Simona Vajnhandl

The status of water reuse in European textile sector.

The textile finishing industry is known as a very fragmented and heterogeneous industrial sector dominated mainly by small and medium enterprises (SMEs). As with many other industrial sectors in Europe, it is obliged to act more sustainably in regard to increasingly limited natural resources such as water. This paper presents in-depth survey of wastewater reuse programmes over the last ten years covering the European textile finishing industry. Different wastewater treatment solutions developed are presented and discussed. Special attention is given to the project AquaFit4Use (7th Framework Programme), where almost five years of project work has resulted in valuable know-how practices in water reuse for the most water consuming sectors in Europe i.e. paper, food, chemical and textile. Only the latter is discussed in this paper. The main negative impacts by the textile finishing sector on the environment are still related to intensive water consumption and wastewater discharge, characterised by greater amounts of organic chemicals and colouring agents, low biodegradability, and high salinity. End of pipe treatment of such complex effluents in order to produce reusable water is not feasible. Therefore, separation of waste effluents regarding their pollution level and their separate treatment was the basic approach used in the project. As a result waste effluents with a big reuse potential could be effectively treated by combination of conventional treatment technologies. Proposed water treatment scenarios enable more than 40% reduction in fresh water consumption. Since different guidelines of minimum water quality to be safely reuse in textile processes exist at this stage this issue is discussed as well.

Textile Finishing Industry as an Important Source of Organic Pollutants

The textile finishing industry is, among all industries in Europe, the greatest consumer of high quality fresh water per kg of treated material and with the natures of their production processes significantly contributing to pollution. Wastewater from the textile industry is also a significant environmental pollution source of persistent organic pollutants. Not only textile wastewater but also textile products often contain chemicals such as formaldehyde, azo-dyes, dioxins, pesticides and heavy metals, that might pose a risk to humans and the environment. Some of these chemicals found in finished products are there as residues from the production of dyes and auxiliary chemicals (the synthesis of dyes involves a large variety of chemicals with complex synthesis paths, during which toxic, carcinogenic and persistent organic compounds can be formed, such as dioxins, and traces can be found in commercial dyes), others are added to give certain characteristics to the products (colour, flame retardancy, anti wrinkling properties etc.) (Križanec & Majcen Le Marechal, 2006), or are already present in the raw textile material. The mentioned compounds have been found in wastewater after home washing, in organic solvent after dry-cleaning and also in the atmosphere after incineration. Possible sources of organic pollutants are also wastewater treatment methods and the incineration of textile materials. The formation of dioxins can occur via dyeing and textile finishing processes with conditions favourable for their generation (high temperature, alkaline conditions, ultraviolet (UV) radiation, and other radical initiators). Textile dyes are designed to be resistant to microbial, chemical, thermal and photolytic degradation. After the dyeing process, a lot of non-bonded dyes are released into the wastewater, which can also be treated by Advanced Oxidation Processes (AOPs) in order to destroy the dye molecule and to decolourise the wastewater and reduce organic pollution. It is well-known that under the experimental conditions of such methods, which can be very useful because of the short-time of treatment, hazardous compounds can be formed due to very powerful oxidizing agents such as hydroxyl radicals (OH). In line with the improvement of people’s living standard and the growing awareness and need to preserve the environment several regulations were introduced also in the textile industry in order to control the use of chemicals in textile processes. Under REACH regulation (REACH regulation controlled the quality of fabric, apparels, and shoes

Water in the Textile Industry

The textile industry is very diverse, heterogeneous, and characterized by high consumption of water, fuel, and chemicals. Environmental problems are mainly associated with wastewater. With regard to globalization and scarcity of water, wastewater treatment and recycling possibilities in the textile industry are of the highest importance. In this chapter, raw materials and processes used in textile industry are briefly discussed, with special attention given to characteristics of textile water supply and wastewater produced from different process steps. The general characteristics of textile wastewater and wastewater-treatment technologies are described and reuse possibilities are discussed.

Comparative Study of Reactive Dyes Oxidation by H2O2/UV, H2O2/UV/Fe2+ and H2O2/UV/Fe° Processes

ABSTRACT The decolorization and mineralization of two reactive dyes C.I. Reactive Blue 4 (RB 4) and C.I. Reactive Blue 268 (RB 268) were studied using various advanced oxidation processes (AOPs) such as H2O2/UV, H2O2/UV/Fe2+, and the H2O2/UV/Fe°. All processes were performed within a laboratory-scale photo-reactor setup. The experimental results were assessed in terms of absorbance (A) and total organic carbon (TOC) reduction. The main degradation products were identified by high resolution gas chromatography/high resolution mass spectrometry analyses. The results of our study demonstrated that the additions of moderate concentrations of H2O2 and Fe catalyst during the AOPs evidently increased the decolorization efficiencies within the first few minutes of the processing time (5–10 min) for both tested dyes, and prolonged irradiation does not necessarily significantly improve decolorization. On contrary, TOC removal rate increased with the processing time and with the addition of the catalyst from 40–50% up to 70–80% at defined experimental conditions. All the tested AOPs were very successful methods for RB 268 decolorization, having very complex structure and much higher molecular weight compared to the dye RB 4. This is important from both economic and ecological points of view.

Synergistic chemo‐enzymatic hydrolysis of poly(ethylene terephthalate) from textile waste

Due to the rising global environment protection awareness, recycling strategies that comply with the circular economy principles are needed. Polyesters are among the most used materials in the textile industry; therefore, achieving a complete poly(ethylene terephthalate) (PET) hydrolysis in an environmentally friendly way is a current challenge. In this work, a chemo‐enzymatic treatment was developed to recover the PET building blocks, namely terephthalic acid (TA) and ethylene glycol. To monitor the monomer and oligomer content in solid samples, a Fourier‐transformed Raman method was successfully developed. A shift of the free carboxylic groups (1632 cm−1) of TA into the deprotonated state (1604 and 1398 cm−1) was observed and bands at 1728 and 1398 cm−1 were used to assess purity of TA after the chemo‐enzymatic PET hydrolysis. The chemical treatment, performed under neutral conditions (T = 250 °C, P = 40 bar), led to conversion of PET into 85% TA and small oligomers. The latter were hydrolysed in a second step using the Humicola insolens cutinase (HiC) yielding 97% pure TA, therefore comparable with the commercial synthesis‐grade TA (98%).

Feasibility study of ultrasound as water disinfection technology

AbstractThis article presents a section of project work related to the use of ultrasound technology as an eco-friendly water disinfection process. Scientific and economical evaluations are presented for two different ultrasound systems. The effects of ultrasound frequencies (20, 279 and 817 kHz), amplitude (acoustic power) and the treatment time for bacteria survival were studied. Experiments performed on a laboratory scale using two biological indicator micro-organisms Bacillus subtilis and Escherichia coli indicated that disinfection efficiency is affected by bacteria morphology, ultrasound frequencies and energy densities entering the system. As the spore-forming bacteria B. subtilis seemed less vulnerable to ultrasound exposure, a significant E. coli inhibition of 2.97 ± 0.58 log was achieved in 5 min treatment time at 817 kHz.

Alternative cleaning of compost leachate using biopolymer chitosan

Compost leachate poses a threat to the environment because it contains many organic and inorganic pollutants. Chemical Oxygen Demand (COD) has been reported at values above 5000 mg/l O2. Heavy metals, such as nickel, lead, chromium are also present within these waters. Thus, in order to comply with the increasingly stringent environmental quality standards such contaminants must be removed effectively. The research approach in this paper is directed towards chelating pre-treatment procedures. Nontoxic and biodegradable biopolymer chitosan was used as a chelator for the removal of dissolved metals from compost leachate. The influence of chemical conditions regarding the chelation efficiency was studied in model solutions. The optimal treatment conditions were applied onto compost leachate which was analysed further regarding metals. In addition, the influence of chitosan was studied on compost leachate toxicity. The most important aspect of this paper is to demonstrate the potential of waste chitosan recycling. Thus, the chitosan chelates were subjected to the electrospinning procedure in order to develop new nano-porous structures, such as, for example, conductive textiles.

Effects of Ultrasound Irradiation on the Preparation of Ethyl Cellulose Nanocapsules Containing Spirooxazine Dye

This article presents the influence of low frequency, high intensity ultrasonic irradiation on the characteristics (average size, polydispersity index) of ethyl cellulose nanocapsules encapsulating a photochromic dye. Photochromic nanocapsules were prepared by the emulsion-solvent evaporation method. The acoustic densities entering the system were systematically studied with respect to their abilities to modify and reduce the average sizes and polydispersity indexes of the nanocapsules. Scanning electron microscope, confocal laser microscope, and dynamic light scattering were utilised to characterise the structure, shape, size, and polydispersity of ethyl cellulose photochromic nanocapsules. We were able to tailor the size of the photochromic nanocapsules simply by varying the acoustic densities entering the system. At an acoustic density of 1.5 W/mL and 60 s of continuous irradiation, we were able to prepare an almost monodispersed population of the nanocapsules with an average size of 193 nm.