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In this study, ferroferric oxide (Fe 3 O 4) was used to accelerate treatment performance of synthetic wastewater containing azo dye reactive black and starch as a sole carbon source. In a batch experiment, 10 g·L-1 of Fe 3 O 4 was confirmed to be optimal to this type of wastewater treatment. Therefore, this concentration was chosen for the follow-up experiment with a continuous system of 10 L anaerobic baffled reactor (ABR). The ABR was run at 30 ℃ with a hydraulic retention time of 18.6 h for 170 days. Fe 3 O 4 was added to each ABR compartment at 10 g·L-1 from day 105. The Fe 3 O 4 supplement significantly enhanced ABR treatment performance. With influent color and chemical oxygen demand (COD) levels of 1300 Pt-Co and 305 mgCOD·L-1, their removal efficiencies increased remarkably from 44% and 42% in the Fe 3 O 4 -free phase to 85% and 76% in the Fe 3 O 4 -added phase, respectively. Interestingly, the ratio of generated methane on removed COD in Fe 3 O 4 -involved phases were lower than that in Fe 3 O 4 -free phase, suggesting a preference of the ABR for decolorization over methanogenesis in an iron-rich condition. Microbial community analysis revealed that Fe 3 O 4 may have immensely contributed to dyeing degradation process through the selective enrichment of key substrate-fermenting and dye-degrading bacteria, especially Clostridium spp. [Display omitted] • Fe 3 O 4 was added to an anaerobic baffled reactor to treat azo dye wastewater. • Fe 3 O 4 significantly enhanced both organic matter and color removal efficiencies. • Enhanced performance was likely due to selective bacterial enrichment under Fe 3 O 4. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dodecylbenzene sulfonic acid functionalized Fe 3 O 4 -biochar enhanced RhB adsorption. • The maximum adsorption capacity of RhB by DBSA-Fe 3 O 4 @BC reached 367.67 mg/g. • RhB adsorption behavior on DBSA-Fe 3 O 4 @BC was chemisorption and monolayer. • High-performance for RhB adsorption by DBSA-Fe 3 O 4 @BC was maintained after 6 cycles. In this study, a novel adsorbent, dodecylbenzene sulfonic acid (DBSA) functionalized magnetic biochar (DBSA-Fe 3 O 4 @BC), was synthesized and used to efficiently remove dyes from aqueous solution. The results indicated that DBSA-Fe 3 O 4 @BC exhibited an excellent adsorption capacity for Rhodamine B (RhB), and the maximum adsorption capacity for RhB at 298 K was 367.67 mg/g, which was approximately 2.3–1.2 folds than that of BC, dodecylsulfonic acid functionalized biochar (DSA@BC), DBSA@BC, Fe 3 O 4 @BC, and DSA-Fe 3 O 4 @BC. The possible adsorption mechanisms for RhB adsorption by DBSA-Fe 3 O 4 @BC included pore filling, electrostatic attraction, H bond, and surface complexation. Importantly, structural control presented that the simultaneous introduction of alkyl and phenyl groups significantly enhanced RhB adsorption by DBSA-Fe 3 O 4 @BC through hydrophobic and π-π interaction. Combined ethanol (EtOH) desorption and H 2 O 2 oxidation regeneration, DBSA-Fe 3 O 4 @BC remained high-performance for RhB adsorption after six cycles (97.44%), indicating its outstanding reusability. In summary, DBSA-Fe 3 O 4 @BC exhibited a prospective application for dyeing wastewater treatment. [ABSTRACT FROM AUTHOR]

A modified internal circulation (MIC) reactor with an external circulation system was proposed and the performance of treating dyeing wastewater using both MIC and typical IC reactor were compared. Utilization of the external circulation system in the MIC reactor could dramatically improve the mixing intensity of the biomass with the wastewater and resulted in better performance. The COD removal efficiency, biogas production, volatile fatty acids and effluent color were approximately 87%, 98 L d −1 , 180 mg L −1 and 100 times, respectively, in the MIC reactor with a hydraulic retention time of 5 h and organic loading rate of 15 kg COD m −3 d −1 . The hydrodynamics of the MIC reactor under different flows rate of external circulation were also analyzed using computational fluid dynamics (CFD) method. The optimal flow rate of external circulation was 12 L min −1 , which resulted in a corresponding up-flow velocity of 40 m h −1 . The consistency of the result between experiment and simulation validated the scientificity of CFD technique applied to numerical simulation of the MIC reactor. [ABSTRACT FROM AUTHOR]

In order to improve the catalytic performance, the wool supported copper-iron bimetal complexes were prepared by adding copper ion in the wool supported iron conplex, and the effect of copper ion on the catalytic performance of wool supported copper-iron bimetal complexes was examined. Then the pseudo first-order kinetic model was employed to fit the experimental data. Finally, the dyeing wastewater after decoloration was reused for the coloration of cotton fabrics by reactive dyes. The results indicated that wool supported copper -iron bimetal complexes exhibited the higher catalytic performance in the presence of copper ions. The reactive dyes exhibited good dyeing capacity for cotton fabrics in the dyeing wastewater after decoloration . [ABSTRACT FROM AUTHOR]

Electron beam technology has been widely investigated for the degradation of recalcitrant organic pollutants in water and wastewater in laboratory scale. However, it needs verification in practical application for long-term operation. Strikingly, for the first time, we have successfully applied electron beam technology to treat the actual dyeing wastewater in capacity of 30,000 m3/d in Jiangmen city, Guangdong Province, China. The continuous monitoring data of the effluent water quality showed that electron beam technology can be used as advanced treatment process to effectively improve the removal efficiency of COD and color. The effluent COD of electron beam unit stayed between 20 and 50 mg/L when the influent COD ranged from 180 to 280 mg/L, and the color of the treated dyeing wastewater decreased to about 10 times. The operational cost of whole wastewater treatment processes was about 2.0–2.5 ¥/m3, including electron beam unit. Based on the monitoring data of more than one year's operation, it can be concluded that electron beam technology could provide a solution for refractory industrial wastewater treatment, which is a high efficient and cost-effective advanced treatment process. • Full application of electron beam technology to treat dyeing wastewater was reported. • 7 electron accelerators were used to treat wastewater with capacity of 30,000 m3/d. • The operational cost of total wastewater treatment processes was about 2.0–2.5 ¥/m3. • Electron beam technology can provide a solution for treating industrial wastewater. [ABSTRACT FROM AUTHOR]

Adsorption technique has been proven its promising advantages in the adsorptive removal of contaminants from dyeing wastewater. However, a rapid adsorption is still difficult for adsorbents due to the limitations of the common driving forces. Aromatic ring structure of organic dyes gives us inspirations to develop π - π stacking interactions to trap adsorbates. Herein, a new kind of organic polymer adsorbent with rich aromatic ring was designed to remove organic dyes. As-obtained aromatic ring-rich polymer adsorbent can capture dye molecules mainly via the enhanced π - π stacking interactions. Thus, a rapid adsorption can be achieved even the adsorption experiments were performed in a wide pH range. After contacting for 3 min, removal efficiency for methylene blue dye reached high up to 94%. Furthermore, the difficulty for regenerating dyes-adsorbed adsorbents by using NaOH or HCl also confirmed the little effect of solution pH values on π - π stacking interactions. This work provides new insight into the design of adsorbents with rich aromatic ring to improve the adsorption rate. [Display omitted] [ABSTRACT FROM AUTHOR]

A pot experiment was conducted on Stem Amaranth and Indian Spinach irrigated by groundwater (control) and seven different types of textile dyeing wastewater to investigate the accumulation of selected heavy metals like copper, zinc, chromium, and nickel in the different parts of these vegetables. The different types of dyeing wastewater were analyzed for heavy metals and compared with irrigation water quality standard. The concentrations of heavy metals in wastewater were well below than the irrigation water quality standard. The concentration of Cu and Zn were within the safe limit in the different parts of these vegetables recommended by Food and Agriculture Organization (FAO). However, the concentration of Ni in both vegetables was found higher than the recommended safe limit of Indian standard for plants irrigated with enzyme treated wastewater (D3). Moreover, the concentration of Cr was higher for plants irrigated with second wash after bath drop (D4) and mixed wastewater (D8) than Indian Standard. Therefore, the results of this research suggest that four types (D2, D5, D6 and D7) of wastewater in cotton fabric and yarn dyeing process could be reused without treatment in irrigation for the cultivation of Stem Amaranth and Indian Spinach considering heavy metals accumulation. In consequence, factory owner can save the wastewater treatment cost and as a result the dependency on groundwater for irrigation will be reduced that in turn, will ultimately save the environment. However, additional studies focusing on organic contaminant need to be carried out for checking suitability of using wastewater for irrigation. [ABSTRACT FROM AUTHOR]

Adsorption is one of the most promising decolorization techniques in dyeing wastewater treatment. Adsorption techniques for wastewater treatment have become more popular in recent years owing to their efficiency in the removal of pollutants too stable for biological methods. Dye adsorption is a result of two mechanisms (adsorption and ion exchange) and is influenced by many factors as dye/adsorbent interaction, adsorbent's surface area, particle size, temperature, pH, and contact time. The main advantage of adsorption recently became the use of low-cost materials, which reduces the procedure cost. The present review firstly introduced the technology process, research history and research hotspot of adsorption. Then, the application of adsorption in treatment of dyeing wastewaters in the past decades was summarized, revealing the impressive changes in modes, trends, and conditions. From this review article, the different philosophy of synthesis of adsorbent materials became evident. [ABSTRACT FROM AUTHOR]

Highlights: [•] Novel composite flocculant was made by PFC and DAM–ECH for dye wastewater treatment. [•] PFC–DAM–ECH provides good floc feature with polyethylene polyamine as cross-linker. [•] Low B value and high MR value are beneficial to better settlable floc formation. [•] Synergic effect promoted large size, high growth rate and wide size distribution. [•] The TWV values were highly and directly related to coagulation mechanism. [Copyright &y& Elsevier]

[Object] The study aimed to discuss the decolorization on indigo dyeing wastewater by laccase from Coriolus versicolor. [Method] Firstly, the effects of temperature, pH, indigo concentration, HBT concentration, laccase dosage on the decolorization of indigo dyeing wastewater by laccase /HBT, and then the synergism of laccase and acid cellulase was analyzed. [Result] Using ABTS as the substrate, the kinetic parameters, Km and Vmax, were 0. 318 mmol/L and 0. 035 5 mmol/(L·min) respectively. The decolorization rate of indigo reached 96. 5% when the laccase acted on indigo for 40 min with HBT as an introducer at temperature 50 °C, pH =4. 5, indigo concentration 100 mg /L, HBT concentration 0. 1% and laccase dosage 100 IU /L. Due to the synergism of laccase and acid cellulase during the bio-finishing of blue jeans, the backstaining degree of blue jeans reduced by 85% when the amount of laccase added was 15 000 IU /kg. Menawhile, the synergism of the laccase and acid cellulase decreased indigo concentration in wastewater by 83. 8%. [Conclusion] The laccase from Coriolus versicolor had a good prospect in the bio-finishing of blue jeans and the decolorization of indigo dyeing wastewater. [ABSTRACT FROM AUTHOR]

Abstract: The removal of C.I. Reactive Blue 19 dye at initial concentration of 1000mg/L was studied using iron scrap process and coagulation/flocculation by a novel synthesized Al(OH)3–PAM inorganic–organic hybrid polymer. A novel synthesized Al(OH)3–PAM was prepared using a redox initiation system while (NH4)2S2O8 and NaHSO3 were used to initiate the polymerization at 50°C in aqueous medium. The Al(OH)3–PAM was characterized using FT-IR spectroscopy, TEM, and XRD. pH of dye solution and Al(OH)3–PAM dosage have been studied while COD reduction and color removal in different settling times were investigated. The results show that 26% of (COD) content and 45% of color have been removed by iron scrap process. Meanwhile 90% of the color and 82% of COD have been removed by Al(OH)3–PAM hybrid polymer in an optimum dosage of 700mg/L and optimum effective pH between pH of 5–6. [Copyright &y& Elsevier]

Abstract: Organic modifier (PSFD) of poly-silicic-ferric (PSF) coagulant was prepared by adding dimethyldiallylammonium chloride (DMDAAC) as additives in PSF, and was characterized by Scanning Electron Microscopy (SEM), Photon Correlation Spectroscopy (PCS) and Fourier Transform Infrared Spectroscopy (FT-IR). Color removal and floc change during coagulation process in treating a simulated dyeing wastewater by PSFD were investigated compared to those of PSF. The results show that a similar silicate of cross-linking matter was generated in PSFD, and PSFD has greater adsorbtion capacity than PSF. The size of PSFD hydrolysis products was larger than that of PSF over a given concentration range. The size of PSFD hydrolysis products tended to change continuously and the small size of products disappeared after its hydrolysis. PSFD has better color removal at given dosage range than PSF, with the largest difference of 30%. The floc growth and settling velocity of PSFD were larger than those of PSF. Larger flocs of PSFD were formed from its small initial flocs over a very short period of time. The floc density of PSFD was greater than that of PSF, leading to a much less amount of PSFD flocs in the finished water than that of PSF. [Copyright &y& Elsevier]

combined process consisting of Moving-Bed Biofilm Reactors (MBBRs) with Polyurethane-Dyeing Sludge Carbonaceous Material (PU-DSCM) foam and chemical coagulation was investigated for dyeing wastewater treatment. The pilot-scale MBBR system was composed of two aerobic MBBRs in series. Each reactor was filled with 20% (v/v) of Polyurethane-Dye Sludge Carbonaceous Material foam (PU-DSCM foam) inoculated with a white-rot fungus, Phanerochaete chrysosporium, for biological treatment followed by chemical coagulation with FeCl or alum. In the MBBR process, 79% of COD and 54% of color (influent COD = 539 mg/L and color = 622 PtCo units) were removed at MLSS concentration of 2900 mg/L attached to the PU-DSCM carrier and 48 hr of short Hydraulic Retention Time (HRT) at steady state. The biologically treated dyeing wastewater was subjected to chemical coagulation. After coagulation with alum at the optimum dosage (1.55 mg alum/mg COD), 95.7% of COD and 73.4% of color were removed in overall. The combined process of fungal MBBRs and chemical coagulation has promising potential for dyeing wastewater treatment. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the removal efficiency of color and COD from industrial dyeing wastewater using paired electrochemical oxidation in a divided flow-by electrochemical reactor. The color and COD were removed by electrogenerated HOCl using a DSA (Ti/RuO2) electrode in the anodic compartment, while in the cathodic compartment, the color and COD were removed by ·OH produced by combing the cathodically generated H2O2 with Fe2+ (Fenton's reagent). Findings showed that the color was more easily removed than the COD. After passing 12,960 C through the cell, the removal efficiencies reached 98.2 % for color and 92.8 % for COD by anodic oxidation and 94.2 % for color and 78.5 % for COD by electro-Fenton oxidation. The color and COD removal efficiencies for anodic oxidation fell slightly with increasing solution pH and rose with increases in the applied current and the amount of added NaCl. In contrast, increasing the amount of added NaCl slightly lowered the removal efficiencies for electro-Fenton. The removal efficiencies rose with increasing applied current up to 0.9 A, and the optimal pH was 3.0 for electro-Fenton. The highest current efficiencies achieved were 94.8 % for anodic oxidation and 75.5 % for electro-Fenton. [ABSTRACT FROM AUTHOR]

The feasibility of application of activated carbon prepared from pyrolusite-augmented sewage sludge was investigated in batch and fixed-bed adsorption systems. An actual dyeing wastewater was chosen as the target pollutant. The results showed that the mineral supplement enhanced the properties of the activated carbon via catalyzing the formation of micro- and meso-pores during pyrolysis. For batch mode adsorption, above 80% of color and 65% of COD were sequestered within the first hour after the commencement of the adsorption and the equilibrium was reached at nearly 7 h. Removal rate of dye increased accordingly with the increase of adsorbent dosage, and the optimum pH value for dye adsorption was determined at pH=3.0. In the fixed-bed system, the breakthrough time decreased as the increase of inflow rate. Three models, Adam's-Bohart, Thomas and Yoon-Nelson models were selected, and the modeled breakthrough curves had a good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

The widespread illegal discharge of industrial wastewater in China has posed significant challenges to the effective management of industrial wastewater treatment plants (IWTPs) and caused or exacerbated critical social issues such as trans-boundary environmental pollution. This study examines two operational strategies, decentralized model and an innovative integrated model, that have been used in the industrial town of Shengze (located in Suzhou City) over the past two decades at IWTPs handling wastewater from the city’s dyeing industry. Our cost-effectiveness analysis shows that, although the operational cost of IWTPs under the integrated model is higher than under the original decentralized model, the integrated model has significantly improved IWTP performance and effectively reduced illegal discharge of industrial wastewater. As a result, the number of reported incidents of unacceptable pollution in local receiving water bodies had declined from 13 in 2000–1 in 2008. Key factors contributing to the success of the innovative integrated model are strong support from municipal and provincial leaders, mandatory ownership transfer of IWTPs to a centralized management body, strong financial incentives for proper plant management, and geographically-clustered IWTPs. [Copyright &y& Elsevier]

Dyeing process of textile consumes large quantities of water, which results in huge amounts of colored wastewater. Most of the dye wastewater treating methods focused on the treatment of wastewater after the rinsing process of dyed textile. In this paper, tetraacetylethylenediamine/hydrogen peroxide (TAED/H2O2) active oxidation (AO) system was developed to rinse dyed textile and decolorize the rinsing wastewater simultaneously. The results indicated that the decolorization ratio of the rinse effluent obtained by AO method were in the range of 51.72%-84.15% according to different dyes and the COD value decreased more than 30% compared with that of traditional rinsing process. The decolorization kinetics investigation showed that the decolorization of dyes during AO rinsing process followed the law of pseudo-first order kinetics. The result of UV-Vis and UPLC-MS analysis demonstrated that the dye was degraded into colorless organic molecular fragments and partly mineralized during the AO rinsing process. [ABSTRACT FROM AUTHOR]

This study investigates the photocatalytic degradation of dyeing wastewater by iron-rich montmorillonite (MMt) under a 25 W low-pressure mercury lamp (λ = 254 nm, I = 48.4 μW/cm2). Exposing MMt to UV irradiation worked to catalyze the photobleaching of wastewater used in the dyeing process. COD removal efficiencies of 65.0% and 74.0% were achieved in 1 g/L MMt suspensions at a pH of 3 in the absence and presence of 30 min of UV irradiation, respectively. A decolorization efficiency of 71.4% was reached with 1 g/L MMt suspensions at a pH of 3 after 30 min of UV irradiation, while only 4.9% decolorization was attained in darkness. These results indicate that iron-rich MMt is a good photocatalyst for decolorization and COD removal in wastewater from dyeing processes. A low pH value is beneficial to the decolorization of dyeing wastewater. A preliminary photocatalytic mechanism is proposed: the iron in the MMt is responsible for the decolorization of the wastewater because it produces a highly oxidative species of hydroxyl radicals (•OH). [ABSTRACT FROM AUTHOR]

A three-stage pilot-scale moving-bed biofilm reactor (MBBRs, anaerobic-anaerobic-aerobic in series) was investigated to treat textile dyeing wastewater. Each reactor was filled with 20% (v/v) of polyurethane-activated carbon (PU-AC) carrier for biological treatment. To determine the optimum operating conditions of MBBRs, the effect of PUAC carrier, its packing percentage (v/v%) and pH control on COD removal were analyzed by batch experiments. The MBBRs were inoculated with activated sludge obtained from a local dyeing wastewater treatment plant. The MBBR process removed 86% of COD and 50% of color (influent COD=608 mg/L and color=553 PtCo unit) using relatively low MLSS concentration (average 3,000 mg/L in biomass attached to PU-AC carrier) and hydraulic retention time (HRT=44 hr). The MBBR process showed a promising potential for dyeing wastewater treatment. [ABSTRACT FROM AUTHOR]

Abstract: In order to enhance the pretreatment effect of dyeing wastewater, comparison experiments of coagulation micro-bubble floatation and coagulation conventional air bubble flotation were carried out. The results demonstrated that coagulation micro-bubble flotation significantly reduced coagulant doses and enhanced the pretreatment rate, because the usage of micro-bubble generator produces fog-like micro-bubbles with diameters in tens of micrometer, which has longer preservation time in the water. In addition, the micro-bubbles could reach a higher oxygen transfer rate: the total mass-transfer coefficient of micro-bubbles was 1.1754min−1, and that of conventional air bubbles was of 0.7535min−1. Under the same conditions, the removal efficiencies of COD, color and oil for the micro-bubble floatation increased 30%, 110% and 40% respectively, compared with the conventional air bubble flotation. Furthermore, the wastewater biodegradabilities were increased from 0.290 to 0.363 after coagulation micro-bubble flotation and to 0.301 after coagulation conventional air bubble flotation. The application of the micro-bubble technology in coagulation processes may provide an efficient and cost-effective approach for the wastewater treatment. [Copyright &y& Elsevier]

Abstract: Two polyferric chloride–polyamine (PFC–EPI–DMA) dual-coagulants with different dosing methods were comparatively investigated in terms of color removal performance and floc aggregation in the treatment of synthetic disperse yellow and reactive red wastewater, and in comparison with PFC and EPI–DMA. The coagulation efficiency was studied by Jar-test, and Photometric Dispersion Analyzer 2000 (PDA 2000) was used to investigate floc aggregation process. The results showed that in two dual-coagulants treatment, PFC dosing followed by EPI–DMA dosing (PFC/EPI–DMA) achieved higher color removal rate for synthetic disperse yellow 201 wastewater, whereas reverse dosing order compared to the former (EPI–DMA/PFC) obtained better color removal performance for synthetic reactive red 24 wastewater. The optimal color removal efficiencies for treating disperse yellow 201 by PFC/EPI–DMA and reactive red 24 by EPI–DMA/PFC were both 97.5% at pH 6.0. The floc aggregation process showed that the floc growth rate of PFC/EPI–DMA was higher than that of EPI–DMA/PFC at the same dosage, whereas both Ratio and the time-weighted ratio variance (TWV) of PFC/EPI–DMA were almost lower than those of EPI–DMA/PFC in the treatment of disperse yellow 201. For reactive red 24 treatment, both floc growth rate and Ratio of EPI–DMA/PFC were higher than those of PFC/EPI–DMA, whereas TWV of EPI–DMA/PFC was lower than that of PFC/EPI–DMA. For disperse yellow 201 treated by PFC/EPI–DMA, the maximums of floc growth rate and Ratio were both reached at pH 6.0, whereas TWV was decreased as the increase of pH. For reactive red 24 treated by EPI–DMA/PFC, the maximums of three parameters were all reached at pH 4.5. [Copyright &y& Elsevier]

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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 rag/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. [ABSTRACT FROM AUTHOR]

Abstract: The anodic and indirect cathodic removals of color and COD from real dyeing wastewater were investigated simultaneously using a stacked Pt/Ti screen anode and a graphite packed-bed cathode in a divided flow-by electrochemical reactor. The anodically generated hypochlorite and cathodically generated hydrogen peroxide were the main species used to remove color and COD in the wastewater. Various experimental operating factors that can affect the removal efficiency were investigated, including the applied current density, the amount of NaCl added, the solution pH in alkaline ranges and the temperature. The color and COD removal efficiencies in the anodic chamber were much higher than those in the cathodic chamber. The overall (anodic plus cathodic) removal efficiencies increased with the applied current density, the amount of NaCl added and the temperature. In contrast, increasing the solution pH decreased the overall removal efficiency. The anodic and cathodic current efficiencies at 20mA/cm2 were 63.50% and 19.57%, respectively. In this work the total treatment cost for removing 1g COD was US $0.643 when an air cylinder was used. [Copyright &y& Elsevier]

Abstract: Three inorganic–organic dual-coagulants were comparatively evaluated in terms of color removal, zeta potential and flocculation dynamics in treating simulative reactive and disperse dyeing wastewater. The flocculation kinetics, including floc growth rate, floc size and floc size difference in the steady-state phase, was investigated using photometric dispersion analyzer (PDA). The first dual-coagulant PFC–PDADMAC was prepared by premixing polyferric chloride (PFC) and polydimethyldiallylammonium chloride (PDADMAC) before dosing. The other two were achieved by dosing PFC and PDADMAC in different order. Results indicated that PFC–PDADMAC gave higher color removal efficiency, stronger entrapment and bridging ability, higher floc growth rate, larger floc size and wider range of floc size distribution in treating Reactive Yellow K-4G. 60.2% color removal was obtained by PFC–PDADMAC at a dosage of 30mg/L. For the removal of Disperse Yellow RGFL, three dual-coagulants gave similar color removal rate, coagulation–flocculation mechanism, floc growth rate, floc size and floc size distribution. The maximal color removal (95.5%) was obtained by PFC–PDADMAC at a dosage of 30mg/L. [Copyright &y& Elsevier]

Abstract: In the present study, the possibility to reuse the indigo dyeing rinsing wastewater originating from a denim textile mill was investigated. Coagulation and filtration processes were selected as the pretreatment alternatives and applied to dyeing wastewater samples. Both physicochemical pretreatment alternatives and nanofiltration technique were optimized to produce an effluent satisfying the reuse criteria for the textile industry. The results showed that coagulation is not an effective and efficient pretreatment due to high dose of coagulant requirement. Microfiltration (MF) through 0.45 mm pore-sized membrane provided 64% removal in color and 29% removal in COD leading to a color value of 2493 Pt-Co and COD of 892 mg/L in the permeate. Furthermore, ultrafiltration (UF) applied after MF revealed additional 62% color and 4% COD removals leading to a color value of 960 Pt-Co and COD of 856 mg/L. Hence, the sequential application of MF and UF and only MF as pretreatment alternatives were found to be promising prior to the application of nanofiltration (NF). NF experiments conducted using pretreated wastewater via only MF provided 99% color and 97% COD removals leading to a color of 15 Pt-Co and a COD of 20 mg/L and hence sequential application of MF and NF was found to be the optimum treatment scheme for the reuse of the dyeing wastewater of the studied textile mill and reuse criteria was satisfied. [Copyright &y& Elsevier]

[Display omitted] • RGO was working as adsorbent to adsorb neutral red (NR) from an aqueous solution. • The adsorption product of NR/RGO was used as bind-free electrode for supercapacitors. • NR/RGO electrode gives an impressive specific capacity of 503 F g−1 at 1.0 A g−1. • A symmetrical solid-state supercapacitor based on NR/RGO has been assembled. Graphene-based materials play an important part as adsorbent for dyeing water treatment. However, the following regeneration methods for absorbents remain complex and might generate new polluting contaminants. Exploring the practical application for adsorbents remains a great challenge. Herein, the reduced graphite oxide (RGO) was used as adsorbent for adsorb neutral red (NR) from an aqueous solution, and the adsorption product of NR/RGO was used as binder-free electrode for supercapacitors. The NR/RGO electrode can supply a specific capacitance of 503 F g−1 and excellent cycle stability. Subsequently, the NR/RGO composite is used to assemble a solid-state symmetrical supercapacitor device. The assembled NR/RGO//NR/RGO device provides a moderate specific energy of 39.7 Wh kg−1 at 350 W kg−1 and an outstanding cycle stability. The use of NR/RGO composite as a binder-free electrode for a supercapacitor offers an innovative practical application of adsorption product for the graphene-based adsorbents for dyeing wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrolysis-Ce(IV) demonstrated excellent RB5 degradation and removal performance. • There is an obvious synergistic and enhanced effect between direct electrochemical oxidation process and Ce(IV) alone. • Direct electrochemical oxidation (39.5%), Ce(IV) catalytic oxidation (50.5%) and OH (1.6%) contributed much on RB5 removal in electrolysis-Ce(IV). • The background ions of HCO 3 −, PO 4 3− and HA have inhibitory effects, while Cl− has a promoting effect for RB5 removal. • Electrolysis-Ce(IV) has reasonable energy consumption. The intermediate products produced have good biochemical properties and low biological toxicity. Reactive black 5 (RB5) dyeing wastewater poses a serious threat to the water environment safety and biological life health. It is of great significance to use an enhanced type of electrolysis-Ce(IV) electrochemical oxidation technology for the efficient treatment of RB5 dyeing wastewater. In this study, the effects of single-factor experimental conditions such as cerium (Ce) ion concentration, pH, current value, different catalytic systems on RB5 degradation effect in electrolysis-Ce(IV) system were investigated. The experimental results showed a significant synergistic and enhanced effect between the direct electrochemical oxidation process and Ce(IV) treatment alone, and their combination (electrolysis-Ce(IV)) could significantly enhance the RB5 treatment with a removal efficiency up to 91.6%. In addition, the background ions HCO 3 −, Cl−, PO 4 3− and HA had an inhibitory effect on the electrolysis-Ce(IV) system, whereas Cl− had an enhanced effect. Meanwhile, reasonable energy consumption for the removal of RB5 was achieved in electrolysis-Ce(IV) with a maximum electrical energy per order (EE/O) value of 4.89 kWh·m−3. There are three possible reaction ways for RB5 degradation, and the generated organic intermediates with low molecular weight and biotoxicity, which facilitates further mineralization of the product and biodegradation. In the electrolysis-Ce(IV) system, the driving force for the oxidative removal of RB5 were direct electrochemical oxidation function, Ce(IV) ions and hydroxyl radicals, where direct electrochemical oxidation function and Ce(IV) ions were the key and dominant effect for RB5 removal. Compared with the direct electrochemical oxidation system alone, the Ce(IV) in the electrolysis-Ce(IV) system contributes much to enhancing and improving the RB5 degradation and is the key and core active degradation substance. [ABSTRACT FROM AUTHOR]

TiO2 and Fe-doped TiO2 thin films were prepared on the substrates (glass plates and glass microballs) after dipped in colloid and calcined at 500°C. The films have been characterized by UV-absorption, x-ray diffraction and atomic force microscopy (AFM). The investigated Fe-doped TiO2 (A nominal 10 wt% Fe2O3 was impregnated) thin films were obtained by sol-gel method. The characterization results suggest that the calcined thin films primarily consist of TiO2 anatase. And the light absorption curve of the TiO2 films modified with Fe showed that red shift had happened by the dope of Fe. TiO2/beads as photocatalyst were used to degrade the simulated dyeing water which contains reactive deep-blue dye (K-R). Through the degradation experiment, we found that the dope of Fe promoted the photocatalytic activities. The results showed that the dyeing water can be decomposed more effectively by the photocatalytic oxidation of Fe/TiO2 film on glass micro-balls than glass plates. [ABSTRACT FROM AUTHOR]

Three treatment methods, raw wastewater (RW) → coagulation → biological treatment (RCB), RW→ pre-ozonation → biological treatment (ROB) and RW → biological treatment → post-ozonation (RBO), were investigated to clarify their effectiveness in treating dyeing wastewater from a treatment plant. The decrease in dissolved organic carbon (DOC) was in the following order: RCB ≥ RBO > ROB. DOC removal of 200 mg/L by biological treatment of RW was clearly higher than that of 12 mg/L by ozonation. On the other hand, only DOC removal of 108 mg/L was observed by biological treatment in RW after ozonation. The decrease in biological oxygen demand (BOD5) was in the following order: ROB ≥ RCB > RBO. Because of the enhancement of biodegradability brought about by ozonation, BOD5 after ozonation in RBO was higher than that of RW after biological treatment. Color was effectively removed by ozonation for both RW and RW after biological treatment, and the decrease in color was in the following order: RBO > ROB ≥ RCB. Adsorbable organic halide formation potential (AOXFP) and toxicity unit (TU15, exposure time is 15 min) were more effectively decreased by biological treatment than by coagulation or ozonation, although the differences among RCB, ROB and RBO were very small. [ABSTRACT FROM AUTHOR]

The efficiency of polyaluminium chloride (PAC) in discoloration of synthetic dyeing wastewater composed of reactive or direct dye has been investigated, taking into account the proven advantages of PAC in water purification processes (compared to the conventional coagulants such as Al2(SO4)3, FeSO4, etc.). The efficiency of PAC was determined by UV/VIS spectroscopy, controlling the UV/VIS absorbance changes of the wastewater samples after their treatment with the appropriate amount of PAC. Coagulant concentration and pH influence on the removal efficiency was followed in order to derive the optimum results. Excellent efficiency of PAC (100%) was found for the treatment of direct dye, Cuprophenil Blau 3 GL, at optimal pH=7.1 and concentration of 15 mg/L Al. The optimal results for reactive dye Bezaktiv Türkisblau V-G, enabling almost 80% dye removal, were obtained at pH=7.1 and PAC concentration of 20 mg/L Al. [ABSTRACT FROM AUTHOR]

Dyeing wastewater was known to have strong color and refractory organic pollutants. In this study irradiation alone was used for dyes wastewater treatment. This paper studies the effect of the concentrations of pollutants to its removal at various dosages using electron beam technology. Irradiation was effective in removing the highly colored and refractory organic compounds. The color removal for initial concentrations of 255 CU, 520 CU, 990 CU and 1900 CU treated using irradiation at 0.5kGy were 61%, 48%, 28% and 16%, respectively. However, at the dose of 108kGy and higher, the color removal between 87% and 96% were recorded with no apparent trend. COD removal also reported similar trend but at relatively lower removal percentage. The COD removal at 0.5kGy for initial COD concentrations of 57mg/l and 515mg/l were 10% and 0%, respectively. At irradiation dose of 108kGy, the removal for initial COD concentrations of 57mg/l and 515mg/l were 37% and 13%, respectively. This showed that concentrations of pollutants and dose of irradiation applied to remove color and COD were dependent to each other. [Copyright &y& Elsevier]

The decolorization and reduction of COD of dyeing wastewater from a cotton textile mill was conducted using catalytic thermal treatment (thermolysis) accompanied with/without coagulation. Thermolysis in presence of a homogeneous copper sulphate catalyst was found to be the most effective in comparison to other catalysts (FeCl3, FeSO4, CuO, ZnO and PAC) used. A maximum reduction of chemical oxygen demand (COD) and color of dyeing wastewater of 66.85% and 71.4%, respectively, was observed with a catalyst concentration of 5kg/m3 at pH 8. Commercial alum was found most effective coagulant among various coagulants (aluminum potassium sulphate, PAC, FeCl3 and FeSO4) tested during coagulation operations, resulting in 58.57% COD and 74% color reduction at pH 4 and coagulant dose of 5kg/m3. Coagulation of the clear fluid (supernatant) obtained after treatment by thermolysis at the conditions previously used resulted in an overall reduction of 89.91% COD and 94.4% color at pH 4 and a coagulant dose of 2kg/m3. The application of thermolysis followed by coagulation, thus, is the most effective treatment method in removing nearly 90% COD and 95% color at a lower dose of coagulant (2kg/m3). The sludge thus produced would contain lower inorganic mass coagulant and, therefore, less amount of inorganic sludge. [Copyright &y& Elsevier]

Dyeing wastewater is notorious for its non-readily-biodegradability because it contains various kinds of refractory chemicals. To set up a strategy for controlling the dyeing wastewater discharged into conventional wastewater treatment plants, obtaining bio-kinetic information such as maximum specific growth rate (µ max ) and half saturation constant (K s ) should first be done. To estimate the biodegradability of the dyeing wastewater, bio-kinetic constants of the artificially formulated dyeing wastewater containing 33 different dyes and auxiliaries were determined by using a respirometer. Activated sludge acclimated to the artificial dyeing wastewater was inoculated to the respirometer and the bio-kinetic constants were determined from oxygen uptake data. The µ max was found to 0.06 hr−1, which is 3 to 15 times smaller than that of the typical activated sludge for sewage treatment. The K s was found to 210 mg/L, which was 3.5 to 21 times higher than that of the normal activated sludge. [ABSTRACT FROM AUTHOR]

This work investigates the removal of color from wastewater that contains low dyestuff concentrations by the Electro-Fenton process. The color was removed by in situ electrogenerated hydrogen peroxides at a three-dimensional graphite cathode with added ferrous sulfates. Experimental runs were conducted to evaluate the effect of the operating parameters, such as the oxygen contact mode, the oxygen sparging rate, the applied current density, the concentration of ferrous ions, the solution temperature and the pH among others, on the removal of color. The removal efficiency of the color in the cathodic chamber reached 70.6% under specified operation conditions in 150min. The removal efficiency was controlled by the mass transfer when the oxygen-sparging rate was less than 0.3dm3/min for the reactor configuration herein. The optimal applied current density was 68A/m2 when the energy consumption was considered. The highest removal efficiency was obtained by adding 20mM Fe(II) to the solution. The optimal solution pH was 3 in this work. The temperature negatively affected color removal. [Copyright &y& Elsevier]

Five different kinds of dye aqueous solutions (Direct Red 75, 80 and 81, and Direct Yellow 8 and 27) were treated with nanofiltration (NF) polyamide (PA) composite membranes to obtain basic information on the dyeing wastewater reuse. The separation of dyes by the NF PA membrane appeared to be a good process for the effective removal of dyes from dyeing wastewater. The extent of the separation of dyes by the membrane was almost 100% for all of the dyes used, producing colorless water. When artificial dyeing wastewater containing Direct Red 75, PVA, NaCl and Na2SO4 as components of the wastewater was used as a feed solution for the membrane separation process, the separation efficiency turned out to be good, especially when one of the chemical coagulants, alum, was used for the pretreatment of the artificial dyeing wastewater. About 20% of improvement of flux was obtained by the pretreatment of the wastewater. [Copyright &y& Elsevier]

The ozonizing – biological aerated filter process was used to treat the acid rose dye containing wastewater. The most suitable conditions were identified as follows: the mass ratio of ozone to dye=4.5, temperature t =18–25°C, HRT=3h and gas/liquid=4:1. Experimental results showed that ozonizing process had an excellent de-color efficiency and could improve the biodegradability of wastewater. With ozonizing the BOD/COD ratio increased from 0.18 to 0.36, and as a result, the subsequent biological aerated filter could be more effective for further reducing COD and SS concentrations, especially for wastewater with low concentration of SS and COD. After treatment the effluent COD was less than 40mg/L, SS about 50mg/L and color less than 20°. It can meet the water quality standards of the treated water reused for industry cooling water. [Copyright &y& Elsevier]

Adding iron salt or iron hydroxide to sludgemixed liquor in an aeration tank of a conventional activated sludge processes (bioferric process) can simultaneously improve the sludge’s filterability and enhance the system’s treatment capacity. In view of this, Fe(OH)3 was added to a submerged membrane bioreactor (SMBR) to enhance the removal efficiency and to mitigate membrane fouling. Bioferric process and SMBR were combined to create a novel process called Bioferric-SMBR. A side-by-side comparison study of Bioferric-SMBR and common SMBR dealing with dyeing wastewater was carried out. Bioferric-SMBR showed potential superiority, which could enhance removal efficiency, reduce membrane fouling and improve sludge characteristic. When volumetric loading rate was 25% higher than that of common SMBR, the removal efficiencies of Bioferric-SMBR on COD, dye, and NH4 +-N were 1.0%, 9.5%, and 5.2% higher than that of common SMBR, respectively. The trans-membrane pressure of Bioferric-SMBR was only 36% of that in common SMBR while its membrane flux was 25% higher than that of common SMBR. The stable running period in Bioferric-SMBR was 2.5 times of that in common SMBR when there was no surplus sludge discharged. The mixed liquor suspended solids concentration of Bioferric-SMBR was higher than that of common SMBR with more diversified kinds of microorganisms such as protozoans and metazoans. The mean particle diameter and specific oxygen uptake rate of Bioferric-SMBR were 3.10 and 1.23 times the common SMBR, respectively. [ABSTRACT FROM AUTHOR]

The effects of pre-ozonation and subsequent biological treatment process on the decrease in dissolved organic carbon (DOC) and color were investigated in a test-scale plant of 5 m3/d capacity using actual raw wastewater (RW) from a dye works. Ozone dosage rate and contacting time were around 70 mg/L on average and 30 min, respectively. The DOC concentration was gradually decreased from 36.1 to 19.3 mg/L on average through the process and the DOC removal rates were 24.4% after ozonation and 46.5% after subsequent biological treatment. The average color value was rapidly decreased from 1.75 to 0.20 after ozonation, and the color removal rate was 88.6%. The values of adsorbable organic halide formation potential (AOXFP) and trihalomethane formation potential (THMFP) were gradually decreased by each treatment process, indicating the increased safety of the treated water. Slight morphological differences due to decomposition of the predominant bacteria by residual ozone were observed. The DOC removal rate brought about by pre-ozonation was slightly higher than that by the process consisted of biological treatment and post-ozonation, although no obvious difference in the color removal was observed between them. [ABSTRACT FROM AUTHOR]