Griffith School of Engineering
7605ENG Industrial Affiliates Program
Final Project Report
The Flocculating Effect of Magnesium Chloride in a Magnapool™ System
Nonso Okafor
2709055
Submitted:
June 25th
Semester 1, 2011
Industry Partner:
Poolrite Research
Industry Supervisor:
Wayne Taylor
Academic Advisor:
Jimmy Yu
A report submitted in partial fulfilment of the requirements for the Master of
Engineering degree in Environmental Engineering
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
Executive Summary
In the wake of increasing stringency in the operating guidelines of the swimming pool
industry, due to recent disease outbreaks and infections being linked with swimming pool water
(Croll et al, 200; Glauner et al, 2005; Perkins, 200; Zwiener et al, 2007; WHO, 2006),
Poolrite Research Pty Ltd. has patented a salt blend rich in magnesium chloride, which they
believe, improves pool water quality by clarification. In the absence of hard facts to
substantiate their marketing claim and to promote public acceptance of this hybrid system,
Poolrite requested for independent research to be conducted by Griffith University to
investigate the flocculating effect of magnesium chloride (MgCl2) in a Magnapool™ System.
This report outlines the concepts behind this study with details on all the investigative
approaches (research and experimental), materials, methods and performance evaluation
criteria used in assessing flocculation performance.
The process of ensuring water clarity as well as controlling the presence of pathogens in a
swimming pool is crucial (Perkins, 2000). This can be achieved by the removal of suspended
and colloidal matter in the pool water body so as to ensure bather safety from diseases by the
removal of particles that shield micro-organisms from the action of disinfectants (WHO,
2006).
Flocculation has been defined as a process whereby destabilised or dispersed particles are
brought together to form aggregate flocs of size, large enough to cause their settling and bring
about clarification of the system. This process occurs by various mechanisms namely;
adsorption and surface charge neutralization, sweep flocculation, electrical double layer
compression and inter-particle bridging. The adsorption and surface charge neutralisation
mechanism was found to be the mechanism by which most hydrolysing inorganic metallic
salts, such as MgCl2, flocculate. Thus, the two stages of the flocculation process according to
Bratby, (2006) are the Perikinetic flocculation stage which ensues from thermal agitation,
usually referred to as Brownian movement and is a naturally random process, and the
Orthokinetic flocculation stage that starts immediately after flash mixing, due to induced
velocity gradients that arise in the slow mixing regime, thereby causing increased particle
contraction and consequent agglomeration of these particles.
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Flocculation in water treatment however, has been carried-out from time immemorial using
aluminium sulphate (generally known as alum) and other chloride salts of aluminium and
Iron. Following several concerns raised by experts in water treatment on the use of these
salts, there is now the need for the use of more environmentally sustainable chemicals in
water treatment. Turbidity reduction was the utmost criteria on which flocculation
performance was based in this study.
A review of previous studies in flocculation showed that MgCl2 had been used in some
industrial processes such as in the dye industry, for colour removal from the waste water. A
Capsule Reports from the USEPA (2010) claimed the use of recycled Magnesium for
coagulation purposes. A study by Karami (2009) showed that magnesium ion can be used to
effect modification on the shape of colloidal particles
In a view to substantiate the numerous literature evidence, experimental investigation became
imperative. The testing approach was aimed at establishing whether the Magnapool™ salt
blend does act as a flocculant in water treatment. Experimental investigations were performed
to comparatively asses the flocculation performance obtainable in the Magnapool™ System
with respect to a traditional salt water pool that uses NaCl as its flocculant. The optimum
dosing rate for the Magnapool™ mineral blend was also investigated and the actual
concentration/effect of MgCl2 in the salt blend determined.
This experimental investigation employed the Jar Tester as the main apparatus.
Contaminated water was simulated by dissolving 0.4grams of ISO test dust in 2000ml of tap
water in each jar. Specific amounts of flocculant salts were added while other water
parameters adjusted (pH, system temperature and conductivity) so as to simulate a typical
Magnapool™ operating condition, before mixing stages ensued on the four separate stirring
points of the Jar Tester having pre-programmed the stirrers to run at 120rpm for two mins
(Flash mixing stage) and at 20rpm for the slow mixing stage. Variable settling time, number
of reading, and at times, duration of mixing was varied across some of the test runs as
required.
Results from the experiments showed that the Magnapool™ salt blend is a highly effective
flocculant, as it reduced water turbidity from 175FTU to 40 FTU within a one hour settling
time. The optimum performing mineral concentration was found to be 3350ppm, although the
margin with which it out-performed other concentrations within the range of 3000-3500FTU
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The Flocculating Effect of MgCl2
was marginal. Experimental results also showed that the active floccing agent ingredient in
the Magnapool™ mineral blend is the divalent inorganic hydrolysing salt of MgCl2 at a
concentration of 500ppm, whose variation in turbidity reduction potential, when used in
isolation from other salts in the mineral blend compared to the reduction in turbidity achieved
with a complete Magnapool™ mineral blend was marginal (48FTU and 40 FTU
respectively). Its flocculating mechanism is by adsorption and charge neutralization, using
the positive magnesium ion Mg2+ to neutralise the surface charge of the negative colloidal
particles and subsequently precipitates these contaminants in water by formation of Mg
(OH)2. However, water properties such as pH and alkalinity were found to be highly
influential in dictating flocculation performance. The optimum pH of the Magnapool™
mineral was determined to be 7.5
Overall, the Magnapool™ system performed better than a traditional Salt-water pool in terms
of turbidity reduction, as the tests were performed under the same conditions and consistent
initial water quality characteristics. Based on the literature research and experimental
outcomes, recommendations were made for a continued use of the Magnapool™ mineral as a
flocculant in swimming pool water treatment and also on the possible exclusion of NaCl in
the mineral blend since it showed no flocculation tendencies. Again, further research into this
study area was recommended so as to establish the combined effect of Poolrite‟s
Magnapool™ mineral blend and DiamondKleen™ on the final turbidity residual of in the
swimming pool water recirculation cycle and also to determine the extent to which the
Magnapool™ mineral constributeses to bio-fouling of the swimming pool filter media.
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The Flocculating Effect of MgCl2
Acknowledgements
The successful completion of this project relied on the unreserved support, motivation,
encouragement and technical assistance rendered to me by a number of people, to whom I
wish to express my sincere appreciation.
The Quality Engineering Group of Poolrite Research Pty Ltd was simply sensational in the
way they harboured and made me part of the team that engineers the company‟s products and
services. I‟m extremely grateful to Wayne Taylor my industry Supervisor, whose effort;
expert and technical initiatives stood out and ultimately provided guidance from inception
though to the completion of this project. Your unflinching support was key to the success of
this project, thank you Wayne. Special thanks to the Boss of the department, Aaron Kelly for
ensuring that work tools and materials were never an issue all through the project cycle. And
to Stuart Anderson, who dedicated his time immensely to ensure that I was always making
progress in my work, I say a huge thank you. Also thanking Jennifer Campbell, a co-student
who ran another project alongside mine, for her co-operation and comradeship all through the
project duration.
I humbly express my profound gratitude to my academic advisor Dr Jimmy Yu, for his
scholarly advice and guidance which helped me maintain track in the project. Thanking you
especially for your patience and understanding while I completed my designated project
tasks. My sincere appreciation also goes to the IAP convenor Dr Graham Jenkins for his
unreserved support and encouragement.
I am grateful to my Uni mates and friends for supporting, encouraging and being there for me
in one way or the other. Special thanks to Matilda Ofosu for her unflinching support and
assistance in reviewing and proof-reading all my assessment item drafts, also to Bahar Nader,
Jay-Jay Okocha, Akin Ajayi, Connie and Sharoo Mkandawire for their assistance.
Finally, I acknowledge the Almighty God, for giving me the wisdom, knowledge and
understanding to see this project to a successful end.
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The Flocculating Effect of MgCl2
Nomenclature
FTU:
Formazin Turbidity Unit
Ksp:
Solubility product constant
mg/l:
Milligrams per litre
rpm:
Revolutions per minute
ppm:
Parts per million
conc:
Concentration
THMs:
Trihalomethanes
β:
Collision frequency
∝:
Collision efficiency
G:
Velocity gradient
ζp:
Zeta potential of particles
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The Flocculating Effect of MgCl2
Contents
Executive Summary.........................................................................................................................1
Acknowledgement..........................................................................................................................4
Nomenclature.................................................................................................................................5
Part I: Introduction..........................................................................................................................8
1 Project Description ............................................................................................................... 10
1.1 Project Scope .............................................................................................................................. 10
1.2 Project Team ............................................................................................................................... 11
1.3 Project Plan ................................................................................................................................. 11
1.4 Project report Outline ................................................................................................................. 11
Part II: Swimming Pool Water Treatment Concept........................................................................13
2 Swimming Pool Water Treatment Process .............................................................................. 13
2.1 Nature and Categories of Swimming pool water Contaminants ................................................ 13
2.2 Swimming Pool water Treatment System................................................................................... 14
3 Existing Legislation ................................................................................................................ 15
4 Overview of Coagulation/ Flocculation in water treatment ..................................................... 17
4.1 A brief history of Coagulation/Flocculation in water treatment ................................................ 17
5 Colloidal Stability and Destabilisation in Water Solution ......................................................... 18
5.1 Colloidal Stability......................................................................................................................... 18
5.2 Destabilisation of Colloidal systems............................................................................................ 19
6 Nature and Categories of Flocculants ..................................................................................... 21
6.1 Inorganic flocculants ................................................................................................................... 21
6.2 Organic flocculants...................................................................................................................... 22
7 MgCl2 as a Flocculant Swimming pool Water Treatment ......................................................... 23
7.1 Magnesium Chemistry ................................................................................................................ 23
7.2 The Solubility Product of MgCl2 .................................................................................................. 24
7.3 Practical Evidence of MgCl2 as a Flocculant ................................................................................ 25
Part III: Flocculation Theory and Process Kinetics..........................................................................27
8 The Science and Process of Flocculation ................................................................................. 27
8.1 Mechanisms of Flocculation ....................................................................................................... 28
8.1.1 Surface Charge Neutralization ............................................................................................. 28
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8.1.2 Double-Layer Compression .................................................................................................. 29
8.1.3 Inter-particle Bridging .......................................................................................................... 30
8.1.4 Sweep Flocculation .............................................................................................................. 30
8.2 Flocculation Kinetics ................................................................................................................... 31
8.2.1 Perikinetic Flocculation ........................................................................................................ 31
8.2.2 Ortho-Kinetic Flocculation ................................................................................................... 32
9 Flocculation Models............................................................................................................... 33
9.1 The Smoluchowski Model ........................................................................................................... 33
9.2 The Argaman Kaufman Model .................................................................................................... 34
9.3 The Population Balance Equation Based Model ......................................................................... 35
10 Evaluation of the practicality of Flocculation models in Swimming Pool Water Treatment
Process ...................................................................................................................................... 36
Part IV: Experimental Design and Methodology............................................................................37
11 Summary of previous Flocculation Experiments at Poolrite ................................................... 37
12 Summary of Academic Review on Experimental Methodology ............................................. 38
13 Project Experimental Design ................................................................................................ 40
13.1 Aims........................................................................................................................................... 40
13.2 Experimental Approach ............................................................................................................ 40
14 Experimental Setup............................................................................................................. 41
14.2 Jar Test Experimental Procedure .............................................................................................. 44
Part V: Results and Discussions.....................................................................................................46
15 Comparative Analysis: Magnapool™ mineral blend Vs NaCl ................................................. 46
15.1 Clarification Test using a typical Magnapool™ mineral blend .................................................. 46
15.2 Clarification Test using NaCl ..................................................................................................... 48
16 Clarification Performance of Magnapool™ mineral blend over Time ....................................... 49
17 Test on the Effect of pH on Flocculation Performance ........................................................... 51
18 MgCl2 in Isolation from the Magnapool™ Blend ................................................................... 52
19 Effect of Contaminant Loading on Flocculation ..................................................................... 53
20 Tests for the Optimum Magnapool™ Flocculant Dose ............................................................. 54
Part VI: Conclusions and Recommendations..................................................................................56
21 Conclusions ......................................................................................................................... 56
21.1 The Magnapool™ salt blend “An Effective Flocculant”............................................................. 56
21.2 MgCl2 is” Key” to the Efficacy of Magnapool™ Mineral as a Flocculant ................................... 56
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21.3 The Magnapool™ provides a safer water environment compared to a Traditional Salt Water
Pool ................................................................................................................................................... 56
21.4 Flocculation Efficiency is highly influenced by Water Chemistry ............................................. 57
22 Recommendations ............................................................................................................... 57
References................................................................................................................................. 58
APPENDICES .............................................................................................................................. 62
List of Tables
Table 1: Project Team Members....................................................................................................11
Table 2: An Outline of the final report..........................................................................................12
Table 3: Operational Guidelines in Swimming Pool water treatment in Australia..........................15
Table 4: Properties of common metallic ions................................................................................24
Table 5: Summary of flocculation previous experiments...............................................................38
Table 6: Blend Information of the Magnapool™ mineral ..............................................................44
(Adapted from Magnapool blend Worksheet)
List of figures
Fig 1: A typical pool water treatment process.........................................................................................................13
Fig 2: Size range of colloidal particles of concern in water treatment .........................................................17
(Adapted from Labreche & Aiyagari, 1997).
Fig 3: The DLVO theory representation........................................................................................................................18
(Adapted from Sincero and Sincero 2003)
Fig 4: A schematic representation of the electrical double layer concept ...................................................19
(Malvern Instruments Ltd, 2011)
Fig 5: A Schematic of the mechanism of colloidal silica modification by Mg+2...........................................25
Fig 6: Deposition of metal hydroxide species on oppositely charged particles...........................................28
(Adapted from Duan & Gregory 2002)
Fig 7: A negatively charged particle surrounded by a charged double layer..............................................29
Fig 8: A diagrammatic representation of a Jar Test Set-Up................................................................................42
Fig 9 (a-d): Experimental Wares and Flocculant Salt samples .........................................................................42
Fig 10: A Pictorial of Jar Testing in Progress ...........................................................................................................43
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Fig 11: Total Alkalinity Vs Magnapool™ Mineral Dose..........................................................................................46
Fig 12: A Plot of Turbidity Residual Vs MgCl2 Dose.................................................................................................46
Fig 13: Total Alkalinity Reduction Vs NaCl Dose......................................................................................................48
Fig 14: A Plot of Turbidity Residual Vs NaCl Dosage..............................................................................................48
Fig 15: A Plot of Turbidity Reduction over Time......................................................................................................50
Fig 16: A Plot of pH Effect on Turbidity Reduction.................................................................................................51
Fig 17: Plot of Turbidity Residual Vs Concentrations of MgCl2.....................................................................................................................52
Fig 18: Turbidity reduction Vs Time (Varying Initial sample water turbidity)..........................................53
Fig 19: A Plot of Turbidity Reduction Vs Time...........................................................................................................54
(At 3000-3500ppm Magnapool™ Mineral Range)
Fig 20: Turbidity Reduction over Time (Magnapool™ Vs Normal Salt Water Pool)................................55
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The Flocculating Effect of MgCl2
Part I: Introduction
This report has been compiled in accordance with the requirements of the Industrial Affiliates
Program, ran by Griffith University with a project offering by the industry partner, Poolrite
Research Pty Ltd. The determination of “The Flocculating Effect of Magnesium Chloride in
a Magnapool™ System” is the project aim, set-out by the industry partner. Thus, this
document reports on all the investigative steps and approaches adopted towards completion
of the project, the conclusions drawn from the outcomes of the investigations and some
recommendations based on the project findings.
1 Project Description
The Magnapool™ system, a brand name in the swimming pool industry has been patented by
Poolrite Pty Ltd. This system has been claimed by the patents to employ a technology that
uses a hybrid salt blend, rich in magnesium ion to generate swimming pool water
disinfectants, while maintaining very high water clarity (minimal turbidity) in the pool. In the
absence of prior exhaustive research and technical data to support their claims, Poolrite
Research has requested that the flocculating effect of magnesium chloride as in water
treatment be researched and experimentally tested.
1.1 Project Scope
In line with the requirements and specifications outlined by the industry partner, the project
completion will be achieved by;

Extensive research into the science and mechanism of flocculation

Standard experimental testing and reporting
o Comparatively analyse the potency of the Magnapool™ mineral against
conventional pool salt.
o Determine the optimum dosage of the Magnapool™ mineral
o Quantify the correct amount of MgCl2 that yields the best floccing effect in
the Magnapool™ mineral blend.
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
The Flocculating Effect of MgCl2
A draft of a final project report with conclusions and recommendations based on the
project findings, for chemical optimization in the overall swimming pool water
sanitation process
1.2 Project Team
The completion of this project involved active interaction between the three keys members
that make up the project team is presented in the table below;
Table 1: Project Team Members
Team Member
Nonso Okafor
Department of Environmental Engineering
Griffith University
Wayne Taylor
Chief Engineer
Poolrite Research
Dr Jimmy Yu
Senior Lecturer
Griffith University
Role
Project Facilitator
Industry Project Supervisor
Academic Advisor
1.3 Project Plan
A planning report was developed in the earlier stages of the project for an efficient
management and timely achievement of the project deliverables. The project however, was
broken down into several milestones, which had to be accomplished towards achieving the
required project outcomes.
This planning report therefore detail the stages, tasks, approaches and methodology to be
adopted in achieving the project deliverables together with a review of some risk factors that
might affect the progress and completion this project. These can be found in the project
planning report document in appendix A.
1.4 Project Report Outline
The structure in which the entire project work was carried towards achieving the expected
deliverables of has been outlined in the table below. As it bears the summary of the major
tasks completed and their relevance towards achieving the milestones set-out in the planning
phase of the project.
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The Flocculating Effect of MgCl2
Table 2: An Outline of the Final Report
Structure of the Final Report
Section
Report
Project Deliverable
Part I: Project Introduction
Project Planning Report
Part II: Swimming Pool
Milestone 1
Literature Review
Milestone 1
Literature Review
Milestone 2
Test Set-up
Milestone 3
Experimental Results and
Water Treatment Concepts
Part III: Flocculation
Theories and Kinetics
Part IV: Experimental
Design and Set-Up
Part V: Experimentation and
Data Collation
Part VI: Conclusions and
Recommendations
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Outcomes
Milestone 4
Data Analysis and Technical
Report
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The Flocculating Effect of MgCl2
Part II: Swimming Pool Water Treatment Concept
2 Swimming Pool Water Treatment Process
Swimming over the years has gained a tremendous popularity as one of the most enjoyable
and satisfying physical activity to indulge in (PWTAG, 2009). In Australia for instance, and
particularly Queensland, there is a big history of recreational activities involving water due to
its climatic conditions (QLD Health, 2003). Zwiener et al (2007) also suggested there are
health benefits associated with swimming as compared to land based recreational activities.
However, several bacterial, fungal and other infectious disease outbreaks have been linked to
the use of swimming pools in recent times (Croll et al, 200; Glauner et al, 2005; Perkins,
2000; Zwiener et al, 2007; WHO, 2006) and this has triggered the regard for pool and
recreational waters as a health priority all round the globe (Zwiener et al, 2007). Following
this trend, there has been a rise in the standard at which these pools are run as regulated by
bodies such as the World Health Organisation, and these guidelines tend to enshrine the core
principles involved in managing pool water (PWTAG, 2009, WHO, 2006).
2.1 Nature and Categories of Swimming Pool Water Contaminants
Bathers in swimming pool may be at risk of contracting infections caused by a number of
micro-organisms in contaminated pool water. The nature of these contaminants (Croll et al,
2007; QLD Health, 2003; Li et al, 2007; WHO, 2006) may be;

Organic: These are usually transmitted into the water body by bathers in the form of
faeces, dead skin, hair, mucus from nose, saliva releases from mouth, accidental
vomit and organic nitrogen compounds of sweat and urine.

Inorganic: These sorts of contaminants could be in the form of sunscreens applied by
pool patrons on their skin and their hair lotions
The nature of pool contaminants highlighted above is conventional with all kinds of
swimming pools, be it an indoor or outdoor set-up. However, another category of
contaminants exist, which are predominantly found in outdoor pools. They are not necessarily
introduced into the pool by the activities of the bathers; rather they originate from
environmental sources (Zwiener et al). Some examples of this category of contaminants
include; silt, sand, grasses and leaves.
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2.2 Swimming Pool Water Treatment System
Ensuring water clarity as well as controlling the presence of pathogens in a swimming pool is
crucial (Perkins, 2000). These could be achieved by the removal of suspended and colloidal
matter in the pool water body so as to ensure bather safety from diseases by removal of
particles that shield micro-organisms from the action of disinfectants (WHO, 2006). An
effective swimming pool water treatment system provides an attractive appearance of the
pool and makes it appealing to swim in (SAHCC, 1992). The figure below shows the layout
of a typical pool treatment system (WHO, 2006).
Coagulant/Flocculants Dosing
Strainer
Pump
Filtration
Water disinfection
pH correction dosing
Balance Tank
Swimming Pool
Fig 1: A typical pool water treatment process
The swimming pool water treatment system above, integrates most of the key
water/wastewater treatment processes of coagulation, filtration and disinfection in a
recirculating loop (PWTAG, 2009). Considering the high level of contamination usually
generated by bathers, swimming pool water can be characterised as a wastewater. Therefore,
the treatment process is designed to comply with the standards of wastewater as well as
drinking water.
The removal of dissolved colloidal particles or suspended material from the pool water is the
main target of every pool water treatment system, as it improves the overall efficiency of the
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entire treatment process. By way of clumping these dissolved colloidal materials together,
they are more easily trapped in the filtration system (PWTAG, 2009; WHO, 2006). This is
enhanced by the process of Flocculation/ Coagulation.
3 Existing Legislation
There are some regulations and guidelines that govern swimming pool water treatment and
management practices both internationally and in Australia. Some of these have been
outlined below according to what each regulation/standard tries to achieve.
Table 3: Operational Guidelines in Swimming Pool water treatment in Australia
(adapted from Poolrite Research (2010), Technical Manual, The Magnapool™ System)
Standards/Regulations/Guidelines
Health Protection
Targets/Requirements
Queensland Public Health, Swimming and
Spa pool Water Quality and Operational
Guidelines



Filtration criteria
Chemical parameters
Testing & recording requirements
Queensland Development Code 2008NMP 1.9, Swimming pool and Spa
Equipment
Australian Pesticides and Veterinary
Medicines Authority (APVMA)
South Australian Health Commission,
Department of Human Services-Standard
for the Operation of Swimming Pools and
Spa Pools in South Australia
Standards Australia, AS 3633-1989,
Private Swimming Pools – Water Quality


Disinfection system
Water Chemistry

Efficacy criteria for pool and Spa
sanitizers
Water Clarity
Disinfection and treatment of water
Breakpoint chlorination
Pool pollution
Chemical and Sanitizer
concentrations
Pool water maintenance
Good practice for by-product
formation minimisation e.g.
disinfection systems with less
chlorine use
Chemical hazards
Exposure to disinfection byproduct
Prediction of life time swimmer
cancer exposure risk to disinfection
by products e.g. Trihalomethanes
Operation and maintenance
Hydraulics and circulation
World Health Organisation, Guidelines for
Safe Recreational Water Environment, Vol
2, Swimming Pools and Similar
Environments, 2006







US EPA, SWIMODEL Exposure Estimation



Pool Water Treatment Advisory Group
(PWTAG), UK-Swimming Pool Water, 2009


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Northern Territory Government,
Department of Health and Families- Public
Health Guidelines for Aquatic Facilities,
August 2006
Environmental Protection
Queensland Environmental Protection Act
1994
Queensland Environmental Protection
(Water) Policy
Australian Pesticides and Veterinary
Medicines Authority
Brisbane City Council, Urban Management
Division, Subdivision and Development
Guidelines, Part C. Water Quality
Management Guidelines-Section 11
Discharges from Swimming Pools, 2000
Environmental Sustainability
Royal Life Saving Society Australia- Best
Practice. Profile Swimming Pools
Maximising Reclamation and Reuse, 2006
The Flocculating Effect of MgCl2













Queensland Government, Department of
Natural Resources and Water

Queensland Water Commission –WG-20,
Water Efficiency Management Plan
(WEMP) for Outdoor Water use at Public
Pools that use less than 10MegaLitres per
year
Government of Western Australia,
Department of Water- Water Quality
Protection Note WQPN 55, Swimming
Pools, February 2009

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



Pool water chemistry
Design and Construction
Circulation and Water Treatment
systems
Water quality testing
Sanitation and operational
requirements
Sect 119- ‘Unlawful environmental
harm’ from an unauthorised act or
omission that causes serious or
material harm
Sect 32- Total water cycle
management method and planning
Exemption of chemical registration
of salt water chlorinators.
Minimise discharges of pool water
to storm water
Encourage development of filters
and chemical regimes that protect
human health
Implementation of water saving
strategies
Installation of ultra fine filtration
systems to reduce backwash
frequency and cycle time
Include technical water saving and
reuse strategies in pool planning
and design
Typical Salinity limits for waters,
including salt water swimming
pools
Water efficiency benchmark
(L/visitor/day)
Decrease backwash frequency
Measure filter loading with
pressure gauges
Wastewater disposal- recycling to
pool
Wastewater disposal- garden
irrigation
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4 Overview of Coagulation/ Flocculation in water treatment
In water treatment, sedimentation of particles may take place naturally, due to the action of
the force of gravity, in situations of large particles. However, some particles will not settle,
due to their chemical interaction with water. An example of such a case as suggested by Faust
and Aly (1983) are the hydrophilic compounds in water.
The process in which destabilisation of particles takes place by the reduction of the repulsive
potential of the electrical double layer, which in turn forces agglomeration and clumping
together of the suspended material, and bringing them out of the solution is called
coagulation/flocculation (Fasemore, 2004; PWTAG, 2009; Zweiner et al, 2007). These
destabilized particles are brought together to form aggregates normally referred to as „flocs‟,
and these are large enough in size to sediment and are eventually separated from the water.
4.1 A brief history of Coagulation/Flocculation in water treatment
Clarification and particle removal during water treatment has been practiced from time
immemorial, using various substances as agents of coagulation. At about 2000BC, the
Romans used chemical coagulants such as alum Al2(SO4)3) for particle removal in water
while the ancient Egyptians used fine crushed smeared almond to clarify water that had been
fetched from the river, by dipping an arm into the water to properly disperse the crushed
almonds for clarification to occur (Faust & Aly, 1983; Bratby, 2006; Fasemore 2004).
In England as suggested by Bratby (2006), alum was more widely used in the treatment of
municipal water supplies. However, iron coagulants were more frequently used as flocculants
in the Americas, as Isiah Smith Hyatt in 1884 patented the use of ferric chloride for water
treatment for the New Orleans water company (Fasemore, 2004).
In modern water treatment practices however, coagulation and flocculation continues to play
a vital role in the overall success of the entire water treatment process. A recent engineering
survey on the quality of water treatment from over 20 water treatment plants have concluded
that chemical pre-treatment of water before the filtration process is the most crucial step, on
which the success of the treatment plant relies (Bratby, 2006).
Hence, the critical nature of the flocculation process in water treatment has now called for a
better understanding of the dynamics and mechanism of the process, considering the
increasingly stringent requirements on particulate removal in water treatment.
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5 Colloidal Stability and Destabilisation in Water Solution
A colloidal system is a medium in which particulates of different size interact but with the
highest particle diameter no greater than 10µm. In this system, the particles that settle due to
gravity have a maximum settling velocity of 0.01cm/sec while remaining particles are held in
suspension (Faust & Aly, 1983).
Molecular
Ultra-fine
Fine
Coarse
Fig 2: Size range of colloidal particles of concern in water treatment (Adapted from
Labreche & Aiyagari, 1997).
In water systems, most solids are usually present in the form of suspended particles, colloids
dissolved solids and molecules. These particles range in size from very large to typically
small particles. Sand particles in the water system have the largest particle size, followed by
microbes in water such as viruses, algae and bacteria (Fasemore, 2004). However, colloids
are very fine particles with diameters between 10nm and 10µm. (Binnie et al, 2002). Coarse
or fine particles are easy to remove by settlement or filtration. Molecules cannot be removed
by these physical processes, unless after precipitation. Therefore, the removal of colloids is
usually the main focus and the most challenging in water treatment processes (Binnie et al,
2002).
5.1 Colloidal Stability
Stability in a colloidal system simply refers to the ability of the particles to remain
independently within a given dispersion (Bratby, 2006). Kovalchuk et al (2009) described
the stability of a colloidal system as an important characteristic since it is determined by the
net balance of the attractive and repulsive forces that exists between the particles in a
colloidal system. The DLVO theory considers colloidal interactions, taking into account their
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dispersion and electrostatic forces. This theory suggests that coagulation occurs when
identical particles make up the composition of a suspension, where the resultant effect of the
dispersion forces is attraction (Kovalchuk et al, 2009).
Fig 3: The DLVO theory representation (Adapted from Sincero and Sincero 2003)
Ideally, the stability of a colloidal dispersion is enhanced by the interfacial forces (Bratby,
2006) due to;

The presence of a surface charge at the colloid-liquid interface

Hydration of the surface layers of the colloid.
In most water treatment conditions, colloidal particles usually possess a negative surface
charge while exhibiting a dipolar characteristic of hydrophilicity (water-loving tendency) and
hydrophobicity (water repelling tendency).
5.2 Destabilisation of Colloidal systems
Destabilisation of a colloidal system may occur as a result of;

a reduction in the effective surface charge of a particle

a reduction in the number of adsorbed water molecules

a reduction in the zone where the surface charge acts.
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These factors cause the particles to approach close enough to each other and are consequently
held together by the Van der Waals force of attraction (Bratby, 2006). In an electrostatically
stable suspension, destabilisation can be instigated by an adjustment in the system pH, which
causes a reduction in the surface potential (Kovalchuk et al, 2009),and also by increasing the
salt concentration in the dispersion medium, which then lowers the thickness of the
electrical double layer. This is shown in the figure 3 below.
Fig 4: A schematic representation of the electrical double layer concept (Malvern
Instruments Ltd, 2011)
The treatment of the diffused part of the double layer has been recognized by Stern (Bratby,
2006), stating that the finite size of the ions will limit the inner boundary of the diffuse part of
the double layer. According to Bratby (2006), a model has been proposed, in which the
double layer is divided into two, separated by a plane called the Stern plane at a hydrated
ionic radius from the surface. The adsorbed ions may be dehydrated in the direction of the
solid surface, so their centres will lie between the solid surface and the Stern plane. However,
when specific adsorption takes place due to electrostatic and Van der waals forces, counterion adsorption generally predominates over co-ion adsorption.
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6 Nature and Categories of Flocculants
Fasemore, (2004), Sharma et al. (2006) and Renault et al, (2008) generally classify the
material used in coagulation/flocculant processes to be of either inorganic or organic nature.
The use of polymeric additives has been used recently to cause agglomeration of flocs. These
are normally referred to as coagulant aids (Rawlings et al. 2006; Renault, 2009)
6.1 Inorganic flocculants
Inorganic flocculants are usually salts of multivalent metals and have been in use since time
immemorial. This category includes: aluminium sulphate, calcium chloride, ferric chloride
etc. They are known to be highly dependent on the pH of the solution (Fasemore 2004) as
each particular inorganic flocculant performs better over a given Ph range. The sludge deposit
formed by these sorts of flocculants normally bears their colour and this, in some cases
replicates in the colour of the water e.g. the brownish colour of ferric chloride appears on the
hydroxides which forms the flocs. Hence, the sludge picks up the colour of the flocculant
used.
However, metallic flocculants have been found to have numerous disadvantages (Fasemore
2004, Sharma et al. 2006 and Renault et al. 2008) as highlighted below:
(i) They are highly sensitive to pH
(ii) Large amounts are required for efficient flocculation which in-turn produces large sludge
volumes
(iii) They can only be applied to a few disperse systems.
(iv) They are usually inefficient towards fine particles.
Recently, inorganic polymeric flocculants have been proposed. These types of flocculants
contain complex poly-nuclear ions, formed by having high molecular weight and high
cationic charge. An example of this is the pre-hydrolysed polyferric chloride (PFC). They are
relatively more effective at a lower dose than conventional flocculants and can be used over a
wide pH range (Renault et al. 2008).
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6.2 Organic flocculants
Technological developments in recent years have ensured a major advancement in
flocculation technology by the development of organic polymers with remarkable purification
efficiency (Sharma et al. 2006, Renault et al. 2008). They are basically of two types:

Natural organic flocculants: normally based on natural polymers like starch, natural
gums, cellulose and their derivatives

Synthetic organic flocculants; based on various monomers like acrylic acid, acryl
amide, diallylmethyl ammonium chloride.
One of the major advantages of polymeric flocculants is their ability to produce thick and
compact flocs with good settling characteristics. They are readily soluble in aqueous systems
and produce less sludge volumes.
In swimming pool water treatment, flocculants function to gather up bacteria, but are
particularly crucial in helping filter three classes of material which otherwise would pass
through the filter (PWTAG 2009):

The cysts of Cryptosporidium and Giardia- usually small and resistant to disinfection

Humic acid- naturally found in some mains water and a significant precursor of
THMs

Phosphates in mains water and a component of some swimming pool water
chemicals.
The review of various literatures has shown that aluminium and ferric compounds, have
found wider industrial application as coagulants in water treatment (Ahiog 2008; Antunes et
al. 2008; Desjardins et al. 2002; Duan and Gregory 2003; Lee et al. 2005; Rodrigues et al.
2008).
However, the increasing awareness in environmental implications of most of these chemicals
has prompted the demand from stakeholders for the use of more environmentally friendly
chemicals in carrying out water treatment so as to minimise the footprint of these processes in
the ecosystem. The metallic salts of aluminium and iron generate large amounts of sludge by
chemical precipitation (Snurer 2003), which creates sludge handling problems and ultimately
increases the cost of the treatment process by carrying out sludge treatment, dewatering and
disposal. Despite the increasing application of synthetic polymers as flocculants, their
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inability to biodegrade coupled with their relatively high cost has been a major issue (Sharma
et al. 2006)
7 MgCl2 as a Flocculant for Swimming Pool Water Treatment
Poolrite Research Pty Ltd has patented this swimming pool mineral salt, which has a
composition with which chlorine generated in the form of hypochlorous acid and
hypochlorite ion, which sanitizes the swimming pool water and checkmates outbreak of
disease and infections in the pool (QLD Health 2003; PWTAG 2009). This mineral is a blend
of Magnesium chloride, potassium chloride and sodium chloride in the ratio of 33%, 55% and
15% respectively.
This sanitisation process produces the magnesium ion in form of Mg2+ which the patents
suggest functions to bind dissolved solids and other impurities in the water and makes them
available for capture during filtration. This flocculating role has been predominantly
performed in the swimming pool industry by aluminium salts (Zhidong et al. 2009; Perkins
2000; Duan & Gregory 2003; UWRAA 1992). However, current practices have seen its
limitations, in the wake of the campaign for more eco-friendly approaches in the industry
(Sharma et al. 2006; QLD Health 2003; WHO 2006).
7.1 Magnesium Chemistry
Magnesium is a metal usually occurring in a mineral form. It‟s common forms are dolomite
[MgCa(CO3)2] and Epsomite (MgSO4.7H2O). Some other minerals that contain reasonable
amounts of magnesium include; magnesium calcite (MgSO4) and chrysolite [asbestos,
Mg3Si2O5(OH)4] (Maguire & Cowan 2002).
In its pure state, magnesium appears silvery in colour with a white shade. It is a highly
reactive metal and therefore exists in a free form as a cation Mg2+ in an aqueous solution or
remains in the combined mineral forms listed above (Hai Tan et al. 1999; Maguire & Cowan
2002). Magnesium ion belongs to group 2 of the periodic table, having two valence electrons
in its outermost shell (+2). This happens to be two thirds of the charge of aluminium with a
valency of +3. However, magnesium and aluminium posses the same ionic radius which
results in the same surface area of the ion (Weiner 2000).The table below compares the size
of the magnesium ion and its other derivatives with metallic ions such as potassium (K+),
sodium (Na+) and calcium (Ca+).
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Table 4: Properties of Common Metallic Ions
Ion
Ionic
Radius
(Å)a
Na+
K+
0.95
1.38
Hydrated
Radius
(Å)
2.75
2.32
Ratio of
radii
Ionic
Volume
(Å3)
2.9
1.7
Ca2+
0.99
2.95
3.0
2+
Mg
0.65
4.76
7.3
Source: Maguire & Cowan (2002)
Hydrated
Volume
(Å3)
Ratio of
volumes
Water
Exchange
rate
(sec-1)
Transport
number
3.6
11.0
88.3
88.3
52.5
24.5
4.8
8 x 108
109
7-13
4-16
4.1
1.2
108
453
26.3
394
3 x 108
105
8-12
12-14
As outlined in the above table, the ionic radius of Mg2+ is relatively smaller in comparison
with the other ions while it‟s hydrated radius is substantially bigger that of the other three
cations. Considering the fact that volume is radius raised to the third power, therefore it
becomes very obvious when a comparison of the hydrated volume and the ionic volume of
each cation is made. Mg2+ ion in its hydrated form is 400times bigger than it‟s dehydrated
ionic from. This occurrence is not consistent for the other cations, as there is only a marginal
increase in thier volumes (Maguire & Cowan 2002). The transport number is another striking
property of these cations as it depicts the average number of solvent molecules that
effectively contacts with the ion and as they move through the solution as the cation diffuses.
Thus, higher transport number means the presence of larger macromolecular complexes
(Weiner 2000), resulting in better flocculation potential.
7.2 The Solubility Product of MgCl2
The solubility product constant is an equilibrium constant denoted as KSP as it defines the
equilibrium between a solid and its respective ion in a solution (Weiner E.R., 2000). In this
case, it shows the degree to which the magnesium chloride salt dissociates in a water
solution. The KSP expression for a salt is the product of the concentration of the ions, with
each concentration raised to a power equal to the coefficient of that ion in the balanced
equation for the solubility equilibrium. i.e.
MgCl2
Mg2+ +
Thus, the solubility product constant KSP is written as;
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KSP = [Mg2+] [
Where [Mg2+] and [
represents the concentrations of the ions of Mg2+ and
However, the solubility constant value for Mg (OH)2 at 25°C and 1000kPa is 5.61 x 10-12. The
higher the KSP of a compound, the more soluble it is in water (Manahan S.E, 2009). This is
well proven by the high solubility of alum in water, as Al (OH)3 has a solubility constant of 3
x 10-34. When these molecules are dissolved in water these molecules are inserted into a
solvent and surrounded by its molecules. But in order for this process to occur, the molecular
bonds between the solute molecules and the solvent molecules need to be broken and
disrupted. Thus, the amount of energy given off when a solute is dissolved in a solvent should
be sufficient to break the bonds between the molecules of the solute and the solvent for
dissolution to occur (Manahan S.E, 2009).
7.3 Practical Evidence of MgCl2 as a Flocculant
According to Ayoub & Semerijan (2002), the efficacy of water treatment using magnesium
compounds dates back to the late 1920s. The magnesium ions used for these coagulation and
precipitation purposes are mainly from magnesium chloride, magnesium carbonate,
magnesium hydroxide, and seawater. They also quoted a study, which they claimed, achieved
significant reduction in the Total Organic Content (TOC) and also reduced the degree of light
absorbance in water caused by the presence of suspended solids.
Hai Tan et al. (1999) has reported a coagulation technique which uses MgCl2 to produce flocs
with dye materials which are then separated from the aqueous dye solution by sedimentation.
During lime treatment, good coagulation has been achieved in the presence of sufficient
magnesium ions while magnesium rich compounds of dolomite and bittern have proved very
effective in achieving turbidity and colour removal (Hai Tan et al. 1999)
US EPA (2010) have published in their technology transfer capsule report that there is a new
magnesium recycle coagulation system which is based on a combination of water softening
and conventional coagulation techniques which can be applied to all types of water.
Magnesium hydroxide is the active coagulant in this system, which offers an alternative
approach to chemical sludge handling as well as reduction in turbidity of raw water. As the
USEPA Capsule report outlines, this technology can be significantly applied to achieve
positive outcomes in the following areas;
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The Flocculating Effect of MgCl2
Reduction or complete elimination of sludge water, as it is recovered as treated water,
which is a good source of saving for the plants

The nature of the flocs formed in this system causes a significant increase in the
clarifier loading rates, which in-turn increases the clarifier capacity.

This system causes water softening and chemically stabilizes soft water.
Modification of colloidal silica surfaces has been achieved using magnesium ions. In a study
by Karami (2009), an addition of increased amount of Mg2+ on the surface growth process of
colloidal silica has caused a corresponding decrease in the mean particle size of the colloidal
silica.
Low concentration of
Seed and Mg2+ ions
High concentration of
Seed and Mg2+ ions
Silicic acid;
Mg2+
Colloidal silica
Modified colloid
Fig 5: A Schematic of the mechanism of colloidal silica modification by Mg2+
As the Mg2+ are adsorbed on the face of the colloidal silica, it becomes modified at the same
time. This can be related with the zeta potential concept, where an increase in the
concentration of the salt in a system lowers the zeta potential and as a result, decreases the
stability of the colloidal silica. Thus, when this is combined with an increasing number of
seeds, gelling and instability occurs in the system (Karami 2009).
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Part III: Flocculation Theory and Process Kinetics
8 The Science and Process of Flocculation
In water and wastewater treatment, the primary aim is usually to make a slowly aggregating
suspension aggregate faster to cause settling. As has been discussed in the earlier chapter, the
distribution of charges in the colloidal system is the main factor that contributes to instability
of the suspension as a build up of these charges on the surface of the particle may lead to an
alteration of the arrangement of molecules in the lattice (Peavy et al. 1985).
Flocculation is therefore a process whereby destabilised or dispersed particles are brought
together to form aggregate flocs of such size, large enough to cause their settling and bring
about clarification of the system. I this way, we can then easily separate the water and the
floc formed (Faust & Aly 1998, Sharma et al. 2006). Naturally, we can have sedimentation of
particles in water, especially where particles in water is large. Faust and Aly (1983) suggested
that hydrophilic compounds in water will have their particles unable to settle as a result of its
chemical interaction with water. However, when particles are too small to be coagulated, the
use of chemical flocculants becomes imperative.
Flocculating agents act on a molecular level, on the surfaces of the particles to reduce the
repulsive forces and systematically increase the forces of attraction between these particles
(Sharma et al. 2006). A negatively charged particle will have an oppositely charged water ion
circling around it, while the negatively charged water ions are not attracted to the particulate
of the colloidal system (Peavy et al. 1985). Hence, two colloids of the same charge will
hardly aggregate together to cause settling as a result of the prevalent like charges in the
water solution. As a result, an electrical potential is created, which increases as distance
between particles decreases (Peavy et al. 1985). To overcome the electrostatic potential or
repulsive force acting between these particles, the Van der Waals force of attraction is
required. This force of attraction decreases exponentially as the distance between particles
increases and happens to be at a maximum when the distance between particles is at a
minimum (Bratby 2006, Peavy et al. 1985).
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8.1 Mechanisms of Flocculation
Flocculation has been said to occur by a number of mechanisms such as an increase in ionic
strength (reduction of the zeta potential) of a system and by adsorption of counter ions to
cause particle neutralization (Duan & Gregory 2002). However there are four generally
accepted destabilization mechanisms in colloidal systems (Binnie et al. 2002). They are as
follows;

Surface charge neutralisation

Double layer compression

Inter-particle bridging

Sweep flocculation
8.1.1 Surface Charge Neutralization
Destabilization can occur in a suspension when the net surface charge of the particles is
reduced (AWWA 1999). This can be readily achieved by the addition of oppositely charged
ions on the colloidal particles, and this leads to the adsorption of the ions on to the colloidal
materials to effect surface charge reduction. This process then promotes agglomeration, due
to the reduction in the electrical forces that separates the particles (Binnie et al. 2002).
Fig 6: Deposition of metal hydroxide species on oppositely charged particles
(Adapted from Duan & Gregory 2002)
AWWA (1999) and Duan & Gregory (2002) suggest that organic and synthetic polyelectrolytes and some of the hydrolysis products formed from hydrolysing metal such as
Mg(OH)2 are more strongly adsorbed on negative surfaces. This adsorption tendency is
usually as a result of poor coagulant-solvent interaction and the chemical affinity of the
flocculant, as they can adsorb on the surface to the extent that a reversal of the net surface
charge occurs and possibly goes on to effect a restabilization of the suspension (AWWA
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1999). These hydrolysing coagulants can neutralize the negative surface charge of many
types of particles including bacteria and clays. Duan and Gregory (2002) went ahead to infer
that the effective charge neutralizing species may be the positively charged colloidal particles
at about pH of not more than 8.
However, restabilization can be controlled in a system by simple pH adjustments with acid or
base. In surfaces with positively charged oxides and hydroxides, the use of simple
multivalent anions such as sulphates will achieve a destabilization of the system by a
reduction of the positive ions (AWWA 1999; Bratby 2006, Sincero &Sincero 2003).
As much as charge neutralization might be the most preferred mechanism of flocculation
(both economically and environmentally) because it enables the coagulant dosage to be
minimized and reduces the residual metal in water, it must be noted that pH control is not
always easy to achieve during water treatment processes (Byun et al. 2005).
8.1.2 Double-Layer Compression
This method of destabilization has been long-existent. The process involves effecting a
compression of the double-layer by the addition of an electrolyte to the solution to increase
its ionic concentration (AWWA 1999; Binnie et al. 2002, Bratby 2006; Sincero & Sincero
2003). This in turn reduces the thickness of the electrical double layer surrounding each
colloidal particle and slows particles to move closer to each other.
Fig 7: A negatively charged particle surrounded by a charged double layer
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A simple electrolyte such as NaCl is added to cause double layer compression. However, the
effectiveness of any electrolyte used, depends on the change in ionic concentration. Thus,
ions of +3 charges are 1000times more efficient than an ions with +1 charge (Binnie et al
2002) but only 20 times more efficient than those with +2 charge (Fasemore 2004; Benefield
et al 1982). This therefore implies that Mg2+ will be 50 times more efficient than Na+
AWWA (1999) maintained that destabilization by double layer compression is not
practicable in most water treatment processes because of its huge salt concentration
requirements and relatively slow rate of floc formation. Binnie et al (2002) also holds that the
effect of the process is only noticed before the formation of insoluble hydroxides and is not a
function of the colloidal material concentration.
8.1.3 Inter-particle Bridging
Destabilization can occur when large organic molecules with multiple electrical charges are
used as flocculants in water treatment. These types of molecules are usually referred to as
anionic or cationic polymers. They are usually of high molecular weight polymers and tend to
form a linkage between the particles by adsorbing on to one or more particles (Sincero &
Sincero 2003). When the polymers come in contact with colloidal particles, some of the
reactive groups on the polymer adsorb on the particle surface, while the remaining extends
into the solution. If the extended groups in the solution become adsorbed to another surface
of a particle, then inter-particle bridging has occurred. However, the suspension might
restabilise when excess polymer has been adsorbed.
8.1.4 Sweep Flocculation
During flocculation, rapid and extensive hydroxide precipitation can achieve optimal particle
removal from the water. Once the hydroxides are precipitated, it causes a rapid aggregation of
the colloidal precipitate particles and an eventual “sweeping out” of these aggregates from
water by an amorphous hydroxide precipitate (Duan and Gregory 2002).
When soluble metallic salts of aluminium or magnesium are added to water at a suitable pH,
hydroxide flocs are precipitated. In the presence of colloids, hydroxides are precipitated using
the particles of the colloid as its nuclei, with floc formation around the colloid particle (Binne
et al. 2002). Thus, contaminants in water are enmeshed in growing hydroxide precipitate and
the effectively swept-out of the suspension.
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The sweep flocculation process tends to achieve better particle removal than in destabilisation
processes due to charge neutralisation. Amitharajah et al. (1991) therefore suggested that the
relationship between the optimum coagulation dose and the concentration of colloidal particle
in a flocculation process is an inverse. This claim was supported by Binnie et al (2002) with
the suggestion that colloidal particles act as a nuclei on which the coagulant precipitate, in a
high colloidally concentrated system while at low concentration of colloids, more precipitated
coagulant is required to entrap the particles of the colloid. Hence, the optimum pH value of a
coagulation process is dependent on the solubility and actual pH of the coagulant
8.2 Flocculation Kinetics
According to Peavy et al. (1985), mixing is a very important aspect of the flocculation
process. He further stressed that for destabilisation to be achieved in a colloidal system, the
Brownian motion operating in that particular system should exceed the system‟s electrostatic
potential. Apart from Brownian motion, a number of other mechanisms which can cause
relative motion and collision between particles in a destabilized suspension include; velocity
gradients in laminar flow, unequal settling velocities and turbulent diffusion (AWWA 1999).
However, when the Van der Waal forces of attraction between particles of the colloidal
system is low while the distance between them is still high, Peavy et al, (1985) proposes the
use of mechanical agitation to increase the collision rate in order to force agglomeration of
the particles, for easy settling out from the system. It is therefore important to utilise
flocculants to achieve agglomeration in systems where mechanical means alone does not
bring about agglomeration of colloidal particles. The two stages of flocculation according to
Bratby, (2006) are the Perikinetic flocculation stage and the Orthokinetic flocculation stage.
8.2.1 Perikinetic Flocculation
This stage of the flocculation process arises from thermal agitation, usually referred to as
Brownian movement and is a naturally random process (Armenante 2007; Bratby 2006). At
this stage, destabilisation is immediate followed by flocculation and is complete within
seconds. This is as a result of the limiting floc size beyond which Brownian motion has little
or no effect. During this stage which entails rapid mixing, hydrolysis, adsorption and
destabilisation all occur (Fasemore 2004; Jiang and Graham, 1998). There is also a reduction
in the potential energy between particles and a significant increase in Brownian movement,
which then leads to collisions between small-sized particles. A reduction in surface potential
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of the colloids occurs and this causes the adsorption of counter-ion s by colloidal particles
during the perikinetic flocculation stage. (Fasemore2004).
Although the potential energy barrier existing between colloidal particles may be overcome
by the thermal kinetic energy of the Brownian motion, as the particles coalesce, the
magnitude of the energy barrier increases approximately proportional to the area of the floc,
so that eventually perikinetic flocculation of such potentially repellent particles must cease
(Bratby 2006).
8.2.2 Ortho-Kinetic Flocculation
At the end of the rapid mixing period of flocculation, there is a stage of slow mixing
(Fasemore, 2004), this stage is called the orthokinetic flocculation stage and it arises from
induced velocity gradients due to mixing of the liquid (Thomas et al. 1999). More particle
contraction is achieved at a higher induced velocity gradient in the liquid and within a given
time, however this high velocity gradient causes floc breakage in the system and eventually
results in smaller floc size formation (Bratby 2006). Thus, low velocity gradients delays the
time taken for flocs to form, but the result is usually a large floc size formation. This
therefore follows that velocity gradient and time are the two key parameters that determine
the rate and extent of particle aggregation and the rate of particle breakup (Bratby, 2006).
Velocity gradients may be induced in flocculation system by various approaches such as;

Passing around baffles or mechanical agitation within a flocculator reactor

Passing through interstices of a granular bed

Differential settlement velocities within the settling basin.
This process sees application in the swimming pool industry in the use of suction and return
lines connected to the pool circulation system to provide effective mixing.
Faust and Aly, (1983) have described the orthokinetic stage as a period when the particles or
flocs formed are large enough that the relative motion due to velocity gradient of the particles
causes a high shear rate in the liquid phase, compared to the initial perikinetic flocculation
stage. The large particles seem to impart their own velocity to the nearby particles.
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9 Flocculation Models
The mathematical representations of the processes of suspended particles destabilization has
been developed from the mechanisms of transport and attachment.
9.1 The Smoluchowski Model
This is a classical expression in the area of flocculation developed as early as 1917 by
Smoluchowski (Amirtharajah et Al. 1991; Bratby 2006; Brostow et al. 2007; Thomas et el.
1999). Von Smoluchowski modelled transport and attachment mechanisms as a rate of
successful collision between two particles of size i and j (Thomas et al. 1999)
rate of flocculation= ∝β(i,j)ninj..............................................................................................................(1)
Where β (i,j) is the collision frequency, ∝= Collision efficiency
Smoluchowski developed a classical analytical expression for the collision frequency for both
Perikinetic and Orthokinetic flocculation based on the following assumptions,

The collision efficiency factor α, is unity for all collisions

Fluid undergoes laminar flow

The particles are mono-dispersed (all of the same size)

No breakage of flocs occur

All particles are spherical in shape

Collision involves two particles
Now based on these assumptions;
In equation (2) above, the subscripts i,j and k stands for the particle sizes. The first term on
the right had side of the equation represents the increase in particle of size k by flocculation
of two separate particles whose total size of particle equals the size of k, and for both
perikinetic and orthokinetic flocculation, the expressions apply;
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In the equations above,
The Flocculating Effect of MgCl2
= Boltzmann‟s constant, T is the absolute temperature and
fluid viscosity, where
is the
is the velocity gradient.
An extension of the above equation was made for orthokinetic flocculation by replacing the
shear velocity, du/dy, with the definition of the root-mean-square velocity gradient, G:
Thus, the collision frequency for differential sedimentation is given by (Thomas et al, 1998);
Where
- gravity constant,
are the fluid and particle densities.
The American Water Works Association (1999) stressed the need of recognising Differential
Settling as a situation that occurs when particles have unequal settling velocities and their
alignment in the vertical direction causes collision. Gravity is the driving force here and the
flocculation rate constant here is given by
........................................................................................... (7)
9.2 The Argaman Kaufman Model
This model is based on the mathematical foundations already set by the Von Smoluchowski
model. It introduced the velocity gradient G; called the root mean square extending the model
to include the turbulent flow regime (Haarhoff and Joubert 2006). It also reviewed the
assumptions of Smoluchowski and included; the concept of floc-breakup and also non-lasting
collisions. The model itself assumed a bimodal floc-size distribution.
..................................................................................................
.......... (8)
Where
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The Flocculating Effect of MgCl2
= break-up constant
9.3 The Population Balance Equation (PBE) Based Model
This model was developed based on physical phenomena which does not contain any
adjustable parameter. However the modelling of flocculation can be achieved by employing
the PBE equation;
Where
is the floc size distribution,
dv is the number of flocs in the range [v, v
+ dv] at time t in a unit volume of the suspension.
Also
is called the aggregation kernel of flocs with volumes u and v
is the breakage frequency and
dv is the number of flocs created
For aggregation
........................................................................................................ (10)
= a velocity gradient
Using Taylor analysis for homogenous isotropic turbulence, Saffman and Turner obtained the
following modified expression for the aggregation kernel of small drops in turbulent flows
..................................................................................... (11)
For breakage
=
Where
...................................................................................................................................................... (12)
and
are coefficients that depend on specific environmental conditions
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The Flocculating Effect of MgCl2
10 Evaluation of the practicality of Flocculation models in Swimming
Pool Water Treatment Process.
From the literatures and theories of flocculation reviewed so far, it is evident that flocculation
is a full-blown chemical treatment process in water treatment, which takes a reasonably long
time to occur, with parameters such as flocculant dosage, system pH, residence time,
flocculating tank dimension, paddle/mixer type and area, velocity gradient of the system and
the mixing regimes as the keys factors that determine the efficiency of flocculation.
In a swimming pool circulation system however, flocculation is not allowed an extended time
to occur as there is usually a few seconds in the pipe circulation system after the flocculant is
dosed before the filter, though this time should be enough for proper mixing to take place,
provided that all other conditions are favourable (PWTAG 2009) .An assessment of the
different processes involved in coagulation and flocculation has revealed that there are no
easily understandable practical models to predict the effect of pH, flocculant dosage and
concentration and the effect of mixing on metallic coagulants used in water treatment
(Fasemore 2004).
Thus, the approach adopted in this study is by experimentally determining how these key
pool water parameters such as Ph, coagulant dosage and concentration, contaminant loading,
temperature and mixing, affect the performance of a flocculant towards achieving improved
swimming water characteristics.
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The Flocculating Effect of MgCl2
Part IV: Experimental Design and Methodology
A norm exists in the swimming pool industry whereby claims on the efficiency of several
features of the swimming pool set-up, ranging from the disinfection systems, filter media and
the entire water circulation system are often made. Unfortunately the claims made are usually
not based on rigorously established facts as they might have presumably been made to project
the image of company products toward greater commercial benefits.
An investigation into research carried out by Poolrite has shown that considerable efforts
have been made in carrying out testing in order to maintain sustained improvements in
product quality where and when the need arises. Thus, it was noticed that most of these tests
might be liable to errors in outcome, probably due to not enough time dedicated to
experiments or as a result of lack of extensive theoretical knowledge in the area, which is key
in order to logically draw conclusions on the outcome of such experiments.
However, flocculation testing has hardly been done in the past in Poolrite Research, except
for an evaluation test carried out to determine the effect of Magnapool™ minerals on filter
media (Babych 2011), which again, was an inconclusive experiment as will be described later
in this section of the report.
Therefore, the method used in carrying out the flocculation experiments was adopted after A
series of academic papers were reviewed and the widely acceptable methodology of
coagulation and flocculation testing in water treatment, generally known as “Jar Testing”
was adopted
11 Summary of previous Flocculation Experiments at Poolrite
In a view to establish the effect which Poolrite‟s Magnapool™ Mineral Blend has on the
filtration performance of the swimming pool system, an experiment was set up, using four
different filtration media namely; DiamondKleen™ (patented by Poolrite), Sand, Zeobrite
and DiamondKleen™ Fine (Babych 2011). The experiment was carried out in two different
stages by running the entire set-up without the Magnapool™ mineral blend in the first stage
and later adding the mineral blend at 4000ppm in the second stage. The material used to
simulate contamination in the system was Diatomaceous Earth (DE), and this having the
characteristics of a media itself caused some problems in the system, lead to non reliable
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The Flocculating Effect of MgCl2
outcomes, since it would not behave like a regular contaminant. However, this test was
inconclusive as a result of the breakdown that occurred along the line. The following
outcomes however, were detected before the collapse of the set up;

The DiamondKleen™ and sand filter media clogged up faster with a very thick crust
of DE sediment on the top

DE penetration level was the highest through the DiamondKleen™ filter

Zeobrite produced the lowest pressure differential
The failure of this testing therefore underlines the need for proper research to be conducted,
before adopting experimental procedures as this goes a long way to provide a good footing of
the performance and the degree to which a simulated process represents the real scenario of
an actual treatment process. Nevertheless, based on the available information provided by this
experiment, one might attribute the quick clogging that occurred with the DiamondKleen™
media during the second stage of the test, to be as a result of easier entrapment of enlarged
aggregate particles probably caused by the addition of Magnapool™ mineral.
12 Summary of Academic Review on Experimental Methodology
Previous academic studies on flocculation have been reviewed and their various experimental
targets, methodology and outcomes are summarised in the table below.
Table 5: Summary of flocculation previous experiments
Test Aim (s) [source]
Experimental setup and
Flocculation
conditions
Performance
Outcome (s)
Indicator
Experimental
determination of

flocculation constants.
Haarhoff, H. and Joubert,
H. (1997)
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
The Jar test
Turbidity
Longer
apparatus was
reduction
settling time
used
(determined by enhanced
40ppm of Kaolinite
measuring
used spiked in
initial and
water to simulate
supernatant
sedimentation
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The Flocculating Effect of MgCl2
contamination

turbidity)
Ferric chloride was
used as the
flocculant
Reproduction of floc

size distributions
obtained at a steady

state from a Jar test
Coufort, C., Bouyer, D.,
Line, A. and Haut, B.
(2007)
The Jar test
Strong or large
(a) A
apparatus
floc formation.
cummulative
A fixed
representation
concentration of
of the floc
30mg/l of
distribution
bentonite was used
identified a
to simulate a
critical floc
particulate
volume Vc
suspension

(b) Beyond
(Al2 (SO4)3. 18H2O)
this Vc,
was used as the
breakage
flocculant
Establishing a

A jar tester was
occurs
Change in the For a given
relationship between
used and also using velocity
measurable quantities
a peristaltic pump
gradient of the particle size
such as zeta potential,
to withdraw water
system
organic matter and pH
200mm below
the pH, salt
in the flocculation
water surface.
concentration
Mud with clay was
and the
used to form a
organic matter
suspension in tap
content of the
water
suspension.
behaviour of mud

Mietta, F., Chassagne, C.,
Manning, A. J.,
Winterwerp, J. C. (2009)

The Ph of the
system was
adjusted using
shear rate, the
depends on
Also there is a
relationship
between the
hydrochloric acid
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
The Flocculating Effect of MgCl2
Two inorganic
zeta potential
flocculants of NaCl
of the particles
and MgCl2 were
and their
used to investigate
flocculation
the effect of mono
characteristics
and divalent ions
at high shear
of Na+ and Mg2+.
rate
13 Project Experimental Design
The design of the experiment to determine the flocculating effect of MgCl2 in a Magnapool™
system entailed considerations on the parameters and the performance indicators against
which our results and analysis will be based. Again, considering the fact that we are carrying
out a swimming pool water treatment process, the operating conditions of a typical
Magnapool™ system™ was adopted so as to actually obtain results that are truly
representative of the real system.
13.1 Aims
In testing for the flocculating effect of the hybrid Magnapool™ mineral blend, the main
target of the test is to; determine the turbidity reduction level achievable in using the
Magnapool ™ mineral blend

Determine the dosage at which optimum performance is achieved

Estimate and the actual amount of MgCl2 in the blend that yields the best result.
13.2 Experimental Approach
The aims of this experimental testing on flocculation performance of MgCl2 in a swimming
pool will be achieved, and presumably justified, by applying the analytical approach as
outlined below;

Testing and comparatively analysing the flocculation performance of the hybrid
Magnapool™ mineral blend against the traditional pool salt of NaCl under the same
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sample water quality and operating conditions. This is targeted at establishing whether
Poolrite‟s patented mineral blend performs the flocculating functions that is claimed
and to which extent it does compared to the conventional flocculating agents.

Performing experiments while taking record of changes in water quality (e.g.
turbidity) over time. This will provide information on the interval where maximum
effect, say of turbidity reduction, is obtained in the entire treatment process.

Performing experiments on sample water of varying qualities, in terms of initial
turbidity, alkalinity organic matter content, using the same flocculant dose. This will
be to simulate varying contaminant loadings in swimming pool water and how an
increase in contamination affects the action of the flocculants and the overall sanity of
the pool water.

Simulating a test water of uniform initial turbidity and then varying the pH across the
various test samples. This is targeted to depict the effect of the pH of sample water on
flocculation performance of the Magnapool™ mineral.

Testing for the turbidity and alkalinity reduction obtainable by isolating other
components of the Magnapool™ mineral blend and floccing with the actual
concentration of the MgCl2 in the blend. This will provide some information towards
making a recommendation on the actual quantity of MgCl2 in the slat blend that gives
best clarification results.

Determining the optimum mineral dose by testing across the range of 3000-3500ppm
of the Magnapool™ mineral salt, which is Poolrite‟s current salt dosage range?
14 Experimental Setup
Based on the academic literature reviewed and the research conducted in the area of
flocculation, as was summarised in Table 4, a Jar Test procedure was adopted as the best
experimental method that will provide adequate information for use in evaluating flocculation
performance. A model Platypus Jar Tester was used; this equipment has four 2-Litre jars with
a tap, an automated speed (in rpm) and time (in min) control pads, with an axial paddle for
sample stirring. Figure 7 below shows the schematic of the Platypus Jar Test apparatus.
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The Flocculating Effect of MgCl2
Fig 8: A diagrammatic representation of a Jar Test Set-Up
14.1 Test materials and Stock Preparations
(a) Experimental / stock preparation wares
(c) 47% MgCl2
(b) 100% KCl Salt
(d) 97.5% NaCl
Fig 9 (a-d): Experimental Wares and Flocculant Salt samples
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The Flocculating Effect of MgCl2
Fig 10: A Pictorial of Jar Testing in Progress
The sample swimming water used in this experiment was simulated by dissolving a given
quantity of ISO Ultrafine fine test particles in tap water to form an even suspension of
particles in water. In all the experiments (excluding the tests for contaminant loading effects
where larger particle amount was used), 0.4g of the ISO Ultra fine test particles were
dissolved in 2litres of tap water in each of the four jars to form a solution of turbidity between
160FTU – 170FTU. This turbidity level was chosen as it is very representative of the actual
turbidity level obtainable in swimming pool water after a reasonably high bather loading
(PWTAG, 2009).
Adjustments on the sample water to the pool condition pH range of 7.2 - 7.6 was made using
37% hydrochloric (mutiaric) acid and an alkaline stock solution formed by dissolving 10
grams of Na2CO3 in a 1 litre jar of deionised water and also the alkalinity reading of the test
water tested and recorded. The Palintest Photometer 7500 was the major electronic
equipment used in reading-off the turbidity, total alkalinity and pH values of the sample
water,
with
a
proper
direction,
while
another
Palintest
device
(Waterproof
pH/Conductivity/TDS meter) was used to record the temperature of the test water and also to
double-check the pH reading of the sample water.
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The Flocculating Effect of MgCl2
The sample Magnapool™ salt blend was formed by mixing; a 47% magnesium chloride
(hexahydrate), 97% sodium chloride and pure potassium chloride in the ratio of 1: 1.06: 3.9
respectively. The quantity of the NaCl needed in one of the experiments was directly
measured out with a weighing scale.
The calculation for formulation of the blend
compositions of the Magnapool™ mineral used in each of the experiments can be seen in
appendix 2-B. The blend calculations were made based on the current Magnapool™ mineral
blend information outlined in table 6 below.
Table 6: Blend Information of the Magnapool™ mineral (Adapted from Magnapool (2010),
Technical Manual, Magnapool blend Worksheet)
Blend Name
MagnaPool™ Minerals (Current)
Blend Composition
Sodium chloride
Magnesium chloride (anhydrous)
Magnesium chloride (hexahydrate)
Potassium chloride
Water
Total
Bag Contents
Total
Direct
(kg)
(kg)
1.5
1.5
0
0
3
3
5.5
5.5
0
0
10
10
Per 10,000l
Alternate Conc'
Conductivity
(kg)
(ppm)
(mS/cm)
0
150
0.2769
0
0
0
0
300
0.3482
0
550
0.9529
0
NA
NA
0
1000
1.578
A listing of all other equipment used in carrying this experiment can be seen from appendix
2-C.
14.2 Jar Test Experimental Procedure
The four separate 2-litre jars, containing the sample water were positioned in the stirring
points on the jar tester as shown in figure 7 above (with all the necessary data recorded the
test report sheet). The Jar tester as has already been programmed begins with a flash mixing
stage of 120 rpm and while the flocculating agent is quickly added to the jars at the required
chloride concentrations (ppm) while observations are made as the fast mixing stage continues
for 2 minutes.
At the end of this stage when dispersion of the coagulant must have occurred, the slow
mixing stage is initiated as the stirring paddles operate at 20rpm and this stage is allowed to
run for 30 minutes for complete agglomeration to take place. At the end of the slow mixing
regime, the paddles were gently withdrawn from each of the jars and a 1 hour settling time
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The Flocculating Effect of MgCl2
was allowed for sedimentation to occur. However, samples were withdrawn at a 10minute
interval in most of the experiments, to test and record the trend of change in turbidity over
time from the tap affixed at a position 1/3 from the top of the jar.
A detailed results of all the experiments performed has been outlined in the next part of this
report. These results have also been analysed in line with the targets set out at the beginning
of experimentation.
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The Flocculating Effect of MgCl2
Part V: Results and Discussion
The results of flocculation experiments performed using the Magnapool ™mineral blend, the
normal pool salt (NaCl) and MgCl2 salt is analysed in this part of the report. However,
flocculation performances have been evaluated against measured test water and supernatant
water qualities such as turbidity and pH.
15 Comparative Analysis: Magnapool™ Mineral Blend Vs NaCl
15.1 Clarification Test using a typical Magnapool™ mineral blend
Initial Turbidity- 165FTU
Final Total Alkalinity (mg/l
CaCO3)
300
250
200
150
Final Alkalinity Vs Magnapool…
100
50
0
0
2500
3000
3500
Magnapool Mineral Dose (ppm)
Fig 11: Total Alkalinity Vs Magnapool™ Mineral Dose
TURBIDITY REDUCTION (FTU)
Initial Turbidity- 165FTU
90
80 0ppm Control
70
60
50
40
30
20
10
0
0
500
2500ppm
3500ppm
3000ppm
1000
1500
2000
2500
3000
3500
4000
Magnapool Mineral Dose (ppm)
Turbidity Residual Vs Magnapool…
Fig 12: A Plot of Turbidity Residual Vs MgCl2 Dose
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Discussion
The final alkalinity of the supernatant water which is a measure of the equivalent dissolved
calcium carbonate in the test water was tested (detailed result has been presented in Appendix
4 and plotted against coagulant dose in Figure 11 above). The control jar which had 0ppm of
the Magnapool™ mineral recorded no noticeable reduction in alkalinity from 250-249mg/l
(CaCO3). This 1 unit change might even be within the limits of error of the photometer
reading. This outcome seems logical as there were no chloride salts (flocculants) dosed into
the water which would have normally triggered the formation of hypochlorite (pool
sanitizers) which are acidic in nature to counter and reduce alkalinity. Conversely a reduction
in alkalinity was achieved with the use of flocculants as there was a drop from 250 to
188mg/l (CaCO3), with 2500ppm of the flocculant and dropped further to 125 in the third jar
(3000ppm) of the flocculant. Thus, there was a further marginal drop to 120 mg/l (CaCO3)
when the mineral was dosed at 3500. This trend however falls in line with the suggestions
made in the Swimming Pool and Spa Guidelines (QLD Health 2003) that the level of stable
alkalinity in a swimming pool should be between 80-200 mg/l (CaCO3). PWTAG (2009) also
stated that correction of the pH of a system becomes very difficult at high alkalinity levels
over 200mg/l CaCO3(this is not a desirable situation) while large changes in pH levels due to
increased dosage of chloride salts which generate sanitizers (in the form of acids) is avoided,
once the alkalinity level is over 80mg/l CaCO3.
In the plot of Turbidity residual Vs Magnapool™ mineral dose, the trend of reduction in
turbidity increased across the jars until the 4th Jar, which saw a marginal increase from the
optimum turbidity reduction point (3000ppm) by 7FTU. The dynamic nature of the
flocculation process in this case is presumably Orthogenetic since floc formation was not
caused by Brownian motion due to thermal influence (since no heating was performed),
rather by turbulent mixing of the colloidal system which then created velocity gradients
amongst the particles to cause agglomeration and eventual flocculation. However, the
mechanism of the process was by charge neutralization using the Mg2+ ion to counter the
negative electrical potential of the colloidal particles and enhance contraction with particles.
Floc sweeping occurs as soon as the Mg (OH)2 precipitate is formed as it enmeshes the
already aggregated flocs and settles them out of the suspension.
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The Flocculating Effect of MgCl2
15.2 Clarification Test using NaCl
This is the second stage of the initial experiment. Thus, the summary of the test process in
this run was the same as in the earlier test performed except for the flocculant being
investigated which was NaCl. It is representative of the system employed in a normal salt
water pool. Appendix 3 has the tabular presentation of the test results.
Initial Turbidity- 165FTU
Total Alkalinity (mg/l CaCO3)
300
250
250
210
200
170
162
6000
6500
150
100
50
0
0
3000
NaCl Dose (ppm)
Fig 13: Total Alkalinity Reduction Vs NaCl Dose
Initial Turbidity- 165FTU
180
6500ppm
160
3000ppm
140
6000ppm
120
Turbidity Residual (FTU)
100
0ppm (Control)
80
Turbidity Reduction Vs NaCl
Dose
60
40
20
0
0
1000
2000
3000
4000
5000
6000
7000
NaCl Dosage (ppm)
Fig 14: A Plot of Turbidity Residual Vs NaCl Dosage
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Discussion
In Figure 13 above, there was no noticeable reduction in the alkalinity of the control set-up,
as would be expected. However, a decrease in the total alkalinity of the water was noticed
across the jars that had various concentrations of the NaCl dose. This would have been as a
result of hypochlorite formation which in turn drops the water pH. This probably explains the
only established effect of NaCl and why it is still in use in most normal salt water pools,
where it is used to generate the pool sanitizers by an electrolytic process (PWTAG 2009). On
the other hand, the highest alkalinity reduction level obtained by sodium chloride (162mg/l
CaCO3) was far less than that achieved by the Magnapool™ mineral blend (125 mg/l
CaCO3). This is seemingly a downside to the use of NaCl compared to the hybrid salt blend.
The plot of turbidity reduction against NaCl dosage in figure 14 clearly showed that the
clarification potential of NaCl is extremely poor. The control set-up showed a drop in
turbidity from 165FTU to 83FTU. This supposedly must have occurred as a result of
gravitational pull which tend to settle out some of the colloidal particles. However, the test jar
dosed with NaCl showed no significant reduction in the turbidity of the system across the
different jars with varying NaCl doses. This might have been as suggested by Binnie et al
(2002), Benefield et al. (1982), Bratby (2006) and UWRAA (1992), that destabilization and
flocculation of colloidal systems can be achieved by inorganic salts of multivalent metals,
which are strong enough to cause a neutralisation of a colloidal system, which is usually rich
in negatively charged particles.
16 Clarification Performance of Magnapool™ Mineral Blend over Time
In this experiment the flocculation performance of varying doses of the hybrid
Magnapoool™ mineral blend is investigated, to depict how each dose of the flocculant
performs in terms of turbidity reduction within every ten minute interval of one hour total
settling time. The summary of the test conditions is provided below, while Appendix 4 has
the breakdown of the results obtained from this investigation.
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The Flocculating Effect of MgCl2
Initial turbidity 175FTU
160
140
120
100
80
60
40
20
0
4.22
4.32
4.42
4.52
5.02
5.12
Jar 1 0ppm Magnapool Mineral
Jar2 2500ppm Magnapool Mineral
Jar3 3000ppm Magnapool Mineral
Jar4 4000ppm Magnapool Mineral
Fig 15: A Plot of Turbidity Reduction over Time
Discussion
Figure 15 represents the trend of performance of the various doses of the Magnapool™
mineral used in the experiment. The least reduction in turbidity occurred in the control test jar
as there was no flocculant dosed into it. However, jars 2 and 4 which had mineral salt doses
of 2500 and 4400ppm experienced rapid turbidity reduction, within the first 20 minutes of the
1 hour settling time. The turbidity action afterwards, became gradual and ultimately attained
a turbidity reduction for initial sample water turbidity of 175FTU to 60 and 85FTU
respectively for the 2500 and 4400ppm Magnapool™ salt doses. This can be explained from
the theory of charge neutralization, as this mechanism was inconclusive (in the case of
2500ppm) to attain effective neutralisation of the negative colloidal particles in the system.
Thus, floc formation was initially rapid and later more or less became ineffective due to low
concentration of the Mg2+. Conversely, excessive mineral dosing which is the suspected issue
at concentrations as high as 4400ppm with the Magnapool™ mineral would have caused
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The Flocculating Effect of MgCl2
initial charge neutralisation in the system. But After a while, the system begins to regain
stability, as the flocs formed might be too large, and will eventually start breaking up.
At a Magnapool™ mineral concentration of 3000ppm, the best turbidity reduction was
achieved, from 175 to 40FTU. This therefore suggests that at such concentration, the mineral
is able to effectively form stable flocs (following adequate initial flax mixing stage), which
strongly binds the contaminants in the suspension and forces them to settle-out at the bottom
of the Jar to improve water clarity.
17 Test on the Effect of pH on Flocculation Performance
Initial Turbidity- 170FTU
160
Residual Turbidity (FTU)
140
120
100
80
Residual Turbidity Vs PH
60
40
20
0
7
7.5
7.9
8.5
Sample Water pH
Fig 16: A Plot of pH Effect on Turbidity Reduction
Discussion
An experiment was conducted to determine the effect of pH on flocculation performance with
the outcomes represented in Figure 16 above. In the plot of turbidity residual against water
pH using a Magnapool™ mineral concentration of 3000ppm, the trend of the line above
showed that the maximum turbidity reduction occurred in the system with pH of 7.5. The pH
range, as explained by Benefield et al. (1982) at which hydrolysis of metals occur is very
important, towards the precipitation of solid hydroxide species. This range however in
swimming pool water treatment has been set at 7.2-7.8 (QLD Health 2003). Therefore,
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having the optimum pH in the experiment to be 7.5 depicts effectiveness of the mineral blend
in flocculation performance, within set guidelines.
18 MgCl2 in Isolation from the Magnapool™ Blend
Initial Turbidity- 175FTU
140
Residual Turbidity (FTU)
120
100
80
0ppm MgCl2
60
500ppm MgCl2
1000ppm MgCl2
40
1500ppm MgCl2
20
0
1
2
3
4
5
6
Time (10 min Interval)
Fig 17: Plot of Turbidity Residual Vs Concentrations of MgCl2
Discussion
The plot of turbidity reduction against MgCl2 (as the known flocculating agent) in the entire
Magnapool™ salt blend is given in Figure 17 above. Significant turbidity reduction levels
were recorded in all the test jars (except the control) that had varying doses of MgCl 2 at 500,
1000 and 1500 ppm respectively. Thus, Jar 2 which had 500ppm of MgCl2 salt achieved the
highest turbidity reduction from 175FTU to 48FTU. Comparing the outcome of this
experiment with Figure 15, where turbidity performance investigation was performed on
Magnapool™ mineral blends of 2500, 3000 and 4400 ppm, which proved 3000ppm as the
best performing concentration, dropping turbidity reading down from 250 to 40FTU, there
seems to be a high degree of consistency, considering that;

Final turbidity reading was 40FTU with the Magnapool™ mineral blend at 3000ppm
and 48FTU with MgCl2 at 500ppm.

The pH of the test systems were the same (7.5)
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
The Flocculating Effect of MgCl2
The slow mixing stages lasted for 15 minutes in both experiments
A close look at the current Magnapool™ mineral blend calculation data sheet (appendix 2-A)
has the final compound concentration of MgCl2 in the blend to be 508.6, which more or less
asserts that MgCl2 alone is responsible for the flocculating characteristics of the
Magnapool™ mineral blend while ultimately raising the question of the need for the presence
of the other constituents of the blend (NaCl and KCl) from flocculation perspective. Probably
they are required as metallic chlorides make-up, for chlorine production and water
disinfection.
19 Effect of Contaminant Loading on Flocculation
Varying Initial Turbidities
300
Turbidity Residual (FTU)
250
200
96 FTU
150
145FTU
215FTU
100
295FTU
50
0
1
2
3
4
5
6
Time (10 min interval)
Fig 18: Turbidity reduction Vs Time (Varying Initial sample water turbidity)
Discussion
In Figure 18 above, turbidity reduction was investigated using sample water of varying initial
turbidity, simulated by dissolving 0.15, 0.25, 0.35 and 0.55 grams of ISO ultra-fine test dust
in 2000ml of tap water. The test dust in this system is representative of the contaminant
loading of a swimming pool water body. From the plot, Jar 1 had the least contamination with
an initial turbidity of 96FTU which was effectively reduced to 8FTU, achieving an 88FTU
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reduction over an hour. This was the best clarification level achieved, although very good
reduction in turbidity was achieved in jars 2 and 3 with initial turbidities of 145 and 215FTU
to 24 and 38FTU respectively. However, the system with the highest contaminant loading
had the least turbidity reduction. This might be as a result of a higher concentration of
colloids in the water and therefore the insufficient flocculant dose could not force
destabilisation to occur. In Jar 1 conversely, the concentration of the Magnapool™ mineral
was presumably sufficient to exceed the solubility of the metal hydroxide, that lead to the
formation of metal hydroxide precipitate which might have caused an almost complete charge
neutralization and enmeshment of the particles.
The consistent pH, ensured across the whole jars, using HCl and Na2CO3 (Soda ash) to effect
pH adjustments, must have had a significant effect on the outcome of this test. This is so
according to Bratby (2006) because the solubility of a metal hydroxide is usually minimal at
a given pH value and increases as the pH increases or decreases from that value.
20 Tests for the Optimum Magnapool™ Flocculant Dose
Initial Turbidity-170FTU
160
Turbidity Reduction (FTU)
140
120
100
80
60
40
20
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Time (10 min Interval)
3000ppm
3150ppm
3350ppm
3450ppm
Fig 19: A Plot of Turbidity Reduction Vs Time (At 3000-3500ppm Magnapool™
Mineral Range)
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Discussion
Figure 19 represents the trend on the performance of various doses of the Magnapool™
mineral blend within the range of 3000 to 3500ppm. This is the range presently adopted by
Poolrite in the mineral dosing of swimming pools. The results showed that very good
turbidity reductions can be achieved within this range of flocculant dose. However the plot
shows that doses of 3000, 3150 and 3450ppm commenced their turbidity reduction action
better than the 3350ppm within the first ten minutes of the 3hours settling time. The 3350ppm
system later improved in its action and ultimately attained a better performance at the end of
the allowed settling. However, the individual turbidity reduction achieved in the four
different systems of 3000, 3150, 3350 and 3450ppm were 48, 44, 42 and 50FTU respectively.
This result tends to justify the operational range of salt dosing employed by the patents and
also positions 3350ppm as the optimum mineral dose.
Overall, a direct comparison of the trends in turbidity reduction obtained over time, using the
Magnapool™ mineral blend and NaCl over 3hour duration of settling time yielded the trend
represented in Figure 20 below. A significant reduction in turbidity from 175 to
approximately 42FTU for the various Magnapool™ doses was followed by an insignificant
reduction in turbidity using NaCl at 6000 ppm (The approximate standard concentration used
in salt water pools)
Turbidity Reduction (FTU)
180
160
140
120
100
80
60
40
20
0
1
2
3
3000ppm
4
5
3150ppm
6
7
8
9
10
11
12
13
Time (10 min Interval)
3350ppm
3450ppm
14
15
16
17
18
6000ppm NaCl
Fig 20: Turbidity Reduction over Time (Magnapool™ Vs Normal Salt Water Pool)
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Part V: Conclusions and Recommendations
21 Conclusions
21.1 The Magnapool™ Salt Blend is “An Effective Flocculant”
Overall, this study has proved the Magnapool™ salt blend, to be very efficient in improving
the clarity of sample water from turbidity levels of about 175ftu down to 40FTU within one
hour duration of settling time. This performance depicts efficiency, as most dissolved
colloidal particles, dissolved organics and pathogenic substances in a swimming pool will
significantly be isolated, improving the aesthetics of the pool water and ultimately rendering
it safe for use. Considering the concerns of threat to bather health, which has recently been
raised by local and international regulatory organisations (WHO 2006; PWTAG 2009; QLD
Health 2003), the level of efficiency in flocculation achievable in a Magnapool™ system
significantly addresses such concerns.
The optimum dosage of the Magnapool™ mineral was achieved at 3350ppm. However,
marginal differences in turbidity reduction were achieved within 3000-3500ppm range, as the
best floccing action in terms of turbidity reduction was achieved within that range.
21.2 MgCl2 is” Key” to the Efficacy of Magnapool™ Mineral as a Flocculant
The active floccing agent in the Magnapool™ mineral blend is the divalent inorganic
hydrolysing salt of MgCl2 (at a concentration of 500ppm) whose variation in turbidity
reduction potential, when used in isolation from other salts in the mineral blend compared to
the reduction in turbidity achieved with a complete Magnapool™ mineral blend was marginal
(48FTU and 40 FTU respectively). Its flocculating mechanism is by adsorption and charge
neutralization, using the positive magnesium ion Mg2+ to neutralise the surface charge of the
negative colloidal particles and subsequently precipitates these contaminants in water by
formation of Mg (OH)2.
21.3 The Magnapool™ Provides a Safer Water Environment Compared to a
Traditional Salt Water Pool
The Magnapool™ system performed better than a model traditional salt water pool in terms
of turbidity reduction, as the tests were performed under the same conditions and consistent
with initial water quality characteristics. This conclusively follows from the assertions made
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by Benefield et al. (1982); Binnie et al. (2002); Bratby et al (2006) and Duan & Gregory
(2002), that flocculation using metallic hydrolysing salts is possible, only for salts of positive
multivalent ion such as Mg2+ and Al3+(sodium being monovalent, N+)
21.4 Flocculation Efficiency is Highly Influenced by Water Chemistry
Good flocculation results can only be achieved when the water conditions are right. Water
properties such as pH, calcium hardness and total alkalinity has to be adjusted before
significant results are achieved. These conditions however vary for different flocculants. The
optimum performance using the Magnapool™ mineral occurred at pH of 7.5.
22 Recommendations
Considering the research outcomes and results of the experimental investigations carried out
in this project work, recommendations are made for;

The continued use of the Magnapool™ mineral as a flocculant in swimming pool
water treatment, as it is rich in MgCl2, which demonstrated high efficacy in
clarification.

Considerations on the possible exclusion of NaCl from the Magnapool™ mineral
blend as its significance in the blend is questionable, knowing that KCl would at least;
contribute to a possible use of the Magnapool ™ system backwash water for irrigation
purposes.

Cost saving strategies in the Magnapool ™ System for swimming pools of heavy
bather loading, by the use of coagulants aids e.g. (bentonitic clay) usually cheap to
acquire, to augment the MgCl2 and save cost on the chemical needed in such scenarios
to effect flocculation.

Further research on;
o The combined effect of Poolrite‟s Magnapool™ mineral blend and
DiamondKleen™ granular filter to determine the ultimate turbidity residual of
the final effluent in the water recirculation cycle.
o The bio-fouling effect of using the Magnapool™ mineral blend on the filtration
system, to determine its benefits and downsides to the filtration system.
o Efficient mixing to cause velocity gradients in water promotes flocculation,
therefore it is recommended that a good recirculation rate is maintained in the
main body of the pool water as this will enhance flocculation.
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APPENDICES
APPENDIX 1
MAGNESIUM ION/ MAGNESIUM CHLORIDE
CHEMISTRY
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APPENDIX 1-A
Periodic Table of the Elements
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
H
18
He
Hydrogen
Helium
Li
Be
B
C
N
O
F
Ne
Lithium
Berylium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Na
Mg⁺⁺
Al⁺⁺⁺
Si
P
Se
Cl
Ar
Sodium
Magnesium
Aluminium
Silicon
Phosphorus
Sulphur
Chlorine
Argon
K
Ca⁺⁺
Sc
Ti
V
Cr
Mn
Fe⁺⁺⁺
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
Potassium
Calcium
Scandium
Titanium
Vanadium
Chromium
Manganese
Iron
Cobalt
Nickel
Copper
Zinc
Gallium
Germanium
Arsenic
Selenium
Bromine
Krypton
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
Rubidium
Strontium
Yitrium
Zirconium
Niobium
Ruthenium
Rhodium
Palladium
Silver
Cadmium
Indium
Tin
Antimony
Tellurium
Iodine
Xenon
Cs
Ba
La-Lu
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
Caesium
Barium
Lanthanide
Hafnium
Tantalum
Tungsten
Rhenium
Osmium
Iridium
Platinum
Gold
Mercury
Thallium
Lead
Bismuth
Polonium
Astatine
Radon
Fr
Ra
Ac-Lr
Rf
Db
Sg
Bh
Hs
Mt
Uun
Uuu
Uub
Uuq
Francium
Radium
Actinide
Rutherfordium
Dubnium
Seaborgium
Bohrium
Hassium
Meitnerium
Ununnilium
Unununium
Ununbium
Ununquadium
La
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Lanthanium
Cerium
Samarium
Europium
Gadolinium
Terbium
Dysprosium
Holmium
Erbium
Thulium
Ytterbium
Lutetium
Molybdenum Technetium
Lanthanide
Praseodymium Neodymium Promethium
Actinide
Ac
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
Actinium
Thorium
Protactinium
Uranium
Neptunium
Plutonium
Americium
Curium
Berkelium
Californium
Einsteinium
Fermium
Mendelevium
Nobelium
Lawrencium
Multivalent Metallic Elements: Flocculants
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APENDIX 1-B: MgCl2 MSDS
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APPENDIX 2
EXPERIMENTATION DESIGN/CALCULATIONS,
APPARATUS LISTING
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APPENDIX 2-A : Magnapool™ Mineral Blend Composition
MagnaPool Minerals (Current)
Blend Information
Blend Name
Blend Composition
Sodium chloride
Magnesium chloride (anhydrous)
Magnesium chloride (hexahydrate)
Potassium chloride
Water
Total
Alternative Material Information
Alternative Material Name
Alternative Material Weight Used
(kg)
Alternate Material Composition
Sodium chloride
Target
Page
MagnaPool Minerals (Current)
Bag Contents
Total
Direct
Alternate
(kg)
(kg)
(kg)
1.5
1.5
0
0
0
0
3
3
0
5.5
5.5
0
0
0
0
10
10
0
0
Fraction
0.00
0.00
0.00
0.00
Water
Total
0.00
0.00
Dosage Information
Target concentration in pool (ppm
NaCl)
Target conductivity in pool
3000
5.69
Conductivity per bag in 10,000l
Bags per 10,000l
Weight per bag
Weight per 10,000l
1.58
3.61
10.00
36.07
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Per 10,000l
Conc'
Conductivity
(ppm)
(mS/cm)
150
0.2769
0
0
300
0.3482
550
0.9529
NA
NA
1000
1.578
(None)
Magnesium chloride (anhydrous)
Magnesium chloride (hexahydrate)
Potassium chloride
Material
Sodium chloride
Magnesium chloride (anhydrous)
Magnesium chloride (hexahydrate)
Potassium chloride
(None)
Total
3000
2
Cost per bag
5.886
Bags per
10,000l
3.61
Cost per dose (10,000l)
21.2310034
2
Final Compound Concentration
Conc'
Compound
(ppm)
NaCl
541.1
MgCl
508.6
2
KCl
1983.9
Total
3033.5
Weight
Cost/kg Cost/bag
1.5
0.286
0.429
0
0
3
0.389
1.167
5.5
0.780
4.29
0
0
10
NA
5.886
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APPENDIX 2-B: Flocculant Dosage Calculations
In line with the Magnapool mineral blend information outlined in appendix 2A, the final
concentration of the constituent salts in the blend is given by
NaCl- 541 ppm; MgCl2 - 508.6ppm; KCl – 1983.9 ppm
Total Concentration = 541 + 508.6 + 1983.9 = 3033.5ppm
To derive other concentrations based on the above composition, ratio of the salts is
determined thus;
:
:
= 1 : 1.06: 3.9 Of MgCl2, NaCl and KCl respectively.
Hence, in forming a Magnapool™ mineral blend of any concentration e g
the following approach is adopted;
ppm
x Targeted Concentration
Thus;
For MgCl2;
⇒ 419.6 mg of MgCl2/litre of water, =0 .42grams/litre
By using a 2litre jar as the sample water volume in all the experiments performed,
we multiply the weight of the salt by 2, to finally have
0.84grams as the MgCl2 content/2litre of water sample for a 2500ppm of
Magnapool™ mineral blend in test water
NaCl2;
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Therefore
⇒ 2 x 0.44 = 0.88 grams of NaCl2 content/2 litre of water sample for a 2500ppm of
Magnapool™ mineral blend in test water.
KCl;
⇒ 2 x 1.64grams = 3.28 grams of KCl in / 2 litre of the test water sample.
The same method was applied in calculating other concentrations of the Magnapool™ mineral
used at various stages of experimental testing.
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APPENDIX 2-C: Experimental Apparatus Listing
No
Equipment/Materials
Specifications
Quantity
40,000ml
Poolrite’s Supply-Available on Site
1
Test water
Backwash water
2
Test Particle Contaminants
ISO 12103-1, A2 Fine Test
Dust
3
Test Particle Contaminants
ISO ULTRAFINE ATD
4
Flocculant-1
Magnapool salt
30kg
5
Glass beakers
2000ml
2
6
Pipettes
Graduated 1ml and 5ml
2
7
Sample Bottles
600ml
12
8
Temperature gauge
Thermometer
1
9
Weighing Balance
Weight Scale
1
10
Timer
Stop watch
1
11
A pH meter
Palintest TDS/pH Meter
1
12
Water Analyser
Palintest photometer
1
Poolrite’s Supply – Stock to be Ordered
13
Flocculant-2
NaCl (Normal Pool Salt)
30kg
14
Stock Base
Distilled water
20000ml
15
pH Adjuster 1
Na2CO3
500g
16
pH Adjuster 2
HCl
1500ml
18
Jar Tester
3G Platypus- 4 Points Stirrer
1
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APPENDIX 3
EXPERIMENTAL SET-UP AND PICTORIALS
Nonso Okafor-2709055
Page 73
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
(i) Platypus Jar Tester Set-Up
(ii) Experimental reagents
Nonso Okafor-2709055
Page 74
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
(iii) Magnesium Chloride Hexahydrate
(iv) A Palintest TDS/pH/Temperature & Conductivity Meter
Nonso Okafor-2709055
Page 75
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
APPENDIX 4
TABULAR SUMMARY OF EXPERIMENTAL
RESULTS
Nonso Okafor-2709055
Page 76
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
1 Comparative Analysis: Magnapool™ mineral blend Vs NaCl
2nd April 2011
1hr/32mins
Magnapool Blend/NaCl
2000ml (2L)
0.4grams of ISO Ultra Fine Test Dust
1.5ml of 37% Hydrochloric acid
7.4
Test Date
Test duration
Flocculant tested
Volume of Test water
Contaminant
pH Adjustments
pH of Sample Water
Water Temperature (°C)
Rapid Mixing Speed/Duration
Slow Mixing Speed/Duration
Number of Readings
22°C
120rpm/ 2 mins
20rpm/ 30 mins
1 (After 1 hour settling time)
1(a) Clarification Test using a typical Magnapool™ mineral blend
Jar ID
Dosage
(ppm)
Initial
Water
Turbidity
Initial Total
Alklinity (mg/l
CaCO3)
Flocculant
Dosage
(ppm)
Residual
Turbidity
Final
Alkalinity
1
2
3
4
0
2500
3000
3500
165
165
165
165
250
250
250
250
0
2500
3000
3500
80
58
26
33
249
188
125
136
1(b) Clarification Test using NaCl
Jar ID
Dosage
(ppm)
Initial
Water
Turbidity
Initial Total
Alklinity (mg/l
CaCO3)
Flocculant
Dosage
(ppm)
Residual
Turbidity
Final
Alkalinity
1
2
3
4
0
5
10
15
165
165
165
165
250
250
250
250
0
2500
3000
3500
83
84
85
85
250
210
170
162
Nonso Okafor-2709055
Page 77
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
2 Clarification Performance of Magnapool™ mineral Blend over Time
Summary of Test Conducted
3rd June 2011
1hr/17mins
Magnapool™ Blend@2500, 3000&4000ppm
2000ml (2L)
0.4grams of ISO Ultra Fine Test Dust
1.5ml of 37% Hydrochloric acid
7.5
Test Date
Test duration
Flocculant tested
Volume of Test water
Contaminant
pH Adjustments
pH of Sample Water
Water Temperature (°C)
Rapid Mixing Speed/Duration
Slow Mixing Speed/Duration
Number of Readings
24°C
120rpm/ 2 mins
20rpm/ 15 mins
6 (At a 10 minute interval of settling time)
Result Summary
Turbidity Residual
Initial Turbidity
Time
Dosage
Jar1
Jar2
Jar3
Jar4
0
2500
3000
4000
150
130
150
110
125
110
130
82
125
95
70
72
83
60
55
70
49
69
60
40
85
175
4.22pm
175
4.32pm
175
4.42pm
175
4.52pm
5.02pm
175
105
95
5.12pm
175
90
Nonso Okafor-2709055
Page 78
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
3. Tests on the Effect of pH on Flocculation Performance
Summary of Test Conducted
Test Date
Test duration
Flocculant Used
Volume of Test water
Contaminant
pH Adjustments
pH of Sample Water
Water Temperature (°C)
Rapid Mixing Speed/Duration
Slow Mixing Speed/Duration
Number of Readings
3rd June 2011
1hr/17mins
Magnapool Blend at 3000ppm
2000ml (2L)
0.4grams of ISO Ultra Fine Test Dust
37% Hydrochloric acid & Na2CO3 Solution
8.2, 7.9, 7.5 and 7.0
24°C
120rpm/ 2 mins
20rpm/ 15 mins
1 (At the end of a 1 hour settling time)
Result Summary
Jar ID
Initial
Turbidity
Initial
Alkalinity
1
2
3
4
170
170
170
170
245
245
245
245
Dosage
(ppm)
Residual
Turbidity
PH
3000
3000
3000
3000
65
46
120
150
7
7.5
7.9
8.2
4. MgCl2 in Isolation from the Magnapool™ Blend
Summary of Test Conducted
Test Date
Test duration
Flocculant tested
Volume of Test water
Contaminant
pH Adjustments
pH of Sample Water
Water Temperature (°C)
Rapid Mixing Speed/Duration
Slow Mixing Speed/Duration
Nonso Okafor-2709055
4th June 2011
1hr/17mins
MgCl2 @ 0, 500, 1000, 1500ppm
2000ml (2L)
0.4grams of ISO Ultra Fine Test Dust
1.5ml of 37% Hydrochloric acid
7.5
24°C
120rpm/ 2 mins
20rpm/ 15 mins
Page 79
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
6 (At 10min interval of settling time)
Number of Readings
Jar ID
Dosage (ppm)
Initial Turbidity
Initial Alkalinity
PH
1
2
3
4
0
500
1000
1500
175
175
175
175
250
250
250
250
7.5
7.5
7.5
7.5
Result Summary
Time
Jar1
11.35
11.45
11.55
12.05
12.15
12.25
90
Experimental Outcome
Jar2
Jar3
100
Jar4
120
130
75
90
120
80
66
110
115
79
60
85
110
81
52
85
110
80
48
75
118
85
5. Effect of Contaminant Loading on Flocculation
Summary of Test Conducted
Test Date
Test duration
Flocculant tested
Volume of Test water
Contaminant
pH Adjustments
pH of Sample Water
Water Temperature (°C)
Rapid Mixing Speed/Duration
Slow Mixing Speed/Duration
Number of Readings
Nonso Okafor-2709055
5th June 2011
1hr/17mins
MgCl2 @ 0, 500, 1000, 1500ppm
2000ml (2L)
0.4grams of ISO Ultra Fine Test Dust
1.5ml of 37% Hydrochloric acid
7.5
24°C
120rpm/ 2 mins
20rpm/ 15mins
6 (At 10min interval of settling time)
Page 80
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
Results Summary
Test Report Log
Test ID
Jar ID
Dosage
(ppm)
Test Start
Time
Initial
Turbidity
Water PH
Temp (°C)
Test End
Time
1
1
2
3
3000
3000
3000
12pm
12pm
12pm
96
145
215
7.5
7.5
7.5
21
21
21
12.17
12.17
12.17
4
3000
12pm
295
7.5
21
12.17
Time
Jar 1
Jar2
Jar3
Jar4
12.27
12.37
60
31
105
84
140
105
275
265
12.47
12.57
1.07
1.17
22
19
11
8
62
49
31
24
76
60
44
38
256
250
242
230
6 Test for the Optimum Magnapool™ Flocculant Dose
Test Date
Test duration
Flocculant tested
Volume of Test water
Contaminant
pH Adjustments
pH of Sample Water
Water Temperature (°C)
Rapid Mixing Speed/Duration
Slow Mixing Speed/Duration
Number of Readings
Nonso Okafor-2709055
6th April 2011
3hrs and 17mins
Magnapool™ Blend@3000, 3150, 3350,
3450ppm
2000ml (2L)
0.4grams of ISO Ultra Fine Test Dust
1.5ml of 37% Hydrochloric acid & Na2CO3
7.5
24°C
120rpm/ 2 mins
20rpm/ 15 mins
18 (every 10 mins of 3hrs settling time)
Page 81
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
Results Summary
Jar ID
Dosage (ppm)
Initial Turbidity
Water PH
Temp (°C)
1
2
3
4
3000
3150
3350
3450
170
170
170
170
7.5
7.5
7.5
7.5
24
24
24
24
Time
Jar 1
Turbidity Residual
Jar3
Jar2
Jar4
12.17
12.27
120
80
130
115
152
125
105
136
12.37
12.47
12.57
1.07
78
78
69
65
103
90
90
86
90
90
83
71
130
110
107
96
1.17
1.27
1.37
1.47
1.57
2.07
2.17
2.27
2.37
2.47
2.57
3.07
61
59
57
53
53
50
49
48
48
48
48
84
78
77
76
68
61
55
48
45
44
44
66
65
60
56
53
46
45
46
44
42
42
90
83
81
81
75
74
60
52
51
52
50
48
44
42
50
Nonso Okafor-2709055
Page 82
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
APPENDIX 5
TEST DATA LOG SHEETS
Nonso Okafor-2709055
Page 83
1(a) Clarification Test using a typical Magnapool™ mineral blend
Test Site: PoolrIte R&D Laboratory
Purpose of Test:
Date:
2/06/2011
Flocculation performance Experiment
Flocculant:
Turbidity Sample Volume Alkalinity
165FTU
2000ml
250mg/l
PH
7.4
Temp
22°C
Magnapool™ mineral blend
Conducted by:
Nonso Okafor
Jar Size
2000ml
TEST CONDITIONS
Mixing Regimes
Rapid Mix
Slow
No Mix
Mixing Speed (rpm) Duration (Min)
120
2
20
30
0
60
Velocity Gradient (Gs⁻1)
195
17.4
0
Test Report Log
Test ID
Jar ID
Stock ID
1
1
2
3
4
1
1
1
1
Dosage Test Start Residual
Final
(ppm)
Time Turbidity Alkalinity
0
2500
3000
3500
1.02
1.02
1.02
1.02
80
58
26
33
249
188
125
136
PH
Temp
(°C)
Test End
Time
7.2
7.2
7.2
7.2
22
22
22
22
1.35
1.35
1.35
1.35
Page 84
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
1(b) Clarification Test using NaCl
Test Site: PoolrIte R&D Laboratory
Purpose of Test:
Flocculation performance Experiment
Flocculant:
97.5% NaCl
Date:
Conducted by:
Jar Size
Nonso Okafor
2/06/2011
Test Water Characteristics
Turbidity Sample Volume Alkalinity
165FTU
2000ml
250mg/l
PH
7.4
Temp
22°C
2000ml
TEST CONDITIONS
Mixing Regimes
Rapid Mix
Slow
No Mix
Mixing Speed (rpm) Duration (Min)
120
2
20
30
0
60
Velocity Gradient (Gs⁻1)
195
17.4
0
Test Report Log
Test ID
Jar ID
Stock ID
1
1
2
3
4
2
2
2
2
Nonso Okafor-2709055
Dosage Test Start Residual
Final
(ppm)
Time Turbidity Alkalinity
0
3000
6000
6500
10.30am
10.30am
10.30am
10.30am
90
150
160
160
250
210
170
162
PH
Temp (°C)
Test End
Time
7.3
7.3
7.3
7.3
21.5
21.5
21.5
21.5
12.02pm
12.02pm
12.02pm
12.02pm
Page 85
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
2 Clarification Performance of Magnapool™ mineral Blend over Time
Test Site: PoolrIte R&D Laboratory
Purpose of Test:
Date:
Flocculation performance analysis of MgCl 2
Flocculant:
Magnapool™ Mineral Blend
Conducted by:
Nonso Okafor
Mixing Regimes
Rapid Mix
Slow
No Mix
Test ID
1
Jar ID
1
2
3
4
Nonso Okafor-2709055
3/06/2011
Turbidity Sample Volume
Alkalinity
160FTU
2000ml 250mg/l
PH
7.4
Temp
24°C
Jar Size 2000ml
TEST CONDITIONS
Mixing Speed (rpm) Duration (Min) Velocity Gradient (Gs
120
2
250.2
20
15
17.4
Time
0
60
0
4.22pm
4.32pm
Test Report Log
4.42pm
Test
Dosage
Temp
Test End
Stock ID
Start
PH
(ppm)
(°C)
Time
Time
4.52pm
1
0
3.50pm 7.4
21
4.12
5.02pm
1
2500
3.50pm 7.4
21
4.12
5.12pm
1
3000
3.50pm 7.4
21
4.12
1
4000
3.50pm
7
21
4.12
Turbidity Residual
Jar1
Jar2
Jar3
150
130
150
125
110
130
125
95
70
105
95
90
83
60
60
55
49
40
Jar4
110
82
72
70
69
85
Page 86
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
3 Tests on the Effect of pH on Flocculation Performance
Test Site: PoolrIte R&D Laboratory
Purpose of Test:
Date:
3/06/2011
Comparison of flocculation performance at varying system PH
Flocculant:
Turbidity Sample Volume
Alkalinity
170FTU
2000ml
245mg/l
PH
Temp
22°C
Magnapool™ Salt blend
Conducted by:
Nonso Okafor
TEST CONDITIONS
Mixing Regimes
Rapid Mix
Slow
No Mix
Jar Size
2000ml
Mixing Speed (rpm) Duration (Min)
120
2
20
15
0
60
Test Report Log
Test ID
Jar ID
Stock ID
1
1
2
3
4
1
1
1
1
Nonso Okafor-2709055
Dosage Test Start Residual
(ppm)
Time Turbidity
3000
3000
3000
3000
11.53am
11.53am
11.53am
11.53am
65
46
120
150
PH
Temp
(°C)
Test End
Time
7
7.5
7.9
8.2
22
22
22
22
12.13
12.13
12.13
12.13
Page 87
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
4 MgCl2 in Isolation from the Magnapool™ Blend
Test Site: PoolrIte R&D Laboratory
Purpose of Test:
Date:
4/06/2011
Turbidity reduction various doses of Flocculant over time
Turbidity Sample Volume
2000ml
PH
7.5
Stock Solutions concetration: 47% MgCl 2 Hexahydrate
Temp
Conducted by:
Nonso Okafor
Jar Size
Alkalinity
24°C
2000ml
TEST CONDITIONS
Mixing Regimes
Rapid Mix
Slow
No Mix
Mixing Speed (rpm)
120
20
0
Duration (Min)
2
15
60
Velocity Gradient (Gs⁻1)
250.2
17.4
0
Time
11.35
Test Report Log
Test ID
1
Jar ID
1
2
3
4
Stock ID
1
1
1
1
Dosage Test Start Initial
Initial
(ppm)
Time Turbidity Alkalinity
0
500
1000
1500
11.07am
11.07am
11.07am
11.07am
160
160
160
160
200
230
200
215
PH
7.5
7.5
7.5
7.5
Temp
(°C)
Test End
Time
24
24
24
24
12.13
12.13
12.13
12.13
11.45
11.55
12.05
12.15
12.25
Experimental Outcome
Jar1
Jar2
Jar3
90
100
120
85
80
79
81
80
75
66
60
52
48
90
110
85
85
75
Jar4
130
120
115
110
110
118
140
Nonso Okafor-2709055
Page 88
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
5. Effect of Contaminant Loading on Flocculation
Test Site PoolrIte R&D Laboratory
Purpose of Test:
Effect of contaminant loading on Flocculation performance
Date:
5/06/2011
Test Water Characteristics
Turbidity Sample Vol Alkalinity
2000ml
PH
7.5
Temp
21
Time
12.27
12.37
Jar 1
60
31
Jar2
105
84
12.47
12.57
1.07
1.17
22
19
11
8
62
49
31
24
Stock concentration: 3000ppm of the Mangapool mineral blend.
Conducted by:
Nonso Okafor
Jar Size
2000ml
TEST CONDITIONS
Mixing Regimes
Rapid Mix
Slow
No Mix
Mixing Speed (rpm) Duration (Min)
120
2
20
30
0
60
Velocity Gradient (Gs⁻1)
17.4
0
Test Report Log
Test ID
1
Jar ID
1
2
3
4
Nonso Okafor-2709055
Dosage Test Start Initial
Water PH
(ppm)
Time Turbidity
3000
3000
3000
3000
12pm
12pm
12pm
12pm
96
145
215
295
7.5
7.5
7.5
7.5
Temp
(°C)
Test End
Time
21
21
21
21
12.17
12.17
12.17
12.17
Jar3
140
105
Jar4
275
265
76
60
44
38
256
250
242
230
Page 89
IAP-FINAL PROJECT REPORT
The Flocculating Effect of MgCl2
6 Test for the Optimum Magnapool™ Flocculant Dose
Test Site PoolrIte R&D Laboratory
Date:
Purpose of Test:
Testing the performance of differennt concenrations of the Magnapool salt.
6/06/2011
Test Water Characteristics
Turbidity Sample Vol Alkalinity
170FTU
2000ml
250mg/l
PH
24°C
Temp
Time
12.17
12.27
Jar 1
120
80
Jar2
130
125
12.37
12.47
12.57
1.07
1.17
1.27
1.37
1.47
1.57
2.07
2.17
2.27
2.37
2.47
2.57
3.07
78
78
69
65
61
59
57
53
53
50
49
48
48
48
48
48
103
90
90
86
84
78
77
76
68
61
55
48
45
44
44
44
Various concentrations of the Magnapool™ mineral
Flocculant:
Conducted by:
Nonso Okafor
Jar Size
2000ml
TEST CONDITIONS
Mixing Regimes
Rapid Mix
Slow
No Mix
Mixing Speed (rpm)
100
20
0
Test ID
Jar ID
1
1
2
3
4
Nonso Okafor-2709055
Dosage
(ppm)
3000
3150
3350
3450
1
Duration (Min)
2
15
60
Test Report Log
Test Start
Initial
Time
Turbidity
11.50am
170
11.50am
170
11.50am
170
11.50am
170
Velocity Gradient (Gs⁻ )
195
17.4
0
Water PH Temp (°C) Test End Time
7.5
7.5
7.5
7.5
24
24
24
24
12.07pm
12.07pm
12.07pm
12.07pm
Jar3
115
105
Jar4
152
136
90
90
83
71
66
65
60
56
53
46
45
46
44
42
42
42
130
110
107
96
90
83
81
81
75
74
60
52
51
52
50
50
Page 90
IAP-FINAL PROJECT REPORT
Nonso Okafor-2709055
The Flocculating Effect of MgCl2
Page 91