Fabrication of TiO2-embedded PVDF membranes and their Application in Algae Membranes ...

74 Pages·2013·2.41 MB·English

by  Wayne Hu

FABRICATION OF TIO -EMBEDDED PVDF
2
MEMBRANES AND THEIR APPLICATION
IN ALGAE MEMBRANE BIOREACTOR
SYSTEMS
A Thesis
presented to
the Faculty of the Graduate School
at the University of Missouri-Columbia
In Partial Fulfillment
of the Requirements for the Degree
Master of Science
By
Weiming Hu
Dr. Zhiqiang Hu, Dr. Baolin Deng, Thesis Supervisor
December 2013
APPROVAL

The undersigned, appointed by the dean of the Graduate School, have examined the thesis
entitled
FABRICATION OF TIO2-EMBEDDED PVDF MEMBRANES AND THEIR APPLICATION
IN ALGAE MEMBRANE BIOREACTOR SYSTEMS
presented by Weiming Hu,
a candidate for the degree of master of Science,
and hereby certify that, in their opinion, it is worthy of acceptance.
Professor Zhiqiang Hu
Professor Baolin Deng
Professor Christine Costello

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ACKNOWLEDGEMENTS

First and most importantly, I would like to express my thanks to my advisors Dr. Zhiqiang Hu and
Dr. Baolin Deng, in the Department of Civil and Environmental Engineering for all the time and
effort they dedicated in providing me with constant guidance, numerous advices and generous
encouragement and support throughout my graduate studies.
I also need to extend my gratitude to Dr. Christine Costello in the Department of Bioengineering
for being my graduation thesis committee, her guidance will always been appreciated.
I would like to extend my thanks to PhD candidate Jun Yin, also in the Department of Civil and
Environmental Engineering for sharing his expert experience in membrane technology and
general lab work aspects. Also, my I am grateful for having known and been working with all my
wonderful colleagues from both Dr. Deng and Dr. Hu’s group throughout these years, especially
for Tianyu Tang, Shengnan Xu, Shashikanth Gajaraj, Chiqian Zhang, Peng Wan, Qi Shen, Jialiang
Guo, Jingjing Dai whose cooperation and help really carried me.
At last, I want to thank my parents for being my backbone and harbor through this two years of
study and the first twenty five years of my life.

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TABLE OF CONTENTS
APPROVAL .......................................................................................................................................................... i
ACKNOWLEDGEMENTS .................................................................................................................................. ii
LIST OF TABLES ................................................................................................................................................ v
LIST OF FIGURES ............................................................................................................................................. vi
ABSTRACT ...................................................................................................................................................... viii
CHAPTER ONE ................................................................................................................................................... 1
LITERATURE REVIEW ..................................................................................................................................... 1
1.1. Microalgae and Algae Cultivation............................................................................................................ 1
1.1.1. Microalgae ........................................................................................................................................... 2
1.1.2. Additional Benefits of Microalgae Cultivation .................................................................................... 5
1.1.3. Cultivation Conditions ......................................................................................................................... 5
1.2. Microalgae for Wastewater Treatment ..................................................................................................... 7
1.2.1. Advances in Algae-based Wastewater Treatment ................................................................................ 8
1.3. Promising of Algae-based MBR for Wastewater Polishing and Water Reuse ......................................... 9
1.4. Membrane Technology........................................................................................................................... 10
1.4.1. Membrane Materials .......................................................................................................................... 12
1.4.2. Membrane Modules ........................................................................................................................... 13
1.4.3. Membrane Fouling ............................................................................................................................. 17
1.4.4. Membrane Fouling Mechanisms ........................................................................................................ 18
1.4.5. Membrane Fouling Control ................................................................................................................ 22
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CHAPTER TWO ................................................................................................................................................ 27
METHODOLOGY ............................................................................................................................................. 27
2.1. Membrane Modification and Module Fabrication .................................................................................. 27
2.1.1. Membrane Fabrication materials ........................................................................................................ 27
2.1.2. Fabrication of PVDF/PVDF+TiO Hollow Fiber Membranes ........................................................... 28
2
2.1.3. Assembly of PVDF/PVDF+TiO Hollow Fiber Membrane Modules ............................................... 30
2
2.2. Algal Cultivation .................................................................................................................................... 31
2.3. High-density Algae MBR System Set-up ............................................................................................... 33
CHAPTER THREE ............................................................................................................................................ 39
RESULTS AND DISCUSSION ......................................................................................................................... 39
3.1. High-density algae cultivation ..................................................................................................................... 39
3.2. Nitrogen and phosphorus removal by algae ................................................................................................. 40
3.3. Invasion of filamentous species during algae MBR operation .................................................................... 41
3.4. Membrane fouling monitoring and resistance change before and after cleaning ......................................... 45
3.5. Hollow Fiber Membrane Characterization by SEM and EDS Analysis. ..................................................... 48
CHAPTER FOUR............................................................................................................................................... 52
DISCUSSION ..................................................................................................................................................... 52
CHAPTER FIVE ................................................................................................................................................ 54
CONCLUSION ................................................................................................................................................... 54
REFERENCES ................................................................................................................................................... 56

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LIST OF TABLES
Table 1. A comparison of land use and biofuel productivity between microalgae and other biodiesel feedstocks
(Mata et al. 2010) .................................................................................................................................................. 3
Table 2. Classification of membrane processes (Van Der Bruggen et al. 2003). ............................................... 11
Table 3. Models developed to describe membrane fouling (modified after (Meng et al. 2009)). ...................... 19
Table 4. Membrane modification methods.(Pinnau et al. 1999) ......................................................................... 25
Table 5. Membrane fabrication parameters. ....................................................................................................... 29
Table 6 Hollow fiber membrane module parameters. ......................................................................................... 31
Table 7. Bold’s basal medium (Bold 1949). ....................................................................................................... 32
Table 8. Chemical composition of the feeding solutions. ................................................................................... 33
Table 9. Operating conditions of the high-density algae MBR systems. ............................................................ 34
Table 10. Recovery of membrane total resistance after membrane cleaning. ..................................................... 46
Table 11. Reversible and irreversible resistance calculation after cleaning........................................................ 46
Table 12. Permeance recovery calculation after cleaning. .................................................................................. 47

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LIST OF FIGURES
Figure 1. Plate-and-frame design for the separation of helium from natural gas (Stern et al. 1965). ................. 14
Figure 2. Tubular Membrane Configuration for ultrafiltration from Koch Membrane Systems Inc. (Courtesy
Koch Membrane Systems Inc.). .......................................................................................................................... 15
Figure 3. Spiral membrane module configuration and its cross section view (Courtesy from Koch Membrane
Systems Inc.). ...................................................................................................................................................... 16
Figure 4. Diagram of hollow fiber membrane module (Courtesy Pall Corporation.). ........................................ 17
Figure 5. A schematic of membrane fouling due to: (a) pore blockage, (b) and cake layer formation (Meng et al.
2009). .................................................................................................................................................................. 18
Figure 6. Fabricated hollow fiber membranes. ................................................................................................... 29
Figure 7. Two hollow fiber membrane module designs, complex design (top) and simple design (bottom). .... 30
Figure 8. Experimental set-up of two parallel high-density algal MBR systems................................................ 34
Figure 9 Biomass concentration monitoring for high-density algae cultivation in two identical bioreactors:
MBR#1 (●), and MBR#2 (●). .......................................................................................................................... 39
Figure 10. Influent (■) and effluent NO --N concentrations of the high-density algae cultivation systems:
3
MBR#1 (●), and MBR#2 (●). .......................................................................................................................... 40
Figure 11. Influent (■) and effluent phosphorus concentrations of the high-density algae cultivation systems:
MBR#1 (●), and MBR#2 (●). .......................................................................................................................... 41
Figure 13. Settling of contaminated algae mix, (1) algae suspension right after string, (2) at 1 min settling, (3) at
1 min 40 s settling. .............................................................................................................................................. 43
Figure 14. Change in algae floc size during the study period. ............................................................................ 44
Figure 15 Fluorescence light source spectrum for algae cultivation tested by Ocean Optics PC2000 PC plug-in
Spectrometer. ...................................................................................................................................................... 44
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Figure 16. The change in total membrane resistance during the study period between the two types of membranes,
PVDF (●) and PVDF+TiO membranes (●). ................................................................................................... 45
2
Figure 17. SEM images of the surfaces of (a), (c) clean PVDF hollow fiber membranes; (b), (d) clean
PVDF+TiO membranes. .................................................................................................................................... 48
2
Figure 18. SEM images of the surfaces of (a), (c) fouled PVDF hollow fiber membranes; (b), (d) fouled PVDF+
TiO membranes after 112 days of operation. .................................................................................................... 49
2
Figure 19. SEM images of the surfaces of (a), (c) cleaned PVDF hollow fiber membranes; (b), (d) cleaned
PVDF+TiO membranes after complete cleaning. ............................................................................................. 50
2

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FABRICATION OF TIO -EMBEDDED PVDF
2
MEMBRANES AND THEIR APPLICATION IN ALGAE
MEMBRANE BIOREACTOR SYSTEMS
Weiming Hu
ABSTRACT
Polyvinylidene difluoride (PVDF) membranes with and without TiO (5% by mass) were
2
fabricated and applied for high-density algae cultivation in membrane algae bioreactors (MBR).
Microalgae species Chlorella Vulgaris was cultivated in the MBR systems fed with artificial
wastewater at a target solids retention time (SRT) of 25 days. Under steady-state conditions, the
MBR systems had an average algae biomass concentration of 2350 mg/L (COD unit) with
simultaneous removal of about 78% of phosphorus and 34% of nitrogen form wastewater. The
anti-fouling characteristics of membranes were evaluated based on the measurement of intrinsic,
reversible and irreversible resistances, and the scanning electron spectroscopy (SEM) study. Total
resistance of TiO -embedded membranes was 65% lower than the control (membranes without
2
TiO impregnation) during 90 days of operation. This research demonstrated that embedding TiO
2 2
into the PVDF membranes resulted in membranes with better antifouling properties for high-
density algae cultivation.
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CHAPTER ONE
LITERATURE REVIEW
1.1. Microalgae and Algae Cultivation
The emission of greenhouse gases including carbon dioxide (CO ), nitrous oxide (N O), and
2 2
methane (CH ) is increasing with the growth of global economy which could lead to an average
4
global temperature increase of 3.6 °C (IEA 2012). Greenhouse gases emissions can also contribute
to other environmental problems. For instance, oceans as one of the biggest consumer of CO
2
absorb approximately 30% of CO emitted by human activities each year, and absorption of CO
2 2
in oceans will lower the pH of water, which can cause the loss of aquatic life and further damage
the marine ecosystem. In 2006 alone, the amount of CO emissions to the atmosphere were 29 Gt,
2
and the estimated removal of CO by natural environment was about 12 Gt (EIA 2006). Hence,
2
mitigation strategies are required to remove excess CO . Finding the solution toward the use of
2
clean and renewable energy sources that produce less greenhouse gases is now one of the most
important and challenging issues facing human societies.
Many renewable energy options are being studied and each has a different degree of success and
challenges for implementation. These options include biofuel, solar energy, wind, and geothermal
applications. For global warming control, techniques such as carbon sequestration have been
proposed. Biofuel production development has shown rapid growth globally, because of its
potential for reducing greenhouse gases and achieving energy security (IEA 2007). Most common
biofuels are biodiesel and bioethanol, both of which can replace fossil fuels such as diesel and
gasoline.
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