recovery of surface active material from municipal wastewater activated sludge

155 Pages·2010·2.03 MB·English

RECOVERY OF SURFACE ACTIVE MATERIAL
FROM MUNICIPAL WASTEWATER ACTIVATED
SLUDGE

by
Flor Yunuén García Becerra

A thesis submitted in conformity with the requirements
for the degree of Doctor of Philosophy
Department of Chemical Engineering and Applied Chemistry
University of Toronto

© Copyright by Flor Yunuén García Becerra 2010
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Recovery of surface active material from municipal Wastewater Activated Sludge
Doctor of Philosophy, 2010
Flor Yunuén García Becerra
Department of Chemical Engineering and Applied Chemistry
University of Toronto

Abstract

Wastewater activated sludge is produced during the biological treatment of wastewater.
After treating the sewage, the sludge is allowed to settle. Part of the settled material is
returned to the treatment process as return activated sludge (RAS) and the excess is removed
as waste activated sludge (WAS). The handling and disposal of the sludge are energy and
capital-intensive treatments, with a significant environmental impact. This work studies the
possibility to utilize RAS (an example of wastewater sludge) as a source of surface active
agents. The results indicate that higly surface active materials can be extracted from RAS,
and that the RAS extract has potential applications as a detergent and wood adhesive. The
results also suggest that recovering a suite of products from RAS, a biological heterogenous
source, can be technically feasible.
An effective alkaline treatment was developed (at pH>12) that can extract up to 75% of
the sludge’s organic matter, a yield higher than previously reported. Increasing the
extraction pH increased the extract surface activity, which is linked to increasing the amount
of higher molecular weight molecules and the presence of phospholipids. Increasing the
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extraction pH beyond 11 was also related to extensive cell lysis, increasing significantly the
amount of recovered material and the surface activity of the extract.
The alkaline extract has properties comparable to commercial detergents. Without further
purification, the extract has a low surface tension (37 mN/m on average) and performs
similarly to synthetic detergents. Further assessment of the RAS extract (insensitivity to pH,
surface tension, interfacial tension) suggests that it may be suitable for commercial
applications.
The RAS extract can also be formulated into wood adhesives using glutaraldehyde as a
crosslinker. The extract fraction with 10-50 kDa constituents at pH 9 achieves high adhesive
shear strengths (4.5 MPa on average, at 30% relative humidity and 25°C) with 40% of wood
failure. The adhesive strength of RAS-based adhesives is strongly correlated to its protein
content.
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Acknowledgments

I would like to express my sincere gratitude and appreciation to the following people and
organizations:

• I am especially grateful to Professor D. Grant Allen and Professor Edgar J. Acosta for
their supervision, encouragement, support, and patience. In their own way, both have
inspired me with their admirable qualities as individuals and scientist. I feel fortunate
to have had such talented mentorship as a graduate student.

• Professors Levente Diosady and Steven Liss for their thoughtful guidance and
dedication as members of my reading committee.

• Professors Mohini Sain and Amarjeet S. Bassi, for their interest in my research and
valuable feedback.

• CONACyT (Mexican Advisory Board of Science and Technology) and the
Environmental Consortium Members of the Pulp and Paper Centre at University of
Toronto for their financial support.

• The administrative and technical staff in the Department of Chemical Engineering
and Applied Chemistry for their kind assistance through out my stay in this
department.

• The summer students and 4th year thesis students that helped me through out my
experiments, many thanks for all your hard work.

• My colleagues in Professor Acosta’s lab: Carol, Jackie, Jessica, Sumit, Suniya; and
Professor Allen’s lab: Alex, Chris, Candida, Elena, Ivy, Nalina, Tyler, and Yaldah.
Thank you for your support, feedback and friendship.

• Elena, Fleur, Maida, Megan and Sabina for their invaluable experience as graduate
students, brilliant scientists, and lovely friendship.

• All those friends who made my life richer and made me stronger as an individual.

• Dr. Levine for providing me the tools to move forward and mi Angelito to help me
appreciate the life in me.

• Jesus and Palas Atenea for our childhood friendship and dreams of becoming
someone great.

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• My mother, Silvia Aurora Becerra Langarica and my father, Martin Garcia
Hernandez for their love, support, inspiration, the family they gave me and for
providing me with the best gift in my life: my sister Silvia Patricia Garcia Becerra.

• To the beautiful Patricia of my heart, my sister of blood and soul.

• Finalmente, le doy gracias a Dios por sus bendiciones, por las oportunidades de
crecimiento, sonrisas brindadas. Finally, I would like to thank God for the blessings,
growth opportunities, and the smiles that have been given to me.

No te salves Don’t save yourself
(by Mario Benedetti)
No te quedes inmóvil Don't stay motionless
al borde del camino by the roadside
no congeles el júbilo don't freeze joy
no quieras con desgana or love halfheartedly
no te salves ahora don't save yourself now
ni nunca or ever

No te salves Don't save yourself
no te llenes de calma don't become serene
no reserves del mundo don’t make of the world
sólo un rincón tranquilo only a safe place
no dejes caer los párpados don't let your eyelids close
pesados como juicios heavy as judgements
no te quedes sin labios don't stay without lips
no te duermas sin sueño don't sleep without dreams,
no te pienses sin sangre imagine youself bloodless
no te juzgues sin tiempo or judge yourself in haste

Pero si But if
pese a todo in spite of everything
no puedes evitarlo you can't help it
y congelas el jubilo and you freeze joy
y quieres con desgana and you love halfheartedly
y te salvas ahora and you save yourself,
y te llenas de calma become serene,
y reservas del mundo and you make of the world
sólo un rincón tranquilo only a safe place,
y dejas caer los párpados and let your eyelids drop
pesados como juicios heavy as judgements
y te secas sin labios and stay without lips
y te duermes sin sueño and sleep without dreams,
y te piensas sin sangre imagine yourself bloodless,
y te juzgas sin tiempo judge yourself in haste
y te quedas inmóvil and stay motionless
al borde del camino by the side of the road
y te salvas and you save yourself
entonces then
no te quedes conmigo don't stay with me.

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Table of contents
Table of contents..................................................................................................................................................vi
List of tables.........................................................................................................................................................ix
List of figures........................................................................................................................................................x
CHAPTER 1 INTRODUCTION.................................................................................1
1.1 Statement of research............................................................................................................................1
1.2 Industrial significance of the resulting products.................................................................................2
1.3 Hypotheses and objectives.....................................................................................................................4
1.3.1 Hypotheses..........................................................................................................................................4
1.3.2 Research objectives.............................................................................................................................4
1.4 Thesis outline..........................................................................................................................................5
1.5 Publications and conference participations derived from this thesis.................................................8
CHAPTER 2 LITERATURE REVIEW.....................................................................10
2.1 Potential of wastewater activated sludge as a raw material of value added products....................10
2.2 Wastewater activated sludge constituents..........................................................................................11
2.3 Microbial exopolymeric polysaccharides and proteins.....................................................................14
2.3.1 Microbial exopolysaccharides...........................................................................................................14
2.3.2 Microbial exoproteins........................................................................................................................15
2.4 Biologically based surface active agents.............................................................................................17
2.4.1 Biological emulsifiers........................................................................................................................17
2.4.2 Biological adhesives..........................................................................................................................18
2.5 Analytical extraction of EPS from wastewater sludge......................................................................19
2.6 Extraction of value added products from wastewater sludge..........................................................22
2.7 Product recovery..................................................................................................................................23
2.7.1 Biopolymer fractionation using ultrafiltration...................................................................................26
2.8 Significance of this research................................................................................................................28
CHAPTER 3 ALKALINE EXTRACTION OF WASTEWATER ACTIVATED
SLUDGE BIOSOLIDS.............................................................................................30
3.1 Abstract.................................................................................................................................................30
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3.2 Introduction..........................................................................................................................................30
3.3 Materials and Methods........................................................................................................................34
3.3.1 Materials............................................................................................................................................34
3.3.2 Methods.............................................................................................................................................35
Determination of extraction pH range.............................................................................................................35
Determination of cell lysis during alkaline extraction.....................................................................................35
Effect of extraction pH on extract yield and composition...............................................................................36
3.4 Results and Discussion.........................................................................................................................39
3.4.1 Long-term extraction studies.............................................................................................................39
3.4.2 Short-term extraction studies (48 h)..................................................................................................42
3.4.3 Effect of extraction pH on extract yield and composition.................................................................44
3.4.4 Extraction kinetics and yield.............................................................................................................45
3.4.5 Chemical composition (protein, polysaccharide, and lipid content)..................................................48
3.4.6 Physical properties of the extracts.....................................................................................................53
3.4.7 Fractionation and NMR characterization of the extract.....................................................................56
3.5 Conclusions...........................................................................................................................................59
3.6 Acknowledgments................................................................................................................................60
CHAPTER 4 SURFACTANT-LIKE PROPERTIES OF ALKALINE EXTRACTS
FROM WASTEWATER BIOSOLIDS.......................................................................61
4.1 Abstract.................................................................................................................................................61
4.2 Introduction..........................................................................................................................................62
4.3 Materials and Methods........................................................................................................................66
4.3.1 Materials............................................................................................................................................66
4.3.2 Methods.............................................................................................................................................66
Effect of extraction pH on surface activity......................................................................................................66
Interfacial activity and detergency performance of the pH 12.6 extract..........................................................68
4.4 Results and Discussion.........................................................................................................................70
4.4.1 Effect of extraction pH on surface activity........................................................................................70
4.4.2 Surface activity, interfacial activity and detergency performance of pH 12.6 extract.......................77
4.4.3 Potential applications and outlook.....................................................................................................83
4.5 Acknowledgments................................................................................................................................84
CHAPTER 5 WOOD ADHESIVES BASED ON ALKALINE EXTRACTS FROM
WASTEWATER BIOSOLIDS..................................................................................85
5.1 Abstract.................................................................................................................................................85
5.2 Introduction..........................................................................................................................................85
5.3 Materials and Methods........................................................................................................................88
5.3.1 Materials............................................................................................................................................88
5.3.2 Methods.............................................................................................................................................89
Production of RAS extract...............................................................................................................................89
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Preparation of alkali-modified MSPI...............................................................................................................91
Characterization of the RAS extract, RAS fractions, and modified MSPI......................................................92
Formulation of adhesives.................................................................................................................................93
5.4 Results and Discussion.........................................................................................................................94
5.4.1 Chemical and physical characterization of RAS extract, extract fractions, and modified MSPI.......94
5.4.2 Rheological properties of formulated adhesives................................................................................98
5.4.3 Analysis of adhesive strength on wood...........................................................................................101
CHAPTER 6 PRELIMINARY FEASIBILITY ASSESSMENT OF THE
PRODUCTION OF DETERGENTS AND ADHESIVES FROM MUNICIPAL
RETURN ACTIVATED SLUDGE (RAS)................................................................106
6.1 Process description.............................................................................................................................106
6.1.1 Recovery of detergents from RAS...................................................................................................106
6.1.2 Recovery of Adhesives from RAS..................................................................................................109
6.2 Preliminary analysis for the production of value-added surface active agents from RAS..........109
6.3 Recommendations for future work...................................................................................................111
6.3.1 Extraction........................................................................................................................................112
6.3.2 Recovery..........................................................................................................................................112
6.3.3 Formulation.....................................................................................................................................113
6.3.4 Additional issues.............................................................................................................................114
6.4 The importance of utilizing RAS as a resource...............................................................................114
CHAPTER 7 OVERALL DISCUSSION AND SIGNIFICANCE OF RESEARCH
FINDINGS..............................................................................................................116
7.1 Effective extraction of biopolymers from a heterogeneous culture...............................................117
7.2 Potential of RAS to produce surface active agents..........................................................................118
7.2.1 Detergents........................................................................................................................................120
7.2.2 Adhesives........................................................................................................................................121
7.3 Additional Comments........................................................................................................................124
CHAPTER 8 CONCLUSIONS AND RECOMMENDATIONS...............................125
8.1 Conclusions.........................................................................................................................................125
8.2 Recommendations..............................................................................................................................127
REFERENCES......................................................................................................129
APPENDICES........................................................................................................139

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List of tables

Table 2-1 Characterization of EPS from municipal activated sludges with respect to protein and polysaccharides
....................................................................................................................................................................12
Table 2-2 Effect of polysaccharide composition on physical properties (Sutherland, 2001)...............................14
Table 2-3 Effect of molecular properties of proteins on physical properties (Magdassi, 1996)...........................16
Table 2-4 Surface tension, γ, of commercial hydrocolloids and proteins (Bhattacharjee, 1994; Garti & Leser,
2001)...........................................................................................................................................................18
Table 2-5 Shear strengths of various biopolymers as adhesives (Haag et al., 2006; Haag et al., 2004)...............19
Table 2-6 Comparison of selected EPS extraction methods.................................................................................20
Table 2-7 Separation techniques for biotechnological products commonly used for industrial applications
(Ghosh, 2003; Henry & Yonker, 2006)......................................................................................................25
Table 4-1 Extraction parameters for material recovered at pH 12.0, 12.6, and 12.9 from municipal aerobic return
activated sludge. RAS Sample collected in 2007. The concentration of the extracts are given in grams of
total organic carbon (TOC) per L. Yield is defined on the basis of dry mass total organic carbon (TOC) of
the concentrated RAS sample. Errors indicate the 95% confidence intervals...........................................70
Table 4-2 Elemental analysis (metallic content) of the 2008 extract. All values in mg/L. The Na concentration
in the blank (pH 12.6) is 2267 mg/L. Other metals that were assayed are not reported as they were all
below the detection limit.............................................................................................................................71
Table 5-1 Mass balance on Total Organic Carbon (TOC) bases for the downstream process suggested in
Chapter 4. The yield is calculated with respect to the RAS extract...........................................................91
Table 5-2 Rheological parameters of RAS extract and fractions..........................................................................99
Table 6-1 Historical average values (TOC basis) of the concentrated RAS and RAS extract (2005-2009).......107
Table 6-2 Calculations for the production of 1 kg of detergent or adhesives from RAS. The prices of NaOH is
of January 2010 at $0.17/kg (Anonymous, 2010a) and glutaraldehyde at $310/kg (Duvic, 2010)...........110

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List of figures

Figure 1-1 Simplified diagram of the Activated Sludge Treatment........................................................................1
Figure 1-2 Experimental approach for this thesis..................................................................................................5
Figure 1-3 Distribution of the experimental phases in the thesis............................................................................7
Figure 3-1 Influence of extraction pH on extraction yield (a) and surface tension of the extract (b). The extract
yield is presented as grams of Total Organic Carbon (TOC) content in the supernatant (extract) obtaining
from treating the equivalent of 100 grams of TOC in the return activated sludge (RAS). Extraction time:
5 weeks. Controls in surface tension measurements: Distilled Water, 70.5 mN/m; NaOH at pH 12.6, 65
mN/m. RAS sample collected in January 2006, Initial TOC = 3500 mg/L................................................40
Figure 3-2 Effect of extraction time and extraction pH on TOC extraction yield (a) and DNA release from the
extracts (b). The extract yield is presented as grams of TOC content in the supernatant (extract) obtaining
from treating the equivalent of 100 grams of TOC in RAS. Extraction conditions: pH range from 9 to 13;
extraction time up to 48h; room temperature. Total DNA extracted from the concentrated RAS was
measured to be 45 mg/L. RAS sample collected in March 2009, Initial TOC = 6500 mg/L......................43
Figure 3-3 Sodium hydroxide (NaOH) required to increase the pH of the concentrated RAS sample. TOC in
concentrated RAS sample: 5.8±0.7 g/L, samples obtained in June-July of 2007. Error bars indicate the
95% confidence intervals............................................................................................................................44
Figure 3-4 Extraction kinetics of alkaline and CER extractions. TOC content in the extracts (supernatants) as a
function of extraction time. Extraction conditions for alkaline extraction: pH range from 12.0 to 12.9;
extraction time up to 24 h; room temperature. TOC in concentrated RAS sample: 5.8±0.7 g/L, samples
obtained in June-July of 2007. Error bars indicate the 95% confidence intervals......................................45
Figure 3-5 Extraction yield in log -log plot. Influence of extraction time on the extraction yield..................47
10 10
Figure 3-6 Extraction yield towards protein (a), polysaccharides (b), and lipids (c) as a function of extraction
time. These yields were calculated as grams of TOC of the particular fraction measured obtained from the
equivalent of 100 grams of TOC in the concentrated RAS. For proteins the surrogate compound used in
the calculations was BSA and for carbohydrates, D-glucose. TOC in concentrated RAS sample: 5.8±0.7
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