Using Coagulation and Dissolved Air Flotation to Treat Algae-Laden Water

208 Pages·2017·4.68 MB·English

by  Kaiyao Gu

Using Coagulation and Dissolved Air Flotation to Treat Algae-Laden Water

by

Kaiyao Gu

A Thesis
presented to
The University of Guelph

In partial fulfilment of requirements
for the degree of
Master of Science
in
Engineering

Guelph, Ontario, Canada

© Kaiyao Gu, December, 2017
Abstract
Using Coagulation and Dissolved Air Flotation to Treat Algae-Laden Water
Kaiyao Gu Advisor: Professor Hongde Zhou
University of Guelph, 2017

Algae inhabit in natural lakes and rivers. They often cause the clogging of filters, increase
chemical costs and produce disinfection by-products (DBPs). Many methods have been used to
remove algae in water treatment industry, among which are coagulation treatment and dissolved
air flotation (DAF). The objectives of this study were to evaluate the performance of coagulation
and DAF in treating algae-laden water. A series of experiments were conducted to study the
effectiveness of coagulation and dissolved air flotation on removing Chlorella, Merismopedia,
Microcystis and Aulacoseira by varying the coagulant dosage and water quality. The process
performance was assessed by measuring turbidity, UV absorbance and TOC. Result showed
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that both two treatment methods could achieve over 80% algae removal. Moreover, the single-
cell algae with oval shape were easier to be removed using coagulation process while DAF showed
high cell removal efficiency for algae that form rectangular colonies.
ACKNOWLEDGEMENTS

First of all, I would like to thank Dr. Hongde Zhou for his great help throughout the entire project.
I couldn’t finish the experiments without his insight and guidance. Every time I had a trouble
about my research, Dr. Zhou always provided useful suggestions that inspired me to solve the
problems. I could not imagine a better advisor for my master study.
Also, I would like to thank Dr. Sheng Chang who served as my advisory committee member. I
am grateful for his help and support for this project.
My sincere thank also go to Dr. Andreas Heyland and Dr. Reynald Tremblay, who provided me
the opportunity to culture algae in their biological laboratory. They provided me many helps during
the algae cultivation.
I would thank all my labmates for their great assistance during the experiments: Edwin Castilla
Rodriguez, Bei Wang, Yu Hou, Craig Duvall and David Rogala. Especially Edwin, who co-
worked with me during coagulation experiments, gave me many advices on testing procedures.
I also appreciated Joanne Ryks, Phil Watson and other university staff for their support and
assistance.
Finally, I would like to thank my family: my parents Jianguo Gu, Chao Ya and my wife Yawen
Fan for keeping support and encouragement throughout my life.
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Table of Contents
1 Introduction ............................................................................................................................. 1
1.1 Problems caused by algae ................................................................................................ 1
1.2 Current status in treating algae-laden water ..................................................................... 1
2 Literature review ...................................................................................................................... 3
2.1 Algae contaminated water sources ................................................................................... 3
2.1.1 Algae bloom distribution .......................................................................................... 3
2.1.2 Cyanobacteria, chlorophyta and diatom ................................................................... 4
2.1.3 Algae characteristics ................................................................................................. 6
2.2 Processes to remove algae from water ............................................................................. 9
2.2.1 Coagulation ............................................................................................................... 9
2.2.2 Dissolved air floatation ........................................................................................... 14
3 Research Objectives .............................................................................................................. 17
4 Methodology .......................................................................................................................... 19
4.1 Materials ......................................................................................................................... 19
4.1.1 Raw water sampling ................................................................................................ 19
4.1.2 Algae cultivation ..................................................................................................... 21
4.1.3 Chemicals ................................................................................................................ 26
4.2 Coagulation .................................................................................................................... 28
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4.2.1 Experimental set-up ................................................................................................ 28
4.2.2 Operating procedure................................................................................................ 29
4.2.3 Sampling ................................................................................................................. 30
4.3 Dissolved air flotation .................................................................................................... 30
4.3.1 Experimental set-up ................................................................................................ 30
4.3.2 Operating procedure................................................................................................ 31
4.3.3 Sampling ................................................................................................................. 33
4.4 Experimental plan .......................................................................................................... 33
4.5 Analysis .......................................................................................................................... 34
4.5.1 Algae cell counting ................................................................................................. 34
4.5.2 Routine water quality analysis ................................................................................ 36
4.6 QC/QA ........................................................................................................................... 36
5 Results and Discussion .......................................................................................................... 38
5.1 Algae and diatom growth ............................................................................................... 38
5.1.1 Chlorella ................................................................................................................. 38
5.1.2 Merismopedia ......................................................................................................... 40
5.1.3 Aulacoseira ............................................................................................................. 42
5.1.4 Microystis ................................................................................................................ 43
5.1.5 Algae cell density under steady state conditions .................................................... 45
5.2 Individual species in de-ionized water ........................................................................... 46
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5.2.1 Jar test results .......................................................................................................... 47
5.2.2 Comparison between coagulants............................................................................. 53
5.3 Mixed species in de-ionized water ................................................................................. 56
5.3.1 Coagulation ............................................................................................................. 56
5.3.2 Dissolved air flotation ............................................................................................. 58
5.4 Mixed species in river water .......................................................................................... 60
5.4.1 Coagulation ............................................................................................................. 61
5.4.2 Dissolved air flotation ............................................................................................. 79
6 Conclusions and Recommendations ...................................................................................... 85
6.1 Conclusions .................................................................................................................... 85
6.2 Recommendations .......................................................................................................... 86
7 References ............................................................................................................................. 87
8 APPENDICES ....................................................................................................................... 98

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List of Figures
Figure 2-1 Distribution of documented HAB outbreaks in North America ................................... 3
Figure 4-1 Raw river water smapling location ............................................................................. 19
Figure 4-2 Stationary stage algae in the cultivation system ......................................................... 24
Figure 4-3 Cultivation condition during stationary stage ............................................................. 25
Figure 4-4 Jar test set-up ............................................................................................................... 29
Figure 4-5 DAF set-up .................................................................................................................. 31
Figure 4-6 Neubaueer chamber details ......................................................................................... 34
Figure 5-1 Chlorella cultivation data ............................................................................................ 38
Figure 5-2 Chlorella cell density versus turbidity and dryweight standard curve ........................ 39
Figure 5-3 Merismopedia cultivation data .................................................................................... 40
Figure 5-4 Merismopedia cell density versus turbidity and dryweight standard curve ................ 41
Figure 5-5 Aulacoseira cultivation data ........................................................................................ 42
Figure 5-6 Microcystis cultivation data ........................................................................................ 43
Figure 5-7 Microcystis cell density versus turbidity and dryweight standard curve .................... 44
Figure 5-8 Algae cell counting, turbidity and dry weight at steadt state ...................................... 45
Figure 5-9 Deionized algae-laden water turbidity removal using aluminum sulfate ................... 47
Figure 5-10 Deionized algae-laden water turbidity removal using ferric sulfate ......................... 49
Figure 5-11 Deionized algae-laden water turbidity removal using poly-ferric sulfate ................. 51
Figure 5-12 Coagulant dosage required to achieve 90% removal for Chlorella and Microcystis 53
Figure 5-13 Coagulant dosage required to achieve 60% removal for Merismopedia and
Aulacoseira ................................................................................................................ 54
Figure 5-14 Turbidity removal from mixed algae-laden water .................................................... 56
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Figure 5-15 Turbidity removal from high hardness river water using aluminum sulfate ............. 61
Figure 5-16 Low hardness river water turbidity removal using aluminum sulfate....................... 62
Figure 5-17 High hardness river water TOC&UV removal using aluminum sulfate ................... 64
Figure 5-18 Low hardness river water TOC&UV removal using aluminum sulfate ................... 65
Figure 5-19 High hardness river water turbidity removal using ferric sulfate ............................. 66
Figure 5-20 Low hardness river water turbidity removal using ferric sulfate .............................. 67
Figure 5-21 High hardness river water TOC&UV removal using ferric sulfate .......................... 68
Figure 5-22 Low hardness river water TOC&UV removal using ferric sulfate ........................... 69
Figure 5-23 High hardness river water turbidity removal using PACl ......................................... 70
Figure 5-24 Low hardness river water turbidity removal using PACl.......................................... 71
Figure 5-25 High hardness river water TOC&UV removal using PACl ...................................... 72
Figure 5-26 Low hardness river water TOC&UV removal using PACl ...................................... 73
Figure 5-27 High hardness river water turbidity removal using PFS ........................................... 74
Figure 5-28 Low hardness river water turbidity removal using PFS ............................................ 75
Figure 5-29 High hardness river water TOC&UV removal using PFS ........................................ 76
Figure 5-30 Low hardness river water TOC&UV removal using PFS ......................................... 77
Figure 5-31 Effects of coagulant doses on DAF performance using aluminum sulfate ............... 79
Figure 5-32 Dosage influence on DAF performance using PACl ................................................ 80
Figure 5-33 pH influence on DAF performance using PACl ....................................................... 81
Figure 5-34 Dosage influence on DAF performance using PACl with modified water ............... 82
Figure 5-35 pH influence on DAF performance using PACl with modified water ...................... 83
Figure 5-36 Additional tests with high hardness water ................................................................ 84

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List of Tables

Table 2-1 Comparison of Cyanobacteria, Chlorophyta and Diatom characteristics ...................... 6
Table 2-2 Comparison of test algae characteristics ........................................................................ 9
Table 2-3 Examples of algae removal using conventional water treatment processes ................. 11
Table 2-4 Characteristics of different coagulants used in this study ............................................ 13
Table 2-5 Summary of DAF operating parameters ....................................................................... 15
Table 2-6 Examples of DAF processes ......................................................................................... 16
Table 4-1 Analyltical methods for test water samples .................................................................. 20
Table 4-2 Composition of algae-spiked water .............................................................................. 21
Table 4-3 Cultivation condition during initial and exponential stages ......................................... 22
Table 4-4 Components of cultivation system ............................................................................... 23
Table 4-5 Composition of BBM medium ..................................................................................... 26
Table 4-6 Composition of BG-11 medium ................................................................................... 27
Table 4-7 Composition of CHU-10 medium ................................................................................ 27
Table 4-8 Main characteristics of coagulants used in this study .................................................. 28
Table 4-9 Experimental plan for coagulation tests ....................................................................... 33
Table 4-10 Experimental plan for DAF tests ................................................................................ 34

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List of Abbreviations
AOM Algal organic matter
C Solubility of air
r
DBPs Disinfection by-products
EOM Extracellular organic matter
DAF Dissolved air flotation
HAB Harmful algal bloom
IOM Intracellular organic matter
K Henry's law solubility constant for nitrogen
n
K Henry's law solubility constant for oxygen
o
MIB 2-Methylisoborneol
NOM Natural organic matter
P Partial pressure of nitrogen
n
P Partial pressure of oxygen
o
TOC Total organic carbon
T&O Taste and odor

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