Scholarly article on topic 'Bioremediation of the textile waste effluent by Chlorella vulgaris'

Bioremediation of the textile waste effluent by Chlorella vulgaris Academic research paper on "Chemical sciences"

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Abstract of research paper on Chemical sciences, author of scientific article — Hala Yassin El-Kassas, Laila Abdelfattah Mohamed

Abstract The microalgae biomass production from textile waste effluent is a possible solution for the environmental impact generated by the effluent discharge into water sources. The potential application of Chlorella vulgaris for bioremediation of textile waste effluent (WE) was investigated using 22 Central Composite Design (CCD). This work addresses the adaptation of the microalgae C. vulgaris in textile waste effluent (WE) and the study of the best dilution of the WE for maximum biomass production and for the removal of colour and Chemical Oxygen Demand (COD) by this microalga. The cultivation of C. vulgaris, presented maximum cellular concentrations C max and maximum specific growth rates μ max in the wastewater concentration of 5.0% and 17.5%, respectively. The highest colour and COD removals occurred with 17.5% of textile waste effluent. The results of C. vulgaris culture in the textile waste effluent demonstrated the possibility of using this microalga for the colour and COD removal and for biomass production. There was a significant negative relationship between textile waste effluent concentration and C max at 0.05 level of significance. However, sodium bicarbonate concentration did not significantly influence the responses of C max and the removal of colour and COD.

Academic research paper on topic "Bioremediation of the textile waste effluent by Chlorella vulgaris"

Egyptian Journal of Aquatic Research (2014) xxx, xxx-xxx

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National Institute of Oceanography and Fisheries Egyptian Journal of Aquatic Research

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Egyptian Journal of Aquatic Research

FULL LENGTH ARTICLE

Bioremediation of the textile waste effluent by Chlorella vulgaris

Hala Yassin El-Kassas a *, Laila Abdelfattah Sallam b

a Hydrobiology Department, Marine Environment Division, National Institute of Oceanography and Fisheries, Kayet Bay, El-Anfoushy, Alexandria, Egypt

b Marine Chemistry Department, Marine Environment Division, National Institute of Oceanography and Fisheries, Kayet Bay, El-Anfoushy, Alexandria, Egypt

Received 10 March 2014; revised 24 August 2014; accepted 24 August 2014

KEYWORDS

Chlorella vulgaris; COD;

Colour removal;

Microalgae;

Textile waste effluent

Abstract The microalgae biomass production from textile waste effluent is a possible solution for the environmental impact generated by the effluent discharge into water sources. The potential application of Chlorella vulgaris for bioremediation of textile waste effluent (WE) was investigated using 22 Central Composite Design (CCD). This work addresses the adaptation of the microalgae C. vulgaris in textile waste effluent (WE) and the study of the best dilution of the WE for maximum biomass production and for the removal of colour and Chemical Oxygen Demand (COD) by this microalga. The cultivation of C. vulgaris, presented maximum cellular concentrations Cmax and maximum specific growth rates imax in the wastewater concentration of 5.0% and 17.5%, respectively. The highest colour and COD removals occurred with 17.5% of textile waste effluent. The results of C. vulgaris culture in the textile waste effluent demonstrated the possibility of using this microalga for the colour and COD removal and for biomass production. There was a significant negative relationship between textile waste effluent concentration and Cmax at 0.05 level of significance. However, sodium bicarbonate concentration did not significantly influence the responses of Cmax and the removal of colour and COD.

© 2014 Production and hosting by Elsevier B.V. on behalf of National Institute of Oceanography and

Fisheries.

Introduction

The world is facing a number of environmental challenges. Consequently, Egypt has directed significant concern to resolve the pressing environmental problems by taking several measures

* Corresponding author.

E-mail address: halayassin12@yahoo.com (H.Y. El-Kassas). Peer review under responsibility of National Institute of Oceanography and Fisheries.

including ratifying various international environmental conventions and treaties that are to be harmonized into the national legislative framework. The textile industry and its waste waters have been increasing proportionally, making it one of the main sources of severe pollution problems worldwide (IPPC 2003).

Synthetic dye usage has increased in the textile and dyeing industries because of their ease and cost-effectiveness in synthesis, firmness, high stability to light, temperature, detergent and microbial attack and variety in colour compared with natural dyes (Nawar and Doma, 1989; Couto, 2009). The major

http://dx.doi.org/10.1016/j.ejar.2014.08.003

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environmental problem associated with the use of dyes is their lose during dyeing process since the fixation efficiency ranges from 60 to 90% (Sugiura et al., 1999).

Fifteen percent of the total world production of dyes is lost during dyeing process and is released in the textile effluents. The release of coloured wastewaters in the ecosystem is a dramatic source of esthetic pollution, eutrophication, and perturbations including decrease in the photosynthetic activity and dissolved oxygen (DO) as well as alteration of the pH, increase in the biochemical oxygen demand (BOD) and chemical oxygen demand (COD), in aquatic life (Amin et al., 2008). Therefore, treatment of these industrial effluents is necessary prior to their final discharge to the environment. Various physical/ chemical methods have been used for the removal of dyes from wastewaters (dos Santos et al., 2007; Saratale et al., 2011). These methods have some drawbacks, such as not all dyes, currently used can be degraded or removed with physical and chemical processes and sometimes the degradation products are more toxic (Abadulla et al., 2000; Nerud et al., 2001; Sharma et al., 2002). So that treatment methods must be tailored to the chemistry of the dyes (ICABRU, 2009).

Biological techniques which are cheaper and easier to operate have become the focus in recent studies of dye degradation and decolorization. Microbial and enzymatic decolorization and degradation of azo dyes have significant potential to address this problem due to their environmentally-friendly, inexpensive nature, and also they do not produce large quantities of sludge (Saratale et al., 2011).

Micro algae are known to remove dyes by bioadsorption, biodegradation and bioconversion. Microalgae degrade dyes for nitrogen source, by removing nitrogen, phosphorus, and carbon from water, it can help reduce eutrophication in the aquatic environment (Olguin, 2003; Ruiz et al., 2011) and, are unique in sequestering carbon dioxide, one of the main contributors to the greenhouse effect (Mata et al., 2011). Moreover, microalgae can grow at a rapid pace and, in inhospitable conditions, using water unfit for human consumption (Mata et al., 2010, 2011).

In this study, statistical experimental design was employed. These designs have many advantages and were used in many successful degradative studies (Saravanan et al., 2008). Compared to conventional one factor at a time experiments, statistical based factorial design of experiments gave more meaningful information on the effects, main and interaction, of the factor involved in the given study. Furthermore, the added advantage of reduction in the number of experiments to be performed. Employing such techniques proves more attractive for systematic investigations without compromising the accuracy of representation of the environmental system (Montgomery, 2004). On the other hand, single variable optimization methods are not only tedious, but also can lead to miss interpretation of results, especially because the interaction effects between different factors are over looked (Wenster-Botz, 2000).

Therefore, this research article aims to phytoremediate a textile waste effluent generated from Kafr Eldwar Dying Textile Industry, local textile dying industry, near Alexandria-Egypt. The present study was designed to identify microalgae strains present in the waste effluent. In addition, the ability of the dominant algal strain, Chlorella vulgaris was evaluated as an efficient phytoremediator to decolorize, detoxify and degrade this effluent. This work addresses the adaptation of the microalgae C. vulgaris in a textile waste effluent and studies

the ideal wastewater dilution as well as sodium bicarbonate concentration for the maximum reduction of colour and Chemical Oxygen Demand (COD).

Materials and methods

Textile effluent characterization

The textile waste effluent (WE) was collected from a property located near Alexandria, Egypt and stored under cooling to 4 0C. Physio-chemical analyses of the water sample were carried out following the methods described by APHA (2000).

The microalgal flora in the effluent was identified following the Utermohl's (1958) method. The samples were immediately fixed with 4% formaldehyde for laboratory analysis and mic-roalgae were counted and identified using 2 ml settling chambers with a Nikon TS 100 inverted microscope at 400x magnification. The dominant algal strain, Chlorella vulgaris was used throughout the study work.

The alga strain and growth conditions

The alga strain C. vulgaris was isolated and purified in axenic cultures and used throughout this study. It was cultivated as batch cultures in 1 l Erlenmeyer flasks with Bold's Basal Medium (BBM) (Nichols, 1973) at an initial count of 4 x 103 cells ml-1. For the production of biomass, exponentially growing algae culture was transferred into fresh sterile medium [10% (v/v) of inoculums]; Cultures were illuminated by tubular fluorescent lamps (PHILIPS Master TL-D 85W/840). The light intensity at the surface of the culturing vessels was 100 i mol photons m-2 s-1 with a photoperiod of 16:8 h light: dark at 25 ± 1 oc.

The culture medium for the runs was the final textile effluent itself, which was used after dilution according to a Factorial Design. Algal cells were inoculated at a concentration of 20% (Vinoculation/Vmedia) in 500 ml Erlenmeyer flasks incubated at a thermo-statically controlled environmental chamber at 25 ± 1 oc with a luminance of 3.000 lux and with a 12 hours light/dark photoperiod (Tanticharoen et al., 1994) for 15 days. The experiment was carried out in triplicate and average values were recorded.

Factorial design

A 22 Central Composite Design (CCD) was used to study the influence of the wastewater concentration and sodium bicarbonate concentration on the C. vulgaris growth and the removal of wastewater pollutants. The maximum wastewater concentration for the Factorial Run Design was stipulated from the preliminary cultivation tests of the microalgae in the textile waste effluent, using as standard. Table 1 shows the real and coded values of the variables used in the 22 Central Composite Design (CCD). Distilled water was used for the dilutions of the waste effluent.

Monitoring of algal growth

Data of the cell density using a haemocytometer slide versus culture times were plotted and submitted to polynomial

Table 1 Physicochemical characteristics of the textile industrial effluent WE.

Parameter Unit Value

Colour intensity Absorbance at 660 nm 0.114

pH - 8.05

Conductivity mS 10.23

TS mgP1 735

TDS mg P1 506

TSS mg P1 229

COD mgO2 T1 51.2

CL% 0.26

SO4 mg P1 88.67

TP mg P1 1.51

P igr1 0.96

TN % 0.105

no2 IgT1 0.55

NO3 IgT1 1.95

Ca mg P1 140.28

Mg mg P1 159.72

Heavy metals

Cu mg P1 7.05

Zn mg P1 8.61

Cr mg P1 6.33

Mn mg P1 10.5

Fe mg P1 380.4

adjusts. The polynomial equations obtained were used to calculate the maximum cellular concentration (Cmax, cells ml-1), for each run of the 22 Central Composite Design (CCD). The maximum specific growth rate (imax, d-1) was obtained through exponential adjustment in the logarithmic phase of growth. The results of Cmax and imax of the runs were analyzed statistically through the analysis of variance and response surface methodology. Similarly, pH, electric conductivity (EC), and dry weight (DW) were measured at zero-time and at the end of the experimental period.

Analysis of pollutants removal

The determinations of pollution parameters including colour and COD were accomplished at the beginning and at the end of each run, in agreement with the methodology described by APHA (2000). The percent reductions of these parameters were calculated by the equation:

Parameter reduction (%) = x; — xf/xf x 100 being :

xi = Parameter before the biomass growth and xf = Parameter after the biomass growth. The results of colour and COD removal of the CCD runs were analyzed statistically through the analysis of variance (ANOVAs) at 95% confidence interval and response surface methodology.

Determination of total dye

Eight commercially textile azo dyes are used in this textile dying industry. They are Metanil yellow, Fast Orange, Fast Red, Direct Blue, Acid Fast Red, Direct Fast Scarlet, Congo Red and Acid Fast N Blue. The final textile sample effluents just before discharging were taken and their light absorbance was measured at wavelengths of 660 nm. UV-Vis spectra were

determined using a spectrophotometer Spekol 1300, Analytika Jena, Spain.

Results

Physicochemical characteristics of the WE

The results presented in Table 1 revealed that the values of pH, conductivity, TS, TDS and TP obtained for the WE used in this study were 8.05, 10.23 mS, 735 mgP1, 506 mgP1, and 1.51 mgP1, respectively. However, COD (51.2 mgO2 P1). The heavy metal contents of the WE range from 6.33 mg P1 for Cr to 380.4 mg P1 for Fe.

Microalgae flora present in the WE

Algal flora that occurred in the WE were identified. The results revealed that the species belonging to 4 families were identified during January, 2013 (Table 2, Fig. 1). The mean total phyto-plankton cell abundance was 353, 552, 4 cells P1. The temporal pattern showed the presence of 26 taxons recorded that Chlorophyta made up the highest number (44.65%) and are represented by (8 genera, 14 species) Chlorella vulgaris Beyer-inck, Ankistrodesmus falcatus (Corda) Ralfs, Ankistrodesmus setigerus (Schroder) G.S.West., Coelastrum microporum Nägeli, Crucigenia rectangularis (Nageli) Gay, Crucigenia tetrapedia (Kirchner) Kuntze, Crucigenia quadrata Morren, Kirchneriella contorta (Schmidle) Bohlin, Pediastrum simplex Meyen, Pedia-strum tetras (Ehrenberg) Ralfs, Scenedesmus bijugatus Küt-zing, Scenedesmus dimorphus (Turpin) Kützing, Scenedesmus quadricauda Chodat, and Tetraedron trigonum (Nageli) Hans-girg, Followed by Bacillariophyta (39.05%), 7 genera and 10 species, including Amphora ovalis (Kützing) Kützing, Bacillar-ia paradoxa J.F.Gmelin, Cyclotella meneghiniana Kützing, Cyclotella glomerata H.Bachmann, Aulacoseira granulata (Ehrenberg) Simonsen, Navicula gracilis Lauby, Nitzschia apicu-lata (W.Gregory) Grunow, Nitzschia obtusa W.Smith, Nitzschia palea (Kützing) W.Smith, Nitzschia sigma (Kützing) W.Smith and Synedra ulna (Nitzsch) Ehrenberg , then Cyanophyta (12.3%); (6 genera, 9 species), Aphanocapsa delicatissima West & G.S.West , Chroococcus dispersus (Keissler) Lemmermann, Chroococcus minutus (Kützing) Nageli, Dactylococcopsis acicularis Lemmermann, Merismopedia punctata Meyen, Microcystis aeruginosa (Kützing) Kützing, Oscillatoria limnetica Lemmermann, Oscillatoria irrigua Kützing ex Gomont and Oscillatoria tenuis C.Agardh but there was a remarkably low number of Euglinophyta (4.00%) were represented by 2 genera and 3 species that are Euglena caudata Hübner, Phacus curvicauda Svirenko and Phacus pyrum

Table 2 Taxonomic composition and proportional representation of the microalgae groups at the WE during January, 2013.

Group Genus Species Cells P1 %

Chlorophyta 7 9 156,763,9 44.65

Bacillariophyta 3 6 137,102,4 39.05

Cyanophyta 6 9 456,423 12.3

Euglenophyta 2 2 140,438 4.00

Total 18 26 353,552,4 100

*Cyanophyta%

* Chlorophyta% 44.65; 45%

* Euglenophyta%

* Bacillariophyta%

43.4; 43% 39.05; 39%

Fig. 1 Percentage abundance of the microalgae groups in the WE.

(Ehrenberg) W.Archer. Chlorella vulgaris is the most dominant species of Chlorophyta.

Cultivation of the microalga C. vulgaris and pollutants removal alga growth

The results presented graphically in Figs. 2-4 show the growth curves of C. vulgaris obtained for each run of factorial design. The results recorded in Table 3 represents the maximum specific growth rate (imax) and Cmax of the 1st to 10th runs of the factorial design for evaluating the influence of the concentrations of both wastewater and sodium bicarbonate on the growth of the microalga C. vulgaris, as well as the reduction of colour and COD. The largest SBC in 3rd run (13.5%), compared to 1st run (6.5%), caused no increasing of the values of imax and Cmax. The 5th run, which was accomplished with the smallest WC (5.0%), SBC of 10.0 gP1, obtained the largest Cmax of 270,009 cells mP1.

The 2nd run (WC = 26.5%; SBC = 6.5 g P1), 4th run (WC = 26.5%; SBC = 13.5 g P1) and 6th run (WC = 30.0%; SBC = 10.0 g P1) presented cellular death of culture and consequently the smallest values of Cmax was 211,070 cells mP1. The comparison of 7th run (WC = 17.5%; SBC = 5.0 g l^1) and 8th run (WC = 17.5%; SBC = 15.0 g P1), revealed that the addition of sodium bicarbonate in the superior level resulted in obtaining higher values of imax and Cmax of 0.52 d-1 and

^ 250 | 200 Is 150

§ 100

4 6 8 10

Incubation period (days)

Fig. 2 Time course of C. vulgaris cell numbers (cells ml ^ for 14 runs of the CCD. 1st run (WC = 8.5%; SBC = 6.5 g P1); the 2nd run (WC = 26.5%; SBC = 6.5 g P1); the 3rd run (WC = 8.5%; SBC = 13.5 g P1) and 4th run (WC = 26.5%; SBC = 13.5 g P1). WC: wastewater concentration; SBC: sodium bicarbonate concentration.

- 50 U

4 6 8 10

Incubation period (days)

Fig. 3 Time course of C. vulgaris cell numbers (cells ml 1) for 58 runs of the CCD. The 5th run (WC = 5.0%; SBC = 10.0 g P1); the 6th run (WC = 30.0%; SBC = 10.0 g P1); the 7th (WC = 17.5%; SBC = 5.0 g P1) and the 8th run (WC = 17.5%; SBC = 15.0 g P1). WC: wastewater concentration; SBC: sodium bicarbonate concentration.

гг 200 i

4 6 8 10

Incubation period (days)

Fig. 4 Time course of C. vulgaris cell numbers (cells ml ) for the 9th and 10th runs of the CCD. The 9th run (WC = 17.5%; SBC = 10.0 g P1) and 10th run (WC = 17.5%; SBC = 10.0 g P1). WC: wastewater concentration; SBC: sodium bicarbonate concentration.

218,080 cells ml-1for 8th run, in comparison to 0.26 d-1 and

210,090 cells ml-1 for 7th run.

The 9th and 10th runs, which are replicates (WC = 17.5%; SBC = 10.0 gl-1), wherever the result of imax was found in run 10 (0.52 d-1) and of Cmax in run 9 (224,030 cells ml-1). The growth curves of the 9th and 10th runs presented a similar behavior and log phase. Beside dyes, the WE contains other pollutants such as COD. Growth of C. vulgaris reduces both the colour and other pollutants, resulting in the bioremediation

Table 3 Coded and real values of wastewater concentration (WC, %) and sodium bicarbonate concentration (SBC, g P1) and results of maximum specific growth rate (imax, d1), maximum cellular concentration (Cmax, cells mP1) and removal of colour (%), COD (%), in the CCD runs.

Run (WC, %) SBC, g l-1 Colour removal % COD removal % Cmax (cells ml ') Mmax Dry wt (g l-1)

1 8.5 (-1) 6.5 (-1) 74.6 69.25 260,000 0.89 1.74

2 26.5 (+1) 6.5 (-1) 73.7 65.60 211,070 0.42 1.88

3 8.5 (-1) 13.5 (+1) 72.8 67.50 252,090 0.87 1.68

4 26.5 (+1) 13.5 (+1) 71.16 51.25 220,002 0.47 0.90

5 5.0 (-a) 10 (0) 72.07 53.75 270,009 0.53 0.77

6 30.0 ( + a) 10 (0) 74.66 63.13 220,123 0.56 0.88

7 17.5 (0) 5 (-a) 71.28 63.50 210,090 0.26 0.86

8 17.5 (0) 15 ( + a) 76.32 49.10 218,080 0.53 1.55

9 17.5 (0) 10 (0) 75.40 63.75 224,030 0.52 1.50

10 17.5 (0) 10 (0) 75.68 69.90 208,011 0.52 1.49

of the WE. The concentrations of COD recorded at the end of all runs were smaller than the initial ones, evidencing the COD removal during the time of this research study.

The results presented in Fig. 5a, b and c show the surface responses of Cmax, colour and COD removal due to WC and SBC. The results indicates that the SBC concentration did not influence significantly the responses of Cmax and the removal of colour and COD. However, the linear effects of WE concentration evidenced significant influences in the answers of Cmax (p > 0.05). Largest imax, Cmax were obtained in the small WE concentration added, in the order of 8.5%, while highest colour and COD removals were obtained in the other level of WC (17.5%). Parallel to the largest imax and Cmax, the maximal algal dry weight records were observed.

Discussion

The characteristics of the WE were highly variable but comparable to those reported by a previous study (Rahman, 1993). The physicochemical characteristics of the WE were within the range of the values recorded by Lim et al. (2010) during their study on bioremediation of Malaysian textile wastewater. Copper and chromium compounds have known uses in textile manufacturing, particularly for dyeing processes (IPPC, 2003) Copper has also been previously reported in some dye plant effluents (Sharma et al., 2007). However, the constituents of the textile waste effluents differ according to the raw materials used in this industry.

The largest SBC in 3rd run, compared to 1st run containing the lowest SBC, caused the increase of the values of lmax and Cmax. The addition of sodium bicarbonate in the superior level during 7th run leads to obtaining higher values of lmax and during 8th runs resulted in obtaining higher values of Cmax. However, 5th run, which was accomplished with the smallest waste concentration and moderate SBC, obtained the maximum Cmax. Using larger WE concentrations, observed in 7th run and 8th runs, the control of the pH through the sodium bicarbonate buffer is necessary due to the fact that the wastewater causes a decrease of the pH in the medium, making the micro alga growth unfeasible. It can be predicted that the low WE concentration does not cause pH variations that limit the growth of the micro alga, thus the buffer effect of the bicarbonate is necessary. However, the statistical analysis revealed that the concentrations of bicarbonate did not significantly affect the variables lmax and Cmax.

The cellular deaths observed in 2nd, 4th and 6th runs may be attributed to the high WE concentration. Lim et al. (2010) studied the cultivation of C. vulgaris, from textile waste effluent; they stated that the dilution of the textile waste effluents is an important factor affecting the algal growth and biomass productivity. Moreover C. vulgaris grew in 100% waste effluent; although the final biomass attained was significantly lower (p < 0.05) than that grown in 20-80% textile waste concentration. However, Phang and Chu (2004) reported that C. vulgaris UMACC 001 was shown to be a versatile alga that is able to grow under various harsh conditions.

In this study C. vulgaris succeeded in decolorizing the WE during all the studied runs. In this respect, Acuner and Dilek (2004) reported that several species of Chlorella were capable of degrading azo dyes to their aromatic amines and to further metabolize the aromatic amines to simpler organic compounds or CO2 and thereby detoxifying them. Furthermore, El-Sheekh et al. (2009) reported the ability of C. vulgaris to decolorize a variety of azo dyes via algal azo dye reductase enzyme.

Gupta et al. (2006) and Ozer et al. (2006) suggested that the dye removal may be attributed to the accumulation of dye ions on the surface of algal biopolymers and further to the diffusion of the dye molecules from aqueous phase onto solid phase of the biopolymer. Moreover, Daneshvar et al. (2007) stated that colour removal by algae was due to three intrinsically different mechanisms of assimilative utilization of chromophores for the production of algal biomass, CO2 and H2O transformation of coloured molecules to non-coloured molecules, and adsorption of chromophores on algal biomass. Mohan et al. (2002) attribute the decolorization to biosorption followed by bioconversion and biocoagulation.

The final COD concentrations recorded at the end of all runs were smaller than the control value, confirming the COD removal during the time of this research study. However, it was observed that the COD removal occurred in runs, in addition to those that presented cellular death. This can be explained by the fact that Photosynthetic organisms and microalgae produce oxygen that enhances the biological degradation of the organic matter in the wastewaters (Aslan and Kapdan, 2006; Brito et al., 2007; Hodaifa et al., 2010a,b). COD removal might not have been accomplished exclusively by C. vulgaris; but also by other factors including the chemical oxidation caused by the aeration of the culture as well as microorganisms in the waste-water, which can promote the COD reduction of the medium according to Metcalf and Eddy (1993).

Fig. 5 Interaction effect between wastewater concentration (WC) and sodium bicarbonate concentration (SBC) on Cmax (A); colour removal % (B); and COD removal % (C).

The phytoremediation of the textile industrial WE may be accomplished by phosphorous removal which could have started by two different mechanisms: by the biological assimilation during the biomass growth and by the chemical precipitation that occurred predominantly when the biomass concentration decreases, as during the decline phase or cellular death (Laliberte et al., 1997).

During the different treatments, reduced Electric Conductivity (EC) values (uS) were observed in the 1st run which are parallel to the maximum reductions in COD, colour, and the highest recorded values of Cmax, imax and this may be due to the ability of algal species to consume the nutrients during the algal growth. In this respect, Oswald (1988) stated that

total dissolved salts is one of the important factors that define the relationship of culture medium species in the cultivation of microalgae during nutrient and xenobiotic compound removal with the aid of algae-based biosorbents. This agrees with other studies using algae such as Synechocystis and Phormidium for removing colour from reactive dyes (Karacakaya et al., 2009).

The waste grown algal biomass may not be suitable for use as animal feed. However, there has been increased interest in using algae for biodiesel production (Huang et al., 2010). Moreover the amount of lipids in chlorophyta may be raised up to 45% of dry weight by stress or nutrient starvation (Hu et al., 2008). Using the current treatment design employed by the factory, the coloured wastewater is not suitable for final

discharge. The treatment system employing this algal design will be useful to decolorize and detoxify the textile industrial WE before discharge and algal biomass can be analyzed for lipid contents for further use in biofuel production.

Conclusions and future directions

The microalga C. vulgaris, grown on the WE showed Cmax (270,009 cells ml-1), imax (0.53 d-1) in the smaller wastewater concentration added to the cultivation medium (5.0 and 8.5%), while larger COD removals (69.25 and 69.90%) and the largest colour removals (75.68%) were obtained using the moderate waste water concentration in the cultivation medium Thus the cultivation of C. vulgaris in WE demonstrated the capability of biomass production, colour and COD removal; therefore this microalga can be an alternative to assist in the textile culture effluent treatment, reducing the environmental impact caused by their pollutants. The algal biomass generated may be useful as feedstock, fertilizers or for biofuel production.

Acknowledgments

The authors would like to extend their sincere thanks to Prof. Dr. Sawsan Aboulezz for revision of the manuscript. No amount of words can adequately express the debt we owe to our Guide Prof. Dr. Samiha Mahmoud Gharib for her kind assistance during the identification of the algal flora present in the waste effluent.

References

Abadulla, E., Tzanov, T., Costa, S., Robra, K.H., Cavaco-Paulo, A., et al, 2000. Decolorization and detoxification of textile dyes with a laccase from Trametes hirsuta. Appl. Environ. Microbiol. 66, 3357— 3362.

Acuner, E., Dilek, F.B., 2004. Treatment of tectilon yellow 2G by

Chlorella vulgaris. Proc. Biochem. 39, 623-631. Amin, H., Amer, A., El Fecky, A., Ibrahim, I., 2008. Treatment of textile waste water using H2O2/UV system. Physicochem. Probl. Miner. Process. 42, 17-28. APHA American Public Health Association, 2000. Standard Methods for Examination of Water and Wastewater, 21st ed. Washington, DC, USA.

Aslan, S., Kapdan, I.K., 2006. Batch kinetics of nitrogen and phosphorus removal from synthetic wastewater by algae. Ecol. Eng. 28 (1), 64-70. Brito, A., Peixoto, J., Oliveira, J., Oliveira, J., Costa, C., Nogueira, R., Rodrigues, A., 2007. Brewery and winery wastewater treatment: some focal points of design and operation. In: Oreopoulou, V., Russ, W. (Eds.), Utilization of By-Products and Treatment of Waste in the Food Industry. Springer, ISEKI-Food, pp. 109-131. Couto, S.R., 2009. Dye removal by immobilized fungi. Biotechnol.

Adv. 27, 227-235. Daneshvar, N., Ayazloo, M., Khataee, A.R., Pourhassan, M., 2007. Biological decolorization of dye solution containing malachite green by microalgae Cosmarium sp.. Bioresour. Technol. 98, 1176. dos Santos, A.B., Cervantes, F.J., Van Lier, J.B., 2007. Review paper on current technologies for decolorization of textile waste water: perspective for anaerobic biotechnology. Bioresour. Technol. 98, 2369-2385.

El-Sheekh, M.M., Gharieb, M.M., Abou-El-Souod, G.W., 2009. Biodegradation of dyes by some green algae and cyanobacteria. Int. Biodeterior. Biodegrad. 63, 699-704.

Gupta, V.K., Rastogi, A., Saini, V.K., Jain, N., 2006. Biosorption of copper (II) from aqueous solutions by Spirogyra species. J. Colloid Interface Sci. 296, 59-63.

Hodaifa, G., Martinez, M.E., Slnchez, S., 2010a. Influence of temperature on growth of Scenedesmus obliquus in diluted olive mill wastewater as culture medium. Eng. Life Sci. 10 (3), 257-264.

Hodaifa, G., Martinez, M.E., Orpez, R., Slnchez, S., 2010b. Influence of hydrodynamic stress in the growth of Scenedesmus obliquus using a culture medium based on olive-mill wastewater. Chem. Eng. Process: Process Intensif. 49 (11), 1161-1168.

Hu, Q., Sommerfeld, M., Jarvis, E., Ghirardi, M., Posewitz, M., Seibert, M., Darzins, A., 2008. Microalgal triacylglycerols as feedstocks for biofuel production: perspectives and advances. Plant J. 54 (4), 621-639.

Huang, G., Chen, F., Wei, D., Zhang, X., Chen, G., 2010. Biodiesel production by microalgal biotechnology. Appl. Energ. 87, 38-46.

International Conference on Algal Biomass, 2009. Resources and Utilization (ICABRU 09) July 27th-30th.

Integrated Pollution Prevention and Control (IPPC), 2003. Reference Document on Best Available Techniques for the Textiles Industry.

Karacakaya, P., Kilic, N.K., Duyugu, E., Donmez, G., 2009. Stimulation of reactive dye removal by cyanobacteria in media containing triacontrol hormone. J. Hazard. Mater. 172, 1635-1639.

Laliberte, G., Olguin, E.J., de la Noue, J., 1997. Mass Cultivation and Wastewater Treatment Using Spirulina. Taylor and Francis, London.

Lim, S., Chu, W., Phang, S., 2010. Use of Chlorella vulgaris for bioremediation of textile wastewater. Bioresour. Technol. 101, 7314-7322.

Mata, T.M., Martins, A.A., Caetano, N.S., 2010. Microalgae for biodiesel production and other applications. Renewable Sustainable Energy Rev. 14, 217-232.

Mata, T.M., Martins, A.A., Sikdar, S., Costa, C.A.V., 2011. Sustain-ability considerations of biodiesel based on supply chain analysis. Clean Technol. Environ. Policy 13, 655-671.

Metcalf and Eddy, 1993. Wastewater Engineering: Treatment Disposal Reuse. McGraw-Hill, Boston.

Mohan, S.V., Roa, C.N., Prasad, K.K., Karthikeyan, J., 2002. Treatment of simulated reactive yellow 22 (Azo) dye effluents using Spirogyra species. Waste Manage. 22, 575-582.

Montgomery, D.C., 2004. Design and Analysis of Experiments, 5th ed. John Wiley & Sons, New York.

Nawar, S.S., Doma, H.S., 1989. Removal of dyes from effluents using low cost agricultural by-products. Sci. Total Environ. 79, 271-279.

Nerud, F., Baldrian, P., Gabriel, J., Ogbeifun, D., 2001. Decoloriza-tion of synthetic dyes by the fenton reagent and the Cu/pyridine/ H2O2 system. Chemosphere 44, 957-961.

Nichols, H.W., 1973. Growth media freshwater. In: Stein, J. (Ed.), Handbook of Phycological Methods: Culture Methods and Growth Measurements. Cambridge University Press, Cambridge, pp. 7-24.

Olguin, E.J., 2003. Phycoremediation: key issues for cost-effective nutrient removal process. Biotechnol. Adv. 22, 1-91.

Oswald, W.J., 1988. The role of micro algae in liquid waste treatment and reclamation. In: Lembi, C.A., Waaland, J.R. (Eds.), Algae and Human Affairs. Cambridge Univ. Press, Cambridge, England, pp. 255-281.

Ozer, A., Akkaya, G., Turabik, M., 2006. The removal of Acid Red 274 from wastewater: combined biosorption and biocoagulation with Spirogyra rhizopus. Dyes Pigm. 71, 83-89.

Phang, S.M., Chu, W.L., 2004. The University of Malaya Algae Culture Collection (UMACC) and potential applications of a unique Chlorella from the collection. Jpn. J. Phycol. 52, 221-224.

Rahman, R., 1993. Characterization and prospects for biological treatment of textile finishing wastewater. In: Yeoh, B.G., Chee, K.S., Phang, S.M., Isa, Z., Idris, A., Mohamed, M. (Eds.), Waste Management in Malaysia: Current Status and Prospects for

Bioremediation. Ministry of Science, Technology and the Environment, Malaysia, pp. 99-108.

Ruiz, J., Alvarez, P., Arbib, Z., Garrido, C., Barragan, J., Perales, J.A., 2011. Effect of nitrogen and phosphorus concentration on their removal kinetic in treated urban wastewater by Chlorella vulgaris. Int. J. Phytorem. 13, 884-896.

Saratale, R.G., Saratale, G.D., Chang, J.S., Govindwar, S.P., 2011. Bacterial decolorization and degradation of azo dyes: a review. J. Taiwan Inst. Chem. Eng. 42, 138-157.

Saravanan, P., Pakshirajan, K., Saha, P., 2008. Kinetics of phenol and m-cresol biodegradation by an indigenous mixed microbial culture isolated from a sewage treatment plant. J. Environ. Sci. 20, 15081513.

Sharma, H.R., Wati, L., Singh, D., 2002. Decolorization and COD reduction of digested distillery spent wash by mixed cyanobacterial culture. Indian J. Microbiol. 42, 267-268.

Sharma, N.K., Rai, A.K., Singh, S., Brown, R.M., 2007. Airborne algae: their present status and relevance. J. Phycol. 43, 615-627.

Sugiura, W., Miyashita, T., Yokoyama, T., Arai, M., 1999. Isolation of azo-dye-degrading microorganisms and their application to white discharge printing of fabric. J. Biosci. Bioeng. 88, 577-581.

Tanticharoen, M., Reungjitchachawali, M., Boonag, B., Vonktavee-suk, P., Vonshak, A., Cohen, Z., 1994. Optimization of yy-linolenic acid (GLA) production in Spirulina platensis. J. Appl. Phycol. 6, 295-300.

Utermohl, H., 1958. Zur Vervollkommnung der quantitativen phytoplankton-methodik. Mitt. Int. Ver. Theor. Angew. Limnol. 9, 1-38.

Wenster-Botz, D., 2000. Experimental design for fermentation media development: statistical design or global random search? J. Biosci. Bioeng. 90, 473-483.