Simple Treatment of Textile Industry Wastewater For Reuse And Recycling

The aim of the present work is at describing a simple physico-chemical treatment for the textile wastewater of a local plant to bring its characteristics to that used within the plant. Lime and polyelectrolyte were employed individually to aid the removal of pollutants. The effectiveness of the treatment was indicated by measuring parameters like biochemical oxygen demand, BOD, turbidity, electrical cond uctivity, EC, total suspended solids, TSS, to tal dissolved solid, TDS, for the produced water a fter filtration through s imple sand f ilter. The treatment was supported by a n extensive study of the coagulation/flocculation a nd filtration processes. Color dyes adsorb efficiently onto the coagulant particles and separates from the original liquor. Pollutants removal efficiency (Turbidity, TSS, TDS, and color), by (87-90%, 81-85%, 30-32% 40-45%) respectively could be obtained by using lime solution of concentration 35-40 mg/L without addition of cationic polyelectrolyte. Increasing lime concentration results in some difficulties like high pH value of water discharged, dewatering problems and sand filter clogging.


‫ﺍﻟﺘﺩﻭﻴﺭ‬ ‫ﺃﻋﺎﺩﺓ‬ ‫ﺒﻬﺩﻑ‬ ‫ﺍﻟﻨﺴﻴﺞ‬ ‫ﺼﻨﺎﻋﺔ‬ ‫ﻤﻥ‬ ‫ﺍﻟﻌﺎﺩﻤﺔ‬ ‫ﻟﻠﻤﻴﺎﻩ‬ ‫ﺒﺴﻴﻁﺔ‬ ‫ﻤﻌﺎﻟﺠﺔ‬ ‫ﻭﺍﻻﺴﺘﺨﺩﺍﻡ‬
Textile processing industry is one of the water intensive consumptive industries in almost every stage for processing and requires volumes of water about 100-150 m 3 /ton and produces high volumes of effluent wastewater, which is mainly characterized by salts, organic matter and color [3].The standard methods of treating textile wastewater are biological, chemical or physical process.These methods can be used to remove color in the wastewater with varying effectiveness depending on the types of colors and their concentration.
Physical-chemical methods are always used for color removal, and other organic and inorganic impurities.Some of the methods are relatively expensive especially those including advanced filtration like ultrafiltration, UF, nanofiltration, NF and reverse osmosis, RO.These filters are sensitive for impurities and colors which cause damage [4].Sand filters are widely used in the treatment as they are characterized by simple technology for design and production, low cost and easy maintenance than advanced filters.The coagulation/ flocculation process is an important part of surface water and wastewater treatment.It has a direct impact on the reliability of plant operations and final water quality together with cost control [5].The aim of the present work is at finding the most effective coagulant and its most advantageous dose, besides determining the best dose of the coagulant aid (cationic polyelectrolyte), to get best results, the coagulation, flocculation periods must be satisfied, and the other operation conditions (speed of mixing, for both coagulation and flocculation processes).

Experimental Apparatus
The jar test experiments were carried out a Floc Tester CHC supplied from Hoelze and Chelus com.KG (W.Germany) to study the coagulation and flocculation.The pH measurements were performed on a pH 211supplied from HANNA with accuracy of ±0.1%.The instrument was also employed for measuring PDF created with pdfFactory Pro trial version www.pdffactory.comtemperature and electrical conductivity.Turbidity of water samples was tested using Hach A 2001-Lab Turbidity meter) which is characterized by accuracy of ± 0.5% T. The HI 83000 Multi-parameter (Bench photometers) was used for color measurements over a range of 0.0 to 500 Pt/Co with accuracy of ± 0.5%. in accordance with APHA [6].Total Dissolved Solids (TDS)and electrical conductivity (EC) measurements were taken with model 214 EC HANA , accuracy ± 0.4% according to (APHA, A series of sieves were used in the sieving analysis of media of sand filter that is (sand and gravel) materials in order to prepare sand with the proper effective size (Es) and uniformity coefficient (UC) for filtration purposes.The shaker was a AS 200-digit manufactured by Retsch Electric Co. Sand Filter: A 1000 cm 3 graduated cylinder filled for a height of 12 cm of sand and 4 cm of gravel was used to filter the treated water next to the coagulation process.
Standard tests were employed for the evaluation of Chemical oxygen demand (COD) and Total Suspended Solids (TSS).
Stock suspension of 1% of lime in water was prepared by homogenizing 10 gm of CaO with water at 80˚C, to make 1000 ml with tap water.Similarly a 1% FeCl 3 solution was prepared.The polyelectrolyte solution was prepared by dissolving 1.0 gm of the polymer in 10 ml of ethyl alcohol to be completed to one liter with tap water.Thus, 1 ml of these solutions when added to 1 L of water sample will be equivalent to 1 mg/L of the coagulant.The shelf life of the coagulant solutions is given in Table 1.
The color dyes used to prepare the synthetic wastewater are acid-blue and acid-red blended with basic-blue.They are used for textile colorizations.

Determination of the best doses:
The standard jar test was employed to determine the best dose of coagulant and polyelectrolyte with the 6-place stirrer in six (1000 ml) beakers by following this procedure: PDF created with pdfFactory Pro trial version www.pdffactory.com1.One liter of wastewater was placed in each of the six beakers.
2. Appropriate quantity of coagulant (10-60 mL of the stock coagulant solution) was added.
3. The speed of the stirring paddles was adjusted initially at 100 rpm then to 120 rpm.
4. The coagulation period was chosen in accordance with the wastewater type, G factor and coagulant dose.The period is about (1 -3) min after the addition of the coagulant, then speed was reduced to 30 -80 rpm for 15-30 min depending on the flocculation time provided in the treatment plant.
5. Time required from the coagulant addition until the first appearance of visible, discrete floc particles in each beaker was recorded.
6.After a suitable period for flocculation the agitation step should be stopped and the treated water was left for 10-30 min for settling.The time needed for the settling of the majority of the flocs formed is recorded.
7. An aliquot of 100 mL of the supernatant liquid was decanted and kept for analysis.

Velocity Gradient Determination
The coagulation, flocculation velocity gradient experiments were conducted by a jar test, using various doses of coagulant agent and coagulant aid inside a 1000 ml graduated cylinder and mixed at various speeds (80 -130 rpm) using a G value of 130-280 sec -1 for the coagulation and 20-50 rpm using a G value of 22 -33 sec -1 for the flocculation process, accuracy ± 1.2% in accordance with the Phipps and Bird jar test WHO.
The choice of the best coagulation /flocculation periods depends upon optimum removal of turbidity and suspended solids.wastewater (initial turbidity 41 NTU) in different doses.Ferric chloride, however, was the least effective additive of the group.Comparatively, the (CPE) gave better efficiency of turbidity removal than ferric chloride and close to that of lime which was the most effective coagulant giving turbidity removal increased up to 70% at the 25 mg/l dose of lime and more than 75% for TSS removal efficiency at the same dose.As a result, ferric chloride was omitted from the comparison studies.The following sections will deal with the action of lime and CPE and their combination.

Effective Dose of Lime:
Starting with textile effluents of various turbidities, experiments were carried out to apply various lime doses and follow the product water quality parameters like (Turbidity, TSS, Color COD and pH).The results are shown in Fig 3 and 4. It appears that lime doses of 35 -40 mg/L gave maximum turbidity removal efficiency and TSS reduction for all wastewater samples.Wastewaters of low turbidity undergo higher reduction efficiency.Many authors reported similar results for coagulant dose effect, with different operating conditions [7,8].
The alkaline nature of lime affects the pH value of the treated wastewater and pH range (7-12) could be attained by using lime dose of 10 -50 mg/L.The high pH values of treated wastewater are not acceptable to achieve high quality of product water, since high pH values reduce the floc particles growth and formation.At high pH, the Zeta potential will be highly affected and the colloids of the solution are very stable [9].Thus lime dosage in the range of 25-35 mg/ L was adopted throughout this study.Such a result enhances the economic side of the study by using lower lime quantities for treatment as well as limiting any additive materials.Table 4 shows the pH behavior changes with lime dosage.
During the study on the effect of lime dose on the color removal it can be seen from Table 5 that a significant color reduction could be achieved at lime dosage ranging from 30 -40mg/L.Further increase in lime dose causes a poor result in color removal which is in agreement with some results published [5,10].The organic nature of color dyes and their high solubility in water lead to high level of COD.Therefore, any reduction in this parameter will be important.The use of lime as a coagulant is helpful to increase COD reduction to a level 58 t0 60 mg/L of wastewater with initial COD 114 mg/L, as can be seen in Fig. 5.

Effective Dose of The Cationic Polyelectrolyte .
Table 6 shows the effect of CPE as a coagulant on color removal efficiency.It is clear that doses in the PDF created with pdfFactory Pro trial version www.pdffactory.comrange of 1-1.25 mg/l have significant effect on the removal of color.At higher CPE doses, the removal performance drops, due to the ability of the CPE to fold back itself at this point [5,11].Similarly, the turbidity removal is enhanced with increasing dose of CPE up till a range of 1-1.25 mg/L (Fig. 6).Further increase in CPE dose tends to reduce the turbidity removal.However, the use of cationic polyelectrolyte alone is not favorable because of the weak structure of the flocs formed and the rapid clogging of the sand filter surface, in addition to the cost of the material [12].For the TSS removal, Fig. 7 shows that 1.25 mg/l stands as the acceptable CPE dose which is in agreement with published cases [13,14].Starting with wastewater with initial COD value of 114 mg/l, the test results shown in the Fig .8 indicated that the significant effect of CPE on the COD removal.Maximum removal efficiency could be obtained in the range of 1-1.25 mg/l.[11]  The use of cationic polyelectrolyte alone at concentrations of 1.25-1.5 mg/l.causes low pollutants removal efficiencies, and causes rapid clogging for sand filter due to its physical nature.Further, CPE is not effective at high levels of turbidity and TSS, besides it cost much money.References [4]Chen X., Shen Z, Zhu X. and Fan Y. ( 2004)" Advanced Treatment of Textile Wastewater for Reuse Using Electrochemical Oxidation and Membrane Filtration", 2004.
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Fig. 1
Fig. 1 and Fig. 2 show a comparison of the effect of FeCl 3 , CaO and cationic polyelectrolyte (CPE) on the removal efficiency of turbidity of

Table 2
obtained similar results.

TABLE ( 2) TYPICAL CONDITIONS OF COAGULATION AND FLOCCULATION PROCESSES
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TABLE ( 3) MAIN CHARACTERISTICS OF FEED WATER AND EFFLUENT OF SOME IRAQI TEXTILE FACTORIES.
*Reference 6.

Table ( 4) Effect of Lime doses on pH values of the wastewater samples with various turbidities (initial turbidity ranging from 6.5-7.5) Turbidity of wastewater Turbidity. 41 NTU Turbidity 88 NTU Turbidity 129 NTU Turbidity 213 NTU pH values of treated water Lime dose mg/ l
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TABLE ( 6) EFFECT OF CATIONIC POLYELECTROLYTE (CPE) DOSE ON COLOR REMOVAL EFFICIENCY WITH VARIOUS TURBIDITY LEVELS Turbidity of wastewater Turbidity. 41 NTU Turbidity 88 NTU Turbidity 129 NTU Turbidity 213 NTU Color removal efficiency CPE dose mg/ l Color removal% Color removal% Color removal%
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