Elsevier

Journal of Hazardous Materials

Volume 344, 15 February 2018, Pages 1109-1115
Journal of Hazardous Materials

Treatment of textile dyeing industry effluent using hydrodynamic cavitation in combination with advanced oxidation reagents

https://doi.org/10.1016/j.jhazmat.2017.12.005Get rights and content

Highlights

  • Textile dyeing industry effluent was treated using hydrodynamic cavitation based hybrid methods.

  • Optimum operating conditions for all processes were addressed.

  • Use of Fenton’s reagent in combination with HC led to higher reduction in TOC, COD and color.

Abstract

Treatment of textile dyeing industry (TDI) effluent was investigated using hydrodynamic cavitation (HC) and in combination with advanced oxidation reagents such as air, oxygen, ozone and Fenton’s reagent. Slit venturi was used as the cavitating device in HC reactor. The effects of process parameters such as inlet pressure, cavitation number, effluent concentration, ozone and oxygen flow rate, loading of H2O2 and Fenton’s reagent on the extent of reduction of TOC, COD and color were studied. Efficiency of the hybrid treatment processes were evaluated on the basis of their synergetic coefficient. It was observed that almost 17% TOC, 12% COD, and 25% color removal was obtained using HC alone at inlet pressure of 5 bar and pH of 6.8. The rate of reduction of TOC and COD decreased with dilution of the samples. HC in combination with Fenton’s reagent (FeSO4·7H2O:H2O2 as 1:5) was most effective with reduction of 48%TOC and 38% COD in 15 min and 120 min respectively with almost complete decolorization (98%) of the TDI effluent. Whereas HC in combination with oxygen (2 L/min) and ozone (3 g/h) produced reduction of 48% TOC, 33% COD, 62% decolorization and 48% TOC, 23% COD, 88%, decolorization of TDI effluent respectively.

Introduction

In recent years, effluents from the textile processing industry have become a cause of serious environmental concern. The use of synthetic chemical dyes by the textile industries in the various textile processing operations such as dyeing, printing, bleaching and finishing operations has resulted in the release of large amounts of dye-containing industrial wastewater. There are about 2324 textile industries in India [1]. More than ten thousands dyes are being used commercially and approximately 7 × 105 tons of synthetic dyes are produced per annum worldwide [2], [3]. Textile wastewaters are found to have large quantity of suspended particles, varied pH, dark colored, with high chemical oxygen demand (COD) and high total organic carbon (TOC) [4], [5], [6]. The presence of highly suspended solid particles with their strong color provides high turbidity in the textile effluents. Even very low concentration of these dyes (less than 1 ppm for some dyes) induce color in water that is highly observable and undesirable and adversely affects the water bodies such as rivers, lakes etc. [7], [8]. Most of the dyes are toxic and bio-recalcitrant in nature and therefore conventional biological processes are found to be inefficient for treatment of textile effluents [3]. The untreated textile wastewaters due to the presence of carcinogenic compounds are therefore very hazardous and toxic to human beings and animals also. Considering the fact that the aquatic environment is damaged by the wastewaters discharged from textile dyeing industries, it is required to develop an eco-friendly and energy efficient technique to treat the textile effluent before its discharge into the aquatic environment. Several conventional strategies comprised of various combinations of physical, chemical, and biological oxidation processes were developed for treatment of textile effluents in last one decade [6], [9], [10], [11], [12], [13]. However, these processes produce large amount of secondary pollutants which ultimately increase the load on overall treatment facility [5], [13]. In recent years, cavitation as an advanced oxidation process (AOP) has been receiving greater attention for the treatment of wastewater [14], [15], [16]. Cavitation comprises of the nucleation, growth, and subsequent collapse of micro-bubbles or cavities, occurring in a small time interval at multiple locations in the reactor and thus releases large magnitude of energy [17]. The collapse of cavities creates the ‘hot spots’ (a very high temperature and pressure region) resulting in the formation of radical dotOH, radical dotH, HO2radical dot and also H2O2 [18], [19]. In the last two decades, ultrasonication has been studied for wastewater treatment [20], [21], [22], however it has not found any application so far on an industrial scale due to the higher maintenance costs involved and lower energy efficiency [15]. An alternative cavitation technology i.e. HC has been found to be more energy efficient as compared to acoustic cavitation for the degradation of organic pollutants and which can also be operated in a continuous mode [14], [17], [23], [24], [25], [26]. The degradation efficiency of HC can be improved by combining with other advanced oxidation processes/oxidizing agents such as H2O2, Fenton’s reagent, ozone and photocatalytic oxidation [15], [16], [24], [27], [28], [29]. Mishra and Gogate [27] investigated the degradation of Rhodamine B dye using HC in the presence of intensifying additives. They found that almost 59.3% degradation and 30% TOC reduction were achieved using HC alone at an optimized inlet pressure of 4.84 atm and solution pH of 2.5. The degradation efficiency was further increased to 99.9% along with 55% reduction in TOC when HC was combined with hydrogen peroxide (200 mg/L). Gogate and Bhosale [28] studied the combined approach for the degradation of Orange Acid II dye and reported that combination of HC with oxidizing agents such as sodium persulfate, H2O2 and NaOCl was found to be better as compared to use of the individual oxidants. Almost complete degradation of Orange Acid II was obtained in 60 min using HC in combination with sodium persulfate (535.72 mg/L) oxidant.

Although many studies report on the degradation of synthetically prepared dye wastewater using HC coupled with various oxidative additives mostly at low concentration ranges (i.e. 50–100 ppm), however no study has been reported so far for real textile dying industry (TDI) effluent. It is necessary to study the efficacy of HC and its hybrid processes for treating real TDI effluents before applying on an industrial scale. This study focuses on investigating the performance of HC system for treating the TDI effluent. Effects of process parameters (operating inlet pressure and dilution) on the TOC, COD and color reduction were investigated. In order to enhance the efficiency of HC, the effect of advanced oxidative reagents such as oxygen, ozone, and Fenton in combination with HC were also studied.

Section snippets

Textile dyeing industry (TDI) effluent

TDI effluent was taken from the collection tank after dyeing, printing, and finishing processes in a textile dyeing industry (details not given due to confidentiality issues), located at Sanganer industrial zone, Jaipur, India. The characteristic of the TDI effluent is presented in Table 1. Dyes (reactive, direct, and acid dyes), detergents, chlorinated compounds and dissolved salts are the likely pollutants that make up the TOC and COD of the TDI effluent. The TDI effluent was initially

Effect of operating inlet pressure

The inlet pressure and cavitation number are the two major parameters that affect the cavitational conditions inside the cavitating device and influencing the efficiency of HC system [15], [16], [17]. In order to investigate the effect of inlet pressure on the treatment of TDI effluent, experiments were performed by varying inlet pressure from 3 to 10 bar. The obtained results are shown in Fig. 2 and Table 2 presents the cavitation number, velocity, and flow rate through cavitating device. It

Conclusions

The present work reports the effective use of HC in combination with advanced oxidative reagents such as air, oxygen, ozone and Fenton’s reagent to reduce TOC, COD and color of the TDI effluent. The efficiency of HC reactor is affected by process parameters such as inlet pressure and dilution. Maximum reduction in TOC, COD, and color were 17.27%, 12%, and 25% respectively using HC alone at 5 bar operating inlet pressure. The dilution study did not show any significant impact on the actual

Acknowledgement

Dr.Virendra Kumar Saharan would like to thank Department of Science & Technology, New Delhi, India for providing financial support under Inspire Faculty Fellowship (DST/INSPIRE Faculty Award/2013/IFA13-ENG49).

References (38)

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