 0 0 32.2 32.2 32.2 32.2
NaOH 0.36% (µl) 560 560 8 8 12 12
CaCl2 (µl) 0 0 0 0 27.4 27.4
pH 5.18 5.15 5.25 4.97 5.11 5.08
VIS 0.815 0.759 1.44 0.972 1.09 1.04
UV 10.3 9.95 18 12.7 14.3 13.9
Table 6.7 Results from Experiment 6G (2015-02-23).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 0 0 0 0
81% PIX (µl) 0 0 32.2 32.2 32.2 32.2
NaOH 0.36% (µl) 560 560 8 8 12 12
CaCl2 (µl) 0 0 0 0 27.4 27.4
pH 5.12 5.22 4.92 5.26 5.27 5.17
VIS 0.753 0.688 0.904 1.51 1.47 1.09
UV 10.2 9.89 11.9 18.6 18.2 14.2
6.1.1 Experiment 7 - 100%pix + 20 resp. 40 mol% CaCl2 based on 56.5g/m3
Setup:
Optimum PIX dosage: 56.5 g, m-3 (2015-02-25, 2015-02-26, 2015-03-10, 2015-03-11 and 2015-03-
12).Used PIX dosage: 56.5g, m-3. 20 and 40mol% CaCl2 based on 56.5g/m3 PIX dose. Addition of PIX
with 3 seconds remaining of rapid mixing.
46
Figure 7.1 Results from Experiment 7A to F (2015-02-25 and 2015-02-26).
Figure 7.2 Results from Experiment 7G to N (2015-03-10, 2015-03-11 and 2015-03-12).
8,5
9
9,5
10
10,5
11
11,5
12
12,5
13
13,5
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
4,7 4,8 4,9 5 5,1 5,2 5,3
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
100% PIX VIS
100% PIX & 20% CaCl2 VIS
100% PIX & 40% CaCl2 VIS
100% PIX UV
100% PIX & 20% CaCl2 UV
100% PIX & 40% CaCl2 UV
8,5
9
9,5
10
10,5
11
11,5
12
12,5
13
13,5
0,6
0,7
0,8
0,9
1
1,1
1,2
4,7 4,8 4,9 5 5,1 5,2 5,3
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV -VIS
100% PIX VIS
100% PIX with 20% CaCl2 VIS
100% PIX with 40% CaCl2 VIS
100% PIX UV
100% PIX with 20% CaCl2 UV
100% PIX with 40% CaCl2 UV
47
Figure 7.3 Results from Experiment 7A to N (2015-03-10, 2015-03-11 and 2015-03-12).
Table 7.1 Results from experiment 7A (2015-02-25).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 560 560 560 560 560 560
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 5.11 5.03 4.99 5.09 5.19 4.96
VIS 0.725 0.79 0.762 0.715 0.823 0.869
UV 9.64 10.1 9.8 9.47 10.8 10.4
Table 7.2 Results from experiment 7B (2015-02-25).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 560 560 560 560 560 560
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 4.97 5.02 5.02 5.05 4.99 5.05
VIS 0.817 0.73 0.721 0.74 0.701 0.729
UV 9.87 9.34 9.28 9.7 9.26 9.72
Table 7.3 Results from experiment 7C (2015-02-25).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 560 560 560 560 560 560
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 5.2 5.24 4.98 4.9 5.07 5.09
VIS 0.773 0.745 0.823 0.948 0.757 0.726
UV 10.3 10.3 10.2 11.3 9.99 9.89
8,5
9
9,5
10
10,5
11
11,5
12
12,5
13
13,5
0,6
0,7
0,8
0,9
1
1,1
1,2
4,7 4,8 4,9 5 5,1 5,2 5,3
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV -VIS
100% PIX VIS
100% PIX with 20% CaCl2 VIS
100% PIX with 40% CaCl2 VIS
100% PIX UV
100% PIX with 20% CaCl2 UV
100% PIX with 40% CaCl2 UV
48
Table 7.4 Results from experiment 7D (2015-02-26).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 560 560 560 560 560 560
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 4.79 4.94 4.93 4.95 4.97 4.98
VIS 1.05 0.999 0.788 0.835 0.766 0.802
UV 11.9 10.9 9.97 10.5 9.86 10.1
Table 7.5 Results from experiment 7E (2015-02-26).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 560 560 560 560 560 560
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 4.79 5.12 5.03 5.13 5.2 5.14
VIS 1.23 0.796 0.684 0.712 0.66 0.674
UV 13.2 10.4 9.13 10 9.7 9.67
Table 7.6 Results from experiment 7F (2015-02-26).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 560 560 560 560 560 560
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 4.88 4.83 5.03 5.13 4.94 4.86
VIS 0.928 1.03 0.706 0.758 0.77 0.83
UV 10.7 11.5 9.33 10.5 10.1 10.5
Table 7.7 Results from experiment 7G (2015-03-10).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 570 570 570 570 570 570
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 4.81 4.86 4.85 5.09 5.12 4.94
VIS 0.941 0.841 0.793 0.658 0.668 0.731
UV 11.3 10.5 10.1 9.38 9.63 9.66
Table 7.8 Results from experiment 7H (2015-03-10).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 570 570 570 570 570 570
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
49
pH 4.82 4.99 4.99 4.98 5.03 4.75
VIS 0.895 0.77 0.798 0.81 0.719 1.19
UV 10.7 10.1 10.2 10.2 9.51 12.8
Table 7.9 Results from experiment 7I (2015-03-11).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 640 640 640 640 640 640
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 4.95 5.04 5.18 4.83 4.97 5
VIS 0.8 0.675 0.71 0.873 0.666 0.654
UV 9.97 9.27 10.1 10.5 9.07 9.08
Table 7.10 Results from experiment 7J (2015-03-11).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 640 640 640 640 640 640
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 5.03 4.96 4.93 5.11 4.96 5.05
VIS 0.689 0.749 0.687 0.728 0.757 0.739
UV 9.36 9.75 9.11 9.74 9.55 9.71
Table 7.11 Results from experiment 7K (2015-03-11).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 640 640 640 640 640 640
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 4.93 4.9 4.98 5.13 4.92 5
VIS 0.762 0.878 0.783 0.714 0.755 0.683
UV 9.73 10.6 9.94 10.1 9.86 9.48
Table 7.12 Results from experiment 7L (2015-03-12).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 640 640 640 640 640 640
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 4.98 5.16 4.92 4.94 5.05 5.02
VIS 0.643 0.733 0.825 0.803 0.768 0.694
UV 8.93 10.3 10.2 10.1 10.2 9.47
50
Table 7.13 Results from experiment 7M (2015-03-12).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 640 640 640 640 640 640
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 4.97 5.18 5.15 5.07 5.02 4.99
VIS 0.738 0.7 0.745 0.709 0.773 0.818
UV 9.62 10 10.3 9.25 9.76 10.1
Table 7.14 Results from experiment 7N (2015-03-12).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 640 640 640 640 640 640
CaCl2 (µl) 0 0 6.36 6.36 12.72 12.72
pH 4.95 4.93 5 4.93 4.98 5.04
VIS 0.759 0.744 0.81 0.843 0.793 0.788
UV 9.73 9.63 10.4 10.3 9.97 10.1
51
4.2.2 Experiment 8 - 100% PIX + 40 resp. 80 mol% CaCl2
Setup:
Optimum PIX dosage: 56.5 g, m-3 (2015-03-17, 2015-03-18, 2015-03-19 and 2015-03-20).Used PIX
dosage: 56.5g, m-3. 40 and 80mol% CaCl2 based on 56.5g/m3 PIX dose. Addition of PIX with 3 seconds
remaining of rapid mixing.
Figure 8.1 Results from Experiment 8A to G (2015-03-17, 2015-03-18, 2015-03-19 and 2015-03-20).
Table 8.1 Results from experiment 8A (2015-03-17).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 680 680 680 680 680 680
CaCl2 (µl) 0 0 12.72 12.72 25.4 25.4
pH 4.93 4.9 4.9 4.9 5.01 5.02
VIS 0.647 0.753 0.737 0.713 0.673 0.694
UV 8.99 10 9.77 9.52 9.33 9.61
Table 8.2 Results from experiment 8B (2015-03-18).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 700 700 700 700 680 680
CaCl2 (µl) 0 0 12.72 12.72 25.4 25.4
pH 4.92 5.12 5.03 4.98 4.92 4.98
VIS 0.707 0.671 0.636 0.675 0.662 0.71
UV 9.47 9.72 9.03 9.42 9.24 9.71
8
9
10
11
12
13
14
0,5
0,55
0,6
0,65
0,7
0,75
0,8
0,85
0,9
0,95
1
4,8 4,9 5 5,1 5,2
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
100% PIX VIS
100% PIX with 40% CaCl2 VIS
100% PIX with 80% CaCl2 VIS
100% PIX UV
100% PIX with 40% CaCl2 UV
100% PIX with 80% CaCl2 UV
52
Table 8.3 Results from experiment 8C (2015-03-18).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 700 700 700 700 680 680
CaCl2 (µl) 0 0 12.72 12.72 25.4 25.4
pH 4.98 5.01 4.98 5.16 4.92 5.15
VIS 0.667 0.632 0.668 0.613 0.657 0.64
UV 9.06 8.9 9.08 9.45 9.06 9.67
Table 8.4 Results from experiment 8D (2015-03-19).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 700 700 700 700 680 680
CaCl2 (µl) 0 0 12.72 12.72 25.4 25.4
pH 4.89 5.07 5.07 4.95 4.92 5.04
VIS 0.639 0.64 0.596 0.694 0.645 0.592
UV 8.92 9.31 8.93 9.44 9 8.83
Table 8.5 Results from experiment 8E (2015-03-20).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 700 700 700 700 680 680
CaCl2 (µl) 0 0 12.72 12.72 25.4 25.4
pH 4.92 4.93 4.95 4.97 4.98 4.87
VIS 0.58 0.613 0.533 0.567 0.548 0.662
UV 8.63 8.98 8.33 8.7 8.58 9.17
Table 8.6 Results from experiment 8F (2015-03-20).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 700 700 700 700 680 680
CaCl2 (µl) 0 0 12.72 12.72 25.4 25.4
pH 4.96 4.91 5.01 5.03 5 5.07
VIS 0.669 0.671 0.604 0.593 0.61 0.62
UV 9.15 9.11 8.75 8.7 8.82 9.07
Table 8.7 Results from experiment 8G (2015-03-20).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 700 700 700 700 680 680
CaCl2 (µl) 0 0 12.72 12.72 25.4 25.4
pH 4.91 4.92 4.93 4.98 4.94 4.87
VIS 0.637 0.651 0.633 0.638 0.683 0.721
53
UV 8.93 9.07 8.92 9.11 9.34 9.59
Table 8.3 Average UV-VIS results from Experiment 8.
Experiment 8 pH Range Average pH Average VIS Average UV
100% PIX 4.89-5.12 4.96 0.656 9.16
100% PIX with 80% CaCl2 4.87-5,15 4.98 0.651 9.22
CaCl2 Effect -1% 1%
Experiment 9 - 100% PIX + 100% PIX with 40 % CaCl2
Setup:
Optimum PIX dosage: 56.5 g, m-3 (2015-03-26 and 2015-03-27).Used PIX dosage: 56.5g, m-3. 40mol%
CaCl2 based on 56.5g/m3 PIX dose. Addition of PIX with 3 seconds remaining of rapid mixing.
Figure 9.1 Results from Experiment 9A to F (2015-03-26 and 2015-03-27).
Table 9.1 Results from experiment 9A (2015-03-26).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 800 800 800 800 800 800
CaCl2 (µl) - - - 12.72 12.72 12.72
pH 4.93 5.02 5.02 5.01 5.09 5.04
VIS 0.637 0.566 0.571 0.596 0.659 0.639
UV 8.97 8.65 8.63 8.78 9.64 9.27
8,5
8,7
8,9
9,1
9,3
9,5
9,7
9,9
10,1
10,3
0,5
0,55
0,6
0,65
0,7
0,75
4,9 5 5,1 5,2 5,3
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
100% PIX VIS
100% PIX with 40% CaCl2 VIS
100% PIX UV
100% PIX with 40% CaCl2 UV
54
Table 9.2 Results from experiment 9B (2015-03-26).
Beaker 1 2 3 4 5 6
100% PIX (µl) x x 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) x x 920 920 920 920
CaCl2 (µl) x x - 12.72 12.72 12.72
pH x x 5.19 5.22 5.2 5.23
VIS x x 0.584 0.59 0.583 0.598
UV x x 9.03 9.22 9.05 9.35
Table 9.3 Results from experiment 9C (2015-03-26).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 920 920 920 920 920 920
CaCl2 (µl) - - - 12.72 12.72 12.72
pH 5.2 5.18 5.18 5.23 5.2 5.24
VIS 0.589 0.578 0.64 0.629 0.643 0.626
UV 9.22 9.09 9.47 9.46 9.58 9.51
Table 9.4 Results from experiment 9D (2015-03-27).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 940 940 940 940 940 940
CaCl2 (µl) - - - 12.72 12.72 12.72
pH 5.15 5.26 5.13 5.25 5.19 5.26
VIS 0.581 0.646 0.605 0.677 0.606 0.646
UV 8.81 9.92 9.03 10.1 9.25 9.91
Table 9.5 Results from experiment 9E (2015-03-27).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 940 940 940 940 940 940
CaCl2 (µl) - - - 12.72 12.72 12.72
pH 5.23 5.18 5.19 5.16 5.22 5.2
VIS 0.644 0.634 0.663 0.649 0.66 0.702
UV 9.89 9.65 9.86 9.56 9.89 10.2
Table 9.6 Results from experiment 9F (2015-03-27).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 940 940 940 940 940 940
CaCl2 (µl) - - - 12.72 12.72 12.72
pH 5.13 5.07 5.13 5.18 5.14 5.15
55
VIS 0.618 0.655 0.669 0.604 0.59 0.665
UV 9.32 9.47 9.71 9.3 9.08 9.86
Experiment 10 - 100% PIX + 100% PIX with 0.4 g/l CaCl2
Setup:
Optimum PIX dosage: 56.5 g, m-3 (2015-04-09).Used PIX dosage: 56.5g, m-3. Addition of PIX with 3
seconds remaining of rapid mixing.
Figure 10.1 Results from Experiment 10A (2015-04-09).
Table 10.1 Results from experiment 10A (2015-04-09).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 - - -
80% PIX - - - 31.8 31.8 31.8
NaOH 0.36% (µl) 850 850 850 120 120 120
CaCl2 (µl) 820 820 820 820 820 820
pH 5.05 5.05 5.05 4.95 4.95 4.95
VIS 0.766 0.762 0.785 1.02 1.03 1.06
UV 10.1 10.1 10.3 13.2 13.1 13.5
8
9
10
11
12
13
14
0,6
0,65
0,7
0,75
0,8
0,85
0,9
0,95
1
1,05
1,1
4,94 4,96 4,98 5 5,02 5,04 5,06
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
100% PIX with 0,4g/l CaCl2 VIS
80% PIX with 0,4g/l CaCl2 VIS
100% PIX with 0,4g/l CaCl2 UV
80% PIX with 0,4g/l CaCl2 UV
56
Experiment 11 - 100%Pix + 100%PIX with 40% CaCl2 aiming at 5.5ph
Setup:
Optimum PIX dosage: 56.5 g, m-3 (2015-04-10).Used PIX dosage: 56.5g, m-3. 40mol% CaCl2 based on
56.5g/m3 PIX dose. Addition of PIX with 3 seconds remaining of rapid mixing.
Figure 11.1 Results from Experiment 11A and B (2015-04-10).
Table 11.1 Results from experiment 11A (2015-04-10).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 1200 1200 1200 1200 1200 1200
CaCl2 (µl) - - - 12.72 12.72 12.72
pH 5.47 5.56 5.5 5.55 5.58 5.49
VIS 0.923 1.36 1.02 1.09 1.32 1.1
UV 13.1 18.1 14.3 15.1 17.5 15
Table 11.2 Results from experiment 11B (2015-04-10).
Beaker 1 2 3 4 5 6
100% PIX (µl) 39.8 39.8 39.8 39.8 39.8 39.8
NaOH 0.36% (µl) 1200 1200 1200 1200 1200 1200
CaCl2 (µl) - - - 12.72 12.72 12.72
pH 5.48 5.54 5.56 5.55 5.55 5.49
VIS 0.957 1.19 1.28 1.15 1.19 0.928
UV 13.6 16.2 17.2 15.8 16.4 13.4
12
13
14
15
16
17
18
19
0,8
0,9
1
1,1
1,2
1,3
1,4
5,46 5,48 5,5 5,52 5,54 5,56 5,58 5,6
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
100% PIX VIS
100% PIX with 40% CaCl2 VIS
100% PIX UV
100% PIX with 40% CaCl2 UV
57
Experiment 12- 43g/m3 ALG 40% by weight CaCl2 and 0.4g/l CaCl2
Setup:
ALG dose: 43g/m3. CaCl2 dose: 40% by weight based on 43g/m3 ALG dose (17.2mg/l) and 0.4g/l.
Addition of ALG when 3 seconds remain
Figure 12.1 Results from Experiment 12A to L (2015-04-14, 2015-04-15, 2015-04-16, 2015-04-17, 2015-04-20,
2015-04-22 and 2015-04-23).
Table 12.1 Results from experiment 12A (2015-04-14).
Beaker 1 2 3 4 5 6
ALG (µl) 215 215 215 215 215 215
NaOH 0.36% (µl) 1300 1300 1300 1300 1400 1400
CaCl2 (µl) - - 35.4 35.4 820 820
pH 5.93 5.96 5.97 5.95 5.97 6.00
VIS 0.687 0.728 0.777 0.689 1.02 1.06
UV 11.9 12.1 12.5 11.7 14.3 14.6
Table 12.2 Results from experiment 12B (2015-04-15). Flocculation was disturbed in beaker 1 and 2 for 1
minute during slow mixing due to complications with the flocculator. This seemed to effect the results in
limited ways.
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 1300 1300 1300 1300 1400 1400
CaCl2 (µl) - - 35.4 35.4 820 820
pH 5.99 6 5.97 5.96 6.01 6.05
10
11
12
13
14
15
16
17
18
19
20
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
5,9 6 6,1 6,2 6,3 6,4 6,5 6,6
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
ALG VIS
ALG with 40% CaCl2 VIS
ALG with 0,4g/l CaCl2 VIS
ALG UV
ALG with 40% CaCl2 UV
ALG with 0,4g/l CaCl2 UV
58
VIS 0.734 0.698 0.686 0.724 1.02 1.06
UV 12.1 11.8 11.5 11.8 14.1 14.3
Table 12.3 Results from experiment 12C (2015-04-15).
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 1300 1300 1300 1300 1400 1400
CaCl2 (µl) - - 35.4 35.4 820 820
pH 5.97 5.96 5.98 5.96 5.99 6.00
VIS 0.74 0.725 0.848 0.806 1.14 1.08
UV 12.1 11.8 12.9 12.4 14.9 14.5
Table 12.4 Results from experiment 12D (2015-04-16).
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 1300 1300 1300 1300 1400 1400
CaCl2 (µl) - - 35.4 35.4 820 820
pH 6.03 6.03 6.04 6.03 6.06 6.05
VIS 0.742 0.766 0.836 0.827 1.08 1.1
UV 12.2 12.4 12.9 12.8 14.7 14.7
Table 12.5 Results from experiment 12E (2015-04-16).
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 1300 1300 1300 1300 1400 1400
CaCl2 (µl) - - 35.4 35.4 820 820
pH 6.01 6.01 6.03 6.08 6.05 6.05
VIS 0.753 0.778 0.837 0.973 1.16 1.13
UV 12.1 12.3 12.8 14.2 15.1 14.9
Table 12.6 Results from experiment 12F (2015-04-17).
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 1700 1700 1700 1700 1800 1800
CaCl2 (µl) - - 35.4 35.4 820 820
pH 6.25 6.23 6.2 6.23 6.24 6.26
VIS 0.897 0.789 0.787 0.82 1.06 1.07
UV 14.2 13.1 12.7 13.3 15.2 15.4
59
Table 12.7 Results from experiment 12G (2015-04-17).
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 1700 1700 1700 1700 1800 1800
CaCl2 (µl) - - 35.4 35.4 820 820
pH 6.26 6.34 6.23 6.25 6.24 6.31
VIS 0.779 1 0.826 0.802 1.02 1.15
UV 13.1 15.7 13.2 13.2 14.9 16.3
Table 12.8 Results from experiment 12H (2015-04-20).
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 1900 1900 1900 1900 2000 2000
CaCl2 (µl) - - 35.4 35.4 820 820
pH 6.35 6.43 6.37 6.36 6.41 6.37
VIS 0.734 1.01 0.852 0.913 1.26 0.938
UV 13.1 16.1 14.1 14.7 17.4 14.9
Table 12.9 Results from experiment 12I (2015-04-22).
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 1900 1900 1900 1900 2000 2000
CaCl2 (µl) - - 35.4 35.4 820 820
pH 6.34 6.34 6.35 6.34 6.33 6.33
VIS 0.788 0.774 0.799 0.824 0.887 1.01
UV 13.5 13.5 13.6 13.9 14.6 15.3
Table 12.10 Results from experiment 12J (2015-04-22).
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 1900 1900 1900 1900 2000 2000
CaCl2 (µl) - - 35.4 35.4 820 820
pH 6.34 6.35 6.34 6.34 6.32 6.32
VIS 0.784 0.817 0.844 0.815 0.988 1.03
UV 13.3 13.8 13.8 13.7 15 15.1
Table 12.11 Results from experiment 12K (2015-04-23).
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 2150 2150 2150 2150 2250 2250
60
CaCl2 (µl) - - 35.4 35.4 820 820
pH 6.45 6.47 6.43 6.45 6.49 6.46
VIS 0.782 0.819 0.794 0.766 0.891 0.773
UV 13.8 14.5 13.8 13.8 15.1 14.1
Table 12.12 Results from experiment 12L (2015-04-23).
Beaker 1 2 3 4 5 6
ALG 215 215 215 215 215 215
NaOH 0.36% (µl) 2150 2150 2150 2150 2250 2250
CaCl2 (µl) - - 35.4 35.4 820 820
pH 6.47 6.5 6.47 6.47 6.45 6.46
VIS 0.761 0.867 0.727 0.784 0.792 0.806
UV 13.8 15 13.5 13.8 14.2 14.2
Experiment 13- 79% ALG 40% resp. 80% by weight CaCl2
Setup: ALG dose: 34g/m3. CaCl2 dose: 40 and 80% by weight CaCl2 based on 43g/m3 ALG dose (17.2mg/l
resp. 34.4g/m3). Addition of ALG when 3 seconds remain
Figure 13.1 Results from Experiment 13A to G (2015-04-28, 2015-04-29, 2015-04-30 and 2015-05-04).
10
12
14
16
18
20
22
0,6
0,8
1
1,2
1,4
1,6
1,8
5,9 6 6,1 6,2 6,3 6,4 6,5 6,6
UV
-ab
s (λ
=25
4 n
m/m
)
VIS
-ab
s (λ
=43
6 n
m/m
)
pH
UV-VIS
79% ALG VIS
79% ALG with 40% CaCl2 VIS
79% ALG with 80% CaCl2 VIS
79% ALG UV
79% ALG with 40% CaCl2 UV
79% ALG with 80% CaCl2 UV
61
Table 13.1 Results from experiment 13A (2015-04-28).
Beaker 1 2 3 4 5 6
ALG 170 170 170 170 170 170
NaOH 0.36% (µl) 1000 1000 1000 1000 1000 1000
CaCl2 (µl) - - 35.4 35.4 70.8 70.8
pH 6.01 5.98 6 6 6.01 6.01
VIS 0.782 0.856 0.895 0.86 0.858 0.885
UV 13 13.4 14 13.6 13.6 13.8
Table 13.2 Results from experiment 13B (2015-04-28).
Beaker 1 2 3 4 5 6
ALG 170 170 170 170 170 170
NaOH 0.36% (µl) 1000 1000 1000 1000 1000 1000
CaCl2 (µl) - - 35.4 35.4 70.8 70.8
pH 5.98 5.98 6 5.99 5.98 6.03
VIS 0.726 0.8 0.979 0.928 0.859 0.986
UV 12.3 13 14.5 14.1 13.5 14.8
Table 13.3 Results from experiment 13C (2015-04-29).
Beaker 1 2 3 4 5 6
ALG 170 170 170 170 170 170
NaOH 0.36% (µl) 1000 1000 1000 1000 1000 1000
CaCl2 (µl) - - 35.4 35.4 70.8 70.8
pH 6.17 6.17 6.15 6.15 6.15 6.14
VIS 1.61 1.56 1.48 1.44 1.25 1.33
UV 21.2 20.8 19.7 19.3 17.9 18.2
Table 13.4 Results from experiment 13D (2015-04-30).
Beaker 1 2 3 4 5 6
ALG 170 170 170 170 170 170
NaOH 0.36% (µl) 900 900 900 900 900 900
CaCl2 (µl) - - 35.4 35.4 70.8 70.8
pH 6.09 6.09 6.12 6.08 6.07 6.09
VIS 1.22 1.29 1.46 1.25 1.06 1.28
UV 17.9 18.5 20.1 17.9 16.3 17.9
Table 13.5 Results from experiment 13E (2015-04-30).
Beaker 1 2 3 4 5 6
ALG 170 170 170 170 170 170
NaOH 0.36% (µl) 900 900 900 900 900 900
CaCl2 (µl) - - 35.4 35.4 70.8 70.8
pH 6.09 6.1 6.08 6.08 6.11 6.07
62
VIS 1.27 1.37 1.22 1.16 1.24 1.22
UV 18.2 19.1 17.6 17.2 18.2 17.6
Table 13.6 Results from experiment 13F (2015-05-04).
Beaker 1 2 3 4 5 6
ALG 170 170 170 170 170 170
NaOH 0.36% (µl) 1100 1100 1100 1100 1100 1100
CaCl2 (µl) - - 35.4 35.4 70.8 70.8
pH 6.17 6.16 6.15 6.16 6.16 6.17
VIS 1.33 1.38 1.3 1.34 1.07 1.25
UV 19.1 19.5 18.3 19 16.7 18.4
Table 13.7 Results from experiment 13G (2015-05-04).
Beaker 1 2 3 4 5 6
ALG 170 170 170 170 170 170
NaOH 0.36% (µl) 1100 1100 1100 1100 1100 1100
CaCl2 (µl) - - 35.4 35.4 70.8 70.8
pH 6.18 6.18 6.17 6.17 6.16 6.17
VIS 1.32 1.36 1.26 1.25 0.958 1.11
UV 18.9 19.3 18.3 18.2 15.5 17
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