Decolorisation of textile effluent using homogeneous photochemical oxidation processes

In this paper, the results of COD and colour removal from textile effluent using homogeneous photochemical oxidation processes in a batch mode are presented. The results show that the best result was obtained using a combined O₃/H₂O₂/UV process, with 97% removal for COD and 99% removal for colour. Optimum conditions for pH and hydrogen peroxide dosage for this process was determined as 3 and 25 mg/l, respectively. Both H₂O₂/UV and O₃/UV combinations were found to result in similar levels of COD and colour removal efficiencies (over 91% removal for COD and 96% for colour). In addition, the associated operating costs of the various advanced oxidation processes were determined in this study. Received: 21 February 2005; Accepted: 14 June 2005.     

Electrochemical treatment of reactive dye effluent using solar energy

The electrochemical degradation of a commonly used textile dye, Reactive Green HE4BD, employing solar energy has been investigated. The influence of parameters such as electrolyte concentration, current density, pH and initial dye concentration were studied. Under optimal conditions, 99% decoloration and a significant reduction in chemical oxygen demand were observed after 5 h treatment. Evaluation of the process showed that degradation of the dye followed pseudo first-order kinetics.     

Colour and COD removal from textile effluent by coagulation and advanced oxidation processes

The aim of this study was to compare the performance of coagulation, Fenton's oxidation (Fe²⁺/H₂O₂) and ozonation for the removal of chemical oxygen demand (COD) and colour from biologically pretreated textile wastewater. FeSO₄ and FeCl₃ were used as coagulants at varying doses and varying colour removal efficiency was measured. For the Fenton process, COD and colour removal efficiencies were found to be 78% and 95% for the Fenton process, and to be 64% and 71% for the Fenton-like process (Fe³⁺/H₂O₂), respectively. Ozonation experiments were conducted at different initial pH values and fixed ozone doses. Ozonation resulted in 43% COD and 97% colour removal whereas these rates increased to 54% and 99% when 5 mg/l hydrogen peroxide was added to the wastewater before ozonation at the same dose. The operating costs of all proposed treatment systems were also evaluated in this study.     

Electrochemical oxidation of textile dye indigo

Electrochemical methods are being used increasingly as an alternative treatment process for the remediation of textile wastewaters. This study focused mainly on the colour removal and chemical oxygen demand (COD) reduction of vat textile dye (CI Vat Blue 1: indigo) from its aqueous solution by electrochemical oxidation. The process was carried out in a batch‐type divided electrolytic cell under constant potential using a Pt cage as anode and Pt foil as cathode. Operating variables such as supporting electrolyte, pH, ultrasonification and treatment time were investigated to probe their effects on the efficiency of the electrochemical treatment. Colour removal was estimated by monitoring the disappearance of the absorbance peak at 681.5 nm. It was found that in acidic conditions the electrolysis was more efficient. At pH 1, an NaCl concentration of 0.24 mol dm^?3, a dyeing solution concentration of 0.1% (w/v) and a period of 90 min of electrolysis, there was almost 100% colour removal and 60% reduction in COD. Voltammetric and IR investigations demonstrated that partial degradation of dye was achieved. The experimental results indicate that this electrochemical method could effectively be used as a pretreatment stage before conventional treatment. Copyright © 2005 Society of Chemical Industry     

Comparison of granular activated carbon bio-sorption and advanced oxidation processes in the treatment of leachate effluent

Landfill leachate is a toxic effluent of a decomposing landfill that is produced when rainwater percolates through the landfill leaching out contaminants and pollutants. Untreated leachate is a potential source for the contamination of soil, surface and ground water. In this study, the treatment processes such as granular activated carbon (GAC) adsorption/bio-sorption (batch), and advanced oxidation processes (AOP) viz. photocatalysis and Fenton’s process were evaluated and compared by using synthetic landfill leachate (SLL) as a contaminant. TiO₂ was used as a catalyst in photocatalysis, and Fenton’s reagent (H₂O₂/Fe⁺²) was used in Fenton’s process. The degradation of SLL effluent by the three above-mentioned processes was characterized by the % TOC removal. The % TOC removed by photocatalysis, Fenton oxidation and bio-sorption (which includes adsorption and biodegradation) was 30, 60 and 85%, respectively. The bio-sorption increased with the increasing GAC dose. The optimum dose of Fenton’s reagent in advanced oxidation was 15 and 400 milli moles of Fe⁺² and H₂O₂, respectively. The Fenton’s process showed faster degradation kinetics compared to biodegradation and photocatalysis.     

高级氧化技术处理染料废水的研究进展

由于染料废水中含有高浓度难降解有机污染物,对其有效处理一直是个难题.综述了近几年国内外采用湿式氧化法、Fenton法、光化学与光催化氧化法、电化学法、臭氧氧化法、微波辅助氧化法和超声氧化法等高级氧化技术处理染料废水的进展情况,并指出了高级氧化技术在染料废水处理中的发展趋势.     

高级氧化处理有机污水技术进展

综述了高级氧化技术的原理，介绍了O3／UV、H2O2／UV、O3／H2O2组合过程及非均相TiO2光催化氧化等几种典型的高级氧化技术，阐述了高级氧化技术降解有机污水的机理以及在水处理中的应用进展。指出，高级氧化过程应用领域应扩展到水体中难降解的持久性有机污染物，并应加强高级氧化过程所需新型反应器的研制，以便进一步强化废水的5降解，提高其处理效率。     

AO和OAO工艺对焦化废水处理效果的比较

采用AO和OAO工艺处理焦化废水并进行对比试验。结果表明,OAO工艺对COD、氨氮的去除率分别为85.55%和93.82%;AO工艺对COD、氨氮的去除率分别为78.57%和91.19%,OAO工艺优于AO工艺,但AO工艺的反硝化效果较好。对于高浓度焦化废水,宜采用OAO工艺,普通的焦化废水则宜采用AO工艺。     

Effects of sewage treatment on textile effluent

Textile effluent is discharged to sewer with little or no destructive treatment. In investigating the effects of sewage treatment on textile effluent we aim to establish the biodegradability of the effluent and the reduction in toxicity exerted on aquatic organisms resulting from standard sewage treatment. Using three separate samples of effluent, the initial toxicity was tested using the aquatic invertebrate Daphnia magna. The samples were biodegraded following the Zahn-Wellens method and then retested. Results showed relatively good biodegradability but negligible toxicity reduction. The ‘hard COD’, or non-degradable, portion of the effluent, which appears to be responsible for exerting toxicity, is not altered by this treatment method.     

Sonophotocatalytic treatment of methyl orange dye and real textile effluent using synthesised nano‐zinc oxide

In this work, experiments were carried out by combining the sonication technique with the photocatalytic technique (ultraviolet light source) for the degradation of methyl orange dye and real textile effluent. Studies were performed with variation in parameters such as oxidant (sodium persulfate), commercially available zinc oxide, methyl orange concentration, and sonochemically synthesised zinc oxide. Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and X‐ray diffraction analysis of synthesised zinc oxide showed that the particle size was in the nano range. Near‐complete colour removal by sonophotocatalytic treatment was observed for a concentration of 10 mg l^?1 of methyl orange with 1 g l^?1 of synthesised zinc oxide and 1500 mg l^?1 of sodium persulfate. For 100 mg l^?1 of methyl orange, the colour removal was 77% for 1 g l^?1 commercially available zinc oxide and 84% for 1 g l^?1 synthesised zinc oxide respectively, with 1500 mg l^?1 sodium persulfate. Similar experimental conditions were applied for the sonophotocatalytic treatment of real textile effluent with different dilutions (1:100, 1:10, and 1:1) and raw effluent. For real textile effluent, sonophotocatalytic treatment was found to be highly effective both in colour and chemical oxygen demand removal. The chemical oxygen demand removal was 88, 65, 63, and 41% for 1:100, 1:10, and 1:1 dilutions and raw effluent respectively.     

Biological treatment of effluent containing textile dyes

Colour removal of textile dyes from effluent was evaluated using a laboratory 'upflow anaerobic sludge blanket' reactor. Several commercial dyes were selected to study the effect of dye structure on colour removal. The anaerobic reactor was fed with glucose, an easily biodegradable organic matter and selected individual dyes. Results show that some of the dyes are readily reduced under anaerobic conditions even at a high concentration of 700 mg/l. The average removal efficiency for acid dyes using this method was between 80 and 90% and that observed for the direct dye used was 81%. Laboratory experiments using the anaerobic reactor with disperse dyes, such as an anthraquinonebased dye, were unsuccessful even at low concentrations of 35 mg/l. Additional experiments were conducted to evaluate the toxicity of a selected disperse dye to an anaerobic environment. Results indicate that the purified dye is more toxic to the biomass than the commercial one.     

Decolourization of the reconstituted dye bath effluent by commercial laccase treatment: Optimization through response surface methodology

This paper aims to study the effect of temperature, pH and enzyme concentration on decolourization of separately two reactive textile dyes (Black Novacron R and Blue Bezaktiv S-GLD 150) used in reconstituted dye bath effluent (textile dye and auxiliary components) and in aqueous dye solutions (dye dissolved in deionised water) by a commercial laccase formulation (DeniLite^® IIS). The central composite design (CCD) matrix and response surface methodology (RSM) have been applied to design experiments for the evaluation of the interactive effects of the three most important operating variables: temperature ‘T’ (25–45 °C), pH (3.0–7.0), and enzyme concentration ‘EC’ (80–240 U/L) on the enzymatic decolourization of the different synthetic dyes solutions at initial dye concentration of 40 mg/L. The RSM indicated that the optimum parameter values were respectively for the reconstituted Black Novacron R and the Blue Bezaktiv S-GLD 150 effluents: T = 43 °C and 41.44 °C, pH 6 and 6.29, EC = 222 and 226.43 U/L. The maximum colour removal was about 98.9% at 593 nm and 79.9% at 400 nm for reconstituted Black Novacron R effluent and about 98.9% at 620 nm for reconstituted Blue Bezaktiv S-GLD 150 effluent. For aqueous dye solutions, RSM has shown that colour removal obtained were quite similar. However, the optimum parameters were different. Hence, enzyme concentration depends on the effluent component.     

Studies on usage of acrylamide copolymers for textile effluent treatment

The copolymers of acrylamide–maleic anhydride and acrylamide–diallyl dimethyl ammonium chloride of different ionicities were used for the removal of color, solids, etc., from effluent generated from textile industry. The studies have been carried out to remove color generated in the effluent. To estimate dye content, we prepared standard curve using UV‐vis spectrophotometer at different dye concentration following the Beer Lambert's Law. The copolymers of acrylamide–maleic anhydride and acrylamide–diallyl dimethyl ammonium chloride of known concentration were dosed in the known concentration of the dye. These polymers made flocks by adsorption with dyes and these colored flocks were filtered out. The intensity of the color of water went down on increasing the concentration of the polymers. The color of the textile effluent was removed to the extent of 97% using above mentioned polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Anaerobic and aerobic treatment of a simulated textile effluent

A simulated textile effluent (STE) was generated for use in laboratory biotreatment studies; this effluent contained one reactive azo dye, PROCION Red H‐E7B (1.5 g dm⁻³); sizing agent, Tissalys 150 (1.9 g dm⁻³); sodium chloride (1.5 g dm⁻³) and acetic acid (0.53 g dm⁻³) together with nutrients and trace elements, giving a mean COD of 3480 mg dm⁻³. An inclined tubular anaerobic digester (ITD) was operated for 9 months on the STE and a UASB reactor for 3 months. For a 57 day period anaerobic effluent from two reactors, a UASB and an ITD, was mixed and treated in an aerobic stage. In days 77–247 68% of the true colour of PROCION Red H‐E7B was removed by anaerobic treatment with no colour removal aerobically and up to 37% COD was removed anaerobically, with a corresponding BOD removal of 71%. For combined anaerobic and aerobic treatment a mean COD removal of 57% and BOD removal of 86% was achieved. Operation of the ITD at a 2.8 day HRT (volumetric loading rate (B _v) 1.24 g COD dm⁻³day⁻¹) and the UASB at a 2 day HRT (B _v 1.74 g COD dm⁻³day⁻¹) gave comparable COD removals but the UASB gave better true colour removal. Effluent from the combined process operating on this simulated waste still contained an average 1500 mg COD dm⁻³, and further treatment would be required to meet consent standards. © 1999 Society of Chemical Industry     

Technical efficiency and cost analysis in wastewater treatment processes: A DEA approach

In light of the growing importance of water reuse as an alternative source of water resources in many regional areas, the objective of this paper is to analyse the efficiency of wastewater treatment plants as a basic requisite to improve the potential of the water reuse. The analytical benchmarking methodology Data Envelopment Analysis (DEA) is used to calculate efficiency measurements. An efficiency index is obtained for each plant by means of mathematical programming techniques, aiming to minimise the inputs used in the water treatment process. This indicator is used as a reference to analyse plants' activity through a series of variables including the size of the plant or its cost structure. Given the importance of wastewater treatment in the Valencia Region (Spain), empirical research has been carried out for 338 plants located in this area. We verify the fact that the largest plants run more efficiently than smaller plants, as was to be expected. At the same time, there is evidence that a series of representative variables in the treatment process are clearly linked to efficiency. Maintenance and waste management costs are the most important factors to explain the differences between plants in terms of efficiency. Finally, the benchmarking methodology (Data Envelopment Analysis) is confirmed as a very useful management tool for the study of wastewater sector.     

Optimization of continuous electrocoagulation-adsorption combined process for the treatment of a textile effluent

The aims of this study is to design and optimize the functioning of a full continuous combined process based on electrocoagulaion-adsorption on crude Tunisian clay to treat a real textile effluent. The clay characterization shows that the used clay is a rich-smectite clay. The response surface methodology (RSM) technique based on Box-Behnken design (BBD) was used to optimize the process. At optimum conditions which are initial pH solution of 8.24, effluent flow rate of 0.5 L·min^-1, voltage of 70 V, and added suspension of clay flow rate of 100 ml·min^-1 the achieved color, chemical oxygen demand (COD) and total suspended solid (TSS) removal efficiencies were respectively 96.87%, 89.77% and 84.46% with 0.75USD·m^-3 as total cost. The additional laboratory experiments at optimum conditions agree with the predicted results, which confirm the accuracy and the capability of RSM to predict results in the defined space. Finally the designed process could be a good eco-friendly alternative to treat and reuse wastewater in industrial process with reasonable cost.     

Adsorption equilibrium studies of a simulated textile effluent containing a wool reactive dye on gallinaceous feathers

Gallinaceous feathers (from Gallus gallus domesticus, strains Cobb 500 and Label) were used as adsorbent for colour removal from a simulated textile effluent containing a wool reactive dye, the Yellow Lanasol 4G (CI Reactive Yellow 39). A brief chemical and physical characterisation of feathers was performed. Equilibrium studies at different selected temperatures, in the range 10–60 °C, were carried out. The equilibrium data were analysed using the Freundlich and Langmuir isotherm models. Adsorption capacity strongly increases with temperature. A maximum adsorption capacity of around 300 mg g^?1 was obtained for Gallus gallus feathers, strain Cobb 500, at 60 °C, while for strain Label, 200 mg g^?1 was obtained at 50 °C. For each type of feather a generalised model, valid for a given temperature range, was obtained. The isosteric heat of adsorption calculated was positive, so the mechanism involved in the adsorption process should correspond to endothermic chemisorption. This study provides important information concerning the use of gallinaceous feathers without any chemical treatment for colour removal from real textile wastewaters. The results in this study indicated that gallinaceous feathers, when compared with activated carbon, open promising perspectives concerning their utilisation for colour removal from textile effluent discharged at high temperatures; moreover, it would be an alternative for the valorisation of this waste.     

Cost analysis for the degradation of highly concentrated textile dye wastewater with chemical oxidation H2O2/UV and biological treatment

The efficiency and cost‐effectiveness of H₂O₂/UV for the complete decolorization and mineralization of wastewater containing high concentrations of the textile dye Reactive Black 5 was examined. Oxidation until decolorization removed 200–300 mg g^?1 of the dissolved organic carbon (DOC). The specific energy consumption was dependent on the initial dye concentration: the higher concentration required a lower specific energy input on a weight basis (160 W h g^?1 RB5 for 2.1 g L^?1 versus 354 W h g^?1 RB5 for 0.5 g L^?1). Biodegradable compounds were formed, so that DOC removal could be increased by 30% in a following biological stage. However, in order to attain 800 mg g^?1 overall mineralization, 500 mg g^?1 of the DOC had to be oxidized in the H₂O₂/UV stage. A cost analysis showed that although the capital costs are much less for a H₂O₂/UV stage compared to ozonation, the operating costs are almost double those of ozonation. Thus, while H₂O₂/UV can compete with ozonation when the treatment goal only requires decolorization, ozonation is more cost‐effective in this case when mineralization is desired. Copyright © 2006 Society of Chemical Industry     

Development of a bioprocess combined with membrane technology for the treatment and recycling of textile effluent

A mixed culture of dye-decolorising Pseudomonas spp. was immobilised on polyurethane foam, and used in a bench-scale continuous culture bioreactor to treat textile effluent for colour removal. The provision of soluble wheat starch (0.2% w/v) to the culture medium promoted growth of biomass and enhanced decolorisation of effluent in the bioreactor. The bioprocess was further combined with membrane filtration technology to improve the quality of treated effluent. The treated effluent showed 90, 82 and 60% reduction in COD, BOD₅ and toxicity levels, respectively, and had potential for re-use in dyeing processes. The colour difference of the cotton fabrics dyed using the treated effluent samples compared to those dyed using normal supply water was found to be industrially acceptable. The described process could improve treatment efficiency and allow water recycling within the textile factory.