Reuse of Waste Water of the Textile Industry After Its Treatment With a Combination of Physico-...

8/8/2019 Reuse of Waste Water of the Textile Industry After Its Treatment With a Combination of Physico- Chemiacl Treatme

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DESALINATIONELSEVIER Desalination 149 (2002) 169-174 www.elsevier.com/locate/desal

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

and membrane technologiesA. Bes-Pih*, J.A. Mendoza-Rota, M.I. Alcaina-Miranda, A. Iborra-Clar,

M.I. Iborra-ClarDepartment of Chemical and Nuclear Engineering, Universidad PolitPcnica of Valencia,Camino de Vera s/n, 46071 Valencia, Spain

email: [email protected] 1 February 2002; accepted 15 February 2002

AbstractThis 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 (LJF) 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

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1. Introduction difficult due to the operation problems and tothe costs. Biological treatment by activatedDue to the high water consumption in the sludge offers high efficiencies in COD removal,textile industry it is essential to study its reuse. but does not eliminate completely the colour ofMany processes have been studied to treat the water and frequently operation problemstextile wastewaters [l-4]. However, their like bulking appear. The use of flotation insteadapplication in an industrial plant becomes of sedimentation to separate the treated

wastewater from the activated sludge solvesthis problem, but it increases the depuration

*Corresponding author costs and it makes complicated the plantPresented at the International Congress on Membranes and Membrane Processes (ICOM). Toulouse, France,July 7-12. 2002001 I-91 64/02/$- See front matter 0 2002 Elsevier Science B.V. All rights reservedPII: SO0 1 1-9 164(02)00750-6


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1 7 0 A. Bes-Pick et al. /Desalination 149 (2002) 169-l 74operation. Chemical oxidation by ozone, or acombination of UV-radiation and ozone andH202, 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 withphysico-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 concentrationpolarisation [9, lo].This work is focused in the evaluation of thefinal effluent quality.

2. ObjectivesThe objectives of this work are the

following:- Evaluation of the physico-chemicaltreatment 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 methodsThis study was carried out in three steps.

The first step consisted of the characterizationof the wastewater samples. The analysedparameters 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 thephysico-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., FeC13 andAlr(SO& 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 concentrationbetween 0.5 and 2 mg/L. Finally, the pH valueswere 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-Pi6 et al. /Desalination 149 (2002) 169-I 74 171

7 VALVE 1 MANOMETER6 FEED PUMP 2 REGULATION VALVE9 SPEED CONTROL 3 PERMEATE STREAMIO THERMOMETER 4 STIRRING11 FILTER SYSTEM 5 FEED TANK12 SECURITY VALVE 6 AUXILIARY TANK

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 membranesMembrane reference Cut-off (kD)10 BIOMAX of MILLIPORE 5IRIS 3065 of TECHSEP 40IRIS 3028 of TECHSEP 100

Table 2Tested NF membranesMembranereference

NaCl MgS04 PermeabilityR(%) R(%) (m/m2d.MPa)Dow NF-45 50 95 0.0219Dow NF-70 80 95 0.2309 -

Table 3Wastewater characterizationParameter FeedwaterT (C) 18PH 7.50Conductivity (mS/cm) 2.06S.S. (mg/L) 82.6COD (mg/L) 1640Turbidity (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.


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172 A. Bes-Pici et al. /Desalination 149 (2002) 169-l 744. 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, thebest 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 observedbehaviour.

In Fig. 3, it can be observed that increasingthe 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, Cnk_rr~ 20 = 200 mg/L, &,lco = 1mg/L.Experiments with the other coagulants didnot improve the efficiencies obtained with DK-FER 20.

1600

400

0 L

o COD (mg/L)t Turbidity (NTU)

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

-0.

1000

95033 900E8 8500

800

750

- czz COD (mg/L)- + Turbidity (NTLI)

*k

Y 1

T

50

402

30 gG

20 ^z

IO 2

050 100 150 200

DK-FER coagulant (mg/L)

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

1600

1260s% 960.k.g 640

3200

czx COD (mg/L)-Turbidity (NTU)

0.5 1 I,5 2NALCO floculant concentration (mg/L)Fig. 4. Influence of NALCO concentration on CODand turbidity of treated water.


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A. Bes-Pid et al. /Desalination 149 (2002) 169-I 74 173

40 I +- kD-100.- kD-40

2o i -.- kD-50 I_ ~_.

0 50 100 150 200 250 300 350 400Time (minutes:

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

30 -

5 I ~~-- NF-45d- w-70

1oc -0 50 100 150 200 250 300 350 400

Time (minutes)

Fig. 6. Permeate fluxes of NF membranes with theoperating time.

Figs. 5 and 6 show the evolution of thepermeate fluxes with the operating time in theexperiments carried out with UF and NFmembranes respectively. The membranesfeedwater was the clarified wastewater obtainedusing the conditions described above.

The COD, conductivity and pHmeasurements were obtained for the lastpermeate samples.

In Table 4, the results of the permeateanalysis can be observed. By means of UF, itwas not possible to decrease neither COD (dueto the molecular size of the dyestuffs) norconductivity. However, with NF membranes theCOD removal was almost 100%. Themembrane retention measured as conductivityremoval reached the 85% for the NF-70membrane.

5. ConclusionsThe physico-chemical treatment applied to

this textile wastewater achieves a COD removalefficiency around 50%. The optimal values ofthe parameters were: pH = 8.5, CDK_FER0 = 200mg/L, CNalco = 1 mg/L. These coagulant andflocculant concentrations will be the initialdoses of chemicals for the optimisation of theprocess in an industrial scale. The quality of thewater is not still good enough to be reused inthe industry.

Table 4Analysis of the feed and permeate streams in the different membrane experimentsParameter FeedwaterUF m embranes

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

COD (mg/L) 780 760 800 665 c2.5 c25Conductivity (mS/cm) 3.4 3.36 3.35 3.30 1.1 0.50PH 8.39 8.40 8.30 8.20 8.10 7.90


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174 A. Bes-Pili et al. /Desalination 149 (2002) 169-I 74None of the membranes used in UF tests

reduced significantly the COD of the physico-chemically treated water. However, thepermeates 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 pilotplant with higher membrane surface.

References(11

PI

[31

U. Altinbas et al., Treatability study of wastewaterfrom textile industry, Envir. Technol., 16 (1995)389-394.J.M. Coloma, Optimizacibn de las depuradorasfisico-quimicas, Revista de Quimica Textil, 137(1998) 31-40.D. Orhon et al., A scientific approach towastewater recovery and reuse in the textileindustry, Water Sci. Technol., 43(11) (2001)223-230.

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ASTM. Standard practice for coagulation-flocculation jar test of water, American Societyfor Testing and Materials, 1995.R. Marin, Jar-test en el tratamiento de aguas: unavaliosa herramienta. Tecnologia de1 agua, 181(1998) 25-32.0.0. Hart, G.R. Groves, CA. Buckley, and B.Southworth, A guide for the planning, design andimplementation of wastewater treatment plants inthe textile industry. Part one: Closed looptreatment / Recycle system for textile sizing /desizing effluents. Pretoria, 1983.G. Belfort, (Ed.), Synthetic Membrane Proceses.Academic Press, Inc., New York, 1984.

[IO] M. Mulder, Basic Principles of MembraneTechnology. Kluwer Academic Publishers, 1992.

LA. Balcioglu and I. Arslan, Partial oxidation ofreactive dyestuffs and synthetic textile dye-bathby the 0, and 03/H202 p recesses, Water Sci.Technol., 43(2) (2001) 221-228.M. Crespi, Aplicaci6n de 10s Procesos deMembrana en la Industria Textil in Apuntes de1Curso de Membranas y Medio Ambiente,Universidad PolitCcnica de CataluAa, Barcelona,1992.

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