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The enormous demand for water and the creation of effluent that is dye-rich make the textile industry a hazard to water resources. Electrocoagulation (EC) is considered an appealing approach for treatment, which offers effective color removal in a quick, dependable, and affordable manner. Using 33full factorial design trials, the performance of EC in the treatment of synthetic wastewater including textile coloring, such as methyl orange, was examined using the response surface methodology (RSM). In the presence of iron electrodes, wastewater was electrolyzed at room temperature with a pH of 7 under various working parameters, including initial dye concentration, applied voltage, and electrolysis time. The findings suggested that utilizing EC has been a successful strategy for removing color from textile dyeing effluent. At an applied voltage of 15 V, an electrolysis period of 30 min, and an initial dye concentration of 50 mg/L, the maximum color removal efficiency was 96.6%. The comparable Electrical Energy Consumption (EEC) for these circumstances was 23.7 kWh/m3. It was noticed that 87.5%–91.0% of the color was eliminated during the first 20 min of the process.

The preparation of modified membranes utilizing the UiO-66 framework for wastewater filtration is regarded as one of the most promising approaches to wastewater treatment, owing to its high efficiency and cost-effectiveness. In this study, a post-modified MOF, UiO-66-RSA, was synthesized via the condensation reaction of UiO-66-NH2and 2,4-dihydroxybenzaldehyde. PVDF mixed matrix membranes (MMMs) were fabricated for the first time by mixing UiO-66-RSA into PVDF using the non-solvent induced phase separation (NIPS) method. Compared to pure PVDF membranes, the newly developed membrane, M4, demonstrated enhanced compatibility and superior mechanical strength. In dyeing wastewater treatment applications, M4 showed excellent separation efficiency for dye and heavy metal mixed wastewater, achieving rejection rates exceeding 90 %. Additionally, it maintained a high flux recovery rate (FRR > 90 %) and rejection rate (Rejection > 90 %) after six filtration cycles of dye-containing wastewater, indicating strong recyclability. These findings suggest that MMMs embedded with UiO-66-RSA hold significant promise for dyeing wastewater treatment.

In this paper, the inorganic–organic composite flocculant (PAC/PMAPTAC) was prepared with polyaluminum chloride (PAC) and the self-made PMAPTAC. Then, the flocculation sedimentation experiment was used to evaluate the flocculation performance of single flocculant PAC, PMAPTAC and the composite flocculant PAC/PMAPTAC in dyeing wastewater. At the same time, the flocculation effect of PAC/PDMDAAC was compared with that of PAC/ PMAPTAC under the same condition. Finally, the flocculation mechanism was analyzed by zeta potential and floc morphology. The results showed that compared with PAC, the flocculation performance of composite flocculant PAC/PMAPTAC could be markedly improved, resulting in the higher decolorization rate and CODMnremoval rate. Besides, the increase of (η) or content of PMAPTAC in PAC/PMAPTAC could enhance the decolorization rate and CODMnremoval rate simultaneously. Furthermore, the lower dosage was required to achieve the best removal effect, which meant that the cost of the flocculant was reduced. Moreover, the comparison of flocculation performance turned out that the decolorization rate and CODMnremoval rate of PAC/PMAPTAC were higher than those of PAC/PDMDAAC under the same condition. Finally, the zeta potential and floc morphology analysis showed that the flocculation mechanism of the reactive dye simulated wastewater was mainly charge neutralization and adsorption bridging. The above results not only fill the gaps in the research of PAC/PMAPTAC during the treatment of dyeing wastewater, but also provide an experimental basis for its application in dyeing wastewater and expand the application fields of PMAPTAC.

The low solubility of ozone in water limits its oxidation reaction rate, while microbubbles can enhance the gas–liquid mass transfer process and effectively improve the mass transfer rate of ozone. In this study, we set up an ozone microbubble generation system, with an internal recycle, a self-made releasing device using 3D printing and other designs to keep the system running steadily, with constant pressure, high ozone concentrations, and slow microbubble dissipation rate. This study investigated the ozone feed rate and optimization of mixing conditions through the test. With the increase of ozone feed rate, the average concentration of ozone in the solution tends to increase linearly, then decreases slightly after reaching the maximum 13.75 mg/L. On a stable running of the system, the ozone concentration of the solution could reach 13.29 mg/L. The ozone microbubble was then investigated by calculation and measurement of bubble disappearance time, particle size and mass transfer capacity. This study found the particle size of bubbles was about 42.66 μm and KLa(20) was 10.712 min–1. The system’s applications were then studied to demonstrate the effect of ozone microbubbles. Under strong alkaline conditions and without acid adjustment, COD of printing and dyeing wastewater could reach Chinese first-class A discharge standards after treatment with ozone microbubbles. Another experiment proved that ozone microbubble solution of 8 mg/L had more than 99% killing effect on Escherichia coli.

In the textile industry, the process of washing off dyes requires a substantial amount of water, leading to the generation of heavily polluted wastewater. This study assessed the viability of electrocoagulation (EC) treatment for degradation of reactive orange 84 dye in wash-off liquor and its repetitive utilization in the same process by using a laboratory-scale experimental setup. Optimal operational factors, including electrolysis time, pH and applied current were determined through experimentation, resulting in a maximum color removal efficiency of 99 %. This efficiency was achieved at reaction time of 10 min, pH 7.5 and a current 1.0 A. Evaluation of fabric quality, considering color difference and wash fastness properties, indicated that the color difference values for dyed fabric samples over five repetitive reuses fell within an industrially acceptable range (ΔEcmc <1). Wash fastness properties remained comparable to conventionally washed fabric samples, with negligible differences in color strength (K/S) values. Despite an escalation in pH, COD, TDS, and turbidity level after each reuse, the overall quality of dyeing was not compromised. This work pioneers the integration of iron and aluminum electrocoagulation in practical conditions, demonstrating enhanced contaminant removal efficiency, promoting water reuse in the textile industry, and enhancing environmental sustainability.

Polyamide (PA)/polydopamine (PDA)/poly(vinylidene fluoride) (PVDF) nanocomposite membranes were prepared by the method of dopamine (DA)/polyethyleneimine (PEI) co-deposition integrating with interfacial polymerization (IP) with trimesoyl chloride. Fourier transform infrared spectrometer, scanning electron microscopy, atomic force microscopy and water contact angle were used to characterize the PA/PDA/PVDF nanocomposite membranes. Effects of the co-deposition time, the mass ratio of DA to PEI, the molecular weight of PEI and the content of DA + PEI on the morphologies and roughness of the membrane surface, the cross-section of the selective layer and the performance of the PA/PDA/PVDF nanocomposite membranes were investigated. Results showed that the co-deposition time has significant effect on the rejection of PA/PDA/PVDF nano-composite membranes, the other three factors have few effects on the rejection. All the four factors have remarkable effects on the permeation of the PA/PDA/PVDF nanocomposite membranes. When the rejection of PEG1000 and RB5 was 99%, the permeation of water and reactive black five (RB5) dyeing wastewater was 16.67 and 8.2 L m–2h–1bar–1, respectively. The water flux and the RB5 dyeing wastewater permeation of the PA/PDA/PVDF nanocomposite membranes were 31.14 and 15.03 L m–2h–1bar–1, respectively, when the PEG1000 and RB5 rejections were above 90%. Results above showed that the PA/PDA/PVDF nanocomposite membranes developed in this paper possess the potential application value in the dyeing wastewater treatment and reclamation

The advanced treatment of printing and dyeing wastewater by adsorption using activated coke was studied. Specifically, the effects of adsorption conditions on wastewater treatment were examined by adsorption experiments. Meanwhile, the adsorption behaviors of organic pollutants by activated coke were investigated by the adsorption kinetics and isotherms. The chemical oxygen demand (COD) removal met the printing and dyeing wastewater discharge requirement under the conditions of initial COD concentration 158 mg/L, adsorption time 360 min, activated coke concentration 30 g/L and adsorption temperature 308 K. After adsorption, 53.86% of COD was removed. The adsorption kinetics of COD by activated coke followed the pseudo-second-order model and the adsorption isotherms could be expressed by the Freundlich model. Moreover, thermal regeneration of spent activated coke was studied. Specifically, the effects of regeneration conditions on the thermal regeneration efficiency of spent activated coke were examined by thermal regeneration experiments. Meanwhile, the reusability of activated coke for organic pollutants removal was evaluated by the successive adsorption-regeneration cycles. 98.13% of thermal regeneration efficiency could be achieved under the conditions of regeneration temperature 1,073 K, regeneration time 30 min and CO2flow rate 150 mL/min, and activated coke still maintained 92.54% of regeneration efficiency after ten adsorption-regeneration cycles.

A simple process for the preparation of mesoporous silica microsphere (MSM) as adsorbent was synthesized via sol–gel method between tetraethyl orthosilicate and polyethylene oxide-polypropylene oxide-polyethylene oxide (F127). The influencing factors of MSM on methyl orange simulated dyeing wastewater were investigated in detail. Five adsorption isotherm models, kinetics, thermodynamics, and mechanism were studied. Under the optimum conditions, the adsorption rate was up to 86.44% (only at 21 min). The adsorption process of methyl orange by MSM was indicated as a non-spontaneous monolayer chemical adsorption process, which obeyed the pseudo- second-order kinetic model. The above showed that the MSM as-prepared in this paper was a simple, efficient and promising adsorbent for wastewater treatment, which provided a theoretical basis and technical support for the dyeing wastewater treatment.

After the advanced treatment of textile and dyeing wastewater, the concentration of total nitrogen (mainly nitrate) was still high while it lacked a biodegradable organic carbon source for further biological denitrification. Biological denitrification reactor with iron-based materials (both Fe and Fe/Cu) resulted in higher nitrogen removal efficiency (30% and 20%) compared to control (12%). However, the microbial mechanism was unknown. 16S rRNA genes sequencing and metagenomic sequencing were used to analyze the microbial community structure and functional genes in the process of iron-based materials enhanced biological denitrification of textile and dyeing wastewater. Microbial communities obtained from the two sequencing methods were quite different. The results of 16s rRNA genes sequencing indicated that both Fe and Fe/Cu influenced the microbial communities. Fe/Cu had a more profound effect on the microbial community and the diversity of the microbial community in the Fe/Cu reactor was relatively low. Metagenomic analysis showed that Proteobacteria was dominant in all samples (47%–80%). The biofilm formed on the surface of Fe and Fe/Cu enriched more functional microorganisms, which promoted denitrification of nitrate. The abundance of genes relating to nitrogen metabolism was higher in the samples on the surface of Fe and Fe/Cu, and therefore they had a stronger ability of nitrogen metabolism.

In this study, advanced oxidation processes were applied to the treatment of a textile dyeing wastewater. The effluent presents a dark blue color, with a maximum absorbance peak at 594 nm, alkaline pH (pH = 12.4), high organic contents (COD = 1,400 mg L–1). Experiments were conducted on a lab-scale prototype using UV lamp as light source and pillared natural clay with Fe and Al as catalyst. All the processes examined lead to an effective decolorization and mineralization, but the most efficient process was the photo-Fenton, contributing to 93% decolorization and 88.8% mineralization after 3 h of reaction under UV irradiation. Characteristics of wastewater after treatment were COD below 250 mg L–1, pH 8.5 and uncolored. Thus the resultant water has conditions that are suitable for releasing in public sewage systems.

Chitosan-gelatin composite copper polymer (CG for short) was prepared as an adsorption catalyst. The CG was combined with sodium persulfate to construct a heterogeneous Fenton-like system, which was applied to the decolorization of C.I. Reactive Blue 78 dyeing wastewater. The effects of sodium persulfate, CG, temperature, initial dyeing wastewater pH value and additives (sodium chloride, sodium carbonate) on the decolorization were investigated. The results show that the decolorization percentage of 0.1 g/L C.I. Reactive Blue 78 dyeing wastewater can reach 93.84 % under the conditions of sodium persulfate dosage of 0.3 g/L, CG dosage of 0.8 g/L, decolorization at 40 °C for 30 min. At the same time, the catalytic system has the characteristic of good decolorization effect on C.I. Reactive Blue 78 dyeing wastewater within a wide pH values range of 3–9. Even for dyeing wastewater containing 0.4 g/L high concentration C.I. Reactive Blue 78, the decolorization percentage can reach over 90 % after decolorization at 40 °C for 2 h. Moreover, CG can be reused. After repeated use of CG four times, the decolorization percentage of C.I. Reactive Blue 78 dyeing waste remains above 90 %. In addition, the weight loss rate of CG after each decolorization is less than 12 %. However, the presence of sodium chloride and sodium carbonate in the dyeing wastewater is not conducive to the decolorization of C.I. Reactive Blue 78 by the system.

Improved anaerobic baffled reactor-anoxic/oxic (ABR–A/O) coupling process was used for printing and dyeing wastewater treatment in our full-scale study, which was able to reach the effluent standard stably, especial for the characteristic pollutants and aromatics removal. According to our results of microbial community analysis by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), the divisions of ABR enabled the functional microorganisms to distribute in different compartments and contributed to each compartment of performing its own functions with more efficiency. The first, second, and third compartments are major in macromolecular organics hydrolysis and sulfate reduction, while the main responsibilities of the fourth, fifth, and sixth compartments are aromatic compounds degradation and denitrification. Many kinds of aromatic anaerobic degradation microorganisms were found in our ABR, such as Pseudomonas stutzeri, Dechloromonas aromatic, Pseudomonas putida, and Aromatoleum aromaticum. Initially, abundances of bcrA genes climbed up and then dropped along with the sequential six compartments of ABR and it indicated that the highest aromatics degradation efficiency were obtained at the fifth compartment, rather than other compartments, which was probably caused by its moderate substrate concentration and biodegradability.

The processing of gemstones, mainly the dyeing step, generates a high volume of wastewater containing a high concentration of Rhodamine B. This wastewater is potentially toxic and contains non-biodegradable substances. For this reason, it is necessary to develop methodologies to treat this type of wastewater. Therefore, in this work, a sequential process of electro-Fenton conjugated with adsorption were developed to treat this type of wastewater. The gemstones dyeing wastewater presented between 735.5 and 1,943.0 mg L–1of Rhodamine B. Firstly, the electro-Fenton process was applied, and removal superior to 65% of the RhB concentration were observed. Subsequently, adsorption was applied using a strong cationic resin at a pH of 2.0. In this condition, the adsorption capacity predicted by the Langmuir model was 247.3 mg g–1. The breakthrough curves were inclined with a suitable mass transfer zone. The sequential process of electro-Fenton and fixed-bed adsorption were able to remove 100% of the RhB from the gemstones’ wastewater, being an effective alternative to treat this type of effluent.

Membrane biofouling is an unevadable problem that occurr during the reverse osmosis (RO) desalination of dyeing wastewater; therefore, it is necessary to minutely understand biofouling characteristics of RO membranes to effectively hinder the fouling. In this study, two sets of laboratory-scale desalination systems of biologically treated dyeing wastewater were operated, respectively, for 10 and 30 d, and the performance and biofouling of RO membrane were investigated. The obvious decrease of permeate flux after 10 d of operation reflected a more serious membrane fouling. The analysis on surface morphology, foulant characteristics, and active biomass of membrane fouling layer exemplified that biofouling was perhaps responsible for the permeate flux decline, and the fouling was more serious after operation of 30 d than that of 10 d. Further, bacterial community of biofilm showed that Proteobacteria was the most predominant, followed by Firmicutes and Bacteroidete. The relative abundance of γ-Proteobacteria significantly decreased and that of α-Proteobacteria, Clostridia, and Sphingobacteria increased with operation time, which seemed to facilitate the more developed/mature biofilm formation. The results would provide fundamental information for effective strategy on prevention and control of membrane biofouling during RO desalination of dyeing wastewater.

Textile industry wastewater includes organic dyes and decomposition products which could have toxic and mutagenic effects on life. The majority of industries in this sector use nonbiodegradable, heat-resistant, light, oxidizing agents and therefore synthetic dyes that are difficult to remove color. In this study, Dianix Yellow Brown CC (0.22%), Dianix Rubine CC (0.79%) and Setapers Blue CE3R (0.015%) containing disperse dye have been used in the production of wastewater from the dyehouse. In this study, textile wastewater has been treated which has applied adsorption and photocatalytic methods by using nano-titanium dioxide (nTiO2). Optimum chemical oxygen demand (COD) and color removal efficiencies have been determined for these two methods. Moreover, under the optimum conditions in the adsorption method, the COD removal efficiency has been obtained as 58.07% and also color removal efficiencies have been obtained as 95.24%, 95.15%, 96.83% for 436, 525 and 620 nm, respectively (pH 2, nTiO2dose 2.5 g L–1and 30 min reaction time). Therefore, under the optimum conditions in the photocatalytic method the COD removal efficiency has been obtained as 57.59% and also color removal efficiencies have been obtained as 95.24%, 96.31%, 94.71% for 436, 525 and 620 nm, respectively (pH 2, nTiO2dose 1.5 g L–1and 60 min reaction time). Four different kinetic, that is, first-order kinetic, second-order kinetic, pseudo-first-order, pseudo-second-order, models have been used for the processes adsorption and photocatalytic. The pseudo-second-order kinetic model has been found to be the most suitable model for both processes. As a result, regression coefficients (R2) has been obtained for adsorption as 1 and for photocatalytic as 0.9999 and reaction rate constants (k) have been obtained for adsorption as 6.9 × 10–4L mg–1min–1and for photocatalytic as 2.2 × 10–3L mg–1min–1.

The present study investigates the electrochemical oxidation (EO) of real leather dyeing wastewater coming from a local modern tannery in Fez (Morocco). Experiments were performed in an electro-chemical reactor using Ti/Pt anode. Response surface methodology and full factorial central composite design were used to investigate the combined effect of three independent operating parameters considered for the optimization of the EO process: electrolysis time (t), current density (j) and temperature (T). Chemical oxygen demand (COD) removal (Y1) and specific energy consumption (SEC) in kWh/kg of COD removed (Y2) were used as responses to examine the degradation of wastewater. The obtained quadratic model was statistically tested using analysis of variance. The correlation coefficients for the model (R2) were 0.9986 and 0.9830 for COD removal and SEC, respectively. The best conditions for maximum COD removal and minimum specific energy consumption in the present study were t = 2.11 h, j = 18.70 mA/cm2and T = 286.18 K. Under these optimum conditions, 81.2% of COD removal was observed with energy consumption of 93.85 kWh/kg of COD removal. Fourier transformed infrared spectroscopy analysis was used for the characterization of effluent. Evolution of inorganic ions concentration and changes of turbidity, pH and conductivity of wastewater during the EO process were also followed.

An iron-activated carbon catalyst was prepared by calcination of an activated carbon derived from banana spike previously impregnated with iron sulphate, and then characterized by N2and CO2adsorption–desorption experiments and scanning electron microscopy coupled to energy dispersive spectroscopy. The presence of iron-based nanoparticles highly dispersed in the porosity was demonstrated and the nanoparticles were identified as wüstite (FeO) by X-ray photoelectron spectroscopy. The performances of this catalyst were investigated for the treatment of actual textile wastewater from Bamako handicraft loincloths dyeing by the heterogeneous Fenton process. The response surface methodology was used to optimize the effects of three independent parameters (catalyst dose, H2O2concentration, and initial total organic carbon (TOC) concentration) on the efficiency of wastewater treatment assessed by the rate of TOC reduction. The optimal conditions are found for 2 g/L catalyst, 16.73 mmol/L H2O2and 99.83 mg/L initial TOC corresponding to a prediction of 90.2% reduction of TOC. In these experimental conditions, the measured rate of degradation of 90.4% is in agreement with the proposed model. This high level of mineralization demonstrates that the Fenton process using the prepared catalyst is a viable treatment for the waste water from Bamako handicraft textile dyeing.

AbstractIn this work, the occurrence and removal of polycyclic aromatic hydrocarbons (PAHs) were investigated in a combination process of anoxic baffled reactor (ABR)-hybrid coagulation/membrane bioreactor (HCMBR) for real textile dyeing wastewater treatment. It was found that the target compounds except for the chrysene, benzo(b)fluoranthene, dibenzo(a,h)anthracene, and benzo(g,hi)perylene occurred widely in raw textile dyeing wastewater, treated effluent and sludge samples. In the raw wastewater, two-ring naphthalene was the dominant compound, while three-ring PAHs predominated in the final effluent. The dominant compounds in the raw sludge samples were phenanthrene, while they were pyrene and indeno(1,2,3-cd)pyrene for final discharge sludge. The combination process achieved over 88% removal for all the PAHs. Low molecular weight (LMW) PAHs might be mainly removed by volatilization, adsorption, and sedimentation in the ABR treatment unit. High molecular weight (HMW) PAHs might be mainly removed by adsorption and sedimentation processes after coagulation and solid–liquid separation in the HCMBR treatment unit. The final discharge of treated textile dyeing wastewater and sludge was biologically safe based on the toxicity evaluation test.

AbstractMost natural and synthetic textile dyes, especially vat dyes, are resistant to degradation and decolorization by conventional treatment methods. In this study, the purification of synthetic textile wastewater containing commercial indigo dye by a green technological treatment system was investigated. A vertical-flow constructed wetland model comprising three different bedding materials, sand, gravel, and zeolite, was used to treat synthetic indigo dyeing wastewater. Treatment efficiency was evaluated by measuring color and pollution parameters such as chemical oxygen demand (COD), pH, oxidation–reduction potential, and electrical conductivity. According to the results, the constructed wetland system reduced color by up to 97% and lowered the COD by up to 62%. This study demonstrated that the constructed wetland system is a promising technique for purification of indigo dyeing textile effluents of COD and color as compared to conventional methods.

AbstractThe printing and dyeing wastewater was treated by a pilot-scale hybrid anaerobic baffled reactor (HABR) which was modified from general anaerobic baffled reactor by adding combined packing in the upper part of each compartment and inert carrier at the bottom of the reactor. The start-up of the reactor, the performance of HABR in treating printing and dyeing wastewater, and the transformation of sulfate and removal of bivalent sulfur in the treatment were investigated. The results showed that less time was taken during the start-up in comparison with the general one, and higher COD removal efficiency and sufficient color removal rate were also obtained in the HABR. When the hydraulic retention time was 12–13 h and the sludge return ratio was 0.3, the average COD and color removal rates were 47% and 56%, respectively. The anaerobic bacteria community in each compartment developed well because of available substrates and specific environmental conditions. The results also showed that high reduction rate of was reached in the HABR, and the S2−transformed from could be removed by adding Fe2+into the wastewater in order to reduce the inhibitory effect on the anaerobic bacteria and the odor.

AbstractMixed printing and dyeing wastewater (MPDW) is characterized by a low-strength chemical oxygen demand (COD; average of around 1,000 mg/L), a high fraction of recalcitrant components, a low COD/ratio (approximately 1.0), and a high pH (about 8–10 without adjustment). In this study, a biological system that combined a hybrid anaerobic baffled reactor (HABR) and a cross flow aerobic sludge reactor (CFASR) was successfully used to treat MPDW that was discharged from an industrial zone. The HABR–CFASR system was fed with real MPDW. In the start-up stage, the system had low organic loading rates of 0.66 and 0.45 kg COD/(m3·d) for the HABR and CFASR, respectively. These increased to 2.03 and 1.00 kgCOD/(m3·d), respectively, in the steady stage. The pH of the HABR influent was reduced by adding H2SO4at a decreased dosage over the course of the experiment. Most of the final effluent from the combined treatment process was stable below 100 mg-COD/L and 20 mg-BOD/L after 12 h-HRT in the HABR followed by 20 h in the CFASR. The sulfate removal rate reached 17.59%, and the COD/ratio varied slightly around 1.0, regardless of the Ns (sulfate loading rate), which varied between 1.5 and 2.5 kg/(m3·d). A GC/MS analysis demonstrated that the amount and types of organic compounds declined significantly after the HABR treatment.

The cotton printing and dyeing wastewater obtained from a printing and dyeing mill was treated by supercritical water oxidation (SCWO) in a continuous-flow reactor. The experiments were operated between 400 and 600°C, 25 MPa was selected as a suitable pressure, hydrogen peroxide (H2O2) was used as an oxygen source, and excess oxygen varied from 0 to 300%. The studies indicate that the total organic carbon (TOC) degradation efficiency is over 99.7% when the temperature increases to 600°C at 300% excess oxygen. The influence of oxidants on TOC conversion is obvious at a lower temperature and then evidently weakens with temperature. The ammonia nitrogen (NH3–N) removal by the SCWO reaction from the dyeing wastewater was also discussed. The result shows that a high temperature and the right amount of oxidizing agent are required to achieve a good effect on removing NH3–N. A salt separator was applied for the separation of salts contained in the wastewater and to prevent the reactor block. The desalination rate of the separator during the SCWO reaction process was also discussed. The studies show that the removal efficiency of the total dissolved solids (TDS) can be up to 95.8% when the temperature reaches 647°C. The TDS in effluent after treatment increases with initial TDS concentration rather than remaining unchanged at a certain temperature. It is probable that the changes of one or the total salt concentration in the salt solution influence the salt solubility in SCW, which results in the variations of the salt precipitation rate.

AbstractIn this work the performance of a hybrid coagulation/membrane bioreactor (HCMBR) was assessed for real textile dyeing wastewater advanced treatment. Poly-aluminum chloride (PACl) was selected and used in the experiments. Batch experiment results showed that the optimal dosage was 40 mg Al/L. During the pilot-scale experiment, the suitable dosage and dosing interval were once per day at the dosage of 40 mg Al per L of amount of mixed liquor into the HCMBR system. It was found that membrane fouling was effectively retarded by PACl addition in the running MBR system. Additionally, removal of pollutants according to influent and effluent quality was monitored. HCMBR achieved much higher removal efficiencies than membrane bioreactor (MBR) in CODcr, UV254, and total phosphate, due to PACl coagulation in the HCMBR bioreactor. And the application of PACl was effective in decreasing the content of extracellular polymeric substances and the membrane fouling resistances. The transmembrane pressure of HCMBR developed much slower than that of MBR, which indicated that coagulation with PACl in the MBR could alleviate membrane fouling. PACl addition was practically feasible for real textile dyeing wastewater advanced treatment without large excess sludge production.

The decolorization and chemical oxygen demand (COD) removal of carpet dyeing wastewater by Fenton oxidation process was investigated at various reaction conditions. The initial COD of carpet dyeing wastewater was 2760 mg/l and its color in term of absorbance was 2.7. The effect of various parameters such as pH, ferrous sulphate concentration, hydrogen peroxide concentration, reaction time, and temperature on COD and color removal of carpet dyeing wastewater by Fenton oxidation were studied. Using Fenton oxidation, the optimum operating conditions of pH of 4, FeSO4concentration 4 g/l, H2O2concentration 30 g/l, temperature 25°C, and 30 min reaction time at atmospheric pressure, giving maximum color and COD removals of 93% and 98%, respectively, were found. The carpet dyeing wastewater can be satisfactorily treated by adopting this process. The calorific value of dried residue obtained after thermal treatment was 12.8 MJ/kg, which is about 76% to that of lignite coal and thus could be used as a solid fuel. Also the dye degradation kinetics was studied.

A submerged hollow fiber membrane bioreactor (MBR) with a capacity up to 400 L/d was used for treatment of dyeing wastewater from a printing and dyeing factory in Changzhou, China. The MBR device was operated continuously for 100 days. The removal ratio of COD reached 90% and the COD values of effluent from the reactor were 52–97 mg/L, when the COD values of inlet were 600-1200 mg/L, 10–20% of which were rejected by membranes. The removal ratios for NH3-N and colour were 90–95% and 60-75%, respectively. The result of this work could be used as a reference for the application of MBR technology to dyeing wastewater treatment on an industrial scale.

AbstractPhysicochemical and dyeing properties using reactive dyes of curaua and banana fibers were studied by means of color strength (K/S), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy analyses. SEM analysis of alkali-treated fibers showed an increase in roughness due to surface lignin and hemicellulose defibrillation. DSC analysis showed for all the samples an endothermic and an exothermic peak at 70–80 and 340–360°C due to the loss of adsorbed/absorbed water and to decomposition of α-cellulose, respectively. Alkali-treated fibers displayed a second peak around 290°C attributed to the degradation of hemicellulose. FTIR spectra of the studied fibers show similar bands with different intensities attributed to the main components of cellulose-based materials. Alkali-pretreated fibers demonstrated excellent dyeing ability for all the tested dyes. Dye absorption depends on the chemical fiber, dye structure, and concentration. The results of washing fastness are very good for all the tested fibers. The dyeing effluent treated with an advanced microfiltration method using an improved alumina ceramic membrane shows an average efficiency of 98% in turbidity and color reduction. Low-cost ceramic alumina microfiltration membranes are a very promising advanced treatment for textile industrial effluents allowing water reuse.

AbstractIn this study, an assessment of the performance of combined moving bed biofilm reactors and a membrane filtration system (MBBRs, anaerobic–aerobic in series and MF) for the treatment of azo dye reactive brilliant red X-3B-containing wastewater was performed. Each reactor was filled with 35 vol.% of the suspended biofilm carriers for biological treatment. To assess the performance of the hybrid processes, the removal efficiencies of color, COD, and SS were analyzed by experiments. The average removal efficiencies of color, COD, and SS were 90, 85 and 94% (influent color = 400 Pt–Co unit, COD = 500 mg/L, and SS = 310 mg/L), respectively when the hydraulic retention times in the anaerobic and aerobic reactors are 11 and 5 h, respectively. The combined MBBRs and membrane system was highly efficient for the treatment of azo dye–containing wastewater. The experimental results showed that the combined processes are a viable technique for textile wastewater treatment.

AbstractThis study was carried out to evaluate the efficiency of aerobic submerged hollow fiber membrane bioreactor (HFMBR) in the removal of direct fast red dye-CI 81 from textile wastewater. The effect of hydraulic retention time (HRT), initial dye concentration, and transmembrane pressure (TMP) on the performance of submerged HFMBR was studied. The removal rate of chemical oxygen demand was found to increase with the increasing of HRT and decrease with increasing initial dye concentration and TMP. The rate of dye removal was found to increase with increasing HRT and decrease with the increasing TMP. The optimum color removal was obtained at initial dye concentration of 150–200 ppm. A mass transfer model for the dye removal using submerged membrane bioreactor system was developed and verified. The results revealed that there is a remarkable agreement between the theoretical results and experimental results with a deviation of 14.83%. The membrane fouling was investigated using electron dispersive X-ray (EDX) and scanning electron microscope (SEM) and compared with the EDX and SEM of the original one. SEM images revealed that there are some geometrical changes that occur in the membrane pores with fouling, while EDX mapping showed that most of the foulants deposited on the inner surface of the fiber.

The Al-Alamia Dye Company in Cairo, Egypt faces a variety of problems due to unhealthy conditions resulting from the discharge of dye wastewater into sewer systems. These dyes not only cause enormous environmental pollution problems, but they also interfere with treatment system operations. From study the characterization of the dye wastewater resulting from the company, a physiochemical pretreatment for the wastewater dye effluents as a pretreatment step prior to membrane separation was suggested. The aim of the present work is to characterize the dye wastewater resulting from the dye processes of cotton and polyester and evaluate a proposed physiochemical treatment process for reducing pollution prior to membrane separation. Physiochemical analyses of composite samples for both cotton and polyester wastewater dyes were investigated. The characteristics of the cotton dye wastewater proved high TDS concentration (5,400–14,000 mg/L) and low COD concentration (154–684 mg/L). The analyses of the polyester dye wastewater proved low TDS concentration (350–2,561 mg/L) and high COD concentration (354–3,051 mg/L). A remarkable suspended solids concentration (SS) and heavy metals for both polyester and cotton dye wastewater were determined. The pretreatment proved that aluminum sulfate with 200 mg/L dose is the optimum for reducing SS concentration and COD concentration for cotton wastewater dyeing. Also it was found that a 600 mg/L does of ferric chloride is the optimum for reducing the SS and COD concentration for polyester wastewater dyeing.

To study the effect of salt on decolorization in reactive dyeing wastewater, a chitosan-gelatin composite copper polymer (CG) was prepared as a catalyst, and its structure was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. With the help of CG and H2O2, a heterogeneous Fenton catalytic system was created, and it was then used to decolorize simulated reactive dyeing effluent. The decolorization effect of C.I. Reactive Blue 19 (RB19) in the CG/H2O2catalytic system was studied with and without NaCl. The effects of the initial pH of the decolorization solution, NaCl, and temperature on the decolorization rate and decolorization kinetic properties of RB19 were investigated. The results show that the catalytic decolorization system containing NaCl has a good decolorization effect in a wide range of neutral and alkaline pH values, and the decolorization rate of the CG/H2O2catalytic system on the simulated RB19 dyeing wastewater increases with increasing pH value in the pH range of 5~10 and with increasing NaCl concentration. At 50°C for 30 min under neutral and alkaline conditions, the decolorization rate of simulated RB19 dyeing wastewater by CG/H2O2catalytic system reaches more than 90%. In the CG/H2O2catalytic system, the kinetic models of the catalytic decolorization system with and without NaCl accord with the pseudo-second-order kinetic model. The decolorization rate constant and the initial decolorization rate with NaCl in the dyeing wastewater are more than 3.9 times higher than those recorded without NaCl. The half decolorization time of dyeing wastewater containing NaCl is at least 74% shorter than that of dyeing wastewater without NaCl at the same decolorization temperature.

The fractionation of dye and salt effectively is crucial in the nanofiltration of dyeing wastewater. However, the present commercial nanofiltration membrane often rejected dye and salt simultaneously due to the dense selective layer of the membrane. To obtain nanofiltration membranes with a loose selective layer, β-cyclodextrin (β-CD) was added to the co-deposition of dopamine/polyethyleneimine in the PA/PDA-β-CD/PVDF composite loose nanofiltration membrane by the method of combination of co-deposition and interfacial polymerization. The effect of β-CD content on the structure and morphologies of PA/PDA-β-CD/PVDF composite loose nanofiltration membrane was investigated. The chemical structure, microstructure, surface roughness, and hydrophilicity of the membrane surface were characterized by an infrared spectrometer (attenuated total reflection-Fourier-transform infrared spectroscopy), scanning electron microscope, atomic force microscope, and dynamic water contact angle meter. The filtration performance of the PA/PDA-β-CD/PVDF composite loose nanofiltration membrane was tested by filtration experiments. The results showed that with the increase of β-CD concentration, the hydrophilicity, water flux, and salt permeability of the selective layer were significantly increased, indicating that β-CD had improved the porosity and hydrophilicity of the selective layer. When the β-CD concentration was 2 g/L, the flux of water and dyeing wastewater was the maximum, but the dye rejection was lower than 90%. The performance of the composite nanofiltration membrane with the β-CD concentration of 1 g/L was the best.