Some properties of a sequencing batch reactor systemfor removal of vat dyes

Suntud Sirianuntapiboon a,*, Kanidta Chairattanawan b,Sawanya Jungphungsukpanich a

a Department of Environmental Technology, School of Energy and Materials, King Mongkut’s University of Technology Thonburi (KMUTT),

Bangkok 10140, Thailandb Department of Applied Science, Office of General Education, Sripatum University, Phahonyothin Road, Chatucak, Bangkok 10900, Thailand

Received 6 March 2004; received in revised form 5 February 2005; accepted 5 February 2005Available online 14 July 2005

Abstract

Bio-sludge from a wastewater treatment plant could be used as an adsorbent of vat dye from textile wastewater. Resting bio-sludge gave a higher adsorption capacity than dead bio-sludge. The resting bio-sludge from a textile wastewater treatment plantgave relatively high COD, BOD5 and dye adsorption capacity of 364.4 ± 4.3, 178.0 ± 9.0 and 50.5 ± 1.3 mg/g of bio-sludge, respec-tively, in synthetic textile wastewater containing 40 mg/l Vat Yellow 1. Another advantage of the bio-sludge was that, after washingwith 0.1 N NaOH solution, it was reusable without any activity loss. Through treatment with a sequencing batch reactor (SBR)system, both organic and dye in STIWW could be removed. The maximum dye (Vat Yellow 1), COD, BOD5 and TKN removalefficiencies of the SBR system under an MLSS of 2000 mg/l and an HRT of three days were 98.5 ± 1.0%, 96.9 ± 0.7%,98.6 ± 0.1% and 93.4 ± 1.3%, respectively. Although, the dye and organic removal efficiencies of the SBR system with real textilewastewater were quite low, they could be increased by adding organic matters, especially glucose. The dye, COD, BOD5 and TKNremoval efficiencies of the SBR system with glucose (0.89 g/l) supplemented textile industrial wastewater were 75.12 ± 1.2%,70.61 ± 3.4%, 96.7 ± 0.0%, and 63.2 ± 1.1%, respectively.� 2005 Elsevier Ltd. All rights reserved.

Keywords: Sequencing batch reactor (SBR) system; Textile industry; Vat dye; Adsorption

1. Introduction

Textile wastewater causes significant environmentalpollution (Slokar and Marechal, 1998; Clarke andSteinle, 1995; Horning, 1978; Banat et al., 1996). Textilewastewater contains high concentrations of bothorganic matter and colorants (dyes) (Slokar andMarechal, 1998; Clarke and Steinle, 1995; Horning,1978). Vat dyes are mainly used in textile industry fordying cellulose and silk materials according to resistant

0960-8524/$ - see front matter � 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.biortech.2005.02.052

* Corresponding author. Tel.: +66 2 470 8602; fax: +66 2 470 8660/427 9062.

E-mail address: suntud.sir@kmutt.ac.th (S. Sirianuntapiboon).

with sunlight and detergent (Hu, 1996; Slokar andMarechal, 1998; Wong and Yuen, 1996; Graca et al.,2001; Gupta et al., 1992). They are water insolubledye, but they were dissolved in the water after reductionunder alkaline condition. Chemical treatment processessuch as oxidation, ion exchange, precipitation, coagula-tion and adsorption are commonly used to remove thecolorants from textile wastewaters (Slokar and Mare-chal, 1998; Ramakrishna and Viraraghvan, 1997). How-ever, chemical treatment processes can be unsuitable dueto the high chemical and operating costs and solidwastes generation. Conventional biological treatmentprocesses such as activated sludge, oxidation pondsand aerated lagoons are also used in the textile industry.

The organic matter producing biochemical oxygen de-mand (BOD5) is easily removed by biological treatmentprocesses, but almost all of the colorants remain in thewastewater (being poorly biodegradable compounds)(Slokar and Marechal, 1998; Kim et al., 2002; Banat etal., 1996). This means that the effluent quality of con-ventionally treated biological wastewater, especially col-or intensity and chemical oxygen demand (COD), ishigher than the standard permitted by the Departmentof Industrial Works of Thailand (Department of Indus-trial Works, 1992). During the past 20 years, researchershave concentrated on the use of microorganisms forremoving colorants from textile industrial wastewater(Banat et al., 1996; Fu and Viraraghavan, 2001; Hu,1996; Slokar and Marechal, 1998; Aksu, 2001; Assadiand Jahangiri, 2001; Balan Doralice and Monteiro,2001; Kapdan et al., 2000). The ability to biologicallyremove color was found in both aerobic and anaerobicmicroorganisms (Slokar and Marechal, 1998). Colorantremoval mechanisms are based on either adsorption ordegradation or both (Slokar and Marechal, 1998; Fuand Viraraghavan, 2001; Hu, 1996; Zaoyan et al.,1992; Walker and Weatherley, 2000). Colorants suchas azo, diazo and reactive dyes could be adsorbed byboth dead and living microorganisms (Nigam et al.,1995; Wong and Yuen, 1996; Mitta and Gupta, 1996;Fu and Viraraghavan, 2001). Also, both gram-negativeand gram-positive bacteria in bio-sludge showed color-ant removal ability (Hu, 1996). However, all theseresearchers used single strains of microorganisms to re-move colorants from textile industrial wastewater. In thepresent study, bio-sludge from a biological wastewatertreatment plant was used to remove the colorants of tex-tile wastewater. Two types of bio-sludge namely waste-water treatment plant bio-sludge and textile industrialwastewater treatment plant bio-sludge were tested forcolorant removal efficiency, especially for vat dyes.

Table 1Types and sources of bio-sludgea

Type Source T

Bio-sludgetype A

Bangkok municipal centralwastewater treatment plant, Thailand

Es

Bio-sludgetype B

Textile wastewater treatment plant inSamuthpakarn province, Thailand

Cs

a Bio-sludge was collected from the bio-sludge storage tank of each wastew

Table 2Types and properties of vat dyes that used in the experiments

Scientific name Trade name Color index no.

Vat Black 25 Cibanone olive s. 69525Vat Yellow 1 Mikthrene yellow 70600– Industrial wastewatera –

a From textile factory in Samuthpakarn province, Thailand. The wastewat

The optimum conditions for resting and autoclavedbio-sludge to remove colorant from wastewater weredetermined and the most suitable solvents to elute colo-rants from colorant adsorbed-bio-sludge were investi-gated. The color removal efficiency of living bio-sludgewas tested in a sequencing batch reactor (SBR) systemunder various solid retention times (sludge age).

2. Methods

2.1. Bio-sludge

Two types of bio-sludge were used in this study: bio-sludge type A and bio-sludge type B. Bio-sludge type Awas collected from the Bangkok municipal centralwastewater treatment plant (Siphaya plant), Thailand.The bio-sludge type B was collected from an textile fac-tory wastewater treatment plant in Samuthpakarn prov-ince, Thailand. The characteristics of bio-sludges weredescribed in Table 1. Both types of bio-sludge were usedas resting bio-sludge after washing with 0.1 M acetatebuffer pH 6.0, and tested as autoclaved bio-sludge afterbeing autoclaved at 110 �C for 10 min.

2.2. Dyes

The two types of vat dyes, commonly used in the tex-tile industry were selected for use in this study: CibanoneOlive S (Vat Black 25) and Mikethrene (Vat Yellow 1)(Table 2).

2.3. Textile wastewater

Two kinds of wastewater were used in this study: tex-tile wastewater (TIWW) and synthetic textile wastewater(STIWW). TIWW was collected from a textile factory

reatment system Sludge age (SRT) (days)

xtended activatedludge system

28

onventional activatedludge system

17

ater treatment plant.

Color Wavelength of maximumabsorption (nm)

Dark blue 675Yellow 587Mixed color, dark color 404

er was contaminated with both Vat Black 25 and Vat Yellow 1.

Table 3Chemical properties of textile wastewater (TIWW) from factory inSamuthpakarn province

Chemical properties Concentration

TIWW TIWW + glucosea

COD, mg/l 1851 2638BOD5, mg/l 450 1200TKN, mg/l 21 21pH 2.33 7.0Color intensity (A404 nm), units/ml 0.86 0.86

a TIWW + glucose contained 0.89 g/l of glucose; the final BOD5 ofthe wastewater was about 1200 mg/l.

located in Samuthprakarn province, Thailand. Thechemical properties of TIWW were described in Table 3.STIWW was prepared according to the TIWW qualityabove. The STIWW contained BOD5 and Vat dye(Vat Black 25 and Vat Yellow 1) in the concentrationsof 1200 mg/l and 40 mg/l, respectively. The chemicalcomposition of STIWW is shown in Table 4.

2.4. Dye adsorption test

The adsorptions of dye by both resting and auto-claved bio-sludges were determined by the Jar test sys-tem (Rubin, 1978) using the STIWW containing twokinds of vat dye (Vat Black 25 and Vat Yellow 1). Thedye adsorption yields of both resting and autoclavedbio-sludge were measured using Freundlich�s adsorptionisotherm equation (Rubin, 1978).

2.5. Elution of dye from bio-sludge

Resting and autoclaved types A and B bio-sludge,were kept in both STIWW containing Vat Black 25and STIWW containing Vat Yellow 1 for 12 h (the opti-mal period for maximal dye adsorption, data notshown), were used in the experiment as dye adsorbedbio-sludge. The dye adsorbed bio-sludge samples weretreated with several solutions such as distilled water,0.1 M phosphate buffer pH 7.0, 0.1 N NaOH, 0.1 NHNO3 and 0.1 M EDTA solutions. The amount ofdye eluted in the supernatant was determined after cen-trifugation at 6000g.

Table 4Chemical composition and properties of STIWW

Chemical composition Chemica

Composition Concentration Properti

Glucose, mg/l 1875 COD, mUrea, mg/l 115 BOD5, mFeCl2, mg/l 3.5 TKN, mNaHCO3, mg/l 675 SS, mg/lKH2PO4, mg/l 55 Color inMgSO4 Æ 7H2O, mg/l 42.5 pHVat dyea, mg/l 40

a Two kinds of vat dye as shown in Table 2 were used in this experiment.

2.6. Acclimatization of bio-sludge for the SBR system

Bio-sludge from the Bangkok municipal centralwastewater treatment plant was used as an inoculumof the SBR system. Bio-sludge was acclimatized inSTIWW without vat dyes for one week before using inthe experiments.

2.7. Sequencing batch reactor system (SBR)

Six reactors (each of 10 l capacity) were made fromacrylic plastic (5 mm thick) as shown in Fig. 1. Thedimensions of the reactor were 18 cm in diameter and40 cm in height. The working volume was 7.5 l. A lowspeed gear motor, model P 630A-387, 100 V, 50/60 Hz,1.7/1.3 A (Japan Servo Co. Ltd., Japan) was used fordriving the paddle-shape impeller. The speed of theimpeller was adjusted to 60 rpm. One set of air pumps,model EK-8000, 6.0 W (President Co. Ltd., Thailand),was used for supplying air for two sets of reactors.

2.8. Operation of SBR system

A volume of 1.4 l of acclimatized sludge (10 g/l) wasinoculated in each reactor, and three types of textilewastewater (STIWW, TIWW and TIWW containing0.89 g/l glucose: TIWW + glucose) were added (finalvolume of 7.5 l) within 1 h. During feeding of the waste-water, the system was fully and continuously aerated for19 h. Aeration was then shut down for 3 h. After thesludge was fully settled, the supernatant had to be re-moved (the removed volume of the supernatant wasbased on the operation program (Table 5 or Table 6))within 0.5 h and the system was kept anoxic for 0.5.Then fresh wastewater was added to the reactor up to7.5 l, and the above operating was repeated. The oper-ation parameters of the SBR system with STIWW,TIWW and TIWW + glucose are given in Table 5.

2.9. Chemical analysis

The BOD5, COD, total kjeldahl nitrogen (TKN), sus-pended solids (SS) and color intensity (dye) of influents

l properties

es Concentration

g/l 2200g/l 1200

g/l 60–

tensity (A675 nm), units 0.217.2

Air diffuser

12cm2.5cm

18cm

Timer

Motor

Air pump

40cm

Fig. 1. The SBR system reactor.

Table 5The operating parameters of the SBR system used to treat STIWW, TIWW and TIWW + glucose

Parameters Types of wastewater

STIWW TIWW TIWW + glucosea

MLSS 1000 1500 2000 3000 4000 2000 2000HRT 3 3 3 3 3 3 3Flow rate 2500 2500 2500 2500 2500 2500 2500Hydraulic loading 0.33 0.33 0.33 0.33 0.33 0.33 0.33F/M ratio 0.40 0.27 0.20 0.13 0.10 0.11 0.20BOD5 loading 3.0 3.0 3.0 3.0 3.0 1.70 3.0Volumetric BOD5 loading 0.40 0.40 0.40 0.40 0.40 0.23 0.40Dye loading (g/d) 0.10 0.10 0.10 0.10 0.10 N/Ab N/Ab

Volumetric dye loading (kg/m3 d) 0.013 0.013 0.013 0.013 0.013 N/Ab N/Ab

a TIWW + glucose contained 0.89 g/l of glucose; the final BOD5 concentration was 1200 mg/l.b Cannot be calculated.

Table 6Maximum dye, COD and BOD5 adsorption yields of resting and autoclaved types A and B bio-sludge

Dye Bio-sludge Adsorbed dye (mg/g sludge)

Type Treatment Dye COD BOD5

Vat Black 25 A Resting 39.9 ± 0.9 363.5 ± 7.6 170.0 ± 8.6Autoclaved 21.7 ± 1.0 74.9 ± 2.5 33.3 ± 6.7

B Resting 41.2 ± 0.8 367.6 ± 5.7 180.0 ± 7.1Autoclaved 28.2 ± 1.2 96.0 ± 1.7 16.7 ± 7.5

Vat Yellow 1 A Resting 49.3 ± 1.7 361.6 ± 7.4 177.5 ± 9.2Autoclaved 22.9 ± 0.5 67.1 ± 8.0 33.3 ± 8.1

B Resting 50.48 ± 1.3 364.4 ± 4.3 178.0 ± 9.0Autoclaved 36.00 ± 1.0 119.1 ± 4.9 29.6 ± 4.4

and effluents and mixed-liquor suspended solids (MLSS)were determined by using Standard Methods (APHA,AWWA, WPCF, 1998). SV30 and sludge volume index

(SVI) were measured in imhoff cone. SV30 was definedas the sludge volume after 30 min of settling. SVI wasdefined as a ratio between the sludge volume after

30 min of settling and the sludge solid concentration.Solid retention time (SRT), or sludge age, was deter-mined by measuring the average residence time of thesuspended microorganisms (suspended bio-sludge) inthe system.

2.10. Statistical analysis method

Each experiment was repeated at least three times. Allthe data were subjected to two-way analysis of variance(ANOVA) using SAS Windows Version 6.12 (SAS Insti-tute, 1996). Statistical significance was tested using theleast significant difference (LSD) at the p < 0.05 leveland the results are shown as the mean ± the standarddeviation.

05

10152025

3035

1 2 3 4Replacement (times)

Ads

orpt

ion

capa

city

(mg/

g bi

o-sl

udge

)

Elute by 0.1MNaOH solution

Fig. 2. Adsorption capacities on successive dye adsorption with thereuse of bio-sludge. Symbols: (j) Resting bio-sludge, (m) autoclavedbio-sludge.

3. Results

3.1. The adsorption capacity of bio-sludge

The results are shown in Table 6. The Vat Yellow 1was more extensively adsorbed by the bio-sludge thanVat Black 25. The adsorption capacity of bio-sludgeon Vat Yellow 1 was about 20% higher than that onVat Black 25 and bio-sludge type A showed higherdye adsorption capacity than bio-sludge type B. Theadsorption capacity of resting bio-sludge on Vat Yellow1 was about 49.3 ± 1.7 mg/g bio-sludge while it was only39.9 ± 0.9 mg/g bio-sludge on Vat Black 25. For theadsorption of organics, neither bio-sludge type A norbio-sludge type B showed any difference. Also bothVat Yellow 1 and Vat Black 25 dyes produced no mea-surable effect on organic adsorption by the sludge. TheBOD5 and COD adsorption capacities of the restingbio-sludge in STIWW were about 175 and 360 mg/gbio-sludge, respectively. However, the adsorption capa-cities of the bio-sludge were decreased by autoclaving.The dye, COD and BOD5 adsorption capacities of auto-claved bio-sludge were about 50%, 80% and 80% lower,respectively than those of the resting bio-sludge asshown in Table 6.

Table 7Elution efficiency of several eluents

Type of vat dye Bio-sludge Percentage of dye eluted

Type Treatment Distilled water 0.1 M phobuffer (pH

Vat Black 25 A Resting 7.0 ± 0.06 1.10 ± 0.0Autoclaved 15.02 ± 0.06 5.62 ± 0.0

B Resting 4.88 ± 0.03 0.90 ± 0.0Autoclaved 8.63 ± 0.03 2.48 ± 0.0

Vat Yellow 1 A Resting 9.13 ± 0.07 2.29 ± 0.0Autoclaved 24.37 ± 0.06 13.69 ± 0.0

B Resting 6.85 ± 0.06 2.18 ± 0.0Autoclaved 12.53 ± 0.04 6.25 ± 0.0

3.2. Elution of adsorbed dye from bio-sludge

The results are shown in Table 7. The adsorbed dyewas largely retained by the bio-sludge. The 0.1 N NaOHsolution showed the highest Vat Black 25 elution yieldof 38.89 ± 0.04%, 21.12 ± 0.06% with autoclaved andresting bio-sludge type A, respectively.

3.3. Sequential replacement reaction

The dye adsorption yields in sequential replacementreactions with resting and autoclaved bio-sludge areshown in Fig. 2. Although the adsorption of the dyes de-creased as the replacement was repeated, they recoveredafter washing of both deteriorated bio-sludges with0.1 N NaOH solution. However, the adsorption abilityof washed bio-sludge was about 70% of the initial.

Autoclaved bio-sludge was used for testing the stabil-ity of dye adsorption yield after being washed with 0.1 NNaOH solution.

3.4. Stability of bio-sludge on dye adsorption ability

Both autoclaved bio-sludge types A and B were re-used for dye adsorption after being washed with 0.1 NNaOH solution. The results showed that the autoclavedbio-sludge could be reused after being washed with

sphate7.0)

0.1 N NaOH 0.1 N HNO3 0.1 M EDTA

1 21.12 ± 0.06 0.00 ± 0.00 0.95 ± 0.033 38.89 ± 0.04 0.46 ± 0.01 4.24 ± 0.011 15.25 ± 0.07 0.12 ± 0.01 0.78 ± 0.031 22.79 ± 0.06 0.78 ± 0.04 1.95 ± 0.04

6 16.31 ± 0.03 0.32 ± 0.01 1.97 ± 0.077 38.06 ± 0.04 1.53 ± 0.01 12.16 ± 0.067 11.83 ± 0.04 0.00 ± 0.00 2.16 ± 0.036 20.34 ± 0.04 0.78 ± 0.03 5.47 ± 0.03

Table 8Dye adsorption efficiency of autoclaved bio-sludge after re-washed with 0.1 N NaOH

Type of vatdye

Bio-sludgetype

Relative dye adsorption by sludge after repeated washed with 0.1 N NaOH

Raw bio-sludge(%)

First reusedbio-sludge (%)

Second reusedbio-sludge (%)

Third reusedbio-sludge (%)

Fourth reusedbio-sludge (%)

Vat Yellow 1 A 100 210.8 224.8 226.9 231.2B 100 200.1 199.1 216.5 220.2

Vat Black 25 A 100 225.2 241.7 256.5 257.9B 100 210.9 211.8 241.0 242.7

0.1 N NaOH solution (Table 8). The dye adsorptionof the bio-sludge did not decrease even after beingrewashed four times with 0.1 N NaOH solution. Theadsorption yield of the first reused bio-sludge was about100% higher than the raw autoclaved bio-sludge.

3.5. SBR system for treatment of both STIWW

and TIWW

The four types of wastewater as STIWW containingVat Black 25, STIWW containing Vat Yellow 1, TIWW

0.005

0.010

0.015

0.020

1 3 5 7 9 11 13

1 3 5 7 9 11 13

Time (d

Eff

luen

t co

lor

inte

nsit

y (A

675)

0

0

50

100

150

200

Time (da

Eff

luen

t C

OD

(m

g/l)

0

10

20

30

40

1 6 11 16 21 26

Time (days)

Eff

luen

t B

OD

5 (m

g/l)

Fig. 3. Effluent profiles of SBR system operated with STIWW containing2000 mg/l (m), 3000 mg/l (h) and 4000 mg/l (d).

and TIWW + glucose were used. The results are shownin Figs. 3 and 4, Tables 9 and 10.

3.5.1. STIWW

The SBR system showed stable dye and organic re-moval efficiencies with both STIWW containing VatBlack 25 and STIWW containing Vat Yellow 1 withMLSS of not more than 2000 mg/l (Figs. 3 and 4).The dye removal efficiencies were increased to up tomore than 98% under an optimal MLSS of 2000 mg/land the COD, BOD5 and TKN removal efficiencies

15 17 19 21 23 25 27

15 17 19 21 23 25 27

ays)

ys)

0

2

4

6

8

10

1 6 11 16 21 26Time (days)

Eff

luen

t T

KN

(m

g/l)

40 mg/l Vat Black 25 under MLSS of 1000 mg/l (�), 1500 mg/l (j),

0

0.002

0.004

0.006

0.008

0.010

1 3 5 7 9 11 13 15 17 19 21 23 25 27

1 3 5 7 9 11 13 15 17 19 21 23 25 27

Time (days)

Time (days)

Eff

luen

t co

lor

inte

nsit

y (A

587)

050

100150

200250300

Eff

luen

t C

OD

(m

g/l)

0

10

20

30

1 6 11 16 21 26Time (days)

Eff

luen

t B

OD

5 (m

g/l)

0

2

4

6

8

1 6 11 16 21 26Time (days)

Eff

luen

t T

KN

(m

g/l)

Fig. 4. Effluent profiles of SBR system operated with STIWW containing 40 mg/l Vat Yellow 1 under an MLSS of 1000 mg/l (�), 1500 mg/l (j),2000 mg/l (m), 3000 mg/l (h) and 4000 mg/l (d).

Table 9The bio-sludge qualities of SBR system operated with STIWW, TIWW and TIWW + glucoses

Types of wastewater Dye MLSS (mg/l) SV30 (ml/l) SVI (ml/g) Excess sludge (mg/d) SRT (d)

STIWW Vat Yellow 1 1000 45 ± 5 37 ± 2 1695 ± 150 5 ± 0.41500 60 ± 4 35 ± 2 1680 ± 160 7 ± 0.72000 80 ± 6 37 ± 2 1328 ± 120 12 ± 1.03000 110 ± 10 35 ± 1 1155 ± 100 20 ± 1.74000 150 ± 12 37 ± 2 938 ± 70 33 ± 2.5

Vat Black 25 1000 40 ± 4 34 ± 2 1800 ± 200 4 ± 0.41500 50 ± 5 29 ± 1 1605 ± 150 7 ± 0.72000 90 ± 7 42 ± 2 1365 ± 100 11 ± 0.83000 110 ± 11 35 ± 2 915 ± 60 25 ± 1.74000 150 ± 12 37 ± 2 810 ± 40 38 ± 1.8

TIWW Mixed dyes 2000 40 ± 4 40 ± 2 – –TIWW + glucosea Mixed dyes 2000 90 ± 6 42 ± 2 975 ± 100 16 ± 1.6

a TIWW + glucose contained 0.89 g/l of glucose, the final BOD5 of the wastewater was approximately 1200 mg/l.

were about 96%, 98% and 89%, respectively (Table 9).Also, the effluent SS increased with the increase ofMLSS of the system. The effluent SS of the systemwith both types of STIWW went higher than 80 mg/lunder a MLSS > 2000 mg/l. However, the effluent SSof the system under MLSS of 2000 mg/l was lower than

15 mg/l. The SBR system also showed the best quality(settleability) of bio-sludge (SVI of 37 ± 2 ml/l) withMLSS controlled at 2000 mg/l. The bio-sludge age(SRT: solid retention time) of the system underMLSS operation of 2000 mg/l was about 12 ± 1 days(Table 9).

Tab

le10

Effl

uen

tq

ual

itie

san

dre

mo

val

effici

enci

eso

fS

BR

syst

emw

ith

ST

IWW

,T

IWW

and

TIW

W+

glu

cose

s

Typ

eso

fw

aste

wat

erT

ypes

of

vat

dye

ML

SS

of

the

syst

em(m

g/l)

Ch

emic

alp

rop

erti

es

Co

lor

BO

D5

CO

DT

KN

SS

(mg/

l)

Effl

uen

t(u

nit

/ml)

a%

rem

ova

lE

fflu

ent

(mg/

l)%

rem

ova

lE

fflu

ent

(mg/

l)%

rem

ova

lE

fflu

ent

(mg/

l)%

rem

ova

l

ST

IWW

Vat

Yel

low

110

001.

07±

0.36

97.3

±0.

9318

.3±

0.2

98.5

±0.

189

±18

95.5

±0.

94.

8±

0.3

92.1

±0.

426

±1

1500

0.83

±0.

4097

.9±

1.03

17.7

±0.

498

.5±

0.1

80±

1295

.9±

0.6

4.6

±0.

492

.4±

1.2

24±

220

000.

60±

0.40

98.5

±1.

0017

.0±

0.7

98.6

±0.

161

±13

96.9

±0.

74.

0±

0.4

93.4

±1.

320

±2

3000

1.22

±0.

4597

.0±

1.10

20.9

±0.

498

.3±

0.1

114

±25

94.2

±1.

35.

5±

0.5

91.0

±0.

978

±6

4000

1.34

±0.

5396

.7±

1.29

25.3

±0.

897

.9±

0.1

135

±32

93.1

±1.

75.

8±

0.6

90.4

±1.

084

±5

Vat

Bla

ck25

1000

0.95

±0.

3897

.7±

1.11

17.1

±0.

698

.6±

0.1

81±

1696

.1±

0.7

7.2

±0.

588

.5±

0.7

20±

115

000.

74±

0.38

98.2

±0.

7315

.9±

1.0

98.7

±0.

174

±13

96.4

±0.

76.

9±

0.4

89.0

±0.

820

±2

2000

0.56

±0.

3098

.7±

0.72

14.5

±1.

098

.8±

0.2

64±

1296

.8±

0.6

6.4

±0.

689

.9±

1.0

19±

130

001.

34±

0.36

96.7

±0.

8717

.2±

0.5

98.6

±0.

192

±19

95.4

±1.

07.

4±

0.5

88.2

±0.

985

±4

4000

1.43

±0.

5596

.5±

1.28

19.2

±1.

098

.4±

0.1

107

±23

94.7

±1.

38.

5±

0.5

86.4

±0.

990

±6

TIW

WM

ixed

colo

ran

ts20

000.

698

±0.

0219

.1±

2.6

400

±12

11.1

±0.

116

19±

7212

.5±

7.2

19.0

±2.

111

.96

±0.

229

±2

TIW

W+

glu

cose

bM

ixed

colo

ran

ts20

000.

215

±0.

0175

.1±

1.2

40±

0.0

96.7

±0.

077

5±

9070

.6±

3.4

8.0

±0.

263

.2±

1.1

125

±7

aT

he

dye

con

cen

trat

ion

of

efflu

ent

was

rep

rese

nte

das

the

op

tica

ld

ensi

ty,

un

its/

ml.

Th

ew

avel

engt

hfo

rV

atY

ello

w1,

Vat

Bla

ckan

dT

IWW

wer

e67

5,58

7an

d40

4n

m.

bT

IWW

+gl

uco

seco

nta

ined

0.89

g/l

of

glu

cose

,th

efi

nal

BO

D5

of

the

was

tew

ater

was

app

roxi

mat

ely

1200

mg/

l.

3.5.2. TIWW

The effluent quality of the system with TIWW waspoor and fluctuated during operation, as shown in Fig.5. The organic and dye removal efficiencies were about11.1 ± 0.1% and 19.1 ± 0.1%, respectively (Table 9).However, effluent bio-treatment by the SBR system im-proved and became more stable when 0.89 mg/l glucosewas added to TIWW (TIWW + glucose). The dye,COD, BOD5 and TKN removal efficiencies of the sys-tem with TIWW + glucose under MLSS of 2000 mg/lwere 75.1 ± 1.2%, 70.6 ± 3.4%, 96.7 ± 0.0% and63.2 ± 1.1%, respectively.

4. Discussions and conclusions

Sludge from biological wastewater treatment plantscould be used as the adsorbent of both organic matterand dyes in textile wastewater. Bio-sludge from the tex-tile wastewater treatment plants showed a higher degreeof dye adsorption than the other types of bio-sludgetested. This may be explained by the dye adsorption abil-ity being induced by growth in presence of textile dye(Ohmomo et al., 1988; Sirianuntapiboon et al., 1991,1998). The dye adsorption capacity was dependent onthe type of the dye influenced by the structure of thedye (Sirianuntapiboon et al., 1998; Sirianuntapiboonand Chaiyasing, 2000). However, the organic and dyeadsorption abilities of bio-sludge were reduced by auto-claving (Sirianuntapiboon et al., 1991; Ohmomo et al.,1988) and the dilute acid and EDTA solutions elutedthe dye poorly. This shows the advantage of using ofbio-sludge as a dye adsorbent. Also, the dye adsorptionability of bio-sludge was quite stable, even if washed indilute alkaline solution. This phenomenon could be sim-ilar to that reported for the elution of melanoidin (darkbrown color of molasses) from the mycelia of Aspergillus

oryzae No. Y-2-32 (Ohmomo et al., 1988). On the repeat-ability of dye adsorption by the same sludge, the dyeadsorption gradually decreased with repeated replace-ment, and the deteriorated bio-sludge recovered itsadsorption ability on washing with a dilute alkaline solu-tion. This phenomenon showed that the adsorption sitesfor dye were filled, and that adsorbed dye was releasedupon the alkaline washing. This was also reported in mel-anoidin adsorption by fungi (Ohmomo et al., 1988). Andalso the dye adsorption capacity of the raw bio-sludgewas increased about 100% after washing with 0.1 NNaOH solution, because of the release of other impuri-ties from the adsorption site (Ohmomo et al., 1988).

On the treatment of STIWW with the SBR system,both organic matter and vat dyes could be rapidly re-moved with high efficiency. The system showed the sameremoval efficiency on both Vat Yellow 1 and Vat Black25, due to both the adsorption and degrading activitiesof living bio-sludge in the SBR system (Ohmomo et al.,

00.10.20.30.40.50.60.70.8

Time (days)

Eff

luen

t C

olor

inte

nsit

y (A

404)

0

500

1000

1500

2000

Time (days)

Eff

luen

t C

OD

(m

g/l)

0

100

200

300

400

1 6 11 16 21 26

Eff

luen

tB

OD

5 (m

g/l)

0

5

10

15

20

1 6 11 16 21 26

Time (days)Time (days)

Eff

luen

t T

KN

(m

g/l)

1 3 5 7 9 11 13 15 17 19 21 23 25 27

1 3 5 7 9 11 13 15 17 19 21 23 25 27

Fig. 5. Effluent profiles of SBR system operated with TIWW (m) and TIWW + glucose (j) under an MLSS of 2000 mg/l.

1988; Pala and Tokat, 2002; Wong and Yuen, 1996; Slo-kar and Marechal, 1998; Walker and Weatherley, 2000).The same two types of activity were recently reported fordecolorization of azo dyes by yeast and decolorization ofmelanoidin by fungi (Ohmomo et al., 1988; Sirianuntapi-boon et al., 1991). The removal efficiency of the SBR sys-tem was increased with the increase of MLSS up to2000 mg/l. The good quality of bio-sludge was indicatedby an SVI of less than 40 mg/g (Metcalf & Eddy Inc.,1991; Sirianuntapiboon and Chaiyasing, 2000; Pala andTokat, 2002). However, the efficiency of the system withreal TIWW was quite low due to low concentration ofBOD5 (450 mg/l) and the BOD5 of the real TIWW mightbe poorly biodegradable compounds (Sirianuntapiboonet al., 1991). To increase the efficiency of the system, glu-cose (simple and easily biodegradable compounds) wasadded into the TIWW which also resulted in an increasein BOD5 removal efficiency and growth of bio-sludge(Metcalf & Eddy Inc., 1991). The dye and BOD5 removalefficiencies of the system went up to 75.1 ± 1.2% and96.7 ± 0.0%, respectively.

From the above result, it could be suggested thatboth bio-sorption and biological degradation processescould be applied for the removal of dye from textile

industrial wastewater. Both resting and dead bio-sludgewere used as adsorbents in the bio-sorption process andthe bio-sludge could be reused several times after wash-ing in dilute alkaline solution. For the biological degra-dation process, the SBR system was more suitable dueto high organic and dye removal efficiencies.

Acknowledgements

We wish to express our thanks to the Department ofEnvironmental Technology, School of Energy andMaterials, King Mongkut�s University of TechnologyThonburi for providing the research materials and fund-ing. We deeply thank Dr. Sadahiro Ohmomo of theJapan International Research Center for AgriculturalSciences (JIRCAS), Ministry of Agriculture, Forestryand Fisheries, Tsukuba, Japan for his advice.

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