Search

Textile dyeing wastewater is characterized by low biodegradability and high nitrogen strength, which is difficult to meet the increasingly stringent discharge requirements. Therefore, the tertiary nutrient and refractory organics removal is considered and aerated biofilter is often adopted. However, the aerobic condition and carbon source shortage restrict tertiary biological nitrogen removal. In this study, iron scrap was introduced as the filter medium to enhance the pollutant removal capacity, and three aerobic biofilters were constructed. Biofilter Fe-CE was filled with iron scrap and ceramisite; biofilter Fe-AC was added with iron scrap and granular activated carbon, and biofilter CE only had ceramisite to pad as control system. After the biofilters were acclimatized by synthetic wastewater and actual dyeing wastewater, the optimal operation parameters based on nitrogen removal were determined as pH 7, gas-water ratio 5:1, hydraulic retention time 8 h and C/N ratio 8.5:1. The iron scraps improved total nitrogen (TN) removal significantly, with TN removal efficiency of 68.7% and 57.3% in biofilter Fe-AC and biofilter Fe-CE, comparing with biofilter CE of 29.9%. Additionally, phosphorus and COD had better removal performance as well when iron scrap existed. Further investigation interpreted the reason for iron's facilitating effect on tertiary nutrient and refractory organics removal. The introduction of iron scrap made the habitat conditions such as pH values, DO concentrations and biomass contents inside the biofilters change towards the direction beneficial for pollutant elimination especially for nitrogen removal. In iron containing biofilters, the majority of nitrogen, phosphorus and organic pollutants were removed in the iron scrap layers, and more pollutants types appeared, implying that iron triggered pollutants to go through more diverse degradation or transformation pathways. Moreover, the phylum Proteoabcteria dominated in samples of ceramisite-containing biofilters, with abundances more than 40%. The iron scrap existence increased the abundances of phyla Bacteroidetes and Firmicutes, and triggered higher abundance of denitrification bacteria., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Azo dye is a type of reactive dyes with a stable structure. Its discharge into the environment affects the human health and growth of aquatic organisms. The color and nitrogen removal through an integrated hydrolysis/acidification and anoxic/aerobic (AO) process for the treatment of wastewater containing reactive red 2 (RR2) was investigated. The color, chemical oxygen demand (COD), and ammonia nitrogen were removed efficiently, with removal efficiencies of 71.0%, 92.2%, and 83.5%, respectively. The dominant azo dye degradation bacterium in the hydrolysis/acidification reactor was Desulfovibrio . The dominant nitrifying bacterium in the AO reactor was Nitrospira , while the denitrifying bacteria were Thauera and Dechloromonas . When increasing the hydrolysis/acidification temperature from 25℃ to 35℃, the color removal efficiency improved by 141.2%. When the concentration of COD increased from 200 mg·L -1 to 800 mg·L -1 at 25℃, the color removal efficiency improved by 208.9%. Nitrite accumulation occurred in the AO reactor with a nitritation efficiency of 73.8%. The RR2 did not inhibit the nitrification, while aniline inhibited the nitrification. At an aniline concentration of 6 mg·L -1 , the ammonia oxidation was the slowest.

Heterogeneous photocatalysis namely titanium dioxide (TiO 2 ) supported on coconut shell biochar (BC) was synthesized by sol-gel method (calcined at 450 °C) in the paper, which was innovatively applied to the decolorization of Reactive Brilliant Blue KN-R. The transmission electron microscopy (TEM) and X-ray diffraction patterns (XRD) results demonstrated that anatase TiO 2 film was firmly immobilized on the surface and pores of BC. The photocatalysis tests under UV high pressure xenon lamp (300 W) showed highest decolorization efficiency occurred at strong acid and alkali conditions (pH = 1 and 11) reached as 99.71% and 96.99% respectively within 60 min. Therefore, the TiO 2 /BC composites demonstrated both photocatalytic and adsorption capacity on KN-R decolorized, and presented quite durable and reusable in regeneration cycles, indicating a widely application possibility in anthraquinones dyeing wastewater treatment., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In present study, a hydrolysis acidification (HA) reactor was used for simulated dyeing wastewater treatment. Co-substrates included starch, glucose, sucrose, yeast extract (YE) and peptone were fed sequentially into the HA reactor to enhance the HA process effects. The performance of the HA reactor and the microbial community structure in HA process were investigated under different co-substrates conditions. Results showed that different co-substrates had different influences on the performance of HA reactor. The highest decolorization (50.64%) and COD removal rate (60.73%) of the HA reactor were obtained when sucrose was as the co-substrate. And it found that carbon co-substrates starch, glucose and sucrose exhibited better decolorization and higher COD removal efficiency of the HA reactor than the nitrogen co-substrates YE and peptone. Microbial community structure in the HA process was analyzed by Illumina MiSeq sequencing. Results revealed different co-substrates had different influences on the community structure and microbial diversity in HA process. It was considered that sucrose could enrich the species such as Raoultella, Desulfovibrio, Tolumonas, Clostridium, which might be capable of degrading the dyes. Sucrose was considered to be the best co-substrate of enhancing the HA reactor's performance in this study. This work would provide deep insight into the influence of many different co-substrates on HA reactor performance and microbial communities in HA process., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A superparamagnetic graphene oxide (GO)/Fe 3 O 4 nanocomposite (MGO) was prepared by a facile in situ co-precipitation strategy, resulting in a prospective material for the application of graphene oxide in wastewater treatment. MGO was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The prepared adsorbent showed a high adsorption efficiency relevant to the purification of dye-contaminated wastewater and could be readily magnetically separated. The maximum adsorption capacity was ca. 546.45 mg g -1 for the common cationic dye methylene blue (MB) and ca. 628.93 mg g -1 for the anionic dye Congo red (CR). The adsorption processes fit the pseudo-second-order kinetic model well, which revealed that these processes may involve the chemical interaction between adsorbate and adsorbent. The thermodynamic parameters indicated that the adsorption reaction was an endothermic and spontaneous process. Furthermore, the prepared magnetic adsorbent had a wide effective pH range from 5 to 11 and showed good stability after five reuse cycles. The synthetic MGO showed great potential as a promising adsorbent for organic contaminant removal in wastewater treatment.

The reverse osmosis (RO) process is of great significance for the desalination and reclamation of dyeing wastewater. However, fouling of RO membranes has been a severe problem and key limiting factor in the widespread application of the RO process. The operating characteristics and fouling characteristics of a RO membrane system for desalination of dyeing wastewater were investigated in an industrial park in Guangdong Province. The results showed that the COD and turbidity of RO influent after ozone oxidation-sand filtration-ultrafiltration (UF) processes were 12.4 mg ·L -1 and<1 NTU, respectively, with a stable desalination rate of the RO system of around 98%. The COD and turbidity of the RO effluent were 0.7 mg ·L -1 and 0.12 NTU, respectively. However, after 3 years of operation, the pressure drop across the membrane reached 0.6 MPa, and the permeate flux decreased to 120 m 3 ·h -1 , which could not be restored to its original flux by chemical cleaning. The organic and inorganic matter occupied (53.5±0.2)% and (46.5±0.2)% of the deposits on the RO membrane, respectively, suggesting both organic and inorganic fouling were the main problems for the RO membrane. Si, Al, and Ca were major inorganic elements on the RO membrane. Large amounts of Si, Al, and organic matter deposited on the RO membrane were dissolved easily by alkaline (NaOH) solution than acid (HCl) solution.

Nano zero-valent iron/activated carbon (nZVI/AC) composites were prepared via liquid phase chemical precipitation and then characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and Brunauer-Emmett-Teller theoretical methods for an analysis of the structure, morphology, physical and chemical characteristics of the composites. The effects of the reaction system, nZVI loading, initial pH, and dosage on antimony removal were investigated and the removal mechanisms were discussed. These results indicate that nZVI/AC can be successfully prepared via liquid phase chemical precipitation. In an N 2 atmosphere, a dosage of 0.2 g·L -1 , 15% nZVI/AC with an initial pH of 7.5 (the pH of raw water) was prepared. After a reaction duration of 2 h, the removal rate of Sb(Ⅴ) had reached 76.2% and the effluent concentration had decreased to only 23.8 μg·L -1 . These results show that Fe 2+ plays a major mechanistic role in the removal of Sb(Ⅴ) from the system and is the major active substance in the reaction process. In combination with an analysis of elemental Sb on the surface of the nZVI/AC before and after reaction, the removal process relies on the reduction of Fe(0) and Fe 2+ , Sb(Ⅴ) reducted into Sb(Ⅲ) and through adsorption removal.

Domestic wastewater treatment plants as a reservoir of antibiotic resistance genes (ARGs) have received much attention, but the effect of dyes on the propagation of ARGs has rarely been investigated. In this study, we investigated the differences in distributions of ARGs and microbial communities using high-throughput qPCR and 16S rRNA gene sequencing, respectively, between mixed (dyeing and domestic) wastewater and domestic sewage. The relative abundance of ARGs in inflows of mixed wastewater (IW2 and IW3) was higher than that of domestic wastewater (IW1). The relative abundance of mobile genetic elements in the inflow of textile dyeing wastewater (IDW3) was 3- to 13-fold higher than that in other samples. Moreover, in IDW3, some distinct high abundance ARGs, particularly operons encoding efflux pumps (such as acrR-01, acrB-01 and acrF), were significantly correlated with Streptococcus of the Firmicutes. To explore why the abundance of ARGs was relatively high in mixed wastewater, six representative types of organic compounds in textile dyeing wastewater were used to test the effect on plasmid-based conjugative transfer from E. coli HB101 to E. coli NK5449. These six compounds all facilitated the transfer of resistance-carrying RP4 plasmid, and the highest transfer frequency (approximately 10 -5 -10 -3 ) was over 4- to 200-fold higher than that in the control group (approximately 10 -6 -10 -5 ). These results illustrated that the six common residual compounds, particularly low-dose substances in IDW3, could facilitate the dissemination of ARGs in aquatic environments. More importantly, this study revealed for the first time that dyeing contaminants influenced horizontal gene transfer (HGT) of ARGs., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

In this study, performance of hydrolysis acidification process treating simulated dyeing wastewater containing azo and anthraquinone dyes in different stages was investigated. The decolorization ratio, COD Cr removal ratio, BOD 5 /COD Cr value, and volatile fatty acids (VFAs) production were almost better in stage 1 than that in stage 2. Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) confirmed the biodegradation of Reactive Black 5 (RB5) and Remazol Brilliant Blue R (RBBR) in hydrolysis acidification process. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analyses revealed that significant difference of microbial community structures existed in stage 1 and 2. The dominant species in stage 1 was related to Bacteroidetes group, while the dominant species in stage 2 was related to Bacteroidetes and Firmicutes groups. From the results, it could be speculated that different dyes' structures might have significant influence on the existence and function of different bacterial species, which might supply information for bacteria screening and acclimation in the treatment of actual dyeing wastewater.

The ability of the bacterial strain Acidithiobacillus thiooxidans to remove sulfur blue 15 (SB15) dye from water samples was examined. This bacterium could not only oxidize sulfur compounds to sulfuric acid but also promote the attachment of the cells to the surface of sulfidic particles, therefore serving as an efficient biosorbent. The biosorption isotherms were better described by the Langmuir equation than by the Freundlich or Dubinin-Radushkevich equation. Also, the biosorption process followed the pseudo-second-order kinetics. At pH 8.3 and SB15 concentrations up to 2000 mg L(-1) in the biomass/mineral salt solution, the dye removal and decolorization were 87.5% and 91.4%, respectively, following the biosorption process. Biodegradation was proposed as a subsequent process for the remaining dye (250-350 mg L(-1)). A central composite design was used to analyze independent variables in the response surface methodology study. Under the optimal conditions (i.e., initial dye concentration of 300 mg L(-1), initial biomass concentration of 1.0 g L(-1), initial pH of 11.7, and yeast extract dose of 60 mg L(-1)), up to 50% of SB15 was removed after 4 days of biodegradation., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

This study investigated the applicability of membrane distillation (MD) to treat dyeing wastewater discharged by the textile industry. Four different dyes containing methylene blue (MB), crystal violet (CV), acid red 18 (AR18), and acid yellow 36 (AY36) were tested. Two types of hydrophobic membranes made of polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) were used. The membranes were characterized by testing against each dye (foulant-foulant) and the membrane-dye (membrane-foulant) interfacial interactions and their mechanisms were identified. The MD membranes possessed negative charges, which facilitated the treatment of acid and azo dyes of the same charge and showed higher fluxes. In addition, PTFE membrane reduced the wettability with higher hydrophobicity of the membrane surface. The PTFE membrane evidenced especially its resistant to dye absorption, as its strong negative charge and chemical structure caused a flake-like (loose) dye-dye structure to form on the membrane surface rather than in the membrane pores. This also enabled the recovery of flux and membrane properties by water flushing (WF), thereby direct-contact MD with PTFE membrane treating 100 mg/L of dye mixtures showed stable flux and superior color removal during five days operation. Thus, MD shows a potential for stable long-term operation in conjunction with a simple membrane cleaning process, and its suitability in dyeing wastewater treatment., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Refractory pollutants in raw and treated dyeing wastewaters were characterized using fractional molecular weight cut-off, Ultraviolet-vis spectrophotometry, and high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI/MS). Significant organics and color compounds remained after biological (pure-oxygen activated sludge) and chemical (Fenton) treatments at a dyeing wastewater treatment plant (flow rate ∼100,000m(3)/d). HPLC-ESI/MS analysis revealed that some organic compounds disappeared after the biological treatment but reappeared after the chemical oxidation process, and some of that were originally absent in the raw dyeing wastewater was formed after the biological or chemical treatment. It appeared that the Fenton process merely impaired the color-imparting bonds in the dye materials instead of completely degrading them. Nevertheless, this process did significantly reduce the soluble chemical oxygen demand (SCOD, 66%) and color (73%) remaining after initial biological treatment which reduced SCOD by 53% and color by 13% in raw wastewater. Biological treatment decreased the degradable compounds substantially, in such a way that the following Fenton process could effectively remove recalcitrant compounds, making the overall hybrid system more economical. In addition, ferric ion inherent to the Fenton reaction effectively coagulated particulate matters not removed via biological and chemical oxidation., (Copyright © 2015 Elsevier B.V. All rights reserved.)

An innovative combination using a sequencing batch reactor (SBR) with iron filing filtration was developed for the treatment of dyeing wastewater. Iron filing filtration served as a pretreatment process to improve the biodegradability of wastewater. Thus the potential of a sequencing batch reactor can be better exerted to decompose toxic substances more efficiently. The experimental results demonstrated that 85% COD and over 90% BODS and color can be removed when the influent COD ranged from 1000 mg/L to 1500 mg/L, BODS from 200 mg/L to 400 mg/Land color from 200 to 800 times. The combination processes were specifically suited for the treatment of dyeing wastewater containing oxidative dyes. [ABSTRACT FROM AUTHOR]

As one of the main pollution sources in Hong Kong, the textile dyeing and finishing industry creates a significant proportion of water pollution in nearby harbor zones. Generally speaking, conventional biological treatment processes have difficulties in degrading many dye chemicals causing high COD and color in dyeing wastewaters. Studies using physical and chemical processes to further reduce COD and colour from dyeing wastewater have been intensively reported. The use of a photocatalytic process in the presence of TiO2 to degrade many different types of dye chemicals has been confirmed. However, how to efficiently separate and reuse TiO2 from treated wastewater became a notable problem in the application of a TiO2photo-oxidation process. This study aims to develop an advanced treatment process for dyeing wastewater treatment. In which dyeing wastewater was initially treated by an Intermittently Decanted Extended Aeration (IDEA) reactor to initially remove those biodegradable matters and further treated by a TiO2 photocatalytic reactor as advanced treatment for complete decolorization and high COD removal. Suspended TiO2 powder used in photooxidation was separated from slurry by a membrane filter and recycled to the photoreactor continuously. The results demonstrated that photocatalytic-oxidation process could degrade those non-biodegradable organic substances in the effluent treated by the biological treatment process and also remove the colour from the effluent completely. TiO2, as catalyst,was successfully recovered by a membrane filter and continuously reused in the photoreactor. The quality of dyeing wastewater treated by the advanced treatment process can be good enough for reuse in the textile dyeing processes. [ABSTRACT FROM AUTHOR]

The treatment of dyeing and printing wastewater from the textile industry by oxidation was studied. The reaction was carried out in a two-litre high pressure reactor. In order to promote the oxidation of organic pollutants present in the wastewater, experiments were conducted using various catalysts including metal salts, metal oxides, and porous alumina supported metals. All catalysts tested were able to enhance the conversion of organic compounds in wastewater, shorten the reaction time, and lower the reaction temperature. The alumina supported catalyst has an advantage over other catalysts in that it can be easily separated from the treated wastewater by filtration and recycled. The conditions in preparing the catalyst supported by porous alumina were experimentally optimised. [ABSTRACT FROM AUTHOR]