Final Project Report - Magnapool · IAP-FINAL PROJECT REPORT The Flocculating Effect of MgCl 2...

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

Nonso Okafor-2709055 Page 1

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.



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



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.



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.



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



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



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



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



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



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.



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 Role

Nonso Okafor

Department of Environmental Engineering

Griffith University

Project Facilitator

Wayne Taylor

Chief Engineer

Poolrite Research

Industry Project Supervisor

Dr Jimmy Yu

Senior Lecturer

Griffith University

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.



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

Water Treatment Concepts

Milestone 1 Literature Review

Part III: Flocculation

Theories and Kinetics

Milestone 1 Literature Review

Part IV: Experimental

Design and Set-Up

Milestone 2 Test Set-up

Part V: Experimentation and

Data Collation

Milestone 3 Experimental Results and

Outcomes

Part VI: Conclusions and

Recommendations

Milestone 4 Data Analysis and Technical

Report



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.



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).

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

Strainer Pump

Coagulant/Flocculants Dosing

Filtration

Water disinfection

pH correction dosing

Balance Tank Swimming Pool



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 Targets/Requirements Health Protection Queensland Public Health, Swimming and Spa pool Water Quality and Operational Guidelines

Filtration criteria Chemical parameters Testing & recording requirements

Queensland Development Code 2008- NMP 1.9, Swimming pool and Spa Equipment

Disinfection system Water Chemistry

Australian Pesticides and Veterinary Medicines Authority (APVMA)

Efficacy criteria for pool and Spa sanitizers

South Australian Health Commission, Department of Human Services-Standard for the Operation of Swimming Pools and Spa Pools in South Australia

Water Clarity Disinfection and treatment of water Breakpoint chlorination Pool pollution

Standards Australia, AS 3633-1989, Private Swimming Pools – Water Quality

Chemical and Sanitizer concentrations

Pool water maintenance World Health Organisation, Guidelines for Safe Recreational Water Environment, Vol 2, Swimming Pools and Similar Environments, 2006

Good practice for by-product formation minimisation e.g. disinfection systems with less chlorine use

Chemical hazards Exposure to disinfection byproduct

US EPA, SWIMODEL Exposure Estimation Prediction of life time swimmer cancer exposure risk to disinfection by products e.g. Trihalomethanes

Pool Water Treatment Advisory Group (PWTAG), UK-Swimming Pool Water, 2009

Operation and maintenance Hydraulics and circulation



Pool water chemistry Northern Territory Government, Department of Health and Families- Public Health Guidelines for Aquatic Facilities, August 2006

Design and Construction Circulation and Water Treatment

systems Water quality testing Sanitation and operational

requirements Environmental Protection Queensland Environmental Protection Act 1994

Sect 119- ‘Unlawful environmental harm’ from an unauthorised act or omission that causes serious or material harm

Queensland Environmental Protection (Water) Policy

Sect 32- Total water cycle management method and planning

Australian Pesticides and Veterinary Medicines Authority

Exemption of chemical registration of salt water chlorinators.

Brisbane City Council, Urban Management Division, Subdivision and Development Guidelines, Part C. Water Quality Management Guidelines-Section 11 Discharges from Swimming Pools, 2000

Minimise discharges of pool water to storm water

Encourage development of filters and chemical regimes that protect human health

Environmental Sustainability

Royal Life Saving Society Australia- Best Practice. Profile Swimming Pools Maximising Reclamation and Reuse, 2006

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

Queensland Government, Department of Natural Resources and Water

Typical Salinity limits for waters, including salt water swimming pools

Queensland Water Commission –WG-20, Water Efficiency Management Plan (WEMP) for Outdoor Water use at Public Pools that use less than 10MegaLitres per year

Water efficiency benchmark (L/visitor/day)

Decrease backwash frequency Measure filter loading with

pressure gauges Government of Western Australia, Department of Water- Water Quality Protection Note WQPN 55, Swimming Pools, February 2009

Wastewater disposal- recycling to pool

Wastewater disposal- garden irrigation



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.



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



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.



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, counter-

ion adsorption generally predominates over co-ion adsorption.



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).



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



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

+).



Table 4: Properties of Common Metallic Ions

Ion Ionic

Radius

(Å)a

Hydrated

Radius

(Å)

Ratio of

radii

Ionic

Volume

(Å3)

Hydrated

Volume

(Å3)

Ratio of

volumes

Water

Exchange

rate

(sec-1

)

Transport

number

Na+ 0.95 2.75 2.9 3.6 88.3 88.3 24.5 8 x 10

8 7-13

K+

1.38 2.32 1.7 11.0 52.5 4.8 109 4-16

Ca2+

0.99 2.95 3.0 4.1 108 26.3 3 x 108 8-12

Mg2+

0.65 4.76 7.3 1.2 453 394 105 12-14

Source: Maguire & Cowan (2002)

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

Mg

2+ +

Thus, the solubility product constant KSP is written as;



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;



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).



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).



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 poly-

electrolytes 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



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



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.



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



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.



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;



In the equations above, = Boltzmann‟s constant, T is the absolute temperature and is the

fluid viscosity, where 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



= 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

= ...................................................................................................................................................... (12)

Where and are coefficients that depend on specific environmental conditions



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.



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



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

conditions

Flocculation

Performance

Indicator

Outcome (s)

Experimental

determination of

flocculation constants.

Haarhoff, H. and Joubert,

H. (1997)

The Jar test

apparatus was

used

40ppm of Kaolinite

used spiked in

water to simulate

Turbidity

reduction

(determined by

measuring

initial and

supernatant

Longer

settling time

enhanced

sedimentation



contamination

Ferric chloride was

used as the

flocculant

turbidity)

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

apparatus

A fixed

concentration of

30mg/l of

bentonite was used

to simulate a

particulate

suspension

(Al2 (SO4)3. 18H2O)

was used as the

flocculant

Strong or large

floc formation.

(a) A

cummulative

representation

of the floc

distribution

identified a

critical floc

volume Vc

(b) Beyond

this Vc,

breakage

occurs

Establishing a

relationship between

measurable quantities

such as zeta potential,

organic matter and pH

in the flocculation

behaviour of mud

Mietta, F., Chassagne, C.,

Manning, A. J.,

Winterwerp, J. C. (2009)

A jar tester was

used and also using

a peristaltic pump

to withdraw water

200mm below

water surface.

Mud with clay was

used to form a

suspension in tap

water

The Ph of the

system was

adjusted using

hydrochloric acid

Change in the

velocity

gradient of the

system

For a given

shear rate, the

particle size

depends on

the pH, salt

concentration

and the

organic matter

content of the

suspension.

Also there is a

relationship

between the



Two inorganic

flocculants of NaCl

and MgCl2 were

used to investigate

the effect of mono

and divalent ions

of Na+ and Mg2+.

zeta potential

of the particles

and their

flocculation

characteristics

at high shear

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



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.



Fig 8: A diagrammatic representation of a Jar Test Set-Up

14.1 Test materials and Stock Preparations

(a) Experimental / stock preparation wares (b) 100% KCl Salt

(c) 47% MgCl2 (d) 97.5% NaCl

Fig 9 (a-d): Experimental Wares and Flocculant Salt samples



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.



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 Bag Contents Per 10,000l

Total Direct Alternate Conc' Conductivity

(kg) (kg) (kg) (ppm) (mS/cm)

Sodium chloride 1.5 1.5 0 150 0.2769

Magnesium chloride (anhydrous) 0 0 0 0 0

Magnesium chloride (hexahydrate) 3 3 0 300 0.3482

Potassium chloride 5.5 5.5 0 550 0.9529

Water 0 0 0 NA NA

Total 10 10 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



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.



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

Fig 11: Total Alkalinity Vs Magnapool™ Mineral Dose


Fig 12: A Plot of Turbidity Residual Vs MgCl2 Dose

0

50

100

150

200

250

300

0 2500 3000 3500Fin

al T

ota

l Alk

alin

ity

(mg/

l C

aCO

3)

Magnapool Mineral Dose (ppm)

Final Alkalinity Vs Magnapool …

0ppm Control

2500ppm

3000ppm

3500ppm

0102030405060708090

0 500 1000 1500 2000 2500 3000 3500 4000TUR

BID

ITY

RED

UC

TIO

N (

FTU

)

Magnapool Mineral Dose (ppm)

Turbidity Residual Vs Magnapool …

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.



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.


Fig 13: Total Alkalinity Reduction Vs NaCl Dose


Fig 14: A Plot of Turbidity Residual Vs NaCl Dosage

250

210

170 162

0

50

100

150

200

250

300

0 3000 6000 6500

Tota

l Alk

alin

ity

(mg/

l CaC

O3

)

NaCl Dose (ppm)

0ppm (Control)

3000ppm6000ppm

6500ppm

0

20

40

60

80

100

120

140

160

180

0 1000 2000 3000 4000 5000 6000 7000

Turb

idit

y R

esi

du

al (

FTU

)

NaCl Dosage (ppm)

Turbidity Reduction Vs NaCl Dose

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.



Initial turbidity 175FTU

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

0

20

40

60

80

100

120

140

160

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



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


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,

0

20

40

60

80

100

120

140

160

7 7.5 7.9 8.5

Re

sid

ual

Tu

rbid

ity

(FTU

)

Sample Water pH

Residual Turbidity Vs PH



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


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 MgCl2 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)

0

20

40

60

80

100

120

140

1 2 3 4 5 6

Re

sid

ual

Tu

rbid

ity

(FTU

)

Time (10 min Interval)

0ppm MgCl2

500ppm MgCl2

1000ppm MgCl2

1500ppm 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

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

0

50

100

150

200

250

300

1 2 3 4 5 6

Turb

idit

y R

esi

du

al (

FTU

)

Time (10 min interval)

96 FTU

145FTU

215FTU

295FTU



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

Fig 19: A Plot of Turbidity Reduction Vs Time (At 3000-3500ppm Magnapool™

Mineral Range)

0

20

40

60

80

100

120

140

160

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Turb

idit

y R

ed

uct

ion

(FT

U)


3000ppm 3150ppm 3350ppm 3450ppm



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)

Fig 20: Turbidity Reduction over Time (Magnapool™ Vs Normal Salt Water Pool)

0

20

40

60

80

100

120

140

160

180

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Turb

idit

y R

ed

uct

ion

(FT

U)


3000ppm 3150ppm 3350ppm 3450ppm 6000ppm NaCl



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



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.



References

American Water Works Association (1999). Water Quality and Treatment- A Handbook of

Community Water Supplies, (5th

ed.), Chapt. 6, McGraw-Hill Inc.

Amirtharajah, A., Clark, M. M. and Trussell, R. R. (1991). Mixing in Coagulation and

Flocculation, American Water Works Research Foundation, USA.

Babych, A., Taylor, W., Kelly, A. (2011). The flocculation effect of a Magnapool™ mineral

mix in different filter media, Technical Report: Poolrite Research and

Development.

Benefield, L. D., Judkins, J. F. and Weand, B. L. (1982). Process Chemistry for Water and

Wastewater Treatment. Prentice-Hall INC, New Jersy.

Binnie, C., Kimber, M. and Smethurst, G. (2002). Basic Water Treatment, (3rd

ed.), IWA

publishing Alliance House, London, UK.

Bratby, J. (2006). Coagulation and Flocculation in Water and Wastewater Treatment, (2nd

ed.), IWA Publishing, Alliance House, UK.

Bodner Research Web (2011). Solubility- Whydo Solids Dissolve in Water, Viewed on the

1st of April 2011, at

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch18/soluble.php

Brostow, W., Hagg Lobland, H. E., Pal, S. And Singh, R.P. (2008). Settling Rates for

Flocculation of Iron and Manganese Ore-Containing Suspensions by Cationic

Glycogen, Journal of Polymer Engineering and Science

Brostow, W., Pal, S. and Singh, R. P. (2007). A model of flocculation. Material letters 61,

4381-4384

Bouyer, D., Coufort C., Line, A. and D-Quang, Z. (2005). Experimental analysis of floc size

distributions in a 1-L jar under different hydrodynamics and physicochemical

conditions, Journal of Colloid and Interface Science 292, 413-428

Byun, S., Oh, J., Lee, B. and Lee, S. (2005). Improvement of coagulation efficiency using

instantaneous flash mixer (IFM) for water treatment, Colloids and Surfaces:

Physiochem. Eng. 268, 104-110



Coufort, C., Bouyer, D., Line, A. and Haut, B. (2007). Modelling of Flocculation using a

population balance, Journal of Chemical Engineering and Processing 46 (2007)

1264-1273

Croll, B. T., Hayes, C.R., Moss, S. (2007). Simulated Cryptosporidium removal under

swimming pool filtration conditions, Water and Environment Journal 1747-

6585

Duan, J. and Gregory, J. (2002). Coagulation by Hydrolysing Metal Salts, Advances in

Colloid and Interface Science.

Faust, S.D. and Aly, O.M. (1983). Chemistry of Water Treatment, Butterworth Publishers,

Stoneham, pp. 277-363

Fasemore, O.A (2004). The Flocculation of Paint Water Using Inorganic Salts,

Witwatersrand, Johannesbourg.

Haarhoff, H. and Joubert, H. (1997) Determination of Aggregation and Breakup Constants

during Flocculation, Water Science Tech. Vol. 36. No. 4. pp. 33-40

Hai Tan, B., Teng, T.T. and Omar, M.A.K (1999). Removal of Dyes and Industrial Dye

Waste by Magnesium Chloride, Water Research, Vol. 34 597-601

IAP (2011) Program Agreement (Okafor_Nonso_EVE_PA), Industrial Affiliates Program

(IAP) Griffith University

Karami, A. (2009). Study on Modification of Colloidal Silica Surface with Magnesium ions,

Journal of Colloid and Interface Science, 379-383

Kovalchuk, N., Starov, V., Langston, P. and Hilal, N. (2009). Formation of Stable Clusters in

Colloidal Suspensions, Advances in Colloid and Interface Science 147-148,

144-154

Lee, R. (2008) Jar Testing Machines. American Water Works Association Spring Conference,

Brown and Caldwell.

Zhidong, L., Na, L., Honglin, Z. and Dan, L. (2009). Studies and Applications Processes on

Flocculants in Water Treatment in China, EJGE Vol. 14.



Maguire, E.M. and Cowan, J.A. (2002). Magnesium Chemistry and Biochemistry,

BiomMetals 15: 203-210

Malvern Instruments Ltd. (2011). "Zeta potential measurement using laser Doppler

electrophoresis (LDE) " Retrieved 30/04/2011, from

http://www.malvern.com/LabEng/technology/zeta_potential/zeta_potential_LD

E.htm

Mietta, F., Chassagne, C., Manning, A. J., Winterwerp, J. C. (2009) Influence of shear rate,

organic matter content, Ph and salinity on mud flocculation, Ocean Dynamics

59: 751-763

Neupane, D. R., Riffat, R., Murthy, S. N., Peric, M. R. and Wilson, T. E. (2008). Influence of

Source Characteristics, Chemicals and Flocculation on Chemically Enhanced

Primary Treatment, Water Environment Research 80, 331-338

Olivier, P. P. and Ducoste, J. J. (2006). Modelling spatial distribution of floc size in turbulent

process using the quadrate method of moment and computational fluid

dynamics, Chemical Engineering Science 61, 75-86

Okafor, N. M. (2011). The flocculating effects on magnesium chloride in a Magnapool™.

Project Planning Report, Industrial Affiliates Programme, Griffith University,

Nathan campus.

Peavy, H.S., Rowe, D.R. and Tchbanoglous, G. (1985). Environmental Engineering,

McGraw-Hill, Singapore, pp 11-56, pp. 131-140.

Perkins, P H (2000). Water circulation and Water Treatment. Swimming Pools (4th ed.).

Chapter 8: London: E & FN Spon.

Poolrite (2011). Magnapool™ System Description and Compliance Verification. A Technical

Manual for the Magnapool System, QEG S/N: 650-661-2464-01-11

Poolrite (2009). Poolrite Price Book on Poolrite Supplies 2009/2010

PWTAG (2009) Swimming Pool Water Treatment and Quality Standards for Pools and Spas,

Pool Water Treatment and Advisory Group, (2nd

ed.), Micropress Printers Ltd.

http://www.malvern.com/LabEng/technology/zeta_potential/zeta_potential_LDE.htm

http://www.malvern.com/LabEng/technology/zeta_potential/zeta_potential_LDE.htm



QLD Health. (2003). Swimming and Spa Pool Water Quality and Operational Guidelines,

Qld Health.

Rattanakawin, C. and Hogg, R. (2001). Aggregate size distributions in flocculation.

Physicochemical and Engineering Aspects 177, 87-98

Renault, F., Sancey, B., Badot, P.M. and Crini G. (2009). Chitosan for

coagulation/flocculation process- An eco-friendly approach, European Polymer

Journal 45, 1337-1348

Satterfield, P.E (2005) Jar Testing: Tech Brief, Vol. 5, Issue 1, The National Environmental

Service Centre

Semerijan, L. and Ayoub, G. M. (2003). High-Ph-magnesium coagulation-flocculation in

wastewater treatment, Advances in Environmental Research Volume 7, Issue

22, pp 389-403.

Sharma, B. R., Dhuldhoya, N. C. and Merchant, U. C. (2006). Flocculants- An Ecofriendly

Appraoch, J Polym Environ 14, 195-202

Sincero, P.A. and Sincero, A.G. (2003). Physical-Chemical Treatment of Water and

Wastewater. IWA Publishing. CRC Press.

Thomas, D. N., Judd, S. J and Fawcett, N. (1999). Flocculation Modelling: A Review, Water

Research Vol. 33, No 7, pp. 1579-1592

Tranfloc Polymer Technology. The Process and Jar Testing. Viewed on the 3rd

May 2011 at

http://www.tramfloc.com/tf29t.html

US EPA (2010). Magnesium Carbonate- A Recycled Coagulant for Water Treatment, EPA

Technology Transfer, Capsule Report

UWRAA (1992). Coagulants for Water Treatment: A Generic Guide.Urban Water Research

Association of Australia, Research Report No 42, Melbourne and Metropolitan

Board of Works.

Water and Wastewater Engineering- WEE (2010). Mechanism of flocculation- Rapid mixing

coagulation flocculation. Viewed 28th

March 2011. http://nptel.iitm.ac.in/

http://www.tramfloc.com/tf29t.html



Water Specialist Technology (2010). Jar Test Procedure for Precipitants, Coagulants and

Flocculants, Viewed on 4th March 2011,

http://www.waterspecialists.biz/html/jar_test.html

Weiner, E.R. (2000). Applications of Environmental Chemistry. A Practical Guide for

Environmental Engineers, Lewis Publishers, CRC Press LLC

WHO (2006). Managing Water and Air Quality. Guidelines for Safe Recreational Water

Environments (Chapt. 5), World Health Organisation.

WHO (2006). Guidelines for safe recreational waters, Volume 2 - Swimming pools and

similar recreational-water environments Chapter 5: Managing Water and Air

Quality Switzerland, World Health Organisation (WHO) Press: 80-99

Zweiner, C., Richardson, S.D., De Marini, D.M., Grummt, T., Glauner, T. and Frimmel, F.H.

(2007). Drowning in Disinfection Byproducts? Assesing Swimming Pool Water,

Environmental Science and Technology, Vol. 41, 363-372

http://www.waterspecialists.biz/html/jar_test.html



APPENDICES

APPENDIX 1

MAGNESIUM ION/ MAGNESIUM CHLORIDE

CHEMISTRY



APPENDIX 1-A

Multivalent Metallic Elements: Flocculants Halogens (water disinfectants)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

H 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 Molybdenum Technetium 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

Lanthanide

La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Lanthanium Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium

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

Periodic Table of the Elements



APENDIX 1-B: MgCl2 MSDS



APPENDIX 2

EXPERIMENTATION DESIGN/CALCULATIONS,

APPARATUS LISTING



APPENDIX 2-A : Magnapool™ Mineral Blend Composition MagnaPool Minerals (Current)

Target 3000

Page 2

Blend Information Blend Name MagnaPool Minerals (Current)

Blend Composition Bag Contents Per 10,000l

Total Direct Alternate Conc' Conductivity (kg) (kg) (kg) (ppm) (mS/cm)

Sodium chloride 1.5 1.5 0 150 0.2769

Magnesium chloride (anhydrous) 0 0 0 0 0

Magnesium chloride (hexahydrate) 3 3 0 300 0.3482

Potassium chloride 5.5 5.5 0 550 0.9529

Water 0 0 0 NA NA

Total 10 10 0 1000 1.578

Alternative Material Information Alternative Material Name (None)

Alternative Material Weight Used (kg) 0

Alternate Material Composition Fraction

Cost per bag

Sodium chloride 0.00

5.886

Magnesium chloride (anhydrous) 0.00

Bags per 10,000l

Magnesium chloride (hexahydrate) 0.00

3.61

Potassium chloride 0.00

Cost per dose (10,000l)

Water 0.00

21.2310034

2

Total 0.00

Dosage Information

Final Compound Concentration

Target concentration in pool (ppm NaCl) 3000

Compound

Conc' (ppm)

Target conductivity in pool 5.69

NaCl 541.1

Conductivity per bag in 10,000l 1.58

MgCl

2 508.6

Bags per 10,000l 3.61

KCl 1983.9

Weight per bag 10.00

Total 3033.5

Weight per 10,000l 36.07

Material Weight Cost/kg Cost/bag

Sodium chloride 1.5 0.286 0.429 Magnesium chloride (anhydrous) 0 0 Magnesium chloride (hexahydrate) 3 0.389 1.167 Potassium chloride 5.5 0.780 4.29 (None) 0 0 Total 10 NA 5.886



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 ppm

the following approach is adopted;

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;



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.



APPENDIX 2-C: Experimental Apparatus Listing

No Equipment/Materials Specifications Quantity

Poolrite’s Supply-Available on Site

1 Test water Backwash water 40,000ml

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



APPENDIX 3

EXPERIMENTAL SET-UP AND PICTORIALS



(i) Platypus Jar Tester Set-Up

(ii) Experimental reagents



(iii) Magnesium Chloride Hexahydrate

(iv) A Palintest TDS/pH/Temperature & Conductivity Meter



APPENDIX 4

TABULAR SUMMARY OF EXPERIMENTAL

RESULTS



1 Comparative Analysis: Magnapool™ mineral blend Vs NaCl

Test Date 2nd April 2011

Test duration 1hr/32mins

Flocculant tested Magnapool Blend/NaCl

Volume of Test water 2000ml (2L)

Contaminant 0.4grams of ISO Ultra Fine Test Dust

pH Adjustments 1.5ml of 37% Hydrochloric acid

pH of Sample Water 7.4

Water Temperature (°C) 22°C

Rapid Mixing Speed/Duration 120rpm/ 2 mins

Slow Mixing Speed/Duration 20rpm/ 30 mins

Number of Readings 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 0 165 250 0 80 249

2 2500 165 250 2500 58 188

3 3000 165 250 3000 26 125

4 3500 165 250 3500 33 136

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 0 165 250 0 83 250

2 5 165 250 2500 84 210

3 10 165 250 3000 85 170

4 15 165 250 3500 85 162



2 Clarification Performance of Magnapool™ mineral Blend over Time

Summary of Test Conducted

Test Date 3rd June 2011


Flocculant tested Magnapool™ Blend@2500, 3000&4000ppm








Number of Readings 6 (At a 10 minute interval of settling time)

Result Summary

Turbidity Residual

Time Initial Turbidity

Jar1 Jar2 Jar3 Jar4

Dosage

0 2500 3000 4000

4.22pm 175

150 130 150 110

4.32pm 175

125 110 130 82

4.42pm 175

125 95 70 72

4.52pm

175

105 83 55 70

5.02pm 175 95 60 49 69

5.12pm 175 90 60 40 85



3. Tests on the Effect of pH on Flocculation Performance


Test Date 3rd June 2011


Flocculant Used Magnapool Blend at 3000ppm



pH Adjustments 37% Hydrochloric acid & Na2CO3 Solution

pH of Sample Water 8.2, 7.9, 7.5 and 7.0




Number of Readings 1 (At the end of a 1 hour settling time)

Result Summary

Jar ID

Initial Turbidity

Initial Alkalinity Dosage

(ppm) Residual Turbidity

PH

1 170 245 3000 65 7

2 170 245 3000 46 7.5

3 170 245 3000 120 7.9

4 170 245 3000 150 8.2

4. MgCl2 in Isolation from the Magnapool™ Blend


Test Date 4th June 2011


Flocculant tested MgCl2 @ 0, 500, 1000, 1500ppm










Number of Readings 6 (At 10min interval of settling time)

Result Summary

Experimental Outcome

Time Jar1 Jar2 Jar3 Jar4

11.35 90 100 120 130

11.45 85 75 90 120

11.55 80 66 110 115

12.05 79 60 85 110

12.15 81 52 85 110

12.25 80 48 75 118

5. Effect of Contaminant Loading on Flocculation


Test Date 5th June 2011


Flocculant tested MgCl2 @ 0, 500, 1000, 1500ppm







Slow Mixing Speed/Duration 20rpm/ 15mins

Number of Readings 6 (At 10min interval of settling time)

Jar ID Dosage (ppm) Initial Turbidity Initial Alkalinity PH

1 0 175 250 7.5

2 500 175 250 7.5

3 1000 175 250 7.5

4 1500 175 250 7.5



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 3000 12pm 96 7.5 21 12.17

2 3000 12pm 145 7.5 21 12.17

3 3000 12pm 215 7.5 21 12.17

4 3000 12pm 295 7.5 21 12.17

Time Jar 1 Jar2 Jar3 Jar4

12.27 60 105 140 275

12.37 31 84 105 265

12.47 22 62 76 256

12.57 19 49 60 250

1.07 11 31 44 242

1.17 8 24 38 230

6 Test for the Optimum Magnapool™ Flocculant Dose

Test Date 6th April 2011

Test duration 3hrs and 17mins

Flocculant tested Magnapool™ Blend@3000, 3150, 3350, 3450ppm



pH Adjustments 1.5ml of 37% Hydrochloric acid & Na2CO3





Number of Readings 18 (every 10 mins of 3hrs settling time)



Results Summary

Jar ID Dosage (ppm) Initial Turbidity Water PH Temp (°C)

1 3000 170 7.5 24

2 3150 170 7.5 24

3 3350 170 7.5 24

4 3450 170 7.5 24

Turbidity Residual


12.17 120 130 115 152

12.27 80 125 105 136

12.37 78 103 90 130

12.47 78 90 90 110

12.57 69 90 83 107

1.07 65 86 71 96

1.17 61 84 66 90

1.27 59 78 65 83

1.37 57 77 60 81

1.47 53 76 56 81

1.57 53 68 53 75

2.07 50 61 46 74

2.17 49 55 45 60

2.27 48 48 46 52

2.37 48 45 44 51

2.47 48 44 42 52

2.57 48 44 42 50

3.07 48 44 42 50



APPENDIX 5

TEST DATA LOG SHEETS

1(a) Clarification Test using a typical Magnapool™ mineral blend

Test Site: Date:

Purpose of Test: Turbidity Sample Volume Alkalinity

165FTU 2000ml 250mg/l

PH 7.4

Temp 22°C

Conducted by: Jar Size

TEST CONDITIONS

Mixing Regimes Mixing Speed (rpm) Duration (Min) Velocity Gradient (Gs⁻1)

Test ID Jar ID Stock IDDosage

(ppm)

Test Start

Time

Residual

Turbidity

Final

AlkalinityPH

Temp

(°C)

Test End

Time

1 1 1 0 1.02 80 249 7.2 22 1.35

2 1 2500 1.02 58 188 7.2 22 1.35

3 1 3000 1.02 26 125 7.2 22 1.35

4 1 3500 1.02 33 136 7.2 22 1.35

120 2

Nonso Okafor 2000ml

Rapid Mix 195

Magnapool™ mineral blend

PoolrIte R&D Laboratory 2/06/2011

Flocculation performance Experiment

Flocculant:

0

Test Report Log

No Mix 0

20 30

60

Slow 17.4



1(b) Clarification Test using NaCl

Test Site: Date: 2/06/2011

Turbidity Sample Volume Alkalinity

165FTU 2000ml 250mg/l

PH 7.4

Jar Size Temp 22°C

TEST CONDITIONS



(ppm)

Test Start

Time

Residual

Turbidity

Final

AlkalinityPH Temp (°C)

Test End

Time

1 1 2 0 10.30am 90 250 7.3 21.5 12.02pm

2 2 3000 10.30am 150 210 7.3 21.5 12.02pm

3 2 6000 10.30am 160 170 7.3 21.5 12.02pm

4 2 6500 10.30am 160 162 7.3 21.5 12.02pm

Flocculation performance Experiment

0 60 0

97.5% NaClFlocculant:

Conducted by:

PoolrIte R&D Laboratory

Test Report Log

Test Water Characteristics

Nonso Okafor 2000ml

Rapid Mix 120 2 195

Slow 20 30 17.4

No Mix

Purpose of Test:



2 Clarification Performance of Magnapool™ mineral Blend over Time

Test Site: Date:

Purpose of Test: Turbidity Sample VolumeAlkalinity

160FTU 2000ml 250mg/l

PH 7.4

Temp 24°C



4.22pm 150 130 150 110

4.32pm 125 110 130 82

4.42pm 125 95 70 72


(ppm)

Test

Start

Time

PHTemp

(°C)

Test End

Time4.52pm 105 83 55 70

1 1 1 0 3.50pm 7.4 21 4.12 5.02pm 95 60 49 69

2 1 2500 3.50pm 7.4 21 4.12 5.12pm 90 60 40 85

3 1 3000 3.50pm 7.4 21 4.12

4 1 4000 3.50pm 7 21 4.12

No Mix 0 60

120 2

Slow 20 15


Flocculation performance analysis of MgCl2

Turbidity Residual

Flocculant: Magnapool™ Mineral Blend

Test Report Log

Mixing Regimes Mixing Speed (rpm) Duration (Min)

250.2

17.4

0

Velocity Gradient (Gs

TEST CONDITIONS

Nonso Okafor 2000ml

Rapid Mix



3 Tests on the Effect of pH on Flocculation Performance

Test Site: Date:

Purpose of Test: Turbidity Sample VolumeAlkalinity

170FTU 2000ml 245mg/l

PH

Temp 22°C


TEST CONDITIONS

Mixing Regimes Mixing Speed (rpm) Duration (Min)


(ppm)

Test Start

Time

Residual

TurbidityPH

Temp

(°C)

Test End

Time

1 1 1 3000 11.53am 65 7 22 12.13

2 1 3000 11.53am 46 7.5 22 12.13

3 1 3000 11.53am 120 7.9 22 12.13

4 1 3000 11.53am 150 8.2 22 12.13

Test Report Log

Slow 20 15

No Mix 0 60

Nonso Okafor 2000ml

Rapid Mix 120 2

Flocculant: Magnapool™ Salt blend


Comparison of flocculation performance at varying system PH



4 MgCl2 in Isolation from the Magnapool™ Blend

Test Site: Date:

Turbidity Sample Volume Alkalinity

PH 7.5

Temp 24°C



11.35 90 100 120 130


(ppm)

Test Start

Time

Initial

Turbidity

Initial

AlkalinityPH

Temp

(°C)

Test End

Time11.45 85 75 90 120

1 1 1 0 11.07am 160 200 7.5 24 12.13 11.55 80 66 110 115

2 1 500 11.07am 160 230 7.5 24 12.13 12.05 79 60 85 110

3 1 1000 11.07am 160 200 7.5 24 12.13 12.15 81 52 85 110

4 1 1500 11.07am 160 215 7.5 24 12.13 12.25 80 48 75 118

Stock Solutions concetration: 47% MgCl2 Hexahydrate

Purpose of Test:


Turbidity reduction various doses of Flocculant over time

Nonso Okafor 2000ml

Rapid Mix 120 2 250.2

Test Report Log

Experimental Outcome

2000ml

TEST CONDITIONS

Velocity Gradient (Gs⁻1)Duration (Min)Mixing Speed (rpm)Mixing Regimes

Slow 20 15 17.4

No Mix 0 60 0

140



5. Effect of Contaminant Loading on Flocculation

Test Site Date:

Turbidity Sample Vol Alkalinity

2000ml

PH 7.5

Temp 21

Jar Size


12.27 60 105 140 275

12.37 31 84 105 265

Test ID Jar IDDosage

(ppm)

Test Start

Time

Initial

TurbidityWater PH

Temp

(°C)

Test End

Time12.47 22 62 76 256

1 3000 12pm 96 7.5 21 12.17 12.57 19 49 60 250

2 3000 12pm 145 7.5 21 12.17 1.07 11 31 44 242

3 3000 12pm 215 7.5 21 12.17 1.17 8 24 38 230

4 3000 12pm 295 7.5 21 12.17

1

Rapid Mix 120 2

Slow 20 30 17.4

No Mix 0 60 0

Test Report Log

TEST CONDITIONS


Conducted by: Nonso Okafor 2000ml

Stock concentration: 3000ppm of the Mangapool mineral blend.

PoolrIte R&D Laboratory 5/06/2011 Test Water Characteristics

Purpose of Test: Effect of contaminant loading on Flocculation performance



6 Test for the Optimum Magnapool™ Flocculant Dose

Test Site Date:

Turbidity Sample Vol Alkalinity

170FTU 2000ml 250mg/lPH

Temp 24°C

Jar Size


12.17 120 130 115 152

12.27 80 125 105 136

Test ID Jar IDDosage

(ppm)

Test Start

Time

Initial

TurbidityWater PH Temp (°C) Test End Time

12.37 78 103 90 130

1 3000 11.50am 170 7.5 24 12.07pm 12.47 78 90 90 110

2 3150 11.50am 170 7.5 24 12.07pm 12.57 69 90 83 107

3 3350 11.50am 170 7.5 24 12.07pm 1.07 65 86 71 96

4 3450 11.50am 170 7.5 24 12.07pm 1.17 61 84 66 90

1.27 59 78 65 83

1.37 57 77 60 81

1.47 53 76 56 81

1.57 53 68 53 75

2.07 50 61 46 74

2.17 49 55 45 60

2.27 48 48 46 52

2.37 48 45 44 51

2.47 48 44 42 52

2.57 48 44 42 50

3.07 48 44 42 50

Slow 20 15 17.4

1

No Mix 0 60 0

Mixing Speed (rpm) Duration (Min) Velocity Gradient (Gs⁻1)

Rapid Mix 100 2 195

Test Report Log

PoolrIte R&D Laboratory 6/06/2011 Test Water Characteristics

Purpose of Test: Testing the performance of differennt concenrations of the Magnapool salt.

Flocculant: Various concentrations of the Magnapool™ mineral

Conducted by: Nonso Okafor 2000ml

TEST CONDITIONS

Mixing Regimes

Final Project Report - Magnapool · IAP-FINAL PROJECT REPORT The Flocculating Effect of MgCl 2...

Documents

Transcript of Final Project Report - Magnapool · IAP-FINAL PROJECT REPORT The Flocculating Effect of MgCl 2...