PHYCO-REMEDIATION OF AZO DYE CONTAMINATED WASTEWATER BY Muhammad Rashid Waqas M.Sc. (Hons.) Soil Science A thesis submitted in partial fulfillment of the requirement for the degree of DOCTOR OF PHILOSOPHY IN SOIL SCIENCE Institute of Soil and Environmental Sciences University of Agriculture Faisalabad, Pakistan 2014
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PHYCO-REMEDIATION OF AZO DYE CONTAMINATED
WASTEWATER
BY
Muhammad Rashid Waqas
M.Sc. (Hons.) Soil Science
A thesis submitted in partial fulfillment of the requirement for the degree of
DOCTOR OF PHILOSOPHY
IN
SOIL SCIENCE
Institute of Soil and Environmental Sciences
University of Agriculture
Faisalabad, Pakistan
2014
iii
The Controller of Examinations
University of Agriculture,
Faisalabad
“We, the supervisory committee, certify that the contents and form of this thesis
submitted by Mr. Muhammad Rashid Waqas (Reg No. 2003-ag-2368) have been
found satisfactory, and recommend that it be processed for evaluation by the External
Examiner(s) for the award of degree”.
SUPERVISORY COMMITTEE
Chairman _______________________
(Dr. Muhammad Arshad (T.I)
Member _______________________
(Dr. Hafiz Naeem Asghar)
Member _______________________
(Dr. Muhammad Asghar)
iv
DECLARATION
I hereby declare that the contents of the thesis “Phyco-remediation of azo dye
contaminated wastewater” are product of my own research and no part has been copied
from any published source (except the references, standard procedures and protocols etc.). I
further declare that this work has not been submitted for any diploma/degree. This university
may take action if the information provided is found inaccurate at any stage.
Muhammad Rashid Waqas
2003-ag-23688
v
To
Who taught me first word to speak and first step to take
parents
DDeeddiiccaatteedd
vi
ACKNOWLEDGEMENTS
All the praises and thanks to Allah Almighty, the most Merciful Who enabled me to
complete this study. I pay a great tribute to the last prophet of the Creator – Muhammad (Peace be upon him) who is forever torch of guidance and knowledge for humanity as a whole.
I feel great pleasure to express my sincere gratitude to my kind supervisor, Dr. Muhammad Arshad (T.I.), Professor, Dean, Faculty of Agriculture and Director of Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad for his guidance and enormous support concerning my research and education. He elevated my research abilities to their highest and provided enthusiastically guidance and best cooperation in thesis write up.
I am also grateful to my thesis committee, Dr. Hafiz Naeem Asghar, Assistant Professor, Institute of Soil and Environmental Sciences, and Dr. Muhammad Asghar, Professor, Chairman, Department of Chemistry and Biochemistry, University of Agriculture, Faisalabad for their valuable time and insightful comments.
I am also highly thankful to Dr. Azeem Khalid Associate Professor, Department of Environmental Sciences, PMAS Arid Agriculture University, Rawalpindi for his enormous assistance and support in my thesis write up.
I would like to give very Special thanks to Mr. Khaliq-ur-Rehman Arshad, Dr. Zia Chishti and Dr. Sarfraz Hussain, Pesticide Quality Control Lab. Institute of Soil Chemistry and Environmental Sciences AARI, Faisalabad, for their technical support and cooperation in analytical work and in improvement of this manuscript.
I would like to pay profound gratitude to my lab fellows Zulfiqar Ahmad, Dr. Muhammad Imran, Dr. Zia-ul-Hasan, Dr. Masood Saleem, Allah Ditta, Wazir Ahmad, Farhat Bashir and Uncle Sarwar (ISES, UAF) for their company and moral support during my research work. Special thanks to my special friend Muhammad Imran (University of Sargodha), for his support on each and every step.
I would like to give my deepest appreciation to my parents, brothers and sisters who supported me in all my life for all their love, prayers and encouragement – indispensable during the course of these research studies. Very special thanks to my loving, supportive and encouraging wife, Nazia Fakhar, this research work and thesis was simply impossible without her loving support and sacrifices. Special love for my son Muhammad Ayan Rashid, his cute smile always gave me freshness and eagerness to work.
Lastly, I offer my regards and blessings to all of those who supported me in any respect during the completion of the thesis.
Muhammad Rashid Waqas 2003-ag-2368
vii
CONTENTS
Chapter Title Page No.
Chapter 1 INTRODUCTION 1
Chapter 2 REVIEW OF LITERATURE 5
2.1 Textile industry in Pakistan 5
2.1.1 Textile wastewater flows 8
2.1.2 Characteristics of textile wastewater 8
2.2. Azo dyes and their impact on the environment 11
2.3.3. Phycology and phyco-remediation of textile wastewaters 16
Chapter 3 MATERIALS AND METHODS 20
3.1 Sampling of water for the isolation of algae 20 3.2 Analysis of collected water samples 20 3.2.1. Electrical conductivity (EC) 20 3.2.2. pH 20 3.3. Isolation of algal strains 22 3.3.1. Screening of the azo dye degrading algal strains 23 3.4. Optimization of environmental factors 24 3.4.1. Substrate (azo dye) concentration 24 3.4.2. pH 24 3.4.3. Temperature 24 3.4.4. Effect of nitrogen (N) 24 3.4.5. Effect of phosphorus (P) 25
3.4.6. Effect of salinity 25
3.4.7. Effect of light conditions 25
3.4.8. Effect of inoculum size 25 3.5 Phyco-remediation of structurally different azo dyes 25 3.6 Decolorization of mixture of azo dyes 26 3.7. Phycoremediation of real textile wastewater 28 3.7.1. Characteristics of wastewater samples 28
viii
3.8. Toxicity analysis 28
3.8.1. Hemolytic activity 28
3.9. Use of Phyco-remediated wastewater as irrigation 29 3.10. Biodiesel production 30 3.10.1. Oil extraction 30 3.10.2. Trans-esterification 30
3.10.3. Separation of biodiesel 30
3.11. Statistical analysis 30
Chapter 4 RESULTS 31
4.1. Analysis of water samples 31
4.1.1. pH 31
4.1.2. TSS 32
4.2. Isolation and screening of azo dye decolorizing Algae 32
4.4. Phyco-remediation of structurally different azo dyes 48 4.4.1. Phycoremediation of reactive dyes 48 4.4.2. Phycoremediation of direct group dyes 52 4.4.3. Phycoremediation of Disperse group dyes 56 4.5. Phycoremediation of mixture of azo dyes 60 4.6. Phycoremediation of real textile wastewater 62 4.6.1. Case study I (Wastewater from Shaheen Cloth Processing Mills) 62 4.6.2. Case Study II (Wastewater from Qadafi Textile) 65 4.6.3. Case study III (Wastewater from Dawood Textile Mills) 68 4.7 Toxicity analysis 71 4.7.1 Toxicity test of mixture of azo dyes after decolorization by algal
strains 71
ix
4.7.2 Toxicity test of real textile wastewater after decolorization by algal strains
71
4.7.2.1 Toxicity analysis: Case study I 71 4.7.2.2 Toxicity analysis: Case study II 72 4.7.2.3 Toxicity analysis: Case study III 72 4.8. Use of Phyco-remediated wastewater as irrigation 77 4.9. Biodiesel production from algal biomass 79 4.9.1. Algal biomass 79 4.9.2. Biodiesel production 79 4.9.3. Biomass recovery after oil extraction 79
Chapter 5 DISCUSSION 84
SUMMARY 89
LITERATURE CITED 92
x
LIST OF FIGURES S. No. Title
Page No.
4.1 Decolorization of Reactive Blue dye by different algal strains isolated from various water samples through enrichment
34
4.2. Effect of substrate concentration on decolorization of Reactive Blue dye by the selected algal strains
36
4.3. Effect of pH on decolorization of Reactive Blue by the selected algal strains. 38
4.4. Effect of temperature on decolorization of Reactive Blue by the selected algal strains.
39
4.5. Effect of day light conditions on decolorization of Reactive Blue by the selected algal strains.
41
4.6. Effect of inoculums size on decolorization of Reactive Blue by the selected algal strains.
42
4.7. Effect of salinity on decolorization of Reactive Blue by the selected algal strains.
44
4.8. Effect of additional N source on decolorization of Reactive Blue by the selected algal strains.
46
4.9. Effect of additional P source on decolorization of Reactive Blue by the selected algal strains.
47
4.10 Decolorization of Orange RR Reactive azo dye by selected stains of algae. 49 4.11 Decolorization of Red S3B Reactive azo dye by selected stains of algae. 50 4.12 Decolorization of Mixture of Reactive azo dyes by selected stains of algae. 51 4.13 Decolorization of Yellow UG Direct azo dye by selected stains of algae. 53
4.14 Decolorization of Congo Red Direct azo dye by selected stains of algae. 54 4.15 Decolorization of Mixture of direct azo dyes by selected stains of algae. 55 4.16 Decolorization of Disperse Blue ZBLN azo dye by selected stains of algae. 57 4.17 Decolorization of Scarlet Disperse azo dye by selected stains of algae. 58 4.18 Decolorization of Mixture of disperse azo dyes by selected stains of algae. 59 4.19 Decolorization of Mixture of reactive, direct and disperse group azo dyes by
selected strains of algae 61
4.20 Phycoremediation of real textile wastewater sample # 1 (collected from Shaheen Cloth Processing Mills) by algal strains.
63
4.21 Comparitive phycoremediation of real textile wastewater sample # 1 (collected from Shaheen Cloth Processing Mills) by living or dead cells of algae.
64
4.22 Phycoremediation of real textile wastewater sample # 2 (collected from Qadafi Textiles) by two selected algal strains.
66
4.23 Comparison phycoremediation of real textile wastewater sample # 2 (collected from Qadafi Textiles) by living or dead cells of algae.
67
4.24 Phycoremediation of real textile wastewater sample # 3 (collected from Dawood Textiles) by two selected algal strains.
69
4.25 Comparison phycoremediation of real textile wastewater sample # 3 (collected from Dawood Textiles) by living or dead cells of algae.
70
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4.26 Hemolytic activity of Mixture of disperse, reactive and direct azo dyes phycoremediated by selected stains of algae.
73
4.27 Hemolytic activity of real textile wastewater collected from Shaheen Cloth Processing Mills after treated with selected strains of algae
74
4.28 Hemolytic activity of real textile wastewater collected from Qadafi Cloth Processing Mills after treated with selected strains of algae
75
4.29 Hemolytic activity of real textile wastewater collected from Dawood Cloth Processing Mills after treated with selected strains of algae
76
4.30 Growth of selected algal strains on real textile wastewater (phycoremediated) and normal culture medium for period of 5 days.
81
4.31 Biodiesel production of selected algal strains grown on real textile wastewater (phycoremediated) and normal culture medium.
82
4.32 Biomass recovery after oil extraction in case of algae grown on real textile wastewater (phycoremediated) vs. normal culture medium.
83
xii
LIST OF TABLES
S. No.
Title Page No.
2.1 Region wise distribution of large, medium and small textile industries 6
2.2 List of dyes imported in Pakistan (2009 - 2010) and cumulative assessed
value in US$
7
2.3 Estimated Wastewater generated from Textile Processing 9
2.4 Characteristics of wastewater released by textile processing industry 10
3.1 Water samples collected from different sites with their identification number
21
4.1
Water analysis and isolation of algae from water samples collected from different locations
33
4.2 Impact of real and phycoremediated wastewater on wheat growth under axenic conditions
78
xiii
Abstract
Synthetic dyes are widely used in textile, leather and other dye-stuff industries. A large
fraction of the dyes applied during the dyeing processes are released into wastewater.
Therefore, the wastewater from dye-related industries is very colorful, with high chemical
oxidation and biological oxidation demand. This wastewater must be treated prior to
discharge into wastewater streams to prevent pollution of surface and groundwater, and the
risk to public health. The present study was designed with the aim to isolate potential strains
of algae capable of degrading azo dyes for the treatment of textile wastewater. Eighty-eight
algae strains were isolated on agar plates using modified MA medium. About 20 algal strains
were screened by enrichment of the medium with 100 mg L-1 Reactive Blue azo dye. Out of
20 isolates of algae, two strains CKW1 (Spirogyra sp.) and PKS33 (Cladophora sp.) were
able to decolorize 88% and 83% dye, respectively, in seven days incubation time. The
substrate (dye) 100 mg L-1, pH 8, 30 °C temperature and 16 h light duration were found to be
optimum conditions for maximum decolorization of azo dyes by these strains of algae. Under
optimal conditions, both strains were able to completely decolorize the structurally different
synthetic textile dyes and real textile wastewater in 96 h to 120 h. Algal cells showed a better
efficacy in decolorizing real textile effluent than observed with dead algae biomass (dry).
About 60% decolorization of the real textile wastewater was achieved by living cells in only
24 hours and 80% decolorization in 120 h. Toxicity analyses were performed in terms of
hemolytic activity. The results showed that the treated wastewater with algae living biomass
reduced the toxicity of wastewater by 70-80%, while a reduction of 30-35% of the toxicity
was observed in the case of algae dead mass. The treated textile wastewater also improved
significantly wheat growth compared to untreated real wastewater. Using the trans-
esterification method, it was found that the algal biomass produced by the use of textile
treated effluent could be used to produce biodiesel. These findings suggest that algae could
be used to treat wastewater containing textile dyes that can be used for growing crop plants.
1
INTRODUCTION
Textile industry is one of the largest industrial sectors in Pakistan (Kirk and Ehow,
2008; Ahmad, 2011). The textile industry involves numerous wet processes, including
dyeing, bleaching, desizing and printing. The estimated amount of wastewater released by
the textile processing units is 114,41167 m3/day (Govt. of Punjab, 2008). Synthetic dyes have
wide application in the textile and other dye-stuff industry. According to an estimate, global
production of synthetic dyes is more than 700,000 tonnes and textile sector alone consumes
about 60% of the total production of dyes (Robinson et al., 2001; Shinde and Thorat, 2013).
Since dyeing process is not very efficient, production of highly colored wastewater is
enormous. The amount lost in wastewater is a function of the class of dyes and in general,
their loss through discharge in the wastewater can be 2% of the initial concentration of basic
dyes to as high as 50% of a reactive dye (Tan et al., 2000; Boer et al., 2004; Wins and
Murgan, 2010). Thus, the wastewater discharged from the textile industry contains huge
amount of synthetic dyes.
In Pakistan, textile wastewater is commonly used for irrigation to grow crops by
farming community, particularly in urban and peri-urban areas. The wastewater contain
heavy pollution load in terms of high biological oxygen demand (BOD), chemical oxygen
demand (COD), total dissolved solids (TDS), total soluble solids (TSS), and organic (mainly
azo dyes) and inorganic compounds (Pathak et al., 1999; Siddique et al., 2010). Therefore,
textile wastewater could be damaging to the soil health and aquatic ecosystem (Kaur et al.,
2010). Moreover, plants can uptake dye compounds which may affect human health through
food chain (Yousaf et al., 2010).
Azo dyes are a group of synthetic dyes containing one or more azo (–N=N–)
chromophores. Such dyes are considered to be electron-deficient compounds, as they possess
the azo (–N=N–) and sulfonic acid (SO3-) electron withdrawing groups, resulting in a deficit
of electrons in the molecule which renders the compound more sensitive to oxidative
catabolism by microorganisms. Hence, azo dyes tend to persist under aerobic environmental
conditions (Rieger et al., 2002). Many synthetic dyes and their metabolic intermediate
products are found to be toxic, mutagenic and carcinogenic (Poljsak et al., 2010; Dafale et
al., 2010; Sellamuthu et al. 2011; Yang et al. 2013). Because of the toxicity and recalcitrant
nature, azo dyes have been classified as hazardous to the environment (Souza et al., 2010).
2
The treatment of dye-contaminated wastewater in an environmentally safe manner is
essentially required prior to its disposal.
Various physico-chemical methods are used to remove the dyes from textile
wastewater (Wang et al., 2004; Golab et al., 2005; Saxe , 2006; Alinsafi et al. 2007; Arslan-
Alaton 2007; dos Santos et al., 2007; Wang et al., 2009). These include ozonation,
electrolysis, fenton oxidation, UV-H2O2 oxidation, adsorption, membrane filteration and
coagulation-flocculation (Hao et al., 2000; Mohanty et al., 2006; Rao et al., 2006). Usually,
these methods are not cost effective and environment friendly. Production of a large amount
of sludge also reduces their application because sludge requires an additional treatment for
safe disposal (Banat et al., 1996; Verma and Madamwar, 2003; Anjaneyulu et al., 2005).
Microbes alone or in combination with other strategies can be used to remove azo dyes from
wastewater. Several studies have documented the ability of bacteria, fungi and yeasts to
degrade azo dyes (Stolz, 2001, Prasad et al., 2011). However, it has been observed that the
presence of co-substrates into the dye solution is required to accelerate the microbial growth
and decolorization process (Prasad et al., 2011). Moreover, the presence of salts in textile
effluents, and variable pH and high temperature of the effluents can also affect the rate of
biodegradation of azo dyes (Jadhav et al., 2007; Khan et al., 2009; Prasad et al., 2011).
Therefore, microbial treatment may sometimes not function effectively for the removal of
dyes from textile effluents and alternative technologies must also be evolved to treat textile
wastewater.
One of such possible strategies is phycoremediation using algae to remove pollutants
from the environment (Dresback et al., 2001). Olguin (2003) defined phycoremediation in a
much broader sense as the use of macroalgae or microalgae for the removal or
biotransformation of pollutants, including nutrients and xenobiotics from wastewater and
CO2 from waste air. Phycoremediation comprises of several applications, including
oxygenation of the atmosphere, nutrient removal from municipal wastewater and effluents
rich in organic matter, nutrient and xenobiotic compounds removal by biosorption using
algae, treatment of acidic and metal wastewater, CO2 sequestration and biosensing of toxic
compounds by algae.
Over the last few decades, efforts have been done to apply intensive microalgal
cultures to perform the biological tertiary treatment of secondary effluents (De la Noüe et al.,
3
1992, Queiroz et al., 2007). Unicellular green algae such as Chlorella spp. and Scenedesmus
spp. are widely used in wastewater treatment as they often colonize the ponds naturally and
have fast growth rates and high nutrient removal capabilities. Thus, the use of microalgae for
removal of nutrients from different wastes has been described by a number of authors
(Beneman et al., 1980; De-Bashan et al., 2002; Gantar et al., 1991; Queiroz et al., 2007).
Moreover, algae offer a low-cost and effective approach to remove excess nutrients and other
contaminants in tertiary wastewater treatment, while producing potentially valuable biomass,
because of a high capacity for inorganic nutrient uptake (Bolan et al., 2001; Muñoz and
Guieyssea, 2006).
Algae are simple photosynthetic microorganisms that can efficiently use the sun
energy to convert water and carbon dioxide from the air into biomass. These cells have the
ability to convert carbon dioxide to biomass that can further be processed downstream to
produce biodiesel, fertilizer and other useful products. Photosynthetic growth of algae
requires carbon dioxide, water, sunlight and inorganic nutrients such as phosphorus and
nitrogen. Algae considered as green-cell factories that are not only considered good
scavengers of toxic chemicals, but are also involved in oxygenation of the atmosphere and
carbon dioxide sequestration, thereby making them a better candidate among bioremediation
systems. Algae are ideal candidate for the treatment of textile wastewater because not only
huge amount of wastewater is discharged during dyeing process but it is also rich source of
nutrition. In addition, phycoremediation has advantages over other conventional physico-
chemical methods, such as ion-exchange, reverse osmosis, dialysis and electro-dialysis,
membrane separation, activated carbon adsorption and chemical reduction or oxidation, due
to its better nutrient removal efficiency and the low cost of its implementation and
maintenance.
The present study was designed with the following objectives:
Isolation and screening of efficient azo dye degrading algal strains from
textile wastewater streams, saline water and fresh water.
Optimization of the selected algal strains to the environmental and utritional
factors.
4
Comparison of living as well as dead (dried) algae on biodegradation of
structurally different azo dyes.
Testing bioaugmentation potential of the selected algae for phycoremediation
of real textile wastewater.
Study the impact of phycoremediated wastewater on growth of wheat under
axenic conditions.
Production of biodiesel from algal biomass through trans-esterification.
5
REVIEW OF LITERATURE
Many azo dyes and their intermediates are toxic, mutagenic and carcinogenic and
affect higher organisms in both aquatic and terrestrial systems. Azo dyes and their
intermediate degradation products are common contaminants of soil and groundwater in
developing countries where textile and other dye products are produced.
2.1. Textile industry in Pakistan
After independence of Pakistan in 1947, the greatest progress in the textile sector was
observed. Increased industrialization in Pakistan began in 1950 with the textile industry in its
center (Kirk and eHow, 2008). A large number of textile processing units are located in
different parts of Pakistan. However, the main areas where the units are located include
Faisalabad, Lahore, Multan and Karachi districts. Notably, Faisalabad is called the
Manchester of Pakistan. At present, the textile industry plays a central role in Pakistan's
economy. Despite the fundamental and important role in the economy, most textile
manufacturers are small-scale or cottage industry (Table 2.1).
Both and imported and locally manufactured dyes are used in textile industry. Efforts
were made to collect data relating to the manufacture of various types of dyes in Pakistan.
Approximately, 40% of total dyes used are manufactured locally in Pakistan. Accurate
information on the extent of production of dyes is not available because the dye
manufacturers in Pakistan do not reveal their original data relating to the amount of dyes
manufactured. However, a large number of groups are involved in the manufacture of dyes in
Pakistan. Various dyes are also imported from different countries. A list of various dyes
imported in Pakistan from various countries of the world in July 2009 to June 2010 is given
in Table 2.2. Companies and corporations such as International Jans, Alibaba and Shafi
International Corporation are working as importer or wholesalers of dyes in Pakistan and
importing mainly acid, direct, disperse and reactive dyes. Textile industries release large
amounts of wastewater in wastewater streams and soil, which is of great environmental
concern.
6
Table 2.1: Region-wise distribution of large, medium and small textile industries (Govt.
of Punjab, 2008).
Unit Lahore Faisalabad Sialkot Multan Gujranwala Others Total
Large 65 105 25 4 5 8 212
Medium 255 248 98 24 31 20 676
Small 195 208 56 8 33 7 507
Total 515 561 179 36 69 35 1395
7
Table 2.2: List of dyes imported in Pakistan (2009 - 2010) and cumulative assessed
value in US$ (Arshad et al., 2011)
Sr. No. Products Year
1 Dispersive dyes 6,932,564.40
2 Acid dyes 1792979.92
3 Basic dyes 3,178,735.74
4 Reactive dyes 32,022,113.35
5 Dye, synthetic 1,673,106.42
6 Dye, sulphur 2819372.28
7 others 6,780,412.12
8
2.1.1 Textile wastewater flows
Textile industry is a major industrial consumer of freshwater sources and
consequently produces large volumes of wastewater. With increasing demand for textile
products, textile industry and its wastewater have increased proportionally, so it is a major
source of water pollution in developing countries (Asia et al., 2006; Andre et al., 2007).
Water consumption in the textile processing industry varies depending on the types and
number of processes, machinery and production capacity, etc. Textile industry involves many
wet processes, including scouring, decizing, mercerization, bleaching, printing and dyeing.
Estimated effluent generated from knitted and woven textile processing units (based on CTP
database) is given in Table 2.3. Amount of effluent is calculated by multiplying the total
production capacity with an estimated consumption of water to process one unit of kg of
finished product (Govt. of Punjab, 2008).
2.1.2 Characteristics of textile wastewater
Composition of the wastewater generated from different textile units varies from one
industry to another and also depends on other factors such as the technology used, chemicals
and home business practices. The effluent characteristics of weaving, dyeing, printing and
processing industry of knitted garments are given in Table 2.4. The diversity in the
composition of the chemical reagents used in the textile industry contributes too much water
pollution. Wastewater generated by different stages of production of a textile factory has high
The decolorization efficiency in the case of strain CKW1 was 100% after 120 h, while strain
PKS33 showed maximum decolorization of 91% in the same period. In case of
decolorization of Scarlet Disperse type of dyes, both algal strains showed high potential to
decolorize the dye as compared to control (Figure 4.17). Initially, the algal strains showed a
slow decolorization where strain CKW1 decolorized Scarlet Disperse dye by 15% in 12 h,
39% in 24 h and 55% in 48 h. Similarly, decolorization was 11% after 12 h, 25% after 24 h,
35% after 48 h in case of strain PKS33. Complete dye decolorization was achieved by
CKW1 after 120 h, while PKS33 showed 82% decolorization.
Data on decolorization of mixture of disperse group of dyes (disperse blue ZBLN and Scarlet
Disperse dye) is given in Figure 4.18. The strain CKW1 showed a decolorization of 21%,
38% and 53% in 12, 24 and 48 h, respectively. In case of strain PKS33, the dye
decolorization was 11%, 22% and 37% within 12, 24 and 48 h, respectively. The
decolorization of mixture of disperses azo dyes by CKW1 and PKS33 after 72 h was 71 %
and 56% respectively and 84% and 68% after 96 h respectively. The CKW1 strain showed a
complete decolorization after 140 h and PKS33 stains showed up to 95% of decolorization
after 140 h.
57
Fig. 4.16: Decolorization of Disperse Blue ZBLN azo dye by selected strains of algae.
58
Fig. 4.17: Decolorization of Scarlet Disperse azo dye by selected strains of algae.
59
Fig. 4.18: Decolorization of mixture of disperse azo dyes (disperse blue ZBLN and Scarlet Disperse dye) by selected strains of algae.
60
4.5. Phycoremediation of mixture of azo dyes
The results regarding decolorization of mixture of various groups of azo dyes by
living and dead cells of algae are described as under.
Decolorization of a mixture of azo dyes, including Yellow UG Direct, Congo Red Direct,
Disperse Blue ZBLN, Scarlet Disperse, Reactive Blue BRS, Orange RR Reactive and Red
S3B Reactive by algal strains is summarized in Figure 4.19. Like individual dyes, algal
strains CKW1 and PKS33 were also very effective in decolorization of mixture of dyes.
Algal strain CKW1 showed almost complete decolorization in 120 h while PKS33
completely decolorized the mixture of dyes in 144 h. Initially, strain CKW1 decolorized the
mixture of azo dyes up to 10% after 12 h, 25% after 24 h and 50% after 48 h. The almost
similar trend was observed in the case of strain PKS33 where maximum decolorization of
mixture of dyes was 47% within 48 h. After 72 h of incubation, 72% and 63 % decolorization
of the dyes by strain CKW1 and PKS33 was observed whereas decolorization was 87 and
73% after 96 h respectively. In case of application of dead mass of PKS33 and CKW1
strains, the decolorization of mixture of azo dyes by was by 58% and 55% in 12 h and 65%
and 63% in 24 h respectively. Interestingly, no further decolorization was observed after 24 h
by dead mass of both strains. Overall, it was found that algal strains had high potential for
decolorizing individual azo dyes as compared to the mixture of azo dyes. Moreover, strain
CKW1 was more effective in decolorizing both individual dyes as well as mixture of reactive
dyes.
61
Fig. 4.19: Decolorization of mixture of reactive, direct and disperse group azo dyes by selected strains of algae
62
4.6. Phycoremediation of real textile wastewater
Real wastewater was collected from three industrial units of Faisalabad city (Shaheen
Cloth Processing, Qadafi textile and Dawood textile mills Faisalabad) and color removal was
examined using strains CKW1 and PKS33.
4.6.1. Case study I (Treatment of wastewater from Shaheen Cloth Processing Mills)
The efficiency of selected algal strains (CKW1 and PKS33) for treatment of textile
wastewater collected from direct outlet of Shaheen Cloth Processing Mills is presented in
figure 4.20. Both algal strains showed a considerable decolorization of textile effluent,
however, very little decolorization was observed in case of non-augmented (control)
wastewater. In case of control, maximum color removal of 3.8% was observed after 120 h.
Strain CKW1 and PKS33 initially caused 21% decolorization in 12 h, which was further
increased up to 50% in 24 h. Further, CKW1 strain showed up to 74%, 86% and 94% color
removal of wastewater after 48, 72 and 96 h, respectively. Similarly, algal strain PKS33
decolorized the wastewater up to 69%, 81% and 88% after 48, 72 and 96 h respectively. The
complete color removal of textile wastewater occurred in 120 h by algal strain CKW1
whereas the strain PKS33 exhibited 94% decolorization.
In case of dead algal mass, both strains showed a higher efficiency than living mass and
about 66% decolorization of textile wastewater was observed in 12 h. Further, CKW1 (dead)
was able to remove color in wastewater by 74%, 77%, 79% and 82% after 24, 48, 72 and 96
h, respectively. While strain PKS33 (dead) caused decolorization up to 83% after 96 h.
Maximum decolorization (85%) was recorded with CKW1 (dead) after 120 h.
Optical density (biomass) of algal strains is illustrated in figure 4.21 which indicated that the
dead algal strain had a lower optical density than living algal biomass. In general, the living
algal strains showed a relatively slow decolorization during first 24 h and then decolorization
rate increased till 120 h. Overall, a direct relationship was found between biomass of algal
strain and decolorization of wastewater. The increase in decolorization was observed with the
increase in algal biomass.
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Fig. 4.20. Phycoremediation of real textile wastewater sample # 1 (collected from Shaheen Cloth Processing Mills) by algal strains.
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Fig. 4.21. Comparative phycoremediation of real textile wastewater sample # 1 by living and dead cells of algae.
65
4.6.2. Case Study II (Treatment of wastewater from Qadafi Textile)
Both algal strains were able to decolorize the real textile wastewater collected Qadafi Textile
dyeing unit. About 26% color removal was observed within 12 h by strain CKW1 after
augmentation, which was almost double (51%) after 24 h (Fig. 4.22). Decolorization was
73% and 88% with strain CKW1 after 48 and 72 h, respectively. In the case of strain PKS33,
decolorization up to 21% and 43% in 12 and 24 h, respectively, was recorded. Strain PKS33
was able to remove color up to 71% and 82% after 72 and 96 h, respectively. Strain CKW1
showed a complete decolorization of wastewater after 96 h, whereas PKS33 showed
maximum decolorization up to 90% after 120 h. Maximum color removal was 4.7% after 120
h in the case of control.
Application of dead algal mass of CKW1 and PKS33 resulted in 57% and 60% color
removal, respectively, after 12 h (Fig. 4.23). Maximum decolorization was 80 and 82% by
dead mass of strain CKW1 and PKS33 after 120 h. Strain CKW1 (dead) showed a
decolorization up to 67, 71, 75 and 78% after 24, 48, 72 and 96 h, respectively while
decolorization by strain PKS33 (dead) was 70, 73, 77 and 79% after 24, 48, 72 and 96 h,
respectively. Overall, the results revealed that dead algal mass of both strains (CKW1 and
PKS33) was able to decolorize most of the wastewater during first 24 h. It is also evident
from figure 4.23 that the optical density (OD) of algal strains was lower initially within 24 h,
but kept on increasing till 120 h. However, the OD of dead mass of algae was lower than
living algae.
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Fig. 4.22. Phycoremediation of real textile wastewater sample # 2 (collected from Qadafi Textiles) by algal strains.
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Fig. 4.23. Comparison phycoremediation of real textile wastewater sample # 2 (collected from Qadafi Textiles) by algal strains with their optical density at 600nm.
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4.6.3. Case study III (Treatment of wastewater from Dawood Textile Mills)
The algal strains CKW1 and PKS33 exhibited promising results for phycoremediation of real
textile wastewater (Figure 4.24). Decolorization was only 3% after 120 h in the case of non-
augmented wastewater. Strain CKW1 was able to decolorize the wastewater completely in
120 h. Algal strain PKS33 decolorized wastewater up to 90% in 120 h.
Maximum decolorization by dead algal mass of CKW1 and PKS33 was 86 and 87%,
respectively, after 120 h (Fig. 4.25). A very low optical density was observed with the dead
algal mass. Overall, a direct relation was found between OD and decolorization of
wastewater. The increase in OD of algal strain also increased decolorization of wastewater.
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Fig. 4.24. Phycoremediation of real textile wastewater sample # 3 (collected from Dawood Textiles) by algal strain.
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Fig. 4.25. Comparison phycoremediation of real textile wastewater sample # 3 (collected from Dawood Textiles) by algal strains with their optical density at 600nm.
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4.7. Toxicity Analysis
4.7.1. Toxicity test of mixture of azo dyes after decolorization by algal strains
Toxicity of mixture of azo dyes was examined by measuring the hemolytic activity and data
is presented in figure 4.26. Mixture of azo dyes (control) caused negative impact on human
red blood cells where 58 cells (out of 100) were lysed. The toxicity of azo dyes after
decolorization with dead algal mass (CKW1) was 30% lower (only 41 lysed) than that
observed in living cells. Similarly, the phycoremediation of azo dyes mixture with dead algal
mass (PKS33) showed 36% decrease in toxicity where 37 cells were lysed out of 100 cells.
Phycoremediation of mixture of azo dyes with living algal strain CKW1 reduced the toxicity
by 86% and only 8 cells were lysed. In the same way, phycoremediation of mixture of azo
dyes with living algal strain PKS33 reduced toxicity by 81%. Generally, it was observed that
phycoremediation of mixture of azo dyes using living mass had a positive effect on reducing
the toxicity.
4.7.2. Toxicity test of real textile wastewater after decolorization by algal strains
4.7.2.1. Toxicity analysis: Case study I
Toxicity analysis of wastewater sample (collected from Shaheen Cloth Processing Mill
Faisalabad) after treatment was performed by measuring the hemolytic activity (Figure 4.27).
The untreated wastewater (control) caused a negative impact on human red blood cells
(RBC) as it lysed 72 RBCs out of 100. The phycoremediation with dead algal mass (CKW1)
reduced the toxicity and 39 cells were lysed. Similarly, with the phycoremediation of
wastewater with dead algal mass of strain PKS33 caused lysis of 34 cells. Phycoremediation
of wastewater with living algal mass (strain CKW1) reduced 74% toxicity as only 12 cells
were lysed. Similarly, phycoremediation of wastewater with living algal strain PKS33 caused
58% reduction in toxicity. Generally, the phycoremediation of wastewater reduced the
toxicity.
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Fig. 4.26: Hemolytic activity of mixture of disperse, reactive and direct azo dyes after treated with selected strains of algae.
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Fig. 4.27. Hemolytic activity of real textile wastewater collected from Shaheen Cloth Processing Mills after treated with selected strains of algae
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4.7.2.2. Toxicity analysis: Case study II
Toxicity analysis (hemolytic activity) of wastewater (collected from Qadafi textile) treated
with selected algal strain was carried out. Results indicated that the application of real
wastewater (control) caused lysis of 57 RBCs (out of 100) (Fig 4.28), whereas 26 and 28
cells were lysed with the application of treated water with strain CKW1 and PKS33 (dead
mass), respectively. Similarly, the wastewater treated with living biomass of CKW1 and
PKS33 lysed 12 and 8 cells, respectively.
4.7.2.3. Toxicity analysis: Case study III
The data regarding toxicity analysis of treated real wastewater collected from Dawood textile
mills Faisalabad is summarized in Figure 4.29. Sixty eight RBCs (out of 100) were lysed by
the application of real wastewater. Algal strains reduced the toxicity of wastewater. The
lowest toxicity was observed in wastewater treated with strain CWK1 and only 12 RBCs
were lysed. The wastewater treated with dead mass of CKW1 caused lysis of 34 RBCs,
whereas dead mass of strain PKS33 caused lysis of 28 RBCs.
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Fig. 4.28. Hemolytic activity of real textile wastewater collected from Qadafi Textiles after treated with selected strains of algae.
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Fig. 4.29. Hemolytic activity of real textile wastewater collected from Dawood Textiles after treated with selected strains of algae.
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4.8. Use of phyco-remediated wastewater for irrigation purpose
A study was conducted under axenic conditions to use phyco-remediated wastewater
as irrigation for the growth of wheat plants. Data presented in Table 4.2 clearly revealed that
irrigation with real textile effluent negatively affected the root and shoot length of wheat
while the phycoremediated wastewater enhanced the root and shoots length. The plants
receiving treated wastewater (PKS33 dead mass) increased root and shoot length up to 60
and 70% respectively as compared to untreated real textile wastewater. Similarly, CKW1
(dead mass) treated wastewater increased root and shoot length by 62 and 56% as compared
to untreated real textile wastewater. The irrigation with wastewater treated with CKW1
(living biomass) improved root and shoot length by 83 and 95% respectively as compared to
real textile effluent. Similarly, the wastewater treated with PKS33 (living biomass) improved
the root and shoot length by 80 and 90% respectively as compared to untreated real textile
effluent.
Application of real textile wastewater suppressed root/shoot weight and plant biomass
compared with phyco-remediated wastewater (Table 4.2). Plant biomass was 30 to 34% more
in case of irrigation with wastewater treated with CKW1 and PKS33 (dead mass) compared
to real textile wastewater irrigation. However, the application of wastewater treated with
living biomass of CKW1 resulted in 89% greater biomass than that observed with untreated
real textile wastewater. Similarly, the wastewater treated with PKS33 (living biomass)
improved plant biomass by 82% compared to real textile wastewater irrigation.
Overall, it was observed that the application of real textile wastewater influenced
negatively on the wheat growth parameters. The application of algae treated wastewater
reduced the negative effect. The living cells had more pronounced effect than dead biomass
of algae.
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Table 4.2. Impact of real and phycoremediated wastewater on wheat growth under axenic conditions
Treated PKS33 (Dead) 12.8 b 22.0 b 0.16 b 0.22 b 0.38 b
Treated CKW1 (Dead) 13.0 ab 20.3 b 0.15 b 0.21 b 0.36 b
Treated PKS33 14.1 ab 24.7 a 0.20 a 0.31 a 0.51 a
Treated CKW1 14.8 a 25.4 a 0.22 a 0.32 a 0.54 a
4.9. Biodiesel production from algal biomass
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The algal biomass obtained after phyco-remediation of wastewater was then used to extract
biodiesel. Algal biomass produced by growing cells on modified MA medium was also run
for comparison. The extracted oil was converted into biodiesel by trans-esterification. The
results are discussed in the following sections.
4.9.1. Algal biomass
The growth of algae was faster on modified MA medium than the algae grown on real textile
wastewater (Fig. 4.30). The algal biomass (strain CKW1) on modified MA medium was
18%, 44%, 76% and 106% more after 2, 3, 4 and 5 days, respectively, than the algal biomass
on real textile wastewater. Similarly, strain PKS33 grown on modified MA medium showed
24% more biomass after 2 days, 56% more after 3 days, 94% more after 4 days and 146%
more after 5 days. When these strains were grown on real textile wastewater, strain CKW1
produced 82% more biomass after 5 days, while PKS33 produced 100% more biomass after
5 days compared to real textile wastewater. Overall, both the algal strains grown on real
textile wastewater had less growth than that observed on modified MA medium.
4.9.2. Biodiesel production
It was found that algal strain CKW1 grown on real textile wastewater (phycoremediated
algae) produced almost 34% less biodiesel compared to CKW1 grown on normal culture
medium. Similarly, algal strain PKS33 (phycoremediated water) produced 37% less biodiesel
ompared to CKW1 grown on normal culture medium. In general, it was observed that CKW1
had the ability to produce 10% more biodiesel than PKS33 from the same amount of biomass
under both normal and phycoremediated conditions.
4.9.3. Biomass recovery after oil extraction
The data presented in Fig. 4.32 clearly illustrated the biomass recovery of algal strains after
extraction of oil for biodiesel production. Algal strain CKW1 grown on real textile
wastewater (phycoremediated algae) recovered 60% more biomass (after oil extraction) than
CKW1 grown on normal culture medium from t he same amount of algal biomass. Similarly,
biomass recovery was 50% more in case of algal strain PKS33 (phycoremediated water) than
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strain CKW1 grown on normal culture medium. In general, biomass recovery was 20% more
in the case of PKS33 than CKW1 in normal culture medium and 11% more under
phycoremediated conditions.
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Fig. 4.30. Growth of selected algal strains on phycoremediated real textile wastewater and normal culture medium over a period of 5 days.
82
Fig. 4.31. Biodiesel production from alglal biomass produced by using real textile wastewater (phycoremediated) and normal culture medium.
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Fig. 4.32. Comparative biomass recovery (after oil extraction) in case of algae grown on phycoremediated real textile wastewater vs. normal culture medium.
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DISCUSSION
The results of this study demonstrated that some algal strains isolated through
enrichment of liquid media with Reactive Blue azo dye were able to decolorize synthetic
dyes that are commonly used by textile industry. Different algal strains showed a variable
potential for decolorization of dyes. In this study, selected strains CKW1 (Spirogyra sp.) and
PKS33 (Cladophora sp.) were capable of decolorizing azo dyes efficiently in liquid medium.
These strains were isolated from textile wastewater and saline water. The results also imply
that a saline dye-contaminated wastewater also contain algae that are able to decolorize azo
dyes in the presence of salts, most likely due to direct exposure and acclimatization to grow
under such conditions. Consequently, these algal strains could perform decolorization
activities efficiently in liquid medium containing dyes and high salt concentration. Various
salts are added in dye baths to improve the dying efficiency. About 40-100 g L-1 NaCl or
NaNO3 is used in fabric dying process (Carliell et al., 1998). Previously, a very few studies
indicated that algae had a potential to decolorize azo dyes (Jinqi and Houtian, 1992; Ogugbue
and Oranusi, 2005).
In this study, it was also observed that the decolorization of Reactive Blue dye was
concentration-dependent. Maximum decolorization of the dye by both algal strains was
observed at 100 mg dye L-1 liquid medium. Decolorization of both strains reduced when the
concentration of dyes increased above 100 mg L-1 liquid medium. High substrate (dye)
concentrations are probably toxic to algae, inhibiting degradation of the dye. Previous
investigations show that the dye concentration can affect the rate of biodegradation of dyes
and the optimum dye level could also vary from species to species. In general, high color
removal efficiencies have been observed at medium dye concentrations (Rajaguru et al.,
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2000; Kapdan and Oztekin, 2003; Sponza and Isik, 2005; Khalid et a l., 2008 a, b).
Furthermore, some azo dyes contain one or more sulphonic-acid groups on aromatic rings,
which can act as a deterrent to inhibit the growth of microorganisms (Chen et al., 2003).
Another reason of the toxicity at higher concentration could be the presence of heavy metals
(metal-complex dyes) and/or the presence of non-hydrolyzed reactive groups in case of
reactive dyes (Sponza and Isik, 2005). The addition of nitrogen and phosphorus in the liquid
medium supported the biodegradation reaction. It is very likely that both nutrients improve
biomass production of algae (Kassim, 2002; Aslan and Kapdan, 2006), resulting in greater
removal of dyes by algae.
An increase in pH from 5 to 7 caused significant increase in the amount of dye
decolorization by algae, however decolorization rate was highest at pH ranging from 7 to 8.
The pH 7-8 was proved to be the best pH for all selected isolates and maximum
decolorization was observed in case of CKW1 and PKS33 at this pH. Most likely pH affects
the enzymatic activity involved in decolorization of dye in addition to cellular growth of
algae. Prasad et al. (2011) reported that biological treatment can effectively decolorize azo
dyes over a wide range of pH (6-9). However, optimum pH for growth and decolorization
was found to be 8 because maximum decolorization (90%) was recorded at this pH.
Maximum dye decolorization by the selected algal strains was observed at 35 °C and further
increase in temperature beyond 35°C inhibited decolorization of Reactive Blue. High
temperature probably caused thermal deactivation of algal enzyme(s) responsible for
decolorization of azo dyes. Previously, Guo et al. (2008) reported that 28 to 35°C may be an
optimal temperature for the decolorization of dyes.
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Both algal strains (CKW1 and PKS33) demonstrated phycoremediation potential for
removal of structurally different azo dyes individually as well as in mixture from dye
medium. Dye decolorization rate was greater in the case of individual dyes than that
observed with the dye mixture. The amount of dye decolorization increased with the increase
in incubation time and complete color removal was observed after 96-120 h in the case of
most of dyes having different structures. Algae grow gradually over a period of time to
achieve high biomass content which results in more phycoremdiation certain time. Our
findings also confirm the previous findings that an increase in algal biomass also increases
phycoremediation (Jinqi and Houtian, 1992; La Rossa, 2009). The acclimation of microbes to
a variety of substrates has been widely reported by various researchers (Mohan et al., 2002;
Mohan et al., 2004).
The selected algal strains were also effective for phycoremediation after
bioaugmentation into real textile wastewater. In some cases, complete color removal was
observed in response to bioaugmentation by CKW1 and 90% decolorization by strain PKS33
within 120 h. The ability of algae to utilize wastewater efficiently as nutrient source provides
a favorable environment to ensure long-term survival of the algae in wastewater streams that
contain adequate levels of azo dyes to support the growth. Some researchers have reported
phycoremediation of leather industry (Rao et al., 2011), carpet mills effluent (Chinnasamy et
al., 2010), pulp and paper industry (Tarlan et al., 2002), dairy manure effluent (Mulbry et al.,
2008) and municipal effluent (Arora and Sexena, 2005).
Dead algal mass was able to decolorize most of the wastewater in its first 12-24 h,
and thereafter color removal was very slow. In contrast, the living strains have shown a
gradual increase in the dye decolorization and complete color of the wastewater was
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observed after 96-120 h. Initially, only substrate is sorbed, resulting in negligible
decolorization of dyes. Sorption by dead mass was reported by Rosu et al. (2008).
The results of present study also reveal positive effect of phycoremediation of
wastewater in reducing the dyes toxicity. Increase in dye decolorization by algal strains
decreased the toxicity of wastewater, probably due to reduction in COD and BOD in addition
to color removal. This premise is well supported by Paramesawary et al. (2010) who reported
algae had the ability to reduce COD and BOD of wastewater. The phycoremediated
wastewater was applied to irrigate wheat plant grown under axenic conditions. Application of
real textile wastewater suppressed the wheat growth. The reduction in growth was possibly
due to high BOD and COD of textile effluent and the presence of toxic substances including
dyes (Robinson et al., 2001; Zalawadia and Raman, 1994; Pathak et al., 1999). Jadhav and
Savant (1975) reported negative growth responses because of increasing soil salinity by using
distillery and textile effluent. Inhibitory effects were prominent at higher concentration of
effluent in winter vegetables (Rehman et al., 2009; Kumar et al., 2006). The growth of wheat
was also improved by the application of wastewater treated with dead algal mass compared
to real textile wastewater, however, the results were more promising in the case of living
cells than dead biomass.
In this study, algal biomass produced after phycoremediation of dye containing textile
wastewater was used for biodiesel production. It was observed that both algal strains grown
on real textile wastewater had a lower growth compared to the growth of algae grown in
modified MA medium. In fact, the presence of adequate nutrition in the modified MA
medium supported the algal growth better than real wastewater. Usually, algae growth is
slower in wastewater than that observed under normal conditions (Ozkan et al., 2012). The
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biodiesel production was also 30% less in the case of algal biomass produced after
phycoremediation than the algal strains biomass produced on normal culture medium. This
might be due to metabolic changes caused by wastewater in algae, affecting lipid contents
and biodiesel production (Woertz, 2007; Baxter, 2012). This premise is also supported by our
findings that the biomass recovery after oil extraction was 20% greater in case of strain
PKS33 than the same amount of biomass produced by strain CKW1 under normal culture
medium and 11% more biomass recovered under phycoremediated conditions.
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SUMMARY
Textile effluents contain a large proportion of the azo dyes which are used in large
quantities in the textile industry because of the ease in synthesis and low-cost as compared
with natural dyes. Azo dye contaminated water represents a serious environmental problem.
Azo dyes also pose a potential danger of bioaccumulation that may eventually affect human
health by transport through the food chain. In Pakistan, the problem is getting worse due to
the direct release (without treatment) of textile effluent in wastewater streams. There is an
urgent need for effective technology for the treatment of wastewater containing azo dyes for
environmental protection.
In the present study, several water samples were collected from the outlets of various
textile industries of Faisalabad, and from sources of freshwater and saltwater. These samples
were analyzed for pH and TSS. A wide variation in the pH of different water samples was
recorded. The pH in the case of textile wastewater was as high as 12.4. Maximum amount of
TSS in textile wastewater, fresh and saline water was 90, 53 and 150 meq L-1, respectively.
To isolate efficient azo dye-degrading strains of algae, 20 isolates (out of 88) were
obtained using the azo dye Reactive Blue as the sole source of C and N in a modified MA
medium. Based on the dye decolorization capacity of algae, two strains (CKW1 and PKS33)
capable of degrading azo dyes efficiently in liquid medium were selected for further studies.
These strains were able to degrade synthetic textile dyes effectively in liquid medium at a
dye concentration of 100 mg L-1, pH 8, and 16 h of day light at 30 oC. These strains could
completely decolorize different groups (reactive, direct and disperse) of azo dyes, both
individually as well as in mixture within 120 h of incubation time. However, the
decolorization rate was slow in case of dyes mixture. The living algae cells showed more
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efficient decolorization of both single dye and mixture of dyes in comparison with algae dead
biomass. Both strains of algae were also able to completely decolorize the real textile effluent
within 120 h while dead biomass decolorized up to 80% dye in 120 h.
Toxicity analysis of real textile wastewater revealed 70-80% reduction in toxicity
after treatment with live algae while 30% reduction after treatment with dead biomass. Wheat
growth was also better in the case of irrigation with treated wastewater than untreated water.
Moreover, the wastewater treated with living algae strains increased wheat growth by almost
100% as compared to the untreated wastewater irrigation. Similarly, up to 50 increases in
wheat growth was observed in the case of wastewater treated with dead algal biomass. Algal
biomass obtained after phycoremediation produced a biodiesel 30-35% less compared to the
same strain of algae grown in modified MA medium.
CONCLUDING REMARKS AND FUTURE PROSPECTIVE
Algae could be used to develop a biological treatment system to address the problem
of azo dyes in wastewater. In this thesis, for the first time a variety of azo dyes individually
and in various combinations were subjected to decolorization by selected strains of algae.
Two strains (PKS33 and CKW1) showed the ability to decolorize a broad variety of azo dyes
and real textile wastewater. This implies that the use of such algae isolates in biological
treatment systems could be helpful in reducing the threat posed by these pollutants in
wastewater from the textile industry. Furthermore, the application of phycoremediated
wastewater to plants will not only help reduce the threat of hazardous materials entering the
food chain, but also increase the reuse of textile wastewater for obtaining better crop
production. Algal biomass production using textile wastewater could possibly help tackle
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fuel shortage problem which recently severely affected Pakistan. In general, the algae could
be potential candidates for the treatment of textile wastewater, so it is useful for the
production of biomass that could be used for the production of biofuel.
92
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Abeliovich, A. 1986. Algae in wastewater oxidation ponds. In: Richmond, A.(Ed.),
Handbook of Micro algal Mass Culture. pp. 331–338. CRC Press, Boca Raton,
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Abeliovich, A., Weisman, D., 1978. Role of heterotrophic nutrition in growth of the alga
scenedesmus obliquus in high-rate oxidation ponds. Applied and Environ.
Microbiol. 35:32-37
Ahmad, Y. 2011. Report on textile industry of Pakistan.