1. reuse of wastewater of the textile industry after physicochemical & membrane

8/8/2019 1. Reuse of wastewater of the textile industry after physicochemical & membrane

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Desalination 149 (2002) 169174

Reuse of wastewater of the textile industry after its treatmentwith a combination of physico-chemical treatment

and membrane technologies

A. Bes-Pi*

, J.A. Mendoza-Roca, M.I. Alcaina-Miranda, A. Iborra-Clar,M.I. Iborra-Clar

Department of Chemical and Nuclear Engineering, Universidad Politcnica of Valencia,

Camino de Vera s/n, 46071 Valencia, Spain

email: [email protected]

Received 1 February 2002; accepted 15 February 2002

Abstract

This work is focused on the treatment of a textile plant wastewater. The industry mainly manufactures socks,stockings and panties, and the water is treated in order to be reused. The wastewater was characterized and jar-tests experiments were carried out with different coagulants and flocculants, at different concentrations and pHin order to obtain clarified water that can be treated by means of ultrafiltration (UF) or nanofiltration (NF). Thecombination of the physico-chemical treatment and the nanofiltration leads to a COD removal of almost 100%.

Keywords: Wastewater; Reuse; Textile industry; Membrane

1. Introduction

Due to the high water consumption in the

textile industry it is essential to study its reuse.Many processes have been studied to treattextile wastewaters [14]. However, theirapplication in an industrial plant becomes

*Corresponding author

Presented at the International Congress on Membranes and Membrane Processes (ICOM), Toulouse, France,

July 712, 2002

0011-9164/02/$ See front matter 2002 Elsevier Science B.V. All rights reserved

difficult due to the operation problems and tothe costs. Biological treatment by activatedsludge offers high efficiencies in COD removal,

but does not eliminate completely the colour ofthe water and frequently operation problemslike bulking appear. The use of flotation insteadof sedimentation to separate the treatedwastewater from the activated sludge solvesthis problem, but it increases the depurationcosts and it makes complicated the plant


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operation. Chemical oxidation by ozone, or acombination of UV-radiation and ozone andH2O2, have great interest but their costs are stillvery high.

The applications of membrane technologiesin textile industries are not yet very common.Until now the reported applications are focusedon the recovery of sizing agents from thedesizing effluents and on the recovery of theindigo from the dyeing effluents byultrafiltration [5,6].

Jar-tests allow the evaluation of a treatmentto reduce dissolved, suspended, colloidal andnonsettleable matter from water by chemicalcoagulation-flocculation followed by gravitysettling [7]. Thus, these tests are a valuable toolin wastewater treatment [8].

The use of membranes in combination with physico-chemicals processes is very interestingto produce water to be reused from the globaleffluent of the industry. The factors that limittheir application are the management of themembranes retentates streams due to their highconductivities and the durability of themembranes due to fouling and concentration

polarisation [9,10].This work is focused in the evaluation of the

final effluent quality.

2. Objectives

The objectives of this work are thefollowing:

Evaluation of the physico-chemical

treatment with jar-tests for textilewastewater from a plant that mainlymanufactures socks, stockings and panties.

Optimisation of pH and coagulant andflocculant concentration in the jar-tests.

Determination of the water quality aftertreating the wastewater with a combinationof physico-chemical treatment andmembrane technologies (ultrafiltration ornanofiltration).

3. Material and methods

This study was carried out in three steps.The first step consisted of the characterizationof the wastewater samples. The analysed

parameters were the pH, conductivity,suspended solids, COD, temperature andturbidity. In the second step a physico-chemicaltreatment was applied to wastewater in order toreduce COD and turbidity. Finally,ultrafiltration (UF) and nanofiltration (NF)experiments were performed in differentlaboratory plants to improve the quality of the

physico-chemical treated wastewater.

3.1. Jar-tests

Physico-chemical experiments were carriedout in a multiple stirrer Jar-Test apparatus fromSELECTA. Tests were performed using DK-FER 20 from ACIDEKA S.A., FeCl3 andAl2(SO4)3 as coagulants and an anionicflocculant from NALCO. The procedureconsisted in introducing 900 mL of the samplein the jars, the coagulant was added and rapidlymixed (180 rpm) during 3 minutes. Then thespeed was reduced (30 rpm) and the flocculantwas introduced into the jars for an additionaltime of 15 minutes. After that, the paddles werewithdrawn so that the particles could settle. Theinfluence of pH, coagulant and flocculantconcentrations were studied. The coagulantconcentration range was varied between 50 and200 mg/L, and the flocculant concentration

between 0.5 and 2 mg/L. Finally, the pH values

were adjusted to 8.0, 8.5, 9.0 and 9.5. The pHof the samples was changed by the addition ofHCl 0.1 N and NaOH 0.1 and 0.5 N.

3.2. Experiments with membranes

Experiments with membranes were carriedout using two different laboratory plants ofultrafiltration (UF) and nanofiltration (NF). Theconfiguration of the plants were very similar.


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A. Bes-Pi et al. / Desalination 149 (2002) 169174 171

Fig. 1. Scheme of the NF laboratory plant.

In Fig. 1 a scheme of the NF laboratoryplant can be observed.

The tested UF and NF membranes arepresented in Tables 1 and 2, respectively.

Table 1Tested UF membranes

Membrane reference Cut-off (kD)

10 BIOMAX of MILLIPORE 5

IRIS 3065 of TECHSEP 40IRIS 3028 of TECHSEP 100

Table 2Tested NF membranes

Membrane NaCl MgSO4 Permeabilityreference R(%) R(%) (m

3/m

2dMPa)

Dow NF-45 50 95 0.0219Dow NF-70 80 95 0.2309

Table 3

Wastewater characterization

Parameter Feedwater

T (C) 18

pH 7.50Conductivity (mS/cm) 2.06

S.S. (mg/L) 82.6COD (mg/L) 1640

Turbidity (NTU) 15.65

NF module is plane with an effectivemembrane area of 0.009 m2, the operatingconditions were 400 L/h of feed flow rate, 1MPa of transmembrane pressure and 20C. Theoperating conditions in UF process were feedtransmembrane pressure of 0.15 MPa, feed flowrate of 0.04 m3/h and temperature of 20C.

The operating time of the plants was 6hours. Permeate fluxes J(L/m2h) and soluteretentions R(%) were determined during theexperiments.

9

1

2

3

4

5

6

7

810

12

11

VALVE

FEED PUMP

SPEED CONTROL

0 THERMOMETER

1 FILTER SYSTEM

2 SECURITY VALVE

1 MANOMETER

2 REGULATION VALVE

3 PERMEATE STREAM

4 STIRRING

5 FEED TANK

6 AUXILIARY TANK

1


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4. Results

Table 3 shows the average values of thetextile wastewater measured parameters. Incomparison with municipal wastewater, CODand conductivity values are quite important andhave to be substantially lowered to producewater with enough quality to be reused. Thesevalues are typical for textile effluents.

In order to reuse the water in rinseprocesses, it is necessary a negligible COD anda conductivity lower than 1 mS/cm.

Fig. 2 shows the variation of COD andturbidity values of the clarified water after jar-tests using DK-FER 20. As it can be seen, the

best result (51.5% COD removal and 68%turbidity removal) was obtained at pH 9.5, butas the increase in the removal efficiency wasnot significant at pH higher than 8.5, this valuewas considered as the optimum. In alkalinemedium, the addition of DK-FER 20 drove tothe formation of positively charged metalhydroxy complexes, that specifically adsorbonto colloids, explaining the observed

behaviour.In Fig. 3, it can be observed that increasing

the coagulant concentration, results in alowering of the COD and turbidity. Coagulantconcentration higher than 200 mg/L hardlyimproved the COD removal efficiency.

Fig. 4 shows the effect of adding both 200mg/L of DK-FER 20 and an anionic flocculant(NALCO). The best results were achieved with1 mg/L of flocculant. At higher flocculantconcentrations, COD and turbidity increased.

This was due to the excess of flocculant, thatremained as colloidal matter in water,contributing to the COD and turbidity of theclarified water.

Thus, the experiments show that theoptimum operating conditions for the physico-chemically treatment of the textile wastewaterare: pH = 8.5, CDK-FER 20 = 200 mg/L, CNalco = 1mg/L.

Experiments with the other coagulants didnot improve the efficiencies obtained with DK-FER 20.

Fig. 2. Influence of wastewater pH on COD andturbidity of treated water using 200 mg/L of DK-FER20.

Fig. 3. Influence of DK-FER concentration on CODand turbidity of treated water.

900780

850 865

0

320

640

960

1280

1600

0,5 1 1,5 2

NALCO floculant concentration (mg/L)

COD

(mg/L)

0

5

10

15

20

25

Turbidity(NTU)

COD (mg/L)

Turbidity (NTU)

Fig. 4. Influence of NALCO concentration on CODand turbidity of treated water.

0

400

800

1200

1600

2000

8 8,5 9 9,5pH

COD

(mg/L)

0

25

50

75

100

125

Turbidity(NTU)

COD (mg/L)

Turbidity (NTU)

750

800

850

900

950

1000

50 100 150 200

DK-FER coagulant (mg/L)

COD

(mg/L)

0

10

20

30

40

50

Turbidity(NTU)

COD (mg/L)

Turbidity (NTU)


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A. Bes-Pi et al. / Desalination 149 (2002) 169174 173

0

20

40

60

80

100

120

140

0 50 100 150 200 250 300 350 400

Time (minutes)

Jv(L/m2h)

kD-100

kD-40

kD-5

Fig. 5. Permeate fluxes of UF membranes with theoperating time.

10

15

20

25

30

0 50 100 150 200 250 300 350 400

Time (minutes)

Jv(L/m2h)

NF-45

NF-70

Fig. 6. Permeate fluxes of NF membranes with the

operating time.

Table 4Analysis of the feed and permeate streams in the different membrane experiments

Parameter Feedwater UF membranes NF membranes

100 kD 40 kD 5 kD NF-45 NF-70

COD (mg/L) 780 760 800 665


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None of the membranes used in UF testsreduced significantly the COD of the physico-chemically treated water. However, the

permeates of NF membranes can be reused inthe industry due to their low COD andconductivity.

Prior to an industrial operation, themembrane durability and the retentate streammanagement have to be studied in a NF pilot

plant with higher membrane surface.

References

[1] U. Altinbas et al., Treatability study of wastewater

from textile industry, Envir. Technol., 16 (1995)389394.

[2] J.M. Coloma, Optimizacin de las depuradorasfsico-qumicas, Revista de Qumica Textil, 137

(1998) 3140.[3] D. Orhon et al., A scientific approach to

wastewater recovery and reuse in the textileindustry, Water Sci. Technol., 43(11) (2001)

223230.

[4] I.A. Balcioglu and I. Arslan, Partial oxidation ofreactive dyestuffs and synthetic textile dye-bath

by the O3 and O3/H2O2 processes, Water Sci.Technol., 43(2) (2001) 221228.

[5] M. Cresp, Aplicacin de los Procesos deMembrana en la Industria Textil in Apuntes delCurso de Membranas y Medio Ambiente,Universidad Politcnica de Catalua, Barcelona,

1992.[6] ASTM. Standard practice for coagulation-

flocculation jar test of water, American Societyfor Testing and Materials, 1995.

[7] R. Marn, Jar-test en el tratamiento de aguas: una

valiosa herramienta. Tecnologa del agua, 181(1998) 2532.[8] O.O. Hart, G.R. Groves, C.A. Buckley, and B.

Southworth, A guide for the planning, design andimplementation of wastewater treatment plants in

the textile industry. Part one: Closed looptreatment / Recycle system for textile sizing /desizing effluents. Pretoria, 1983.

[9] G. Belfort, (Ed.), Synthetic Membrane Proceses.

Academic Press, Inc., New York, 1984.[10] M. Mulder, Basic Principles of Membrane

Technology. Kluwer Academic Publishers, 1992.

1. reuse of wastewater of the textile industry after physicochemical & membrane

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