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Comparative decolorization of dyes in textile wastewater using biological and chemical treatment
Separation and Purification Technology 154 (2015) 149–153
Contents lists available at ScienceDirect
Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur
Comparative decolorization of dyes in textile wastewater using biological and chemical treatment Huma Hayat, Qaisar Mahmood ⇑, Arshid Pervez, Zulfiqar Ahmad Bhatti, Shams Ali Baig Department of Environmental Sciences, COMSATS Institute of Information Technology, Abbottabad 22060, Pakistan
a r t i c l e
i n f o
Article history: Received 6 July 2015 Received in revised form 4 August 2015 Accepted 20 September 2015
Keywords: Decolorization Mineralization Textile wastewater Fenton’s reagent Biological reactor
a b s t r a c t Textile wastewater (TW) is one of the most hazardous wastewaters for the environment when discharged without any proper treatment. A comparative study was conducted to investigate the removal efficiency of color, chemical oxygen demand (COD) and turbidity from real textile industry wastewater using anaerobic IC reactor and Fenton’s process with and without pH adjustment. Color, COD and turbidity removal efficiencies have been studied for 25%, 50%, 75% and 100% textile wastewater. Results demonstrated that a maximum color removal efficiency (>92%) was recorded in Fenton’s process at pH 3 for 100% sample. However, maximum COD removal efficiency of 87% was observed in IC reactor for 100% sample. Thus, Fenton’s reagent at pH 3 was found highly effective for color removal and IC reactor observed to be efficient for COD removal. Furthermore, Fenton’s process without pH adjustment was found higher turbidity removal efficiency as compared to other treatments. Findings from this suggested that the selective treatment process could be highly promising for the decolorization of textile wastewater and can also be practically implementable. Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction Large amount of water used in textile dyeing processes is one of the leading generators of liquid pollutants. The quantity of textile wastewater has been increasing along with the growing demand of textile products [6]. Textile wastewater is characterized by high chemical oxygen demand (COD), biological oxygen demand (BOD), alkalinity and total dissolved solids (TDS). The dyes are stable and difficult to degrade due to their complex aromatic structure and synthetic origin [24,15,16,22]. Textile industry effluents are complex, containing synthetic dyes, dispersants, bases, acids, detergents, salts, oxidants, surfactants, inhibitory compounds, grease and oil, toxicants, many other compounds salts depending on the particular textile process such as scouring, bleaching, dyeing, printing and finishing. Discharge of the colored effluent into streams and rivers results in the depletion of dissolved oxygen, causing anoxic conditions that are lethal to aquatic organisms [11,10,8,9,15,23,25]. In addition, textile industry effluent usually contains 0.6–0.8 g/L dye, but the pollution is due to the durability of the dyes [8]. Various physical, chemical and biological methods such as adsorption, photolysis, chemical precipitation, chemical oxidation ⇑ Corresponding author. E-mail address: [email protected] (Q. Mahmood). http://dx.doi.org/10.1016/j.seppur.2015.09.025 1383-5866/Ó 2015 Elsevier B.V. All rights reserved.
and reduction, electrochemical precipitation have been employed for the removal of dyes from wastewater [24,16,23]. However, these technologies are usually not effective in color removal, or are expensive and less adaptable to wide range of dye containing wastewaters [11,10,24]. Generally, dye degradation means decolorization and mineralization of dye in textile wastewater. Decolorization represents destruction of chromophore group of the dye molecule; likewise degradation of organic compounds into CO2 and H2O is called mineralization [26]. The levels of decolorization and biodegradation by many investigators is determined by measuring the percentage of mineralization by BOD total organic carbon (TOC) and COD removal ratio by measuring the initial and final content [23]. Recently, Fenton reaction was efficiently utilized in wastewater treatment process for the removal of many hazardous organics from wastewater [7,27]. The traditionally accepted Fenton mechanism is represented by following equations [13]. Anaerobic treatment presents more attractive alternative as they can be developed as a renewable and clean energy sources. The anaerobic treatment is best suited for handling load fluctuations, high BOD wastewater and low energy requirement as no oxygen has to be supplied and it also has potential for energy production [25]. Fenton’s oxidation has been used for treating different types of industry wastes containing toxic organic compounds such as formaldehyde, dyestuff, phenol, and can be
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used for wastewaters, contaminated soils and sludges, toxicity reduction, organic pollutant destruction, BOD/COD removal and color and odor removal [28,6,22]. It has been successfully used to detoxify, decolorize and to enhance the biodegradability of textile wastewater and dyes [20,1,21]. In this study, an attempt has been made to compare anaerobic (i.e. IC reactor) and oxidation (i.e. Fenton’s oxidation) processes for the removal of dye pollution. Decolorization and mineralization efficiency of treatments has been investigated in terms of color and COD removal. Thus, the aims of this study were to investigate the decolorization efficiency of textile wastewater using anaerobic inner loop reactor and Fenton process and to compare the efficiency of anaerobic process and Fenton process in treating real textile wastewater. 2. Materials and methods 2.1. Wastewater collection Raw textile wastewater sample was taken from a textile finishing industry located in Rawalpindi (Koh-i-Noor textile Mills), Pakistan, where reactive dyes are being used to color cotton fabric. The samples were used after dilution to 25%, 50%, 75% and in full concentration (100%). The reactor was operated at HRT of 24 h at room temperature. Sampling cans were rinsed and cleaned with distilled water and then washed with sample during sample collection. Ambient pH, TDS, conductivity and DO and turbidity were measured using portable digital meters. The samples were delivered to the laboratory within a day of being taken and analyszed within 1 day. The samples were kept at 4 °C without any chemicals addition. Physico-chemical characteristics of wastewater are given in Table 1. 2.2. Experimental setup The laboratorial-scale experiments were involved two types of treatment processes (a) biological treatment of the industrial wastewater using IC reactor, (b) chemical oxidation using Fenton’s reagent with and without pH 3 adjustments of samples. 2.2.1. Startup of inner loop reactor Raw textile industry wastewater was treated in a pilot scale IC reactor (diameter 12 cm, total height 160 cm, total tank capacity of 3.5 L). The reactor was provided with conical bottom of 20 cm length and a feed inlet pipe of 1.5 cm diameter avoid chocking during operation. An outlet weir was provided at the top (1.51 m), which is connected to an outlet gutter and outlet pipe to the effluent collection tank. The reactor had ports for sampling, feeding, effluent and gas collection. The peristaltic pump was used for pumping of influent into the reactor. The reactor was operated during summer when room temperature was around 35 ± 3 °C, so thermostat was not operated to save the energy.
The sludge used in the IC reactor was taken from anaerobic digester degrading industry wastewater. During the startup, the reactor was fed with tap water containing 400 mg/L dextrose as the carbon source. To gradually expose the microbial community with the inhibitory organic compounds an acclimation period was necessary, allowing the development of enzyme producing agents that are essential to induce biodegradation of dye intermediates. Measurement of COD reduction was used to assess stabilization of reactor. It has taken almost 30 days to have steady state COD reduction. Then the reactor was fed with effluent. 2.2.2. Fenton’s oxidation All the tests were performed in 250 mL glass beakers containing 100 mL sample. The calculated amount of ferrous sulfate powder and hydrogen peroxide (35% w/w) dose were added into the sample. The solution was stirred for 30 min using jar test apparatus. After 30 min of settling supernatant was collected, caustic soda was added to cease the reaction and been analyzed for color (kmax), COD, pH, temperature, DO, conductivity, turbidity, TS, TDS, TSS and heavy metals. PAM was not added in the reaction mixture so save the operational cost. The dose of Fenton’s reagent for each dilution is given in Table 2. 2.3. Analytical procedures The pH of the solutions and samples was monitored by using digital pH Meter (Jenway model 520). EC of the samples was determined by using conductivity meter (Jenway model 470) as lS. COD was analyzed using a colorimetric method after digestion of the samples in a COD digester (model TR320, Merck Spectroquant), according to standard method [2]. The spectrum was taken with UV–Vis Spectrophotometer (IRMeCO UV–Vis, U2020). Turbidity of the samples was measured by using Turbidimeter (Eutech, TN-100). Dissolved oxygen of the samples was determined by using DO meter (Jenway, 970). Sample stirring for Fenton’s oxidation was performed using Jar test apparatus. Heavy metals were measured by using Atomic absorption Spectroscopy (Perkin Elmer Model 920). Total solids were determined by following the standard method described [2]. Color was measured using UV/Vis spectrophotometer from 190 to 1100 nm wavelengths; the absorbance values of supernatants were measured. All the experiments were carried out in 4 mL quartz cuvette. COD removal efficiency of samples is calculated using formula (Eq. (1))
C0 Ct 100 C0
ð1Þ
where C0 is the initial concentration of COD of the textile wastewater, and Ct is the concentration of COD at the corresponding time (t).
Table 1 Characteristics of the sample wastewater used in this study. Parameter
Unit
Concentration
pH DO Temperature Conductivity Turbidity Total solids Total dissolved solids Total suspended solids COD
– mg/L °C ls NTU mg/L mg/L mg/L mg/L
7.7 ± 0.115 0.3 ± 0 25.7 ± 0 145 ± 1.01 188.6 ± 0.57 1731.6 ± 8 86.7 ± 0.28 1697 ± 7 1132.6 ± 2.5
Table 2 Dose of Fenton’s reagent for different dilutions. Sample
25% 50% 75% 100% *
Dose pH 3
pH 7–8
1:25* 1:25* 1:25* 1:25*
1:25* 1:25* 1:25* 1:25*
The ratios mean 1 part ferrous sulfate and 25 parts H2O2.
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Glucose was fed to IC reactor during start up which was organic substrate for the anaerobic heterotrophs present in the reactor. The COD removal efficiency during start up period was in range of 70–95%. During last seven days, the removal efficiency remained above 90% which was considered as success of start up. Table 3 present the characteristics of raw wastewater and its various dilutions. It is evident from the Table that the raw wastewater contained high TS, alkaline pH, lower DO, higher COD and excessive turbidity levels.
% Color removal
3. Results
100 90 80 70 60 50 40 30 20 10 0
(a)
25%
50%
75%
100%
Wastewater samples
3.2. COD removal efficiency Fig 2a–c presents COD removal efficiency of IC anaerobic reactor, with and without pH adjustments using Fenton’s reagent. In IC anaerobic reactor the removal efficiency of COD in 25%, 50%, 75% and 100% sample after treatment with IC reactor was 76.8%, 60.1%, 69.6% and 87%, respectively (Fig. 2a). COD removal efficiency of Fenton’s reagent with pH adjustment in 25%, 50%, 75% and 100% sample was 28.8%, 89%, 40.4% and 28%, respectively (Fig. 2b). Fenton reagent found to be effective for COD removal except for 50% sample. However, the findings were quite surprising in treatment without pH adjustment. COD removal efficiency of Fenton’s reagent without pH adjustment in 25%, 50%, 75% and 100% sample
100 90 80 70 60 50 40 30 20 10 0
(b)
25%
50%
75%
100%
Wastewater samples
% Color removal
Anaerobic IC reactor has been used for the decolorization of textile wastewater. The sample was used in % solutions in order to acclimatize microbes grown within. Fig. 1a–c presents color removal efficiency of IC reactor, Fenton’s reagent without and with pH adjustments. Maximum color removal efficiency was shown for 25% sample and minimum for 100% sample and color removal efficiency of IC reactor for 25%, 50%, 75% and 100% sample was 82%, 29.2%, 62% and 19%, respectively. However, Fenton’s reagent has been used to compare the decolorization of textile wastewater. Color removal efficiency using Fenton’s process without pH adjustment for 25%, 50%, 75% and 100% sample was 74%, 77.3%, 37% and 88.8%, respectively. Fenton reagent found to be quite effective for color removal without pH adjustment as compare to IC reactor. In addition, color removal efficiency of Fenton’s process with pH adjustment for 25%, 50%, 75% and 100% sample was 83%, 81.9%, 63% and 92.5%, respectively (Fig. 1c). The results demonstrated that the Fenton’s process with pH adjustment was found highly effective for the removal of color in textile wastewater.
% Color removal
3.1. Color removal efficiency
100 90 80 70 60 50 40 30 20 10 0
(c)
25%
50%
75%
100%
Wastewater samples Fig. 1. Color removal efficiency of (a) anaerobic IC reactor, (b) Fenton’s reagent and (c) Fenton’s reagent with pH 3 for all samples.
was 26.6%, 21.2%, 33% and 26%, respectively (Fig. 2c). Thus, the findings revealed that the IC reactor was found comparatively higher COD removal efficiency as compared to other treatments.
Table 3 Parameters determined for each sample dilution solutions before treatment. Parameters
pH DO (mg/L) TS (mg/L) TSS (mg/L) TDS (mg/L) Conductivity (ls) COD (mg/L) Turbidity (NTU) Temperature (°C) Manganese (mg/L) Lead (mg/L) Chromium (mg/L) Zinc (mg/L) Nickel (mg/L)
Dilution 25%
50%
75%
100%
7.23 ± 0.047 2.73 ± 0.094 506.3 ± 5.79 697 ± 6.16 26.0 ± 0.047 58.3 ± 0.047 282.9 ± 0.69 47.25 ± 0.04 23.4 ± 0 0.003 ± 0.001 0.092 ± 0.04 2.61 ± 0.001 0.024 ± 0.002 0.021 ± 0.001
6.89 ± 0 0.103 ± 0.004 884.3 ± 2.05 812.5 ± 2.05 51.8 ± 0 79.6 ± 0 560.5 ± 4.74 86.6 ± 0.47 25.2 ± 0 0.08 ± 0 0.210 ± 0.001 3.45 ± 0.004 0.485 ± 0 0.043 ± 0.002
7.08 ± 0.008 0.3 ± 0 1444.6 ± 7.58 1225.9 ± 5.78 80.3 ± 0.047 114 ± 0.1 851.6 ± 2.49 180 ± 1.63 25 ± 0 0.009 ± 0.015 0.266 ± 0.02 4.80 ± 0.01 0.631 ± 0.02 0.063 ± 0.02
7.80 ± 0.11 0.3 ± 0 1731.6 ± 8 1697 ± 7 86.7 ± 0.28 145 ± 1.01 1132.6 ± 2.5 188.6 ± 0.57 25.7 ± 0.05 0.012 ± 0.02 0.385 ± 0.01 6.45 ± 0.03 0.085 ± 0.03 0.086 ± 0.01
H. Hayat et al. / Separation and Purification Technology 154 (2015) 149–153
100 90 80 70 60 50 40 30 20 10 0
(a) %Turbidity removal
% COD removal
152
25%
50%
75%
100%
100 90 80 70 60 50 40 30 20 10 0
(a)
25%
100 90 80 70 60 50 40 30 20 10 0
(b)
100 98
25%
50%
75%
50%
75%
100%
Wastewater samples
%Turbidity removal
% COD removal
Wastewater samples
(b)
96 94 92 90 88 86 84 82
100%
80
Wastewater samples
25%
50%
75%
100%
100 90 80 70 60 50 40 30 20 10 0
(c)
100 90
25%
50%
75%
100%
Wastewater samples Fig. 2. COD removal efficiency of (a) anaerobic IC reactor, (b) Fenton’s reagent and (c) Fenton’s reagent with pH 3 for all samples for all samples.
3.3. Turbidity removal efficiency Fig. 3a–c presents turbidity removal efficiency of anaerobic IC reactor, with and without pH adjustments using Fenton’s reagent. Turbidity removal efficiency of IC reactor for 25%, 50%, 75% and 100% sample was 70%, 55%, 82.3% and 36.4%, respectively (Fig. 3a). However, turbidity removal efficiency using Fenton’s process with pH adjustment for 25%, 50%, 75% and 100% was 92.6%, 93.4%, 90.8% and 93.4%, respectively, which was found to be higher as compared to IC reactor. But the turbidity removal efficiency of Fenton’s process without pH adjustment for 25%, 50%, 75% and 100% sample was 87.9%, 72%, 73%, 94.3%, respectively (Fig. 3c). As result Fenton’s process without pH adjustment was found higher turbidity removal efficiency as compared to other treatments. 4. Discussion The present study was conducted to investigate the decolorization and mineralization efficiency of anaerobic biological IC reactor and Fenton’s reagent as a chemical treatment with and without pH adjustments. The purpose of running different concentrations of
%Turbidity removal
% COD removal
Wastewater samples
(c)
80 70 60 50 40 30 20 10 0
25%
50%
75%
100%
Wastewater samples Fig. 3. Turbidity and color removal efficiency of (a) IC reactor, (b) Fenton reagent at pH 3, and (c) Fenton reagent without pH adjustment.
sample was to acclimatize the anaerobes to wastewater characteristics and gradually exposing them to high concentrations. In the past several physicochemical methods have been employed for the removal of dyes from textile wastewater effluent [23]. However, enzymatic or microbial degradation and decolorization is an eco-friendly cost-competitive option that could help reduce water consumption compared to physicochemical treatment methods. Biological treatment was found to be quite effective; however, most of the organic matter in the effluent is toxic and or not so biodegradable, so biological treatment alone is not efficient [4]. Consequently, the tighter international regulations and increased public concern challenged the textile industry to explore and go for new alternatives to minimize environmental problems associated with dye containing wastewater. It is well established that the oxidation processes can be successfully used for the remediation of contaminated surface, ground and industrial wastewaters containing non-biodegradable organic pollutants [28,3,5,12]. Fenton oxidation is one of the powerful advanced oxidation processes. Fenton Oxidation mechanism is based on the generation of hydroxyl radicals as a result of the
H. Hayat et al. / Separation and Purification Technology 154 (2015) 149–153
reaction of hydrogen peroxide with ferrous ions a catalyst under acidic conditions [22]. The Fenton reaction has significant advantages such as a short reaction time respective to all other advanced oxidation processes, reagents are cheap and non-toxic; there is no complexity in carrying on the reaction [5,14]. Although Fenton’s reagent can decolorize the dye wastewater, it has its own limitations as the high reagent costs, generation of aromatic amines and production of sludge which needs safe disposal [17,28,22]. Many investigators have reported that Fenton’s reagent is effective for partial degradation and complete color removal of complex organic matter [17,10]. Color and COD removal efficiency of anaerobic IC reactor has been studied in the present study. Maximum color removal of 82% for 25% sample while minimum was 19% for 100% sample was recorded. Therefore, IC was found not too effective for color removal except for 25% sample (Fig. 1a). Dye concentration may play a role in the color removal process. The applied dye concentrations in several studies largely exceed the 10–250 mg/L range in textile effluents. High dye concentrations negatively affect the anaerobic color removal efficiency, either by causing toxicity for microbes or by exceeding the reactor’s dye reduction capacity [18]. Studies investigating the effect of different dye concentrations usually reported higher net color removal efficiencies at lower dye concentrations [29]. In this study, Fenton’s reagent with and without pH adjustment was used for the removal of color and COD. Fenton’s reagent was found to be highly efficient in terms of color removal with minimum efficiency not less than 63.5%. However, COD removal efficiency was in the range of 21.2–33% demonstrating a poor response for COD removal. Other studies also revealed that Fenton process along with oxidation and coagulation was effective for the removal of color rather than COD. But a photo-Fenton process was found to be more effective (>98%) for decolorization [19]. 5. Conclusions A comparative study using two removal processes (IC reactor and Fenton’s reagent with and without pH adjustment) for the removal of color, COD and turbidity removal from a real textile industry wastewater was evaluated in this study. Color removal efficiency in Fenton’s process with and without pH adjustment was found to be highly efficient. However, minimum color removal efficiency was shown by anaerobic IC reactor in comparison to other treatments. In all cases maximum COD removal efficiency was shown by anaerobic IC reactor in comparison to other treatments. It was found that Fenton’s reagent with pH 3 is best for color removal and IC reactor for COD removal. Furthermore, findings from this suggested that the selective treatment process could be more effective for the removal of targeted pollutants from textile wastewater. References [1] D.A. Aljuboury, P. Puganeshwary Palaniandy, H.B.A. Aziz, S. Feroz, A review on the fenton process for wastewater treatment, J. Innov. Eng. 2 (3) (2014) 1–21. [2] APHA, Standard Methods for the Examination of Water and Wastewater, 21st ed., American Public Health Association, Washington, D.C, 2005.
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[3] A.R.T. Bagha, N.M. Mahmoodi, F.M. Menger, Degradation of a persistent organic dye from colored textile wastewater by ozonation, Desalination 260 (2010) 34–38. [4] J. Blanco, F. Torrades, M.D.L. Varga, J.G. Montano, Fenton and biological-Fenton coupled processes for textile wastewater treatment and reuse, Desalination 286 (2012) 394–399. [5] L. Chu, J. Wang, H. Liu, X. Sun, Treatment of coking wastewater by an advanced Fenton oxidation process using iron powder and hydrogen peroxide, Chemosphere 86 (2011) 409–414. [6] N.K. Daud, U.G. Akpan, B.H. Hameed, Decolorization of Sunzol Black DN conc. in aqueous solution by Fenton oxidation process: effect of system parameters and kinetic study, Desalization Water Treat. 37 (2012) 1–7. [7] A. Durn, J.M. Monteagudo, A. Carnicer, Photo-Fenton mineralization of synthetic apple-juice wastewater, Chem. Eng. J. 168 (2011) 102–107. [8] E. Ellouze, N. Tahri, R.B. Amar, Enhancement of textile wastewater treatment process using nanofiltration, Desalination 286 (2012) 16–23. [9] T.M. Elmorsi, Y.M. Riyad, Z.H. Mohamed, H.M.H. Abd EL Bary, Decolorization of Mordant red 73 azo dye in water using H2O2/UV and photo-Fenton treatment, J. Hazard. Mater. 174 (2010) 352–358. [10] C. Fersi, M. Dhahbi, Treatment of textile plant effluent by ultrafiltration and/or nanofiltration for water reuse, Desalination 222 (2008) 263–271. [11] P. Fongsatitkul, P. Elefsiniotis, A. Yamasmit, N. Yamasmit, Use of sequencing batch reactors and Fenton’s reagent to treat a wastewater from a textile industry, Biochem. Eng. J. 21 (2004) 213–220. [12] D.P. Garcia, G. Buitron, Evaluation of three reagent dosing strategies in a photo-Fenton process for the decolorization of azo dye mixtures, J. Hazard. Mater. 217–218 (2012) 293–300. [13] I. Gulkay, G.A. Surucu, F.B. Dilek, Importance of H2O2/Fe2+ ratio in Fenton’s treatment of a carpet dyeing wastewater, J. Hazard. Mater. B136 (2006) 763– 769. [14] M. Karatas, Y.A. Argun, M.E. Argun, Decolorization of antraquinonic dye, Reactive Blue 114 from synthetic wastewater by Fenton process: Kinetics and thermodynamics, J. Ind. Eng. Chem. 18 (2012) 1058–1062. [15] S. Karthikeyan, A. Titus, A. Gnanamani, A.B. Mandal, G. Sekaran, Treatment of textile wastewater by homogeneous and heterogeneous Fenton oxidation processes, Desalination 281 (2011) 438–445. [16] I. Khouni, B. Marrot, P. Moulin, R.B. Amar, Decolorization of the reconstituted textile effluent by different process treatments: enzymatic catalysis, coagulation/flocculation and nanofiltration processes, Desalination 268 (2011) 27–37. [17] B. Lodha, S. Chaudhari, Optimization of Fenton-biological treatment scheme for the treatment of aqueous dye solutions, J. Hazard. Mater. 148 (2007) 459– 466. [18] M.S. Lucas, A. Peres, Decolorization of the azo dye Reactive Black 5 by Fenton and photo-Fenton oxidation, Dyes Pigments 71 (2006) 236–244. [19] M.S. Lucas, J.A. Peres, Removal of COD from olive mill wastewater by Fenton’s reagent: kinetic study, J. Hazard. Mater. 168 (2010) 1253–1259. [20] S. Meric, H. Selc-ukb, V. Belgiomo, Acute toxicity removal in textile finishing wastewater by Fenton’s oxidation, ozone and coagulation–flocculation processes, Water Res. 39 (2005) 1147–1153. [21] M. Punzi, F. Nilsson, A. Anbalagan, B.-M. Svensson, K. Jönsson, B. Mattiasson, M. Jonstrup, Combined anaerobic–ozonation process for treatment of textile wastewater: removal of acute toxicity and mutagenicity, Journal of Hazardous Materials 292 (2015) 52–60. [22] S. Sahinkaya, COD and color removal from synthetic textile wastewater by ultrasound assisted electro-Fenton oxidation process, J. Ind. Eng. Chem. 19 (2013) 601–605. [23] R.G. Saratale, G.D. Saratale, J.S. Chang, S.P. Govindwar, Bacterial decolorization and degradation of azo dyes: a review, J. Taiwan Inst. Chem. Eng. 42 (2011) 138–157. [24] A. Srinivasan, T. Viraraghavan, Decolorization of dye wastewaters by biosorbents: a review, J. Environ. Manage. 91 (2010) 1915–1929. [25] O. Turgay, G. Ersoz, S. Atalay, J. Forssh, U. Wlander, The treatment of azo dyes found in textile industry wastewater by anaerobic biological method and chemical oxidation, Sep. Purif. Technol. 79 (2011) 26–33. [26] D. Vujevic, S. Papic, N. Koprivanac, A.L.I. Bozic, Decolorization and mineralization of reactive dye byUV/Fenton process, Sep. Sci. Technol. 45 (2010) 1637–1643. [27] Wei-Min Wang, J. Song, X. Hana, Schwertmannite as a new Fenton-like catalyst in the oxidation ofphenol by H2O2, J. Hazard. Mater. 262 (2013) 412–419. [28] K. Yetilmezsoy, S. Sakar, Improvement of COD and color removal from UASB treated poultry manure wastewater using Fenton’s oxidation, J. Hazard. Mater. 151 (2008) 547–558. [29] F.P. Zee, S. Villaverde, Combined anaerobic–aerobic treatment of azo dyes-a short review of bioreactor studies, Water Res. 39 (2005) 1425–1440.
Contents lists available at ScienceDirect
Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur
Comparative decolorization of dyes in textile wastewater using biological and chemical treatment Huma Hayat, Qaisar Mahmood ⇑, Arshid Pervez, Zulfiqar Ahmad Bhatti, Shams Ali Baig Department of Environmental Sciences, COMSATS Institute of Information Technology, Abbottabad 22060, Pakistan
a r t i c l e
i n f o
Article history: Received 6 July 2015 Received in revised form 4 August 2015 Accepted 20 September 2015
Keywords: Decolorization Mineralization Textile wastewater Fenton’s reagent Biological reactor
a b s t r a c t Textile wastewater (TW) is one of the most hazardous wastewaters for the environment when discharged without any proper treatment. A comparative study was conducted to investigate the removal efficiency of color, chemical oxygen demand (COD) and turbidity from real textile industry wastewater using anaerobic IC reactor and Fenton’s process with and without pH adjustment. Color, COD and turbidity removal efficiencies have been studied for 25%, 50%, 75% and 100% textile wastewater. Results demonstrated that a maximum color removal efficiency (>92%) was recorded in Fenton’s process at pH 3 for 100% sample. However, maximum COD removal efficiency of 87% was observed in IC reactor for 100% sample. Thus, Fenton’s reagent at pH 3 was found highly effective for color removal and IC reactor observed to be efficient for COD removal. Furthermore, Fenton’s process without pH adjustment was found higher turbidity removal efficiency as compared to other treatments. Findings from this suggested that the selective treatment process could be highly promising for the decolorization of textile wastewater and can also be practically implementable. Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction Large amount of water used in textile dyeing processes is one of the leading generators of liquid pollutants. The quantity of textile wastewater has been increasing along with the growing demand of textile products [6]. Textile wastewater is characterized by high chemical oxygen demand (COD), biological oxygen demand (BOD), alkalinity and total dissolved solids (TDS). The dyes are stable and difficult to degrade due to their complex aromatic structure and synthetic origin [24,15,16,22]. Textile industry effluents are complex, containing synthetic dyes, dispersants, bases, acids, detergents, salts, oxidants, surfactants, inhibitory compounds, grease and oil, toxicants, many other compounds salts depending on the particular textile process such as scouring, bleaching, dyeing, printing and finishing. Discharge of the colored effluent into streams and rivers results in the depletion of dissolved oxygen, causing anoxic conditions that are lethal to aquatic organisms [11,10,8,9,15,23,25]. In addition, textile industry effluent usually contains 0.6–0.8 g/L dye, but the pollution is due to the durability of the dyes [8]. Various physical, chemical and biological methods such as adsorption, photolysis, chemical precipitation, chemical oxidation ⇑ Corresponding author. E-mail address: [email protected] (Q. Mahmood). http://dx.doi.org/10.1016/j.seppur.2015.09.025 1383-5866/Ó 2015 Elsevier B.V. All rights reserved.
and reduction, electrochemical precipitation have been employed for the removal of dyes from wastewater [24,16,23]. However, these technologies are usually not effective in color removal, or are expensive and less adaptable to wide range of dye containing wastewaters [11,10,24]. Generally, dye degradation means decolorization and mineralization of dye in textile wastewater. Decolorization represents destruction of chromophore group of the dye molecule; likewise degradation of organic compounds into CO2 and H2O is called mineralization [26]. The levels of decolorization and biodegradation by many investigators is determined by measuring the percentage of mineralization by BOD total organic carbon (TOC) and COD removal ratio by measuring the initial and final content [23]. Recently, Fenton reaction was efficiently utilized in wastewater treatment process for the removal of many hazardous organics from wastewater [7,27]. The traditionally accepted Fenton mechanism is represented by following equations [13]. Anaerobic treatment presents more attractive alternative as they can be developed as a renewable and clean energy sources. The anaerobic treatment is best suited for handling load fluctuations, high BOD wastewater and low energy requirement as no oxygen has to be supplied and it also has potential for energy production [25]. Fenton’s oxidation has been used for treating different types of industry wastes containing toxic organic compounds such as formaldehyde, dyestuff, phenol, and can be
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used for wastewaters, contaminated soils and sludges, toxicity reduction, organic pollutant destruction, BOD/COD removal and color and odor removal [28,6,22]. It has been successfully used to detoxify, decolorize and to enhance the biodegradability of textile wastewater and dyes [20,1,21]. In this study, an attempt has been made to compare anaerobic (i.e. IC reactor) and oxidation (i.e. Fenton’s oxidation) processes for the removal of dye pollution. Decolorization and mineralization efficiency of treatments has been investigated in terms of color and COD removal. Thus, the aims of this study were to investigate the decolorization efficiency of textile wastewater using anaerobic inner loop reactor and Fenton process and to compare the efficiency of anaerobic process and Fenton process in treating real textile wastewater. 2. Materials and methods 2.1. Wastewater collection Raw textile wastewater sample was taken from a textile finishing industry located in Rawalpindi (Koh-i-Noor textile Mills), Pakistan, where reactive dyes are being used to color cotton fabric. The samples were used after dilution to 25%, 50%, 75% and in full concentration (100%). The reactor was operated at HRT of 24 h at room temperature. Sampling cans were rinsed and cleaned with distilled water and then washed with sample during sample collection. Ambient pH, TDS, conductivity and DO and turbidity were measured using portable digital meters. The samples were delivered to the laboratory within a day of being taken and analyszed within 1 day. The samples were kept at 4 °C without any chemicals addition. Physico-chemical characteristics of wastewater are given in Table 1. 2.2. Experimental setup The laboratorial-scale experiments were involved two types of treatment processes (a) biological treatment of the industrial wastewater using IC reactor, (b) chemical oxidation using Fenton’s reagent with and without pH 3 adjustments of samples. 2.2.1. Startup of inner loop reactor Raw textile industry wastewater was treated in a pilot scale IC reactor (diameter 12 cm, total height 160 cm, total tank capacity of 3.5 L). The reactor was provided with conical bottom of 20 cm length and a feed inlet pipe of 1.5 cm diameter avoid chocking during operation. An outlet weir was provided at the top (1.51 m), which is connected to an outlet gutter and outlet pipe to the effluent collection tank. The reactor had ports for sampling, feeding, effluent and gas collection. The peristaltic pump was used for pumping of influent into the reactor. The reactor was operated during summer when room temperature was around 35 ± 3 °C, so thermostat was not operated to save the energy.
The sludge used in the IC reactor was taken from anaerobic digester degrading industry wastewater. During the startup, the reactor was fed with tap water containing 400 mg/L dextrose as the carbon source. To gradually expose the microbial community with the inhibitory organic compounds an acclimation period was necessary, allowing the development of enzyme producing agents that are essential to induce biodegradation of dye intermediates. Measurement of COD reduction was used to assess stabilization of reactor. It has taken almost 30 days to have steady state COD reduction. Then the reactor was fed with effluent. 2.2.2. Fenton’s oxidation All the tests were performed in 250 mL glass beakers containing 100 mL sample. The calculated amount of ferrous sulfate powder and hydrogen peroxide (35% w/w) dose were added into the sample. The solution was stirred for 30 min using jar test apparatus. After 30 min of settling supernatant was collected, caustic soda was added to cease the reaction and been analyzed for color (kmax), COD, pH, temperature, DO, conductivity, turbidity, TS, TDS, TSS and heavy metals. PAM was not added in the reaction mixture so save the operational cost. The dose of Fenton’s reagent for each dilution is given in Table 2. 2.3. Analytical procedures The pH of the solutions and samples was monitored by using digital pH Meter (Jenway model 520). EC of the samples was determined by using conductivity meter (Jenway model 470) as lS. COD was analyzed using a colorimetric method after digestion of the samples in a COD digester (model TR320, Merck Spectroquant), according to standard method [2]. The spectrum was taken with UV–Vis Spectrophotometer (IRMeCO UV–Vis, U2020). Turbidity of the samples was measured by using Turbidimeter (Eutech, TN-100). Dissolved oxygen of the samples was determined by using DO meter (Jenway, 970). Sample stirring for Fenton’s oxidation was performed using Jar test apparatus. Heavy metals were measured by using Atomic absorption Spectroscopy (Perkin Elmer Model 920). Total solids were determined by following the standard method described [2]. Color was measured using UV/Vis spectrophotometer from 190 to 1100 nm wavelengths; the absorbance values of supernatants were measured. All the experiments were carried out in 4 mL quartz cuvette. COD removal efficiency of samples is calculated using formula (Eq. (1))
C0 Ct 100 C0
ð1Þ
where C0 is the initial concentration of COD of the textile wastewater, and Ct is the concentration of COD at the corresponding time (t).
Table 1 Characteristics of the sample wastewater used in this study. Parameter
Unit
Concentration
pH DO Temperature Conductivity Turbidity Total solids Total dissolved solids Total suspended solids COD
– mg/L °C ls NTU mg/L mg/L mg/L mg/L
7.7 ± 0.115 0.3 ± 0 25.7 ± 0 145 ± 1.01 188.6 ± 0.57 1731.6 ± 8 86.7 ± 0.28 1697 ± 7 1132.6 ± 2.5
Table 2 Dose of Fenton’s reagent for different dilutions. Sample
25% 50% 75% 100% *
Dose pH 3
pH 7–8
1:25* 1:25* 1:25* 1:25*
1:25* 1:25* 1:25* 1:25*
The ratios mean 1 part ferrous sulfate and 25 parts H2O2.
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Glucose was fed to IC reactor during start up which was organic substrate for the anaerobic heterotrophs present in the reactor. The COD removal efficiency during start up period was in range of 70–95%. During last seven days, the removal efficiency remained above 90% which was considered as success of start up. Table 3 present the characteristics of raw wastewater and its various dilutions. It is evident from the Table that the raw wastewater contained high TS, alkaline pH, lower DO, higher COD and excessive turbidity levels.
% Color removal
3. Results
100 90 80 70 60 50 40 30 20 10 0
(a)
25%
50%
75%
100%
Wastewater samples
3.2. COD removal efficiency Fig 2a–c presents COD removal efficiency of IC anaerobic reactor, with and without pH adjustments using Fenton’s reagent. In IC anaerobic reactor the removal efficiency of COD in 25%, 50%, 75% and 100% sample after treatment with IC reactor was 76.8%, 60.1%, 69.6% and 87%, respectively (Fig. 2a). COD removal efficiency of Fenton’s reagent with pH adjustment in 25%, 50%, 75% and 100% sample was 28.8%, 89%, 40.4% and 28%, respectively (Fig. 2b). Fenton reagent found to be effective for COD removal except for 50% sample. However, the findings were quite surprising in treatment without pH adjustment. COD removal efficiency of Fenton’s reagent without pH adjustment in 25%, 50%, 75% and 100% sample
100 90 80 70 60 50 40 30 20 10 0
(b)
25%
50%
75%
100%
Wastewater samples
% Color removal
Anaerobic IC reactor has been used for the decolorization of textile wastewater. The sample was used in % solutions in order to acclimatize microbes grown within. Fig. 1a–c presents color removal efficiency of IC reactor, Fenton’s reagent without and with pH adjustments. Maximum color removal efficiency was shown for 25% sample and minimum for 100% sample and color removal efficiency of IC reactor for 25%, 50%, 75% and 100% sample was 82%, 29.2%, 62% and 19%, respectively. However, Fenton’s reagent has been used to compare the decolorization of textile wastewater. Color removal efficiency using Fenton’s process without pH adjustment for 25%, 50%, 75% and 100% sample was 74%, 77.3%, 37% and 88.8%, respectively. Fenton reagent found to be quite effective for color removal without pH adjustment as compare to IC reactor. In addition, color removal efficiency of Fenton’s process with pH adjustment for 25%, 50%, 75% and 100% sample was 83%, 81.9%, 63% and 92.5%, respectively (Fig. 1c). The results demonstrated that the Fenton’s process with pH adjustment was found highly effective for the removal of color in textile wastewater.
% Color removal
3.1. Color removal efficiency
100 90 80 70 60 50 40 30 20 10 0
(c)
25%
50%
75%
100%
Wastewater samples Fig. 1. Color removal efficiency of (a) anaerobic IC reactor, (b) Fenton’s reagent and (c) Fenton’s reagent with pH 3 for all samples.
was 26.6%, 21.2%, 33% and 26%, respectively (Fig. 2c). Thus, the findings revealed that the IC reactor was found comparatively higher COD removal efficiency as compared to other treatments.
Table 3 Parameters determined for each sample dilution solutions before treatment. Parameters
pH DO (mg/L) TS (mg/L) TSS (mg/L) TDS (mg/L) Conductivity (ls) COD (mg/L) Turbidity (NTU) Temperature (°C) Manganese (mg/L) Lead (mg/L) Chromium (mg/L) Zinc (mg/L) Nickel (mg/L)
Dilution 25%
50%
75%
100%
7.23 ± 0.047 2.73 ± 0.094 506.3 ± 5.79 697 ± 6.16 26.0 ± 0.047 58.3 ± 0.047 282.9 ± 0.69 47.25 ± 0.04 23.4 ± 0 0.003 ± 0.001 0.092 ± 0.04 2.61 ± 0.001 0.024 ± 0.002 0.021 ± 0.001
6.89 ± 0 0.103 ± 0.004 884.3 ± 2.05 812.5 ± 2.05 51.8 ± 0 79.6 ± 0 560.5 ± 4.74 86.6 ± 0.47 25.2 ± 0 0.08 ± 0 0.210 ± 0.001 3.45 ± 0.004 0.485 ± 0 0.043 ± 0.002
7.08 ± 0.008 0.3 ± 0 1444.6 ± 7.58 1225.9 ± 5.78 80.3 ± 0.047 114 ± 0.1 851.6 ± 2.49 180 ± 1.63 25 ± 0 0.009 ± 0.015 0.266 ± 0.02 4.80 ± 0.01 0.631 ± 0.02 0.063 ± 0.02
7.80 ± 0.11 0.3 ± 0 1731.6 ± 8 1697 ± 7 86.7 ± 0.28 145 ± 1.01 1132.6 ± 2.5 188.6 ± 0.57 25.7 ± 0.05 0.012 ± 0.02 0.385 ± 0.01 6.45 ± 0.03 0.085 ± 0.03 0.086 ± 0.01
H. Hayat et al. / Separation and Purification Technology 154 (2015) 149–153
100 90 80 70 60 50 40 30 20 10 0
(a) %Turbidity removal
% COD removal
152
25%
50%
75%
100%
100 90 80 70 60 50 40 30 20 10 0
(a)
25%
100 90 80 70 60 50 40 30 20 10 0
(b)
100 98
25%
50%
75%
50%
75%
100%
Wastewater samples
%Turbidity removal
% COD removal
Wastewater samples
(b)
96 94 92 90 88 86 84 82
100%
80
Wastewater samples
25%
50%
75%
100%
100 90 80 70 60 50 40 30 20 10 0
(c)
100 90
25%
50%
75%
100%
Wastewater samples Fig. 2. COD removal efficiency of (a) anaerobic IC reactor, (b) Fenton’s reagent and (c) Fenton’s reagent with pH 3 for all samples for all samples.
3.3. Turbidity removal efficiency Fig. 3a–c presents turbidity removal efficiency of anaerobic IC reactor, with and without pH adjustments using Fenton’s reagent. Turbidity removal efficiency of IC reactor for 25%, 50%, 75% and 100% sample was 70%, 55%, 82.3% and 36.4%, respectively (Fig. 3a). However, turbidity removal efficiency using Fenton’s process with pH adjustment for 25%, 50%, 75% and 100% was 92.6%, 93.4%, 90.8% and 93.4%, respectively, which was found to be higher as compared to IC reactor. But the turbidity removal efficiency of Fenton’s process without pH adjustment for 25%, 50%, 75% and 100% sample was 87.9%, 72%, 73%, 94.3%, respectively (Fig. 3c). As result Fenton’s process without pH adjustment was found higher turbidity removal efficiency as compared to other treatments. 4. Discussion The present study was conducted to investigate the decolorization and mineralization efficiency of anaerobic biological IC reactor and Fenton’s reagent as a chemical treatment with and without pH adjustments. The purpose of running different concentrations of
%Turbidity removal
% COD removal
Wastewater samples
(c)
80 70 60 50 40 30 20 10 0
25%
50%
75%
100%
Wastewater samples Fig. 3. Turbidity and color removal efficiency of (a) IC reactor, (b) Fenton reagent at pH 3, and (c) Fenton reagent without pH adjustment.
sample was to acclimatize the anaerobes to wastewater characteristics and gradually exposing them to high concentrations. In the past several physicochemical methods have been employed for the removal of dyes from textile wastewater effluent [23]. However, enzymatic or microbial degradation and decolorization is an eco-friendly cost-competitive option that could help reduce water consumption compared to physicochemical treatment methods. Biological treatment was found to be quite effective; however, most of the organic matter in the effluent is toxic and or not so biodegradable, so biological treatment alone is not efficient [4]. Consequently, the tighter international regulations and increased public concern challenged the textile industry to explore and go for new alternatives to minimize environmental problems associated with dye containing wastewater. It is well established that the oxidation processes can be successfully used for the remediation of contaminated surface, ground and industrial wastewaters containing non-biodegradable organic pollutants [28,3,5,12]. Fenton oxidation is one of the powerful advanced oxidation processes. Fenton Oxidation mechanism is based on the generation of hydroxyl radicals as a result of the
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reaction of hydrogen peroxide with ferrous ions a catalyst under acidic conditions [22]. The Fenton reaction has significant advantages such as a short reaction time respective to all other advanced oxidation processes, reagents are cheap and non-toxic; there is no complexity in carrying on the reaction [5,14]. Although Fenton’s reagent can decolorize the dye wastewater, it has its own limitations as the high reagent costs, generation of aromatic amines and production of sludge which needs safe disposal [17,28,22]. Many investigators have reported that Fenton’s reagent is effective for partial degradation and complete color removal of complex organic matter [17,10]. Color and COD removal efficiency of anaerobic IC reactor has been studied in the present study. Maximum color removal of 82% for 25% sample while minimum was 19% for 100% sample was recorded. Therefore, IC was found not too effective for color removal except for 25% sample (Fig. 1a). Dye concentration may play a role in the color removal process. The applied dye concentrations in several studies largely exceed the 10–250 mg/L range in textile effluents. High dye concentrations negatively affect the anaerobic color removal efficiency, either by causing toxicity for microbes or by exceeding the reactor’s dye reduction capacity [18]. Studies investigating the effect of different dye concentrations usually reported higher net color removal efficiencies at lower dye concentrations [29]. In this study, Fenton’s reagent with and without pH adjustment was used for the removal of color and COD. Fenton’s reagent was found to be highly efficient in terms of color removal with minimum efficiency not less than 63.5%. However, COD removal efficiency was in the range of 21.2–33% demonstrating a poor response for COD removal. Other studies also revealed that Fenton process along with oxidation and coagulation was effective for the removal of color rather than COD. But a photo-Fenton process was found to be more effective (>98%) for decolorization [19]. 5. Conclusions A comparative study using two removal processes (IC reactor and Fenton’s reagent with and without pH adjustment) for the removal of color, COD and turbidity removal from a real textile industry wastewater was evaluated in this study. Color removal efficiency in Fenton’s process with and without pH adjustment was found to be highly efficient. However, minimum color removal efficiency was shown by anaerobic IC reactor in comparison to other treatments. In all cases maximum COD removal efficiency was shown by anaerobic IC reactor in comparison to other treatments. It was found that Fenton’s reagent with pH 3 is best for color removal and IC reactor for COD removal. Furthermore, findings from this suggested that the selective treatment process could be more effective for the removal of targeted pollutants from textile wastewater. References [1] D.A. Aljuboury, P. Puganeshwary Palaniandy, H.B.A. Aziz, S. Feroz, A review on the fenton process for wastewater treatment, J. Innov. Eng. 2 (3) (2014) 1–21. [2] APHA, Standard Methods for the Examination of Water and Wastewater, 21st ed., American Public Health Association, Washington, D.C, 2005.
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