Accepted Manuscript

Case Study

Color, organic matter and sulfate removal from textile effluents by anaerobicand aerobic processes

F.M. Amaral, M.T. Kato, L. Florêncio, S. Gavazza

PII: S0960-8524(14)00528-8DOI: http://dx.doi.org/10.1016/j.biortech.2014.04.026Reference: BITE 13322

To appear in: Bioresource Technology

Received Date: 6 February 2014Revised Date: 7 April 2014Accepted Date: 8 April 2014

Please cite this article as: Amaral, F.M., Kato, M.T., Florêncio, L., Gavazza, S., Color, organic matter and sulfateremoval from textile effluents by anaerobic and aerobic processes, Bioresource Technology (2014), doi: http://dx.doi.org/10.1016/j.biortech.2014.04.026

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customerswe are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, andreview of the resulting proof before it is published in its final form. Please note that during the production processerrors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

* Email: savia@ufpe.br (corresponding author)

Color, organic matter and sulfate removal from textile effluents

by anaerobic and aerobic processes

Amaral, F. M.a; Kato, M. T.a; Florêncio, L.a; Gavazza, S.b*

a Laboratory of Environmental Sanitation, Department of Civil Engineering, Federal University of Pernambuco. Av. Acadêmico Hélio Ramos, s/n. Cidade Universitária. Recife PE, Brazil. CEP: 50740-530 b Laboratory of Environmental Engineering, Academic Center of Agreste, Federal University of Pernambuco. Rodovia BR-104, Km 62. Nova Caruaru. Caruaru PE, Brazil. CEP: 55002-970. Phone: +55(81)21268228 *Corresponding author: savia@ufpe.br

Abstract

An upflow anaerobic sludge blanket (UASB)-submerged aerated biofilter (SAB) system

was evaluated to remove color and chemical oxygen demand (COD) from real textile

effluent. The system was operated for 335 days in three phases (P-1, P-2, P-3) with total

hydraulic retention time varying from 21 h to 14 h. The results showed that high sulfate

levels (> 300 mg SO42-.L-1) impaired the dye reduction. The best color removal efficiencies

of 30% and 96% for the UASB and the reactor system, respectively, were obtained in P-1;

the SAB higher efficiency was associated with adsorption. The best COD removal

efficiency of 71% for the reactor system was obtained in P-2. Precipitation of some

material composed mostly of sulfur (98%) and some metals occurred in the UASB.

However, the precipitated sulfur was again oxidized in the SAB. The system also showed

an effective toxicity reduction in tests (Daphnia magna) with the treated effluent.

Keywords: real textile wastewater, anaerobic-aerobic treatment, azo dye, sulfate, salinity.

1. Introduction

The textile industry has been growing extensively in recent decades. According to

Textile Manufacturers, Exporters and Supplier (TMES, 2014) the global textile market

expect to negotiate around $800 billion dollars in 2014, with a global textile production

increase of 25% from 2010 to 2014. However, a proportional increase in the industrial

effluents has been observed, releasing a correspondingly large amount of chemicals that

can have negative effects on the environment. Each kilogram of goods produced can be the

source of approximately 100 liters of waste from dyeing and rinsing processes alone.

Facilities that are involved in the dyeing of goods often turn out more than 3.7 million liters

of wastewater each day (U.S.EPA, 1997).

The composition of textile effluents depends on the different organic-based

compounds, chemicals, and dyes used in the industrial process. The dyes characterize the

textile effluents as highly colored and are responsible for many problems in water bodies,

making regulatory agencies increasingly concerned, especially about the possible

carcinogenicity of some of the compounds (Peng et al., 2008; Rauf and Ashraf, 2009). The

azo dyes are the most used for coloring clothes. In general, the biodegradation process of

azo dyes by microbes occurs in two stages. The first stage involves the reductive cleavage

of the bonds (N=N) under anaerobic conditions, resulting in the formation of aromatic

amines; these compounds are generally free of color but are nonetheless toxic (Mendez-Paz

et al., 2005; Razo-Flores et al., 1996). In the second stage, aerobic microorganisms

transform such amines into organic acids or CO2 and H2O (Tan et al., 2000).

Although already proved to be a feasible method, the biological process for treating

textile effluents is not commonly applied in real scale due to significant variation in

wastewater composition, including the presence of high salinity levels, some bactericidal

compounds and sulfate. Physicochemical processes such as coagulation, flocculation and

sedimentation are the most used in real scale (Solanki et al., 2013), generating large

amounts of sludge, an undesirable by-product. However, the availability of organic matter

that is easily degradable in this type of effluent, highlights the challenge to keep looking for

technological alternatives to the biological treatment (Senthilkumar et al., 2011). Regarding

the treatment of real textile wastewater, few studies have reported good removal

efficiencies for chemical oxygen demand (COD), color and toxicity through the use of

anaerobic-aerobic reactors (Frijters et al., 2006; Ferraz Jr. et al., 2011). However, the

influence of sulfate, especially at high concentrations, was not evaluated in those studies.

Both azo dyes and sulfates are electron acceptors and may compete for the source of

organic matter in anaerobic reactors. The occurrence of sulfate reduction depends on the

ability of the microbial population and the availability of easily degradable organic matter.

As starch is commonly found in textile wastewater (from degumming), it can easily be

converted into volatile acids, mainly acetic, propionic and butyric acids, under anaerobic

conditions, thus, providing a substrate for sulfate reduction. Depending on the

thermodynamic conditions, sulfate removal can overhang the dye reduction. However,

sulfide generated from sulfate reduction may also donate electrons for the reduction of azo

dye.

Recent publications have focused on the use of technological applications to

improve the biological removal of azo dyes, including the use of electrodes (Wang et al.,

2013), electrodes plus redox mediators (Sun et al., 2013) and new materials such as carbon

nanotubes (Pereira et al., 2014). However, very few studies have been published regarding

the treatment of real textile wastewater, and even fewer have reported on the additional

influence of high sulfate levels on the performance of biological systems.

In the present study, a system with an upflow anaerobic sludge bed reactor (UASB)

followed by a submerged aerated biofilter (SAB) was operated to evaluate the behavior of

removing color, organic matter and toxicity from real textile effluents subjected to high

sulfate concentrations (> 300 mg SO42-/L).

2. Materials and Methods

2.1. Experimental setup

The UASB-SAB reactor system was installed in a textile laundry facility, which is

classified as a midsized company, in the city of Caruaru, semi-arid region of Pernambuco,

Brazil. The laundry average monthly water consumption was 500 m3, reaching 1050 m3 at

peak production during the experimental period.

The industrial effluents generated from all processing stages (degumming, dyeing,

neutralization and softening) were equalized in a tank from where they were pumped into a

500-L reservoir. The equalized effluent was then fed into the UASB and SAB by gravity.

The reactors´ diameter was 0.4 m; the heights were 2.0 m and 1.5 m, and the

working volumes were 250 L and 187 L, for the UASB and SAB reactors, respectively. The

SAB expanded clay support materials were spheres (2-cm diameter, 0.389-g.m-3 density,

and water uptake of 10.8%), which remained drowned during the entire period of operation.

The clays particles were chosen because of the easier local availability; and they are

reported as a good material for biomass immobilization (Amorim et al., 2009). The SAB

was provided with a radial aeration system. A compressor (MS 2.3 Air Plus - Schulz)

supplied diffused air, carried by a perforated PVC pipe. Dissolved oxygen (DO) was

continuously measured in the SAB effluent pipe by an oximeter (model LDO HQ10 -

Hach); the concentration of 3.0 mg.L-1 was maintained in that point, by adjusting the air

flow through the SAB reactor.

The UASB reactor was inoculated with anaerobic sludge from a municipal

wastewater treatment plant, which had significant microbial diversity (Lucena et al., 2011).

The SAB reactor was not inoculated.

The reactors UASB and SAB were operated for 335 days with hydraulic retention

times (HRT) respectively of 12 h and 9 h during Phase 1 (P-1, 140 days, from month 1 to 5)

and Phase 2 (P-2, 60 days, from month 8 to 9), and of 8 h and 6 h during Phase 3 (P-3, 135

days, from month 10 to 14). The reactors were out of operation for two months between P-1

and P-2 due to operational problems (months 6 and 7). The phase P-2 was changed to P-3

when the apparent steady state was reached for the COD parameter.

The reactors were monitored daily by measuring the flow rate and pH, as well as by

analyzing color, COD, sulfate, turbidity, total nitrogen, and phosphate, twice a week.

Volatile fatty acids were analyzed on a weekly basis by titration (Dilallo and Albertson,

1961) during the P-1 phase, as well as by gas chromatography (Moraes et al., 2000) during

the P-2 and P-3 phases. At the end of each experimental phase iron was also analyzed and

the effluent toxicity levels, using Daphnia magna as an indicator, were determined.

Biomass profile, measured as total volatile solids (TVS), was conducted in the end of each

experimental phase only in the UASB due to the reactor´s configuration with available

ports. The SAB reactor, however, did not allow the sludge sampling. All parameters were

determined according to the Standard Methods for The Examination of Water and

Wastewater (APHA, 2005). Scanning with light absorption in the range of 200 to 350 nm

was performed with samples of the influent system and effluent of each reactor. The

samples were filtered through a 0.45-µm membrane, to qualitatively evaluate the formation

of aromatic amines, as suggested by Pinheiro et al. (2004).

The chemical composition of the precipitated material was determined by X-ray

fluorescence using aX ZSX Mini II – Rigaku–rays fluorescence spectrophotometer and X-

ray diffraction (Shimadzu XRD) with Cu-Ka radiation (� = 1.54056 A), voltage of 40 kV,

current of 20 mA and scanning angle (2�) ranging from 3 ° to 70 °. The results were

statistically analyzed using a t-test (Montgomery and Runger, 2013).

3. Results and discussion

All dyes used in the laundry during the experimental period were water-soluble azo

compounds, set during the washing operation by using NaCl. The dye most commonly used

during the experimental period was Direct Black 22 (DB22, C44H32N13Na3O11S3; C. I.

35435; CAS 6473-13-8; molecular weight of 1083.97 g.mol-1), which is a tetra-azo dye.

During the period of the reactors´ operation, 779 kg of this dye and over 35 tons of NaCl

were consumed. Another important consumption is concerned with 2764 kg of sodium

metabisulfite, an intermediary of the sulfate formation pathway (Geiser et al., 2003).

3.1. Operating conditions of the system

Table 1 shows the operating conditions of the system. The sludge loading rate

(SLR) applied was not measured in P-1 and P-2 due to the difficulty of collecting sludge

samples in the UASB. Before the start of the P-3 operation, the clogged UASB sludge

collecting points were replaced by new taps. The value obtained for the UASB in P-3 was

0.063 kg COD.kg TVS-1.d-1 which was lower than that obtained in a previous study of

Ferraz Jr. et al. (2011), who applied a load of 0.09 kg COD.kg TVS-1.d-1; these values are

the result of different operational conditions of HTR applied to the UASB reactor, being of

12 h and 8 h, respectively in the present and the previous studies. Concerning the applied

SLR in the SAB reactor, in both studies the values were very similar of around 0.27 kg

COD.kg TVS-1.d-1.. However, the highest organic loading rate (OLR) observed in the

present study for the SAB achieved 1.7 folds higher than the average value. This result

reflects the low ability of UASB of removing organic matter in the present study.

3.2. Cell yield coefficient (Y)

The cell yield coefficient Y obtained for the UASB reactor during P-3 was 0.0125

kg TVS.kg COD-1, lower than that obtained by Tawfik et al. (2010) (0.18 kg TVS.kg COD-

1) for a UASB reactor treating domestic sewage. The very low cell growth found here can

be attributed to the nature of the substrate containing more difficult degradable compounds.

3.3. Monitoring the system

High salinity levels up to 4.4 were also detected in the industrial effluent, thus

classifying it as brackish water. The mean value observed for phosphorus during the

monitoring period in the influent was 5.12 mg P-PO43-.L-1, thus resulting in COD:N:P ratios

of 500:10.6:2.13 and 500:11.6:3.21 for the anaerobic reactor influent in P-1 and P-2, and P-

3, respectively. For the SAB influent, the ratios were 100:4:0.5 and 100:3:0.9, respectively.

There was no phosphorus or nitrogen deficiency in the influent of the UASB reactor,

according to the recommended ratio of 500:5:1 (Metcalf and Eddy, 2003), though some

deficiency may have occurred in the aerobic reactor since the recommended ratio of

100:5:1(Metcalf and Eddy, 2003) perhaps was not followed. Nevertheless, this deficit did

not reflect in a poor operating performance, as discussed below.

During the experimental period, the reservoir feeding the reactors also played a role

in the pre-treatment. The values found of redox potential were -180 mV, -148,6 mV, and -

265,4 mV in P-1, P-2, and P-3, respectively. This reservoir remained covered during the

operational period and the wastewater temperature was approximately 30°C, which was

favorable for anaerobic degradation. In the reservoir and inside of the UASB reactor, the

presence of a shiny grayish precipitate was verified and analyzed by x-ray fluorescence.

The results (Table 2) indicated that the precipitate was mainly composed of sulfur (98% in

the UASB and 86% in the reservoir); some metals (Al, Si, Fe, Mn, and others) with small

concentrations were also found. Some authors (Albuquerque et al., 2005) studied the

addition of sulfate and iron as mediators in the extracellular reduction of azo dyes; they also

observed the presence of a gray precipitate, identified as a metal sulfide. The iron present in

the system influent (5 mg.L-1) was almost completely removed downstream of the

anaerobic reactor (0.1 mg.L-1 in the UASB effluent), suggesting that precipitation of sulfide

and other metals may have caused such removal (Table 2).

3.4. Removal of COD

Fig. 1a displays the results obtained for COD during the operational period. The

average influent COD was 1045 (±730), 1143 (±478), and 1103 (±426) mg O2.L-1 in P-1, P-

2, and P-3, respectively. The corresponding values of OLR for the UASB reactor were 1.84

(±0.96), 2.42 (±1.13), and 2.7 (±0.92) kg COD.m-3.day-1, in the phases P-1, P-2, and P-3,

respectively; and for the SAB reactor, 1.74 (±2.06), 1.66 (±0.4), and 4.5 (±0.76) kg

COD.m-3.day-1, respectively.

The average COD removal efficiencies in the UASB were 40%, 43%, and 34%, in

P-1, P-2, and P-3, respectively, with corresponding values for SAB of 48%, 53%, and 49%,

and for the system of 56%, 71%, and 64%, respectively. Although fluctuations were

observed in the OLR values between P-1 and P-2, there were no significant differences for

COD removal behavior in the UASB (p = 0.14) and SAB (p = 0.68) reactors. It is important

to note that the high variability of the UASB effluent COD usually followed the variability

found in the influent. This variability was probably related with the low cell yield

coefficient found in the UASB reactor, as shown before (item 3.2).

Somassiri et al. (2010) observed a COD removal efficiency of approximately 90%

using anaerobic reactors for real textile wastewater treatment. The presence of precipitated

material and high concentrations of sodium chloride presented in the textile effluent in the

present study may have impaired the removal of organic matter.

3.5. Production of volatile fatty acids

Table 3 presents the concentrations of volatile fatty acids (VFA) detected by gas

chromatography in the system during P-2 and P-3. The acids were quantified as acetic acid

(mg H-Ac/L) by titration in P-1; the results were: 166 ± 70, 112 ± 44, and 54 ± 35 mg.L-1 in

the influent, UASB reactor effluent, and SAB reactor effluent, respectively.

Apart from dyes, starch is another major component of the COD of textile

wastewater because degumming is the first stage of the industrial denim processing.

Acetogenesis was the major metabolic pathway for organic matter removal, with significant

production of acetate in the reservoir feeding the reactors, as shown in Table 3.

The high standard deviations (Table 3) can be attributed to the high variability of

the effluents produced by the industry and the behavior of organic matter removal in the

reactors. Furthermore, in P-2, the aerobic reactor was not able to significantly reduce the

acetate from the UASB effluent, as observed in the other phases. This observation is likely

a consequence of excess precipitated material passing through this reactor in association

with the high loading salt (Table 1) detected in this phase.

Although methanogenic environment had been apparently predominant in the

UASB reactor (average of redox potential of -357 mV), the acetate was not efficiently

consumed in the UASB reactor in any phase. The methanogens were probably inhibited by

the high salinity (4.4), as shown in an early study that reported strong inhibition with

salinity of only 0.08 (McCarty and McKinney, 1961).

3.6. Degradation of sulfate

Sulfate was monitored in the reactor effluent from months 8-14 (141 days of

operation; Fig. 2). The observed values of sulfate in the influent (average of 464 and 269

mg SO42-.L-1 for phases P-2 and P-3, respectively) were higher than the value of 107 mg

SO42-.L-1 obtained by Wang et al. (2008). The increased consumption of sodium

metabisulfite by the textile industry during the experimental period was responsible for the

high values of sulfate in this study. In general, sulfate removal occurred in the anaerobic

reactor, with efficiencies of 41% and 54% for P-2 and P-3, respectively. However, sulfate

removal must have predominantly occurred by reduction to sulfide, followed by

precipitation with metals under anaerobic conditions. Additionally, the results indicate that

during the monitoring period, the precipitated sulfur was oxidized under aerobic conditions

in the SAB, resulting in sulfate concentrations closer to those detected in the system

influent (Fig. 2).

In the present study, the COD:SO4-2 ratios were 2.79 and 2.42 for the UASB

influent for P-2 and P-3, respectively. These ratios indicate that there was no apparent

carbon limitation for sulfate reduction in the UASB reactor. Lens et al. (1998)

recommended a value of 0.67 as adequate for sulfate reducing bacteria (SRB), while ratio

higher than 2.7 is favorable to methane producing bacteria (MPB) (Chen et al., 2008).

Active competition is expected between SRB and MPB within those ratios. Acetate is the

most suitable substrate for sulfate reducing bacteria (Muyzer and Stams, 2008), and the

theoretical demand of acetate (96 and 28 mg H-Ac/L in P-2 and P-3, respectively) to reduce

sulfate (209 and 61 mg SO42-/L in P-2 and P-3, respectively) was available in the UASB

influent (Table 3). Therefore, the acetate was not efficiently removed either by the SAB

reactor. In this case, it can be assumed that the salinity and dye toxicity had the main

influence on the sulfate reduction. Lower salinity of 1.3 was reported as inhibitory for the

acetate oxidizer Desulfobacter halotolerans (Brandt and Ingvorsen, 1997). On the other

hand, Prato-Garcia et al. (2013) investigated the influence of different functional groups

and their relative position to the azo bonds with different types of azo dyes involved in

sulfate reduction. The authors found a slight effect on the sulfate reduction (86% sulfate

removal efficiency) for the azo dyes AB113 (di-azo) and AO7 (mono-azo); and a more

significant inhibition of sulfate reduction (removal efficiency of 54%) for the AR151 azo

dye (di-azo). In the present study, the toxicity of the UASB effluent (section 3.9) in P-2 was

higher than that detected in the textile wastewater itself, which may be attributed to the low

performance of sulfate reducing microbes.

3.7. Color removal

The characteristics of the effluents generated by the textile industry significantly

influenced the color removal, as shown in Fig. 1b. The averages for the UASB reactor were

30%, 37%, and 52% for P-1, P-2, and P-3, respectively. The corresponding maximum

values for color removal, however, reached 77%, 89%, and 88% respectively. The observed

low values of color removal are likely the result from the prioritized use of an electron

donor (like acetate) for sulfate reduction.

Despite the color removal deficiency observed in the UASB, the SAB maintained

high color removal efficiency, especially in its first phase. The average color removal

efficiencies in the SAB were 92%, 62%, and 65% for P-1, P-2, and P-3, respectively. The

corresponding maximum values were 100%, 81%, and 94%, respectively, resulting in high

average system efficiencies of 96%, 68%, and 76%, respectively. The maximum values

corresponding to the system were 100%, 98%, and 97%, respectively (Fig. 1b). In the

beginning of Phase P-2, however, the color removal efficiency gradually decreased in the

SAB. An excess of precipitated material in the SAB, which began to accumulate

dramatically, likely caused that loss of performance. Adsorption may also have been the

mechanism for color removal in the aerobic reactor that was impaired by excess

precipitated material in P-2. Several studies have confirmed the occurrence of color

removal by adsorption (Gupta and Sushas, 2009; Ahmed and Ram, 1992).

3.8. Evaluation of aromatic amine production

Scans of aromatic amines show an intense formation usually in the range of 260-300

nm without interference by contaminants normally present in textile wastewater or

byproducts of anaerobic degradation (Pinheiro et al., 2004). For the present study, Fig. 3

shows the scanning spectrum of the effluent in the range of 200-350 nm. The UASB reactor

effluent displayed absorbance values greater than those of the system influent and SAB

effluent in all phases. This observation indicates that color removal in the UASB reactor

occurred via the formation of aromatic amines and that the amines formed were removed

under aerobic conditions.

3.9. Ecotoxicity assays

The results of the toxicity assays using Daphnia magna as an indicator, expressed as

a dilution factor (DF), were 64, 64, and 1, obtained respectively for the system influent,

UASB effluent, and system effluent during P-2. The DF corresponding values were 16, 4,

and 2 during P-3. The results indicate that the system influent and the UASB effluent

showed the greatest toxicity in P-2. During this phase, the industry consumed a large

amount of dyes and salt that contributed to the high toxicity observed. The lower toxicity

shown in P-3 was coincident with the low productivity rate of the industry, which

corresponded to low intakes of dyes, salt and sodium metabisulfite. The ability of the

system to reduce toxicity and produce effluents with practically no toxicity is noteworthy.

Despite the low color removal efficiency detected in the UASB reactor, the aromatic

amines formed were removed under aerobic conditions, thereby reducing the effluent

toxicity.

Additional points that can be highlighted regarding the UASB reactor behavior

during P-2, are: (i) the acetate in the influent was not efficiently removed, thus indicating

that the methanogenic population was somehow inhibited; (ii) the sulfate reduction was

relatively low (41%); and (iii) the color removal was also low (37%). The high level of

toxicity detected in the UASB effluent at P-2 (DF = 64) most likely reflects the effects of

the formation of aromatic amines in the UASB reactor and the inhibition of those important

steps of anaerobic digestion. The high salinity level detected in the real textile industrial

wastewater also played an important role. Therefore, the combined influence of high

concentration of dye, sulfate and salinity in real textile wastewaters treated by anaerobic

process requires further investigation.

4. Conclusions

The performance of a system composed of a UASB reactor followed by a SAB

reactor to remove color and organic matter from real textile effluents, was quite poor. This

can be attributed to the combined presence of high salinity (4.4) and high sulfate

concentration, greater than 300 mg SO42-/L. Sulfide precipitated under anaerobic conditions

and was oxidized under aerobic conditions, reestablishing a sulfate concentration with

values near those of the system influent. Nevertheless, the anaerobic/aerobic treatment

proved to be very effective for reducing the toxicity levels to aquatic organisms, as

indicated by Daphnia magna in tests with the final effluent of the reactor system used.

5. Acknowledgments

The authors would like to thank the FACEPE for the scholarship provided to the first

author, the CNPq and FACEPE for their financial support, and the Lavanderia Beira Rio,

where the experiment was performed.

6. References

1) Ahmed, M.N., Ram, R.N., 1992. Removal of basic dye from wastewater using silica as

adsorbent. Environ. Pollut. 77, 79-87.

2) Albuquerque, M.G.E., Lopes, A.T., Serralheiro, M. L., Novais, J.M., Pinheiro, H.M.,

2005. Biological sulphate reduction and redox mediator effects on azo dye

decolorization in anaerobic-aerobic sequencing batch reactors. Enz. Microb. Technol.

36, 790-799.

3) Amorim, E.L.C., Barros, A. R., Damianovic, M.H.R.Z., Silva, E.L., 2009. Anaerobic

fluidized bed reactor with expanded clay as support for hydrogen production through

dark fermentation of glucose. Int. J. Hydrogen Energ. 34 (2), 783-790

4) APHA, AWWA, WEF, (2005). Standard Methods for the Examination of Water and

Wastewater, 20ª ed.

5) Chen, Y., Cheng, J.J., Creamer, K.S., 2008. Inhibition of anaerobic process: a review.

Bioresour. Technol. 99, 4044-4046.

6) Dilallo, R., Albertson, O.E., 1961. Volatile acids by direct titration. J. Water Pollut.

Control. Fed. 3, 356-365.

7) Ferraz Jr, A.D.N., Kato, M.T., Florencio, L., Gavazza, S., 2011. Textile effluent

treatment in a UASB reactor followed by submerged aerated biofiltration. Water Sci.

Technol. 64, 1581-1589.

8) Frijters, C.T.M.J., Vos, R.H., Scheffer, G., Mulder, R., 2006. Decolorizing and

detoxifying textile wastewater, containing both soluble and insoluble dyes, in a full

scalecombined anaerobic/aerobic system. Water Res. 40, 1249-1257.

9) Geiser, L., Varesio, L., Veuthey, J.L., 2003. Simultaneous analysis of metabisulfite and

sulfate by CE with indirect UV detection. Application to and validation for a

pharmaceutical formulation. J. of Pharm. Biomed. Anal. 31,1059-1064.

10) Gupta, V.K., Suhas, 2009. Application of low-cost adsorbents for dye removal- A

review. J. Environ. Manage. 90, 2313-2342.

11) Lens, P., Visser, A., Hulshoff Pol, L.W., Lettinga, G., 1998. Long-term competition

between sulfate reducing and methanogenic bacteria in UASB reactors treating volatile

fatty acids. Biotechnol. and Bioeng. 57, 676-685.

12) Lucena, R. M., Gavazza, S., Florencio, L., Kato, M. T., Morais Jr., M. A., 2011. Study

of the microbial diversity in a full-scale UASB reactor treating domestic wastewater.

World J. Microbial. Biotechnol. 27, 2893-2902.

13) McCarty, P.L., McKinney, R., 1961. Salt toxicity in anaerobic digestion. J. Water

Pollut. Control Fed. 33, 399-415.

14) Mendez-Paz, D., Omil, F., Lema, J.M., 2005. Anaerobic treatment of azo dye Acid

Orange 7 under fed-batch and continuous conditions. Water Resour. 39, 771-778.

15) Metcalf and Eddy, 2003. Wastewater Engineering Treatment, Disposal, Reuse. 4th ed.

Ed. Mc. Graw Hill. Nova York.

16) Montgomery, D., Runger, G.C., 2013. Applied Statistics and Probability for Engineers,

6thed. Wiley. USA.

17) Moraes, E.M., Adorno, M.A.T., Foresti, E., 2000. Determination of volatile acids by

gas chromatography in effluents from anaerobic reactors treating liquid and solid waste.

In: Workshop and Latin American Seminar on Anaerobic Digestion, Recife- PE,

University of Pernambuco, Recife. 2, 235-238.

18) Muyzer, G., Stams, A.J.M., 2008. The Ecology and Biotechnology of Sulphate-

Reducing Bacteria. Nature Rev. Microbiol. 6, 441-454.

19) Peng, Y., Fu, D., Liu, R., Zhang, F., Liang, X., 2008. NaNO2/FeCl3 catalyzed wet

oxidation of the azo dye acid orange 7. Chemosphere. 71, 990-997.

20) Pereira, R.A., Pereira, M.F.R., Alves, M.M., Pereira, L., 2014. Carbon based materials

as novel redox mediators for dye wastewater biodegradation. Applied Catalysis B.

Environmental. 144, 713-720.

21) Pinheiro, H.M., Touraud, E., Thomas, O., 2004. Aromatic amines from azo dye

reduction: status review with emphasis on direct UV spectrophotometric detection in

textile industry wastewaters. Dyes Pigm. 61, 121-139.

22) Prato-Garcia, D., Cervantes, F.J., Buitrón, G., 2013.Azo dye decolorization assisted by

chemical and biogenic sulfide. J. Hazard. Mate. 250, 462-468.

23) Rauf, M.A., Ashraf, S.S., 2009. Radiation induced degradation of dyes-An overview. J.

Hazard. Mate. 166, 6-16

24) Razo-Flores, E., Donlon, B.A., Field, J.A., Let-tinga, G., 1996. Biodegradability of N-

substituted aromatics and alkylphenols under methanogenic conditions using granuler

sludge. Water Sci.Technol. 33, 47-57.

25) Senthilkumar, M., Gnanapragasam, G., Arutchelvana, V., Nagarajan, S.,

2011.Treatment of textile dyeing wastewater using two-phase pilot plant UASB reactor

with sago wastewater as co-substrate. Chem. Eng. J. 166,10-14.

26) Solanki, K., Subramanian, S., Basu, S., 2013. Microbial fuel cells for azo dye treatment

with electricity generation: A review. Bioresour. Technol. 131, 564-571.

27) Sun, J., Li, W., Li, Y., Hu, Y., Zhang, Y., 2013.Redox mediator enhanced simultaneous

decolorization of azo dye and bioelectricity generation in air-cathode microbial fuel cell.

Bioresour. Technol. 142, 407-414.

28) Tan, N.C.G., Borger, A., Slender, P., Svitelskaya, A.V., Lettinga, G., Field, J.A., 2000.

Degradation of azo dye Mordant Yellow 10 in a sequential anaerobic and aerobic

reactor. Water Sci. Technol. 42, 337-344.

29) Tawfik, A., El-Gohary, F., Temmink, H., 2010. Treatment of domestic wastewater in

an up-flow anaerobic sludge blanket reactor followed by moving bed biofilm reactor.

Bioprocess Biosyst Eng. 33, 267–276.

30) TEMS - Textile Manufacturers, Exporters & Supplier, 2014.

http://www.teonline.com/industry-overview.html (Accessed 04/03/2014).

31) U.S.EPA - United States Environmental Protection Agency, 1997. EPA Office of

Compliance Sector Notebook Project: Profile of the Textile Industry.

http://www.epa.gov/compliance/resources/publications/assistance/sectors/notebooks/text

ilsn.pdf (Accessed 04/03/2014).

32) Wang, X., Zeng, G., Zhu, J., 2008. Treatment of jean-wash wastewater by combined

coagulation, hydrolysis/acidification and Fenton oxidation. J. Hazard. Mate. 153, 810-

816.

33) Wang, Y. Z., Wang, A. J., Liu, W. Z., Kong, D. Y., Tan, W. B., Liu, C. 2013.

Accelerated azo dye removal by biocathode formation in single-chamber biocatalyzed

electrolysis systems. Bioresour. Technol. 146, 740-743.

Fig. 1. Monitoring results: (a) Variation of the COD during the operational period in the (

) system influent, ( ) UASB reactor effluent, and ( ) SAB effluent; (b) Color removal

efficiency during the experimental period for: ( ) UASB reactor, ( ) SAB reactor, and ( )

system.

Fig. 2. Temporal variation of sulfate concentration in the treatment system: ( ) system

influent, ( ) UASB effluent, and ( ) SAB.

Fig. 3. Scan of the textile effluent in the range of 200 to 350 nm throughout the system:

( ) influent, ( ) effluent from the UASB reactor and ( ) effluent from the

SAB.

!

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

CO

D (m

g O

2 / L)

0 50 100 150 200 250 300 3500

10

20

30

40

50

60

70

80

90

100

Time of operation (days)

Col

or re

mov

al e

ffici

ency

(%)

P-1 P-2 P-3 (a)

(b)

"#$!"

%!"&'

()$*"

+!

!

8 9 10 11 12 13 14

Month of operation

0

100

200

300

400

500

600

700

800C

once

ntra

tion

of S

O42-

(mg.

L-1)

PIB PII P-2 P-3

!

200 225 250 275 300 325 3500.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Wavelength (nm)

Abs

orba

nce

(AB

S)

Table 1. Hydraulic retention time and organic, salt, dye and sodium metabisulfite loads applied to the reactors.

Reactor Phase

HRT (h)

OLR (kg COD.m-3.d-1 )

SLR (kg COD.kg TVS-1.d-1)

Loading dye

(kg.d-1)*

Loading salt NaCl (kg.d-1)*

Loading sodium

metabisulfite (kg.d-1)*

UASB SAB UASB SAB UASB SAB UASB UASB UASB

P-1 12 (12.2±0.4) 9 (9.3±0.3) 1.84 1.74 - - 1.95 98.21 6.96

P-2 12 (12.2±0.3) 9 (9.1±0.5) 2.42 1.66 - - 2.55 112.5 7.45

P-3 8 (8.1±0.35) 6 (6.2±0.5) 2.7 4.5 0.063 0.27 2.07 78.15 6.67

* daily loading obtained from industry data.

Table 2. Chemical elements found in material collected inside of the feed reservoir and inside of the UASB reactor.

Chemical element Percentage of chemical element (%) found in

the precipitated material

Feed reservoir UASB reactor

Al 0.7069 nd* Si 2.5526 0.3839 P 1.9442 nd* S 86.8593 98.7916 Cl 1.9342 0.0763 K 1.4919 0.2108 Ca 1.1682 0.4292 Mn 1.1178 nd* Fe nd* 0.1082

*nd - not detected.

Table 3. Concentrations of volatile fatty acids detected in the system during the P-2 and P-3 operational periods.

Acid Unit System influent UASB effluent SAB effluent

P-2 P-3 P-2 P-3 P-2 P-3

Acetic mg/L 241.0 ± 112.0 428.0 ± 391.0 106.0 ± 121.0 213.7 ± 213.8 125.0 ± 113.0 22.0 ± 41.0

Propanoic mg/L 20.0 ± 20.0 41.0 ± 45.0 4.9 ± 10.0 6.0 ± 14.0 9.7 ± 6.5 3.3 ± 1.9

Isobutanoic mg/L 4.5 ± 3.1 3.1 ± 3.8 1.5 ± 1.7 4.7 ± 3.2 2.3 ± 3.0 1.7 ± 0.2 Butanoic mg/L 4.0 ± 6.0 5.6 ± 5.6 0.5 ± 0.4 1.9 ± 1.6 1.0 ± 1.1 0.9 ± 1

Isopentanoic mg/L 4.0 ± 6.0 6.2 ± 6.0 2.2 ± 2.3 2.3 ± 4.9 2.7 ± 3.7 1.1 ± 1.4 Pentanoic mg/L 0.9 ± 1.6 0.6 ± 1.4 0.2 ± 0.0 0.5 ± 0.2 0.2 ± 0.1 0.2 ± 0.0

COD

SO42-

Dye

Toxicity Incresed level

52%

43%

54%

96%

71 %

Very low toxicity level !

UASB Performance (removal efficiency)

System Performance (removal efficiency)

Air diffusion

UASB Reactor SAB Reactor

sulfate re-oxidation