Textile Wastewater

Following new trends we applied oxygen uptake rate (OUR) tests as well as long-term tests (in two batch bioreactors systems) in order to assess the biodegradability of textile wastewater. Effluents coming from a dyeing factory were divided into two streams which differed in inorganic and organic contaminants loads. Usefulness of the stream division was proved. Biodegradation of the low-loaded stream led to over 97% reduction of biochemical oxygen demand (BOD 5) together with 80% reduction of chemical oxygen demand (COD) and total organic carbon (TOC). Most of the controlled parameter values were below the levels allowed by legislation for influents to surface water, whereas the high-loaded stream was so contaminated with recalcitrant organic compounds that despite the reduction of BOD 5 by over 95%, COD, TOC, total nitrogen and total phosphorus levels exceeded permissible values. OUR tests were aimed at determination of the following kinetic parameters: maximum specific growth rate (μ Max), half-saturation constant, hydrolysis constant and decay coefficient for activated sludge biomass for both types of textile wastewater studied. The values of kinetic parameters will be applied in activated sludge models used for prediction and optimisation of biological treatment of textile wastewater.

Bioflocculation of bacteria isolated from the marine biomass acclimatized to textile wastewater has been achieved. Pseudomonas was the main genus found in the marine biomass. This bacterium showed an important hydrophobicity but slightly weaker than that of pilot plant genera adapted to the conventional sewage. This hydrophobicity provided the bacteria with hydrophobic characters, especially those of the polymeric extracellular substances (ECS) released in the sewage. Whereas some factors such as the divalent cations, calcium and magnesium had an effect on this bacterial hydrophobicity, glucose concentration did not have any impact. Furthermore, the physiological state of the cells hatched in the sewage had an impact on the hydrophobicity. Indeed, during the logarithmic growth phase, cell hydrophobicity increase enhanced floc formation, thus improving wastewater treatment.

The scale-up of a 10 L air pulsed bioreactor for the continuous treatment of textile wastewater by pellets of the white rot fungus Trametes versicolor has been carried out, based on the geometric similitude with lab-scale bioreactors (0.5 and 1.5 L). Decolourisation experiments of 150 mg L À1 Grey Lanaset G dye solution carried out in the pilot-scale bioreactor showed that in both discontinuous and continuous treatment with an HRT of 48 h, the decolourisation levels were higher than 90%. Some operational changes were carried out in the continuous decolourisation treatment of the dye solution in order to adapt the process to industrial conditions such as, non-sterilization of the dye solution, use of tap water instead of distilled water plus macronutrients and micronutrients and the use of industrial quality co-substrate instead of reagent grade. The pilot system was working continuously during 3 months and over 70 days without sterilization of the dye feeding solution, achieving good decolourisation levels (78% average during the treatment). Continuous treatment of real industrial textile wastewater under non-sterile conditions was carried out during 15 days in the pilot-scale bioreactor, with colour reduction levels between 40 and 60%. These dye concentrations are regarded as environmentally acceptable to be discharged into a municipal wastewater treatment plant if necessary according to the local regulation.

Textile wastewater (TW) is one of the most hazardous wastewater for the environment when discharged without proper treatment. Biological treatment technologies have shown encouraging results over the treatment of recalcitrant compounds containing wastewaters. Upflow anaerobic sludge blanket reactor (UASB) was evaluated in terms of colour and the reduction of chemical oxygen demand (COD) with different organic loads using TW containing dyes belonging to different chemical groups. The study was performed using six different dye concentrations (10 mg/L, 25 mg/L, 50 mg/L, 100 mg/L, 150 mg/L, 300 mg/L) with three COD levels (∼1000 mg/L, ∼2000 mg/L, ∼3000 mg/L). Decolourization, COD removal and reactor stability were monitored. Over 85% of colour removal was observed with all dye concentrations with three organic loads. Acid Red 131 and Acid Yellow 79 were decolourized through biodegradation while Acid Blue 204 was decolourized due to adsorption onto anaerobic granules. COD removal was high in all dye concentrations, regardless of co-substrate levels. The reactor did not show any instability during the study. The activity of granules was not affected by the dyes. Methanothrix like bacteria were the dominant group in granules before introducing TW, however, they were reduced and cocci-shape microorganism increased after the treatment of textile wastewater.

Batch and continuous reactors inoculated with white-rot fungi were operated in order to study decolorization of textile dyes. Synthetic wastewater containing either Reactive Blue 4 (a blue anthraquinone dye) or Reactive Red 2 (a red azo dye) was used during the first part of the study while real wastewater from a textile industry in Tanzania was used in the later part. Trametes versicolor was shown to decolorize both Reactive Blue 4 and Reactive Red 2 if glucose was added as a carbon source. Reactive Blue 4 was also decolorized when the fungus was allowed to grow on birch wood discs in a continuous biological rotating contactor reactor. The absorbance at 595 nm, the wavelength at which the dye absorbs at a maximum, decreased by 70% during treatment. The initial dye concentration in the medium was 200 mg/l and the hydraulic retention time in the reactor 3 days. No glucose was added in this experiment. Changes of the absorbance in the UV range indicated that the aromatic structures of the dyes were altered. Real textile wastewater was decolorized by Pleurotus flabellatus growing on luffa sponge packed in a continuous reactor. The reactor was operated at a hydraulic retention time of 25 h.

To develop the waste water solutions challenging task. To design sustainable wastewater solution requires information about new ideas, new systems and latest technology. Generally it is assumed that, decision making needs to involve field experts and engineers to define values and brainstorms solution. This paper describes a decision support system model that is designed to help community planners to identify the solution which balance the environmental, economic and social needs. System will be scalable, adaptable and flexible. Our decision support system will take modular description of components and description of community constraints, suggest the design of alternative waste water system, and facilitates evaluating how well each design satisfies the given constraints. Decision support system will give alternatives with visualization of the effect of various trade-offs and their effect in the relation of the community's goals. I. INTRODUCTION It is notable that, after industrial revolution, population growth and urbanization there is intense need of wastewater management system. As a research, the past few years have been seen significant growth in innovation based on the idea of waste as resource rather than a non-usable material, with a focus on water energy and nutrients. The challenge of providing good management of domestic and industrial sewage is becoming very urgent as the majority of sewage infrastructure in the industrialized area will require changes and replacement in the near future and more than half of the people living in the large cities in the developing world lack access to proper sanitation services. Growing cost in combination with environmental concerns and the challenges involved in securing the quality and quantity of water heighten the urgency of the issue It has been repeatedly observed that successful implementation of scalable management solutions is strongly tied with environmental ,social, economic and political issues at different level and thus requires active engagement of verity of experts in addition to wastewater engineers identifying the most stable solution involves finding solution that minimize negative effects, while maximizing benefits for local and global environments.

The feasibility of employing different photoxidation systems, like Fenton/UV-C and ferrioxalate/H 2 O 2 /solar light in the decolorization and mineralization of an azo dye, has been investigated. Batch experiments were carried out to evaluate, on the first stage, the influence of different processes on Reactive Black 5 (RB5) decolorization. During the second stage were investigated the optimal operational conditions of Fenton/UV-C and ferrioxalate/H 2 O 2 /solar light processes, like pH, H 2 O 2 dosage, iron dosage, RB5 concentration and source of light. The experiments indicate that RB5 can be effectively decolorized using Fenton/UV-C and ferrioxalate/H 2 O 2 /solar light processes with a small difference between the two processes, 98.1% and 93.2%, respectively, after 30 min. Although there is lesser difference in dye decolorization, significant increment in TOC removal was found with Fenton/UV-C process (46.4% TOC removal) relative to ferrioxalate/H 2 O 2 /solar light process (29.6% TOC removal). This fact reveals that UV-C low-pressure mercury lamp although with its small effect on dye decolorization is particularly important in dye mineralization, when compared to solar light. However, ferrioxalate/H 2 O 2 /solar light system shows large potential on photochemical treatment of textile wastewater with particular interest from the economical point of view.

The simultaneous use of Fenton reagent and irradiation for the treatment of textile wastewaters generated during a hydrogen peroxide bleaching process is investigated. The experimental conditions tested during this study provide the simultaneous occurrence of Fenton, Fenton-like and photo-Fenton reactions. The batch experimental results are assessed in terms of total organic carbon reduction. Identification of some of the chemical constituents of the effluent was performed by means of GC-MS. Other pollution related features of the initial effluent-like COD and color were also measured. The main parameters that govern the complex reactive system, i.e., light intensity, temperature, pH, Fe(II) and H2O2 initial concentrations have been studied. Concentrations of Fe(II) between 0 and 400 ppm, and H2O2 between 0 and 10,000 ppm were used. Temperatures above 25 degrees C and up to 70 degrees C show a beneficial effect on organic load reduction. A set of experiments was conducted under diff...

The wastewaters released by textile industries to the environment contain hazardous compounds like toxic refractory dye stuff at high concentration. In this study, electron beam irradiation-induced decoloration and decomposition of C.I. Direct Black 22 aqueous solutions were investigated. The influences of absorbed doses and initial dye concentration on the percent of decoloration, COD and pH of the solutions are described. The results show that the direct dye solutions can be effectively degraded by electron beam irradiation.

— Due to the reduction of groundwater resources, the artificial recharge of these resources through the reuse of treated wastewater (modified water) is an efficient way to tackle the problem. Some of the most important goals to be achieved regarding such a situation are the development of underground resources, building barriers to help avoid the penetration of the saline water to the underground water table in the coastal areas, creating additional levels of water treatment by soil and controlling the soil settlement. The modified water helps to compensate for the underground water. Asthe additional stage of the purification of the modified water offers assurance on the sewage management system, this natural water treatment created underground eliminates the need for costly wastewater treatment processes. Moreover, the groundwater aquifers provide a natural mechanism for the subsurface transfer of the modified water and eliminate the need for the surface storage facilities and associated problems, such as evaporatio n and the growth of algae, which degrade the water quality. One of the most commonly used methods is the aquifer storage and recovery (ASR) technology, which helps overcome the seasonal imbalance associated with the retrieval systems in the world. In the present paper, the methods used to realize this solution, including among others flood spreading, the soil aquifer treatment (SAT) systems, injection in unsaturated areas, and direct injection are examined. Furthermore, the advantages and disadvantages of using the modified water and the required hydraulic analyzes for designing direct injection wells and injection in unsaturated areas will also be investigated.

The electrocoagulation (EC) process was developed to overcome the drawbacks of conventional wastewater treatment technologies. This process is very effective in removing organic pollutants including dyestuff wastewater and allows for the reduction of sludge generation. The purposes of this study were to investigate the effects of the operating parameters, such as pH, initial concentration (C 0 ), duration of treatment (t), current density (j), interelectrode distance (d) and conductivity (Ä) on a synthetic wastewater in the batch electrocoagulation-electroflotation (EF) process. The optimal operating conditions were determined and applied to a textile wastewater and separation of some heavy metals. Initially a batch-type EC-EF reactor was operated at various current densities (11.55, 18.6, 35.94, 56.64, 74.07 and 91.5 mA/cm 2 ) and various interelectrode distance (1, 2 and 3 cm). For solutions with 300 mg/L of silica gel, high turbidity removal (89.54%) was obtained without any coagulants when the current density was 11.55 mA/cm 2 , initial pH was 7.6, conductivity was 2.1 mS/cm, duration of treatment was 10 min and interelectrode distance was 1 cm. The application of the optimal operating parameters on a textile wastewater showed a high removal efficiency for various items: suspended solid (SS) 86.5%, turbidity 81.56%, biological oxygen demand (BOD 5 ) 83%, chemical oxygen demand (COD) 68%, and color over 92.5%. During the EC process under these conditions, we have studied the separation of some heavy metal ions such as iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), lead (Pb) and cadmium (Cd) with different initial concentrations in the range of 50-600 mg/L and initial pH between 7.5 and 7.8. This allowed us to show that the kinetics of electrocoagulation-electroflotation is very quick (<15 min), and the removal rate reaches 95%.

Heterogeneous photocatalytic treatment of two different synthetic dyehouse effluents called RI and RII, that were simulating textile wastewater from an integrated plant and a dyehouse mill and containing various reactive dyestuffs and associated auxiliary chemicals, was investigated by using different TiO 2 types and reaction conditions. The effect of initial pH and effluent dilution ratio on treatment efficiency was examined and photocatalytic activities of novel TiO 2 materials were compared in terms of ultraviolet-visible absorption kinetics, TOC removal, and Adsorbable Organic Halogens (AOX) formation, respectively. For comparative purposes, % photonic efficiencies ζ (%) based on the photocatalytic mineralization rates were calculated for the investigated reaction conditions. The sensitivity of the treatment efficiency to reaction pH was rather pH-independent in the pH range 4-9 for both recipe mixtures and reaction rates were drastically inhibited at higher pH specially for RII effluent due to its high carbonate content. Increasing the strength of the dyehouse effluents had negative influence upon the photocatalytic reaction rates. It was also established that for RI, TOC kinetics could be fitted very well to the empirical Langmuir-Hinshelwood kinetic model (K TOC =29 l mg −1 ; k TOC =0.246 mg (min l) −1) for the Degussa P25-mediated photocatalytic treatment, whereas this model could not be applied to RII. The highest photonic efficiency was obtained with Sachtleben Mikroanatas IF9308/18 TiO 2 powder for recipe mixture RI at pH=10.5 and for RII at pH=4 being 4.9 and 4.6%, respectively. Best obtained overall TOC removals were around 30% for RI at pH=7.0 (P25) and 37% for RII at pH=4.0 (Millenium PC 500 TiO 2 powder) after 1 h treatment. No clear correlation existed between adsorptive properties of the investigated TiO 2 semiconductors and their corresponding reaction rates. Considerable amounts of AOX was formed particularly at pH=4 after the photocatalytic oxidation as a consequence of the high chloride content in the synthetic wastewater.

Membrane bioreactor (MBR) is a reliable and promising technology for wastewater treatment and reclamation applications. In spite of more than a decade of significant advances in developing fouling mitigation methods, different physical and cleaning protocols are still necessary to be developed to limit the membrane fouling. The use of scouring agents in MBR applications has been paid attention as a new approach as an energy-efficient way to control membrane fouling. Recently, mechanical cleaning by scouring agents is becoming as intense research area considering high efficiency of fouling reduction while requiring low energy consumption. In this review, fundamental and comprehensive assessments of the mechanical cleaning concepts and their applications with porous and nonporous scouring agents for MBR system are critically reviewed. The existing challenges and future research prospects on the mechanical cleaning technology associated with scouring agents for the MBR applications are also discussed.

: 991-998 991 Anatomical studies on water hyacinth (Eichhornia crassipes (Mart.) Solms) under the influence of textile wastewater * MAHMOOD Qaisar †1,2 , ZHENG Ping (郑 平) † ‡1 Abstract: Water hyacinth (Eichhornia crassipes (Mart.) Solms) is a prolific free floating aquatic macrohpyte found in tropical and subtropical parts of the earth. The effects of pollutants from textile wastewater on the anatomy of the plant were studied. Water hyacinth exhibits hydrophytic adaptations which include reduced epidermis cells lacking cuticle in most cases, presence of large air spaces (7~50 µm), reduced vascular tissue and absorbing structures. Textile waste significantly affected the size of root cells. The presence of raphide crystals was noted in parenchyma cells of various organs in treated plants.

Electrocoagulation (EC) due to some advantages over chemical coagulation is becoming a popular process to be used for wastewater treatment. The aim of this paper is to investigate the effect of initial addition of a chemical coagulant such as polyaluminum chloride (PAC) or alum on the COD removal efficiency of EC treatment of textile wastewaters. The two salts exhibited the same performance in chemical coagulation, but in the combined electrocoagulation (CEC), PAC was found to significantly enhance the COD removal rate and efficiency, depending on the amount of the total aluminum supplied, by initial addition and electrochemical generation. A comparative operating cost analysis was also given and it was found that with the same operating cost per mass of COD removed, CEC performance was 80%, in contrast to 23% with EC, in 5 min of operation.

In recent decades ultrasound has established an important place in different industrial processes such as the medical field, and has started to revolutionize environmental protection. The idea of using ultrasound in textile wet processes is not a new one. On the contrary there are many reports from the 1950s and 1960s describing the beneficial effects of ultrasound in textile wet processes.

In this study, the wastewater originating from textile industry and its treatment methods together with alternative treatment processes were examined and a general evaluation was performed by compiling previous studies in the literature. Because of increasing population and industrial developments, a huge amount of wastewater is discharged to the environment above the level that the nature can eliminate. One of the most important industrial activities in Turkey with its magnitude of economy and provided employment is the textile industry and wastewater including contaminants (COD, azo dyes, BOD, TSS) in different concentrations is discharged as a result of the activities in this industry. The excess negative properties of textile wastewater for the environment and the health of human beings show how important is to find a solution for this problem. In various stages of textile industry, a significant amount of water is consumed and this situation puts forth the necessity for regular control of textile wastewater into consideration. In order for textile wastewater not to impair the environment and the health of human beings, this water should be discharged to the environment after various treatment methods. The reason for using various treatment methods for textle wastewater is that there are various contaminant parameters (especially azo dyes) present in the wastewater. It's necessary to find the most suitable treatment method for textile wastewater that will minimize the production and investment costs of wastewater treatment plants. One of the most dangerous wastewaters that is discharged from textile industry is dyed wastewater. Since the clour load of dyed wastewater is high and its biological degradation is difficult, it's also difficult to treat it. Nowadays, the treatment of dyed wastewater is performed mostly by physical and chemical methods and nanotechnological textile membrane structures have started to be used for a more effective treatment.

Fenton Process, a type of Advanced Oxidation Processes is an efficient method for treating textile
wastewaters. However, excessive use of hydrogen peroxide and catalyst has made this process
economically non-feasible. Besides, industrial grade hydrogen peroxide costs $390 e500 per ton. One of
the means to overcome this problem is the in-situ production of hydrogen peroxide. In this paper, a
detailed review was conducted on the generation methods, degradation potential and optimum operating parameters for in-situ production of hydrogen peroxide/hydroxyl radicals. Additionally the scavenging aspect for hydroxyl radicals was also investigated. From this review, it can be concluded that
hydroxyl radical is highly oxidative and non selective in nature and its in-situ production can be performed through application of catalyst, ozonation, photocatalysis, electro and microbial fuel cells.
Furthermore, optimization of operating parameters can result in an increase in the yield of hydroxyl
radicals/hydrogen peroxide. Sonolysis as an auxiliary tool has potential to induce synergetic effects in
combination with Advanced Oxidation Processes to increase in-situ hydrogen peroxide production.
However, the problem of the scavenging effect is an aspect that needs to be dealt with, as hydroxyl
radicals are prone to deactivation by scavengers. Therefore based on the review, it is concluded that insitu production of hydrogen peroxide/hydroxyl radical for treating textile wastewater is economically
viable and practically feasible if careful selection of process is conducted through selective research

Membrane Bioreactor (MBR) is used besides municipal wastewater treatment in many industrial scale plants, such as textile sector. It can be operated under normal conditions on a by-pass system, or submerged in the reactor’s vessel, where it works in-line and operates by means of vacuum suction at low trans-membrane pressure. In wastewater treatment, MBR’s have significant advantages in regard to conventional activated sludge configuration due to the conditions and quality of the treated water. This work gives basic operation principle of MBR technology for textile wastewater treatment which is very important technology in nowadays environmental protection as well as analyses some advantages and disadvantages of the MBR process compared to the conventional activated sludge process. Membrane fouling and cleaning processes in MBR are also discussed.

The use of low-cost and ecofriendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. Orange peel was collected from the fields of orange trees in the north of Iran and converted into a low-cost adsorbent. This paper deals with the removal of textile dyes from aqueous solutions by orange peel. Direct Red 23 (DR23) and Direct Red 80 (DR80) were used as model compounds. The adsorption capacity Q 0 was 10.72 and 21.05 mg/g at initial pH 2. The effects of initial dye concentration (50, 75, 100, 125 mg/l), pH, mixing rate, contact time, and quantity of orange peel have been studied at 25 • C. The Langmuir and Freundlich models were used for this study. It was found that the experimental results show that the Langmuir equation fit better than the Freundlich equation. The results indicate that acidic pH supported the adsorption of both dyes on the adsorbent. Orange peel with concentrations of 8 and 4 g/l has shown adsorption efficiencies of about 92 and 91% for DR23 and DR80, respectively. Furthermore, adsorption kinetics of both dyes was studied and the rates of sorption were found to conform to pseudo-second-order kinetics with a good correlation (R 0.998). Maximum desorption of 97.7% for DR23 and 93% for DR80 were achieved in aqueous solution at pH 2. Finally, the effect of adsorbent surface was analyzed by scanning electron microscope (SEM). SEM images showed reasonable agreement with adsorption measurements.  2005 Published by Elsevier Inc.

The main goal of this study is to investigate the effects of alternating current (AC) on dye removal from aqueous solutions by electrocoagulation (EC). An EC system with parallel-connected aluminium electrodes was operated in batch mode. Two different aqueous dye solutions were used: one was obtained from Dianix Yellow CC (DY) and the other was obtained using Procion Yellow (PY). The experiments employing direct current (DC) were carried out using a DC power supply. The AC experiments were conducted using rectangular wave, which is produced with an adjustable time relay connected to the output of DC power supply. This current is called alternating pulse current (APC) in order to refer AC system in this study. Total organic carbon (TOC) and dye removal efficiencies were measured to assess treatment efficiency. Operating cost was calculated for both power supply systems and alternating pulse current was found superior to direct current for the treatment of reactive and disperse dyes used in this study.

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Textile manufacturing consumes a considerable amount of water in its manufacturing processes. The water is primarily utilized in the dyeing and finishing operations of the textile establishments. Considering both the volume generated and the effluent composition, the textile industry wastewater is rated as the most polluting among all industrial sectors. In this study a combined anaerobic-aerobic reactor was operated continuously for treatment of textile wastewater. Cosmo balls were used to function as growth media for microorganisms in anaerobic reactor. Effect of pH, dissolved oxygen, and organic changes in nitrification and denatrification process were investigated. The results indicated that over 84.62% ammonia nitrogen and about 98.9% volatile suspended solid (VSS) removal efficiency could be obtained. Dissolved oxygen (DO), pH were shown to have only slight influences on the nitrification process; and for each 10% removal of nitrogen, only 3% of pH changes were achieved.

The performance of a continuous electrocoagulation (EC) process was investigated for decolorization and chemical oxygen demand (COD) abatement of a synthetic textile wastewater using aluminum electrodes. The effects of the relevant wastewater characteristics such as conductivity, influent pH and inlet dye concentration, but also of the key operating conditions such as current density and residence time were studied in order to optimize process performance. The results showed that color induced by a red dye was effectively removed (with a removal yield higher than 85%) for wastewater with a COD of 2500 mg/L and a dye concentration lower than 200 mg/L when pH ranged from 6 to 9, residence time was 14 min, current density was 31.25 mA/cm 2 and water conductivity was 2.4 mS/cm for an inter-electrode distance of 1 cm. Under these conditions, the COD abatement was also higher than 80%.

The objective of the study was to evaluate the phytoremediation potential of three aquatic macrophytes (Commelina cyanea, Phragmites australis and Water Hyacinth (Eichhornia crassipes)) for treatment of municipal wastewater collected from Federal University of Technology, Akure (Nigeria). Laboratory scale of three constructed wetlands of dimensions 0.43 m x 0.93 m x 0.36 m in width, length and depth respectively, were developed to mimic natural conditions and was operated for a single experimental run with each macrophte at different retention time of 6, 9 and 12 days. These aquatic macrophytes were planted in separate ponds. Domestic wastewater from undergraduate students' hostel was introduced to the ponds. The raw wastewater sample and treated wastewater samples were analysed using standard laboratory methods for physical (Turbidity and Dissolved solids), chemical (pH, Nitrate, Nitrite, Phosphate, Sulphate Chemical Oxygen Demand and Biochemical Oxygen Demand) and bacteriological (Coliform bacteria) parameters. Results showed substantial diminutions in all parameters treated with the phytoremediators during the course of the study. Asides the three plants effectively removing Nitrate, Nitrite, phosphate and Sulphate pollutants, Phragmites australis gave the highest removal efciency for Phosphate (85.8%), Water hyacinth gave the highest removal efciency for pH (11.5%), Biochemical Oxygen Demand and Coliform bacteria and Commelina cyanea gave the highest removal efciency for turbidity (96.9%) and dissolved solids (82.9%) parameters of the domestic wastewater samples. The overall results of the phytoremediation studies indicate that the purication effectiveness of the three aquatic macrophytes were spontaneous, feasible and remarkable.

Photocatalysis with TiO 2 particles immobilised either on a glass slide or on a non-woven glass fiber fabric has been applied to pure reactive dyes' (azo€ ıc and metal phthalocyanines) solutions as well as textile wastewater containing the same dyes under UV and solar irradiation. Decolourization of textile wastewater was in the range 21e74% under solar irradiation, with COD removal rate between 0.2 and 0.9 g COD/h/m 2 . These values are, however, strongly dependent upon the fine chemical structure of the dyes and the global composition of the wastewater. Performance prediction is therefore difficult but the results are encouraging for textile wastewater remediation. The increase of biodegradability is an additional positive factor, as it would improve the efficiency of a biological downstream treatment. No pH adjustment is necessary and wastewater at high pH can be treated directly after suspended solids removal.

AND MAJID MUNEER Department of Chemistry, University of Agriculture, Faisalabad–38040, Pakistan †Environmental Protection Agency, Faisalabad, Pakistan 1Corresponding author&#x27;s e-mail: [email protected] ... The present study was carried out to ...

A white rot fungus Pleurotus ostreatus was employed for degradation of two commercially used disperse azo dyes, Disperse Orange 3 (C.I. No. 11005) and Disperse Yellow 3 (C.I. No. 11855). Decolorization and products from fungal degradation of these azo dyes in liquid medium were determined by UVevisible spectrophotometric method and high performance liquid chromatography (HPLC). Decolorization study showed that both azo dyes were removed by more than 50% in 5 days and HPLC analysis determined several degradation products. These results suggest that P. ostreatus has potential in color removal from textile wastewater containing disperse dyes.

The delivery of colour in the form of dyes onto textile fibres is not an efficient process. The degree of efficiency varies, depending on the method of delivery. As a result, most of the wastewater produced by the textile industry is coloured. It is likely that coloured wastewater was a feature of the first practices of textile dyeing. However, treatment to remove this colour was not considered until the early natural dyestuffs were replaced by synthetic dyes, and the persistence of such synthetic dyes in the environment was recognised (Willmott NJ. The use of bacteria-polymer composites for the removal of colour from reactive dye effluents. PhD thesis, UK: University of Leeds; 1997.). Colour pollution in aquatic environments is an escalating problem, despite the fact that there has been substantial research into the modification of the dyeing process to improve the level of affinity/fixation of the dyestuffs onto the substrate. The recalcitrant nature of modern synthetic dyes has led to the imposition of strict environmental regulations. The need for a cost-effective process to remove the colour from wastewater produced by the textile industry has been recognised (Willmott NJ, Guthrie JT, Nelson G. The biotechnology approach to colour removal from textile effluent. JSDC 1998;114(February):38-41.). Several strategies have been investigated. However, the review presented here concerns the use of whole bacterial cells for the reduction of water-soluble dyes present in textile dyeing wastewater. #

In this paper, the oxidation of dyes from colored textile wastewater by activated carbon (AC)/hydrogen peroxide (H 2 O 2 ) was discussed. Acid Red 18 (AR18), Direct Red 80 (DR80) and Reactive Red 194 (RR194) were used as model dyes. The surface characteristics of AC were investigated using Fourier transform infrared (FTIR). Dye oxidation by AC/H 2 O 2 was studied by UV-Vis spectrophotometer and Ion chromatography (IC). The effects of AC dosage, initial dye concentration, pH and salt on dye oxidation were evaluated. Kinetics analysis indicated that the dye oxidation rates could be approximated at pseudo-second order model. Formate anion was detected as dominant aliphatic intermediate. Results indicated that the AC/H 2 O 2 could be used as an eco-friendly material to degrade dyes from colored wastewater.

The objective of this study was to investigate the performance of a pilot-scale membrane bioreactor (MBR) system for the treatment of a highly concentrated mixed wastewater from wet processes (dyeing, finishing, and sizing) of a denim producing textile industry. The MBR system, containing a submerged hollow fiber membrane module in the aeration tank, was operated aerobically for about 3 months on-site at a continuous flow mode. The system was operated at two different operation stages: (1) no sludge wastage with a typical permeate flux of 20 L/m 2 h and (2) a solids retention time of 25 days with the same flux. During the whole operation period, despite the high dissolved solids content in the influent, very high treatment efficiencies were achieved. The performance of the MBR system was not adversely affected by the variations in the influent characteristics, food/ microorganism ratio, organic loading rate, and specific substrate utilization rate. The average values of some effluent quality parameters found in the entire operation period were color, 53 Pt Co; turbidity, 0.31 NTU; TSS, 0.6 mg/L; BOD 5 , 15 mg/L; COD, 37 mg/L; NH 3 ÁN, 1.0 mg/L; NO 3 ÁN, 9.6 mg/L; and TN, 10.5 mg/L. Reduction in permeate flux due to membrane fouling was observed only once during all operation and such fouling was removed by applying chemical backwashing and chemical cleaning procedures. The results indicated that complex and highly polluted denim textile wastewaters could be treated very effectively by MBR systems. Color values from as high as 8100 Pt Co levels were significantly reduced to about 50 Pt Co levels, indicating that MBR effluent could be reused in the production processes.

Synthesis of Ag3PO4 photocatalyst under the varied concentrations of AgNO3 and Na2HPO4·12H2O as starting material has been successfully synthesized using the co-precipitation method. The concentration of AgNO3 is 0.1, 0.5, 1.0, and 2.0 M, whereas Na2HPO4·12H2O is 0.03, 0.17, 0.33, and 0.67 M, respectively. The co-precipitations were carried out under aqueous solution. As-synthesized photocatalysts were examined to degrade Rhodamine B (RhB) under blue light irradiation. The results showed that varying concentrations of starting materials affect the photocatalytic activities, the intensity ratio of [110]/[200] facet plane, and their bandgap energies of Ag3PO4 photocatalyst. The highest photocatalytic activity of the sample was obtained by synthesized using the 1.0 M of AgNO3 and 0.33 M of Na2HPO4·12H2O (AP-1.0). This is due to the high [110] facet plane and increased absorption along the visible region of AP-1.0 photocatalyst. Therefore, this result could be a consideration for the improvement of Ag3PO4 photocatalyst.

In this study, a new composite coagulant, which was prepared by ployferric chloride (PFC) premixed with polydimethyldiallylammonium chloride (PDMDAAC), was adopted to treat the simulated dye water and the actual textile wastewater. The effect of coagulant dosage and pH of dye water on the color removal was examined. And the color removal results treated by the composite coagulant (PFC-PDMDAAC) were compared with those treated by PFC, PDMDAAC and PFC followed by PDMDAAC (PFC/PDMDAAC), respectively. The following results are discovered. Synergy between PFC and PDMDAAC increases zeta potential of PFC-PDMDAAC and reduces the effect of pH on zeta potential and Fe(III) species of PFC-PDMDAAC. Treatment with PFC-PDMDAAC is very effective in removing disperse blue HGL (98%) and reactive blue STE (86%). And small changes in the color removal efficiency of PFC-PDMDAAC are observed in all pH range. The color removal efficiency for disperse blue HGL and reactive blue STE is higher than 96% and 98% in the pH range 7.5-10.5, respectively. Furthermore, PFC-PDMDAAC is shown to be more effective in removing dye than that of PFC/PDMDAAC. Finally, the treatment of the actual textile wastewater has shown that PFC-PDMDAAC is a more effective coagulant.

A reliable calibration of the parameter k i was possible when data relative to the experiment conducted in the pilot plants for no less than 60 d and in conditions of complete solid retention was utilized. (G. Munz). 1 Tel.: þ39 055 4796317; fax: þ39 055 495333.

The aquatic environment around the textile industries in India was severely affected due to continuous discharge of effluents. In order to avoid further deterioration, the pollution control board of Tamil Nadu, India has enforced zero discharge concepts throughout the state. Consequently, most of the industries have opted membrane technology to recover water. The present study was aimed to find out the efficacy of electrochemical techniques as pretreatment methods to reverse osmosis (RO). The textile wastewater was initially treated by electrocoagulation to remove the suspended solids. After the electrocoagulation, the wastewater was further treated by electrooxidation for COD removal. Mild steel as anode was found to be effective for coagulation of suspended solids. For electrooxidation, graphite and RuO 2 /IrO 2 /TaO 2 coated titanium were used as electrodes. The efficiency of these electrode materials was evaluated in terms of chemical oxygen demand (COD) removal, instantaneous current efficiency (ICE) and electrooxidation index (EOI). The COD was removed to the extent of 90-93% using graphite and 54% with RuO 2 /IrO 2 /TaO 2 coated titanium electrodes. The current efficiency of 40% and 11% was achieved with graphite and RuO 2 /IrO 2 /TaO 2 coated titanium respectively. The degradation of organics was followed using GC-MS and the reason for incomplete degradation of organics in the presence of RuO 2 /IrO 2 /TaO 2 coated titanium was discussed.

The low biodegradability of many dyes and textile chemicals indicates that biological treatment is not always successful in the treatment of cotton textile wastewater, in terms of color removal. In this study, a specific organic flocculant (Marwichem DEC), powdered activated carbon (PAC), bentonite, activated clay and commercial synthetic inorganic clay (Macrosorb) were directly added into the activated sludge laboratory pilot plant model. Before dosage, the optimum sludge retention time and hydraulic retention time were determined as 30 days and 1.6 days, respectively. The Monod kinetic constants were determined as Y ¼ 0:76 kg MLSS/kg COD, K d ¼ 0:026 1/day, K s ¼ 113:3 mg/L, k ¼ 0:42 1/day and m max ¼ 0:32 kg MLSS/kg COD day. Under these conditions the average COD removal was 94% and color removal was 36%. The addition of these materials did not change COD removal significantly. The most effective materials were found to be DEC and PAC for color removal. While the color removal efficiency for 120 mg/L DEC addition was 78%, it was 65% for 100 mg/L, 77% for 200 mg/L and 86% for 400 mg/L PAC addition.

The decolorization of a synthetic textile wastewater was investigated using electrocoagulation (EC) in a batch electrochemical cell. Orange II, a typical mono-azo acid dye, was used. Aluminum and iron electrodes were compared. The respective effects of operational parameters (initial dye concentration, current density, electrolysis time) and wastewater properties (initial pH and conductivity) were analyzed by comparing the performance of color removal, energy input, electrode mass consumption and the amount of sludge produced. Operating costs were deduced. A comparison with chemical coagulation (CC) using the same amount of metal cations as in EC was also carried out. Experimental results showed that EC maximized decolorization (up to 98%) in comparison to CC (limited to 53%). For EC, iron electrodes exhibited the highest decolorization yield and minimized simultaneously energy requirements, the amount of floc and operation costs in comparison to aluminium. As voltage vs. current curves did not differ significantly between Al and Fe, higher current was required with Al electrodes to achieve a similar decolorization yield. This was partly explained by differences in the decolorization mechanism, as Al electrodes seemed to promote the electroreduction of the azo bond of Orange II, contrary to Fe electrodes.

The photodegradation of three non hydrolysed reactive azo dyes (Reactive red 120, Reactive black 5, Reactive yellow 84) in aqueous solution was investigated in a laboratory-scale batch photoreactor equipped with an immersed lowpressure mercury lamp. Six different doses of hydrogen peroxide, at constant initial concentration of the substrate (100 mg/l) were used. The pseudo-first order rate constants have been calculated from the experimental kinetic curves, for the three azo dyes. These rate constants have extreme values of the order of 0.1 min À1 at a H 2 O 2 dose of 24.5 mmol/l. The effectiveness of the UV/H 2 O 2 process has been evaluated by the degree mineralization of the total organic carbon (TOC), as a complementary indicator of the treatment efficiencies. Our results confirm the suitability of the UV/H 2 O 2 process as a textile wastewater pre-treatment step, once optimum operating conditions and cost effectiveness of the method are established. #

In the present investigation an attempt was made to degrade organic pollutants in the textile effluent by homogeneous and heterogeneous Fenton systems. Experiments were carried out under the batch as well as under the continuous operating conditions. The effect of time, pH, H 2 O 2 concentration, FeSO 4 .7H 2 O concentration and the mass of mesoporous activated carbon on the degradation of organics in the wastewater were critically examined. The kinetic constants and the thermodynamic parameters for the oxidation of organics in wastewater were determined. The quantitative removal of COD, BOD and TOC from the wastewater was evaluated. The degradation of organics in textile wastewater was confirmed through FT-IR, UV-Visible spectroscopy, and cyclic voltammetry.

Synthesis of cationic tamarind kernel polysaccharide (Cat TKP), its detailed physicochemical characterization and application as an efficient flocculant for the treatment of textile industry wastewater have been investigated. N-3-Chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) was used as a cationic reagent to introduce quaternary amine groups onto the backbone of tamarind kernel polysaccharide (TKP). Various grades were synthesized to obtain the optimized one. Effect of reaction parameters onto the degree of cationization has also been investigated. The synthesized polymers were characterized by various macromolecular characterization techniques, which confirm that cationization does take place. Afterwards, the applicability of TKP and various grades of Cat TKP's as flocculants for the treatment of textile industry wastewater was investigated. The flocculation experiments showed that TKP alone contributes little to the flocculation. However, cationic TKP led to significant improvement as flocculant for the treatment of textile industry wastewater. The best performing Cat TKP (i.e. Cat TKP 3) was thereafter compared with a commercial flocculant, which is cationic in nature. It has been observed that Cat TKP 3 surpasses the flocculation efficiency over commercial flocculant.

Water scarcity and pollution rank equal to climate change as the most urgent environmental turmoil for the 21st century. To date, the percolation of textile effluents into the waterways and aquifer systems, remain an intricate conundrum abroad the nations. With the renaissance of activated carbon, there has been a steadily growing interest in the research field. Recently, the adoption of titanium dioxide, a prestigious advanced photo-catalyst which formulates the new growing branch of activated carbon composites for enhancement of adsorption rate and discoloration capacity, has attracted stern consideration and supports worldwide. Confirming the assertion, this paper presents a state of art review of titanium dioxide/activated carbon composites technology, its fundamental background studies, and environmental implications. Moreover, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expanding of activated carbons composites material represents a potentially viable and powerful tool, leading to the plausible improvement of environmental conservation.