Elimination and ecotoxicity evaluation of phthalic acid esters from textile-dyeing wastewater

Microcontaminants and microplastics in water from the textile sector: a review and a database of physicochemical properties, use in the textile process, and ecotoxicity data for detected chemicals

Microcontaminants (MCs) and microplastics (MPs) originating from the textile sector are today receiving a great deal of attention due to potential environmental concerns. Environmental pressures and impacts related to the textile system include not only the use of resources (e.g., water) but also the release of a wide variety of pollutants. This review's main objective is to highlight the presence of textile MCs and MPs in water, in their full path from textile factories (from raw materials to the final product) to wastewater treatment plants (WWTPs), and finally to the receiving surface waters. Their environmental fate and ecotoxicity were also addressed. Overall, more than 500 compounds were found, many of which are so called "contaminants of environmental concern" such as per- and polyfluoroalkyl substances (PFAS) and alkylphenol compounds. A database of physicochemical properties, ecotoxicity, and place of detection (specific textile process, WWTP, surface water or sediment) (classification by several international agencies) was compiled for the chemical detected. Preliminary risk assessment was conducted for those MCs for which the reported environmental concentrations exceeded the Predicted No Effect Concentration (PNEC). These chemicals were some nonylphenols, nonylphenol ethoxylates and organophosphate esters. Among MPs, polyester and nylon fibres were the most abundant. The highest concentration of MPs was reported in sludge (about 1.4 × 106 MPs per kg) compared to wastewater and surface water which showed MP concentrations at least two orders of magnitude lower. The role of transboundary contamination due to the release of chemicals from imported textile products was also assessed.

Bioremediation of azo dye: A review on strategies, toxicity assessment, mechanisms, bottlenecks and prospects

The synthetic azo dyes are widely used in the textile industries for their excellent dyeing properties. They may be classified into many classes based on their structure and application, including direct, reactive, dispersive, acidic, basic, and others. The continuous discharge of wastewater from a large number of textile industries without prior treatment poses detrimental effects on the environment and human health. Azo dyes and their degradation products are extremely poisonous for their carcinogenic, teratogenic and mutagenic nature. Moreover, exposure to synthetic azo dyes can cause genetic changes, skin inflammation, hypersensitivity responses, and skin irritations in persons, which may ultimately result in other profound issues including the deterioration of water quality. This review discusses these dyes in details along with their detrimental effects on aquatic and terrestrial flora and fauna including human beings. Azo dyes degrade the water bodies by increasing biochemical and chemical oxygen demand. Therefore, dye-containing wastewater should be effectively treated using eco-friendly and cost-effective technologies to avoid negative impact on the environment. This article extensively reviews on physical, chemical and biological treatment with their benefits and challenges. Biological-based treatment with higher hydraulic retention time (HRT) is economical, consumes less energy, produces less sludge and environmentally friendly. Whereas the physical and chemical methods with less hydraulic retention time is costly, produces large sludge, requires high dissolved oxygen and ecologically inefficient. Since, biological treatment is more advantageous over physical and chemical methods, researchers are concentrating on bioremediation for eliminating harmful azo dye pollutants from nature. This article provides a thorough analysis of the state-of-the-art biological treatment technologies with their developments and effectiveness in the removal of azo dyes. The mechanism by which genes encoding azoreductase enzymes (azoG, and azoK) enable the natural degradation of azo dyes by bacteria and convert them into less harmful compounds is also extensively examined. Therefore, this review also focuses on the use of genetically modified microorganisms and nano-technological approaches for bioremediation of azo dyes.

Season and side-chain length affect the occurrences and behaviors of phthalic acid esters in wastewater treatment plants

Emerging pollutants (EPs) are prevalent in aquatic environments globally. Researchers strive to understand their occurrence and behavior prior to their release into the environment. In this study, we examined five wastewater treatment plants (WWTPs), collected 50 wastewater samples and 10 sludge samples. We explored the sources and destinations of phthalic acid esters (PAEs) within these WWTPs using mass balance equations. Wastewater treatment diminished the frequency and concentration of PAEs, and decreased the fraction of short-chain PAEs. We confirmed the increased concentration of PAEs post-primary treatment and modified the mass balance equation. Calculations suggest that weaker "the mix" in winter than in summer and stronger sedimentation in winter than in summer resulted in high efficiency of PAEs removal by winter wastewater treatment. The mass flux of biodegradation was influenced by the combination of biodegradation efficiency and the strength of the particular type of PAEs collected, with no seasonal differences. Mass fluxes for sludge sedimentation were mainly influenced by season and were higher in winter than in summer. This study enhances our understanding of emerging pollutants in manual treatment facilities and offers insights for optimizing wastewater treatment methods for water professionals.

Phthalate Acid Esters (PAEs) in Indoor Dust from Decoration Material Stores: Occurrence, Sources, and Health Risks

Phthalate acid esters (PAEs) are one of the most widely used plasticizers globally, extensively employed in various decoration materials. However, studies on the impact of these materials on indoor environmental PAE pollution and their effects on human health are limited. In this study, forty dust samples were collected from four types of stores specializing in decoration materials (flooring, furniture boards, wall coverings, and household articles). The levels, sources, exposure doses, and potential health risks of PAEs in dust from decoration material stores were assessed. The total concentrations of Σ9PAE (the sum of nine PAEs) in dust from all decoration-material stores ranged from 46,100 ng/g to 695,000 ng/g, with a median concentration of 146,000 ng/g. DMP, DEP, DBP, and DEHP were identified as the predominant components. Among all stores, furniture board stores exhibited the highest Σ9PAE (159,000 ng/g, median value), while flooring stores exhibited the lowest (95,300 ng/g). Principal component analysis (PCA) showed that decoration materials are important sources of PAEs in the indoor environment. The estimated daily intakes of PAEs through non-dietary dust ingestion and dermal-absorption pathways among staff in various decoration-material stores were 60.0 and 0.470 ng/kg-bw/day (flooring stores), 113 and 0.780 ng/kg-bw/day (furniture board stores), 102 and 0.510 ng/kg-bw/day (wall covering stores), and 114 and 0.710 ng/kg-bw/day (household article stores). Particularly, staff in wall-covering and furniture-board stores exhibited relatively higher exposure doses of DEHP. Risk assessment indicated that although certain PAEs posed potential health risks, the exposure levels for staff in decoration material stores were within acceptable limits. However, staff in wall covering stores exhibited relatively higher risks, necessitating targeted risk-management strategies. This study provides new insights into understanding the risk associated with PAEs in indoor environments.

The concentrations and behavior of classic phthalates and emerging phthalate alternatives in different environmental matrices and their biological health risks

Because of their excellent plasticity, phthalates or phthalic acid esters (PAEs) are widely used in plastic products. However, due to the recognized toxicity of PAEs and legislative requirements, the production and use of emerging PAE alternatives have rapidly grown, such as di-isononyl cyclohexane-1,2-dicarboxylate (DINCH) and di(2-ethylhexyl) terephthalate (DEHTP) which are the primary replacements for classic PAEs. Nowadays, PAEs and emerging PAE alternatives are frequently found in a variety of environmental media, including the atmosphere, sludge, rivers, and seawater/sediment. PAEs and emerging PAE alternatives are involved in endocrine-disrupting effects, and they affect the reproductive physiology of different species of fish and mammals. Therefore, their presence in the environment is of considerable concern due to their potential effects on ecosystem function and public health. Nevertheless, current research on the prevalence, destiny, and conduct of PAEs in the environment has primarily focused on classic PAEs, with little attention given to emerging PAE alternatives. The present article furnishes a synopsis of the physicochemical characteristics, occurrence, transport, fate, and adverse effects of both classic PAEs and emerging PAE alternatives on organisms in the ecosystem. Our analysis reveals that both classic PAEs and emerging PAE alternatives are widely distributed in all environmental media, with emerging PAE alternatives increasingly replacing classic PAEs. Various pathways can transform and degrade both classic PAEs and emerging PAE alternatives, and their own and related metabolites can have toxic effects on organisms. This research offers a more extensive comprehension of the health hazards associated with classic PAEs and emerging PAE alternatives.

Multi-source exposure and health risks of phthalates among university students in Northeastern China

The endocrine disruptor phthalates (PAEs) are widely used as important chemical additives in a variety of areas around the globe. PAEs are toxic to reproduction and development and may adversely affect the health of adolescents. Risk assessments of exposure to PAEs from different sources are more reflective of actual exposure than single-source assessments. We used personal exposure parameters to estimate the dose of PAEs to 107 university students from six media (including dormitory dust, dormitory air, clothing, food, disposable food containers, and personal care products (PCPs)) and three exposure routes (including ingestion, inhalation, and dermal absorption). Individual factors and lifestyles may affect PAE exposure to varying degrees. Based on a positive matrix factorization (PMF) model, the results indicated that the main sources of PAEs in dust were indoor building materials and plastics, while PCPs and adhesives were the major sources of airborne PAEs. The relative contribution of each source to PAE exposure showed that food and air were the primary sources of dimethyl phthalate (DMP) and dibutyl phthalate (DBP). Air source contributed the most to diethyl phthalate (DEP) exposure, followed by PCPs. Food was the most significant source of diisobutyl phthalate (DiBP), benzyl butyl phthalate (BBP), and bis(2-ethylhexyl) phthalate (DEHP) exposure. Additionally, the exposure of DEHP to dust was not negligible. The ingestion pathway was the most dominant among the three exposure pathways, followed by dermal absorption. The non-carcinogenic risk of PAEs from the six sources was within acceptable limits. DEHP exhibits a low carcinogenic risk. We suggest university students maintain good hygienic and living habits to minimize exposure to PAEs.

Innovations in textile wastewater management: a review of zero liquid discharge technology

Zero liquid discharge (ZLD) technology emerges as a transformative solution for sustainable wastewater management in the textile industry, emphasizing water recycling and discharge minimization. This review comprehensively explores ZLD's pivotal role in reshaping wastewater management practices within the textile sector. With a primary focus on water recycling and minimized discharge, the review thoroughly examines the economic and environmental dimensions of ZLD. Additionally, it includes a comparative cost analysis against conventional wastewater treatment methods and offers a comprehensive outlook on the global ZLD market. Presently valued at US $0.71 billion, the market is anticipated to reach US $1.76 billion by 2026, reflecting a robust annual growth rate of 12.6%. Despite ZLD's efficiency in wastewater recovery, environmental challenges, such as heightened greenhouse gas emissions, increased carbon footprint, elevated energy consumption, and chemical usage, are discussed. Methodologies employed in this review involve an extensive analysis of existing literature, empirical data, and case studies on ZLD implementation in the textile industry worldwide. While acknowledging existing adoption barriers, the review underscores ZLD's potential to guide the textile industry toward a more sustainable and environmentally responsible future.

Occurrence and correlation of microplastics and dibutyl phthalate in rivers from Pearl River Delta, China

Microplastics have been identified as the novel contaminants in various environments. Phthalates would be released from plasticized microplastics into a riverine environment while transporting to a marine region, but data on their relationship in rivers have been scarce. In this study, the occurrence, distribution and correlation of microplastics and dibutyl phthalate (DBP) in two rivers from the Pearl River Estuary were investigated. The elevated level of DBP in the Qianshan River (2.70 ± 0.20 μg/L) was in alignment with the presence of highest microplastic concentration at the same sampling site (15.8 ± 9.8 items/L). A positive correlation was observed between microplastics and DBP in all sampling sites (p < 0.05). The results showed that UV irradiation from sunlight was a majorly inducing factor of DBP leaching from polyethylene microplastics. The concentrations of chemical additives in some degrees reflect the microplastic pollution, but environmental factors and multidimensionality of microplastics such as residence times and types may cause spatial differences of chemical additives in aquatic systems.

A comprehensive review on immobilized microbes - biochar and their environmental remediation: Mechanism, challenges and future perspectives

The environment worldwide has been contaminated by toxic pollutants and chemicals through anthropogenic activities, industrial growth, and urbanization. Microbial remediation is seen to be superior compared to conventional remediation due to its low cost, selectivity towards particular metal ions, and high efficiency. One key strategy in enhancing microbial remediation is employing an immobilization technique with biochar as a carrier. This review provides a comprehensive summary of sources and toxic health effects of hazardous water pollutants on human health and the environment. Biochar enhances the growth and proliferation of contaminant-degrading microbes. The combined activity of biochar and microbes in eliminating the contaminants has gained the researcher's interest. Biochar demonstrates its biocompatibility by fostering microbial populations, the release of enzymes, and protecting the microbes from the acute toxicity of surrounding contaminants. The current review complies with the immobilization technique and remediation mechanisms of microbes in pollutant removal. This review also emphasizes the combined utilization, environmental adaptability, and the potential of the combined effect of immobilized microbes and biochar in the remediation of contaminants. Challenges and future outlooks are urged to commercialize the immobilized microbes-biochar interaction mechanism for environmental remediation.

The fate of phthalate acid esters in wastewater treatment plants and their impact on receiving waters

Phthalates (PAEs) are gaining attention and being researched as an endocrine disruptor as global plastic use surge. There is an urgent need to explore the key factors affecting the removal of PAEs from wastewater and the impact of wastewater effluent on receiving water. Here we investigated the levels and distribution patterns of 16 typical PAEs in surface water and five wastewater treatment plants (WWTPs) along the Dongyang River from Yiwu, China, collecting 42 surface water and 31 wastewater samples. We found that influent PAEs concentration and treatment process were the key factors affecting the degradation efficiency of PAEs in primary and secondary treatment, respectively. In primary treatment, long-chain PAEs were more easily removed (and sometimes less likely to accumulate) than short-chain PAEs, regardless of the influent PAEs concentration (a key factor in primary treatment), while in secondary treatment, short-chain PAEs were easily removed regardless of the treatment process (a factor in secondary treatment). This was not the case for long-chain PAEs, which were only more readily removed in the A/A/O process. In addition, by comparing the significant differences between wastewater and surface water, we found that the total PAEs in the treated effluent were significantly lower than in surface water upstream and in built-up urban areas, indicating that wastewater discharges in the study area did not increase PAEs in the receiving water. Finally, river in the city center and artificial treatment facilities in the study area were identified as requiring priority attention. The results of this study can serve as a model for controlling PAEs in other similar developing cities in China and provide valuable information on the fate of endocrine disruptor from wastewater treatment in China and their impact on surface water.

Occurrence, fate and ecological risks of 90 typical emerging contaminants in full-scale textile wastewater treatment plants from a large industrial park in Guangxi, Southwest China

Recent industrial relocation in China causes lots of environment concerns including risks of emerging contaminants (ECs). Herein, the occurrence, fate, removal and ecological risks of 34 per- and polyfluoroalkyl substances (PFAS), 17 endocrine disrupting chemicals (EDCs), 16 phthalate esters (PAEs), and 23 polycyclic aromatic hydrocarbons (PAHs) were investigated in two textile WWTPs (conventional and Fenton-modified) from a large textile industrial park in Southwest China. Totally 50 ECs were identified and the levels followed the order of PAEs > EDCs > PFAS ≈ PAHs. The EDCs predominated in textile washing and rinsing wastewater whereas the PAEs did in desizing wastewater. Biphasic correlations of log K_d and log P, molecular weight, and numbers of rings (r² = 0.63-0.66, p < 0.01) were observed for PAHs, suggesting that hydrophobicity might not facilitate adsorption of super-hydrophobic PAHs onto activated sludge. 63-69% of detected ECs were effectively removed by two textile WWTPs with removal efficiencies ≥ 80%, which were much higher than previous reports. Fenton processing enhanced the removal efficiencies for long-chain PFAS rather than short-chain PFAS. The PAEs and EDCs posed a medium-to-high risk to aquatic organisms and were screened as the priority ECs. To date, such a comprehensive investigation for ECs has not been previously conducted in textile WWTPs and this study provides basic information about regional chemical emission inventory of ECs.

Synergistic removal of sulfamethoxazole and dimethyl phthalate by five constructed wetland substrates

Frequent detection and joint toxicity of sulfonamides (SAs) and phthalate acid esters (PAEs) in water environment have caused serious health and safety problems that can be reduced by vertical flow constructed wetland (VFCW). However, it remains unclear what kind of substrate used in VFCW can synergistically remove SAs and PAEs. In this study, it was determined if biochar, zeolite, vermiculite, peat and sand synergistically removed sulfamethoxazole (SMX) and dimethyl phthalate (DMP) as representatives of SAs and PAEs by using batch and column experiments. The batch experiments showed that pseudo-second-order and intraparticle diffusion kinetics and Freundlich isotherm could better describe the synergistic adsorption of SMX and DMP on each substrate. SMX promoted hydrophobic interaction between DMP and each substrate so that low concentration DMP almost was adsorbed completely at neutral pH. Both neutral and alkaline pH conditions were favorable for synergistic adsorption of SMX and DMP on each substrate. The column experiments showed that removal of SMX or DMP in VFCW by substrate adsorption alone was limited with run time increasing, but SMX and DMP were effectively removed with run time increasing when loaded with simulated wastewater, SMX and DMP. The VFCW not only removed 94.7% SMX and 91.8% DMP after running 50 d, but also improved total nitrogen removal. In conclusion, these results strongly suggest that biochar, zeolite, vermiculite, peat and sand filled in VFCW can synergistically remove SMX and DMP.

Spectral change of dissolved organic matter after extracted by solid-phase extraction and its feasibility in predicting the acute toxicity of polar organic pollutants in textile wastewater

Spectroscopic parameters can be used as proxies to effectively trace the occurrence of organic trace contaminants, but their suitability for predicting the toxicity of discharged industrial wastewater with similar spectra is still unknown. In this study, the organic contaminants in treated textile wastewater were subdivided and extracted by four commonly-used solid-phase extraction (SPE) cartridges, and the resulting spectral change and toxicity of textile effluent were analyzed and compared. After SPE, the spectra of the percolates from the four cartridges showed obvious differences with respect to the substances causing the spectral changes and being more readily adsorbed by the WAX cartridges. Non-target screening results showed source differences in organic micropollutants, which were one of the main contributors leading to their spectral properties and spectral variations after SPE in the effluents. Two fluorescence parameters (C1 and humic-like) identified by the excitation emission matrix-parallel factor analysis (EEM-PARAFAC) were closely correlated to the toxicity endpoints for Scenedesmus obliquus (inhibition ratios of cell growth and Chlorophyll-a synthesis), which can be applied to quantitatively predict the change of toxicity effect caused by polar organic pollutants. The results would provide novel insights into the spectral feature analysis and toxicity prediction of the residual DOM in industrial wastewater.

Impact of textile dyes on health and ecosystem: a review of structure, causes, and potential solutions

The rapid growth of population and industrialization have intensified the problem of water pollution globally. To meet the challenge of industrialization, the use of synthetic dyes in the textile industry, dyeing and printing industry, tannery and paint industry, paper and pulp industry, cosmetic and food industry, dye manufacturing industry, and pharmaceutical industry has increased exponentially. Among these industries, the textile industry is prominent for the water pollution due to the hefty consumption of water and discharge of coloring materials in the effluent. The discharge of this effluent into the aquatic reservoir affects its biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), total suspended solids (TSS), and pH. The release of the effluents without any remedial treatment will generate a gigantic peril to the aquatic ecosystem and human health. The ecological-friendly treatment of the dye-containing wastewater to minimize the detrimental effect on human health and the environment is the need of the hour. The purpose of this review is to evaluate the catastrophic effects of textile dyes on human health and the environment. This review provides a comprehensive insight into the dyes and chemicals used in the textile industry, focusing on the typical treatment processes for their removal from industrial wastewaters, including chemical, biological, physical, and hybrid techniques.

Groundwater contamination pathways of phthalates and bisphenol A: origin, characteristics, transport, and fate - A review

Phthalic acid esters (PAEs) or phthalates and bisphenol A (BPA) are emerging organic contaminants (EOCs) that may harm biota and human health. Humans can be exposed to these contaminants by drinking water consumption from water sources such as groundwater. Before their presence in aquifer systems, phthalates and BPA can be found in many matrices due to anthropogenic activities, which result in long-term transport to groundwater reservoirs by different mechanisms and reaction processes. The worldwide occurrence of phthalates and BPA concentrations in groundwater have ranged from 0.1 × 10^-3 to 3 203.33 µg L^-1 and from 0.09 × 10^-3 to 228.04 µg L^-1, respectively. Therefore, the aim of this review is to describe the groundwater contamination pathways of phthalates and BPA from the main environmental sources to groundwater. Overall, this article provides an overview that integrates phthalate and BPA environmental cycling, from their origin to human reception via groundwater consumption. Additionally, in this review, the readers can use the information provided as a principal basis for existing policy ratification and for governments to develop legislation that may incorporate these endocrine disrupting compounds (EDCs) as priority contaminants. Indeed, this may trigger the enactment of regulatory guidelines and public policies that help to reduce the exposure of these EDCs in humans by drinking water consumption.

Significant riverine inputs of typical plastic additives-phthalate esters from the Pearl River Delta to the northern South China Sea

Phthalate esters (PAEs) are representative additives used extensively in plastics. In this study, 15 PAEs were investigated at the eight riverine outlets of the Pearl River Delta (PRD). The total concentrations of Σ₁₅PAEs, including both the dissolved and particulate phases, ranged from 562 to 1460 ng/L and 679 ng/L-2830 ng/L in the surface and bottom layers, respectively. Dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) dominated in the dissolved and suspended particulate matter (SPM) phases, respectively, accounting for >50 % and > 80 % of Σ₁₅PAEs. Riverine input of wastewater from the PRD was possibly the primary source of the contamination. Higher levels of PAEs occurred at the eastern outlets than at the western ones. The dissolved and particulate PAEs varied seasonally, with significantly higher concentrations observed in the dry season than in the wet season. However, no significant differences of PAE levels in both phases were observed among low, medium, and high tides. The partitioning results demonstrated that SPM is important in the transportation of pollutants in estuaries, where more hydrophobic DEHP was predominantly transported by the SPM phase, while those more hydrophilic ones were regularly transported by the dissolved phase. The total annual flux of Σ₁₅PAEs through the eight outlets to the SCS reached 1390 tons.

Chemical fingerprinting of organic micropollutants in different industrial treated wastewater effluents and their effluent-receiving river

Industry wastewater is considered one of the worst polluters of our precious water ecologies. However, the types of pollutants present in wastewater from industrial wastewater treatment plants (IWTPs) are still unclear. In this study, a simple and effective chemical fingerprinting method for checking the source-sink relationships among different industrial wastewaters and their effluent-receiving river was established. 107, 228, 155, and 337 chemicals were screened out in wastewater from electronics, steel, textile, and printing and dyeing plants, respectively. Chemical fingerprinting of the detected chemicals was performed, and results showed that aromatic compounds were the most prevalent among the pollutant categories (i.e., 56, 189, and 168 in electronics, iron and steel, and printing and dyeing plants, respectively). The traceability analysis of the chemicals selected in the effluent determined the characteristic pollutants of different industrial enterprises. Sixty-eight compounds were identified as the characteristic pollutants in the different process stages of wastewater of the four IWTPs. Of the 84 effluent-receiving river water signature pollutants, 47.6% (n = 40) were also detected in the effluent from the four IWTPs. Effective screening of organic pollutants in industrial wastewater and determining their sources will help accelerate the improvement of industrial wastewater treatment technology.

Iron-biochar production from oily sludge pyrolysis and its application for organic dyes removal

In this study, a single-step pyrolysis approach was developed to directly convert oily sludge (OS) with high iron content into a magnetic iron-char catalyst for organic dyes removal. Magnetic iron-char catalysts were employed to degrade crystal violet (CV), methylene blue (MB), and sunset yellow (SY). The OC800 iron-char catalyst prepared from OS was not only rich in iron (mainly stable Fe₃O₄), but also showed favorable pore structures. Effects of operation parameters like temperature, H₂O₂ dosage, and pH on dye removal based on Fenton degradation were examined. In OC800 Fenton system (0.5 mL H₂O₂, 500 mg/L dye concentration, and pH = 2 in 50 mL solution), the maximum dye removal capacities of SY, CV, and MB were 83.61, 639.19, and 414.25 mg/g, respectively. In dyes degradation experiments, the prepared catalyst could be reused (more than 3 successive cycles) due to higher stability and less leaching of iron. One-step pyrolysis of OS with high iron content thereby represents a promising approach to transform sludge waste to functional biochar that removes hazardous dyes.

Electrochemical degradation performance and mechanism of dibutyl phthalate with hydrophobic PbO2 electrode

A polytetrafluoroethylene (PTFE) doped PbO₂ anode with a highly hydrophobicity was fabricated by electrodeposition method. In this process, vertically aligned TiO₂ nanotubes (TiO₂NTs) are formed by the anodic oxidation of Ti plates as an intermediate layer for PbO₂ electrodeposition. The characterization of the electrodes indicated that PTFE was successfully introduced to the electrode surface, the TiO₂NTs were completely covered with β-PbO₂ particles and gave it a large surface area, which also limited the growth of its crystal particles. Compared with the conventional Ti/PbO₂ and Ti/TiO₂NTs/PbO₂ electrode, the Ti/TiO₂NTs/PbO₂-PTFE electrode has enhanced surface hydrophobicity, higher oxygen evolution potential, lower electrochemical impedance, with more active sites, and generate more hydroxyl radicals (·OH), which were enhanced by the addition of PTFE nanoparticles. The electrocatalytic performance of the three electrodes were investigated using dibutyl phthalate (DBP) as the model pollutant. The efficiency of the DBP removal of the three electrodes was in the order: Ti/TiO₂NTs/PbO₂-PTFE > Ti/TiO₂NTs/PbO₂ > Ti/PbO₂. The degradation process followed the pseudo-first-order kinetic model well, with rate constants of 0.1326, 0.1266, and 0.1041 h^-1 for the three electrodes, respectively. The lowest energy consumption (6.1 kWh g^-1) was obtained after 8 h of DBP treatment using Ti/TiO₂NTs/PbO₂-PTFE compared to Ti/TiO₂NTs/PbO₂ (6.7 kWh g^-1) and Ti/PbO₂ (7.4 kWh g^-1) electrodes. Moreover, the effects of current density, initial pH and electrolyte concentration were investigated. Finally, the products of the DBP degradation process were verified based on gas chromatography-mass spectrometry analysis, and possible degradation pathways were described.

A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety

The synthetic dyes used in the textile industry pollute a large amount of water. Textile dyes do not bind tightly to the fabric and are discharged as effluent into the aquatic environment. As a result, the continuous discharge of wastewater from a large number of textile industries without prior treatment has significant negative consequences on the environment and human health. Textile dyes contaminate aquatic habitats and have the potential to be toxic to aquatic organisms, which may enter the food chain. This review will discuss the effects of textile dyes on water bodies, aquatic flora, and human health. Textile dyes degrade the esthetic quality of bodies of water by increasing biochemical and chemical oxygen demand, impairing photosynthesis, inhibiting plant growth, entering the food chain, providing recalcitrance and bioaccumulation, and potentially promoting toxicity, mutagenicity, and carcinogenicity. Therefore, dye-containing wastewater should be effectively treated using eco-friendly technologies to avoid negative effects on the environment, human health, and natural water resources. This review compares the most recent technologies which are commonly used to remove dye from textile wastewater, with a focus on the advantages and drawbacks of these various approaches. This review is expected to spark great interest among the research community who wish to combat the widespread risk of toxic organic pollutants generated by the textile industries.

Urinary levels of Phthalate metabolite mixtures and pulmonary function in adolescents

Although an association between urinary phthalate (PAE) metabolites and respiratory symptoms and diseases has been reported, knowledge regarding its effect on pulmonary function is limited, especially in adolescents. Using cross-sectional data from 1389 adolescents (aged 10-19 years) in the 2007-2012 National Health and Nutrition Examination Survey, the association of mixed urinary PAE metabolites with pulmonary function was evaluated using the weighted quantile sum. Moreover, multivariate linear regression was performed to investigate associations between each urinary PAE metabolite and pulmonary function indicators and to estimate the interaction effects between urinary PAE metabolites and demographic characteristics. We found that mixed urinary PAE metabolites were negatively associated with forced expiratory volume at the 1 s (FEV1, p < 0.001) and forced vital capacity (FVC, p = 0.008) levels. In individual PAE metabolite analyses, mono (carboxynonyl) pthalate (MCNP), mono-n-butyl pthalate (MnBP), mono-isobutyl pthalate (MiBP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) and mono-benzyl phthalate (MBzP) correlated negatively with both FVC and FEV1 values (Holm-Bonferroni corrected p < 0.05). Mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) was negatively associated with the FVC value. Significant interactions between sex and urinary MnBP or MBzP levels for the risk of FEV1 decrease in girls were found (p = 0.005), as was a significant interaction between sex and urinary MBzP level for the risk of FVC decline. Our findings suggest that higher PAE exposure is associated with respiratory dysfunction; the association is more pronounced among girls.

Photocatalytic dye degradation and photoexcited anti-microbial activities of green zinc oxide nanoparticles synthesized via Sargassum muticum extracts

Drug-resistant superbugs (DRS) were isolated from hospital sewage waste and confirmed by a 16S rDNA molecular technique as B. filamentosus, B. flexus, P. stutzeri, and A. baumannii. Green nanotechnologies provide a new promising alternative pathway that was found to be much safer, eco-friendly, and has economic benefits over physical/chemical methods. Sargassum muticum (SM) mediated zinc oxide nanoparticles (ZnO-NPs) were proved to be photocatalytic and anti-microbial agents. Anti-microbial action was demonstrated by a maximal growth inhibition activity of 18 mm against A. baumannii and a minimal of 12 mm against B. flexus at 80 μg mL-1 concentrations. The anti-microbial mechanism of SMZnO-NPs employed a biphasic phenomenon persuaded by an osmotic shock that can attack the DRS bacterial cells directly and lead to death. In addition, photocatalytic activity was investigated by SMZnO-NPs for the degradation of methylene blue (MB) dye under different light conditions. Natural sunlight irradiation shows effective enhancement with the highest efficiencies of 96% being achieved within 60 min compared to UV-light and visible-light. The reusability of SMZnO-NPs provides up to 6 consecutive cycles towards MB decolorization for environmental water cleansing.

Effect of Chronic Exposure to Textile Wastewater Treatment Plant Effluents on Growth Performance, Oxidative Stress, and Intestinal Microbiota in Adult Zebrafish (Danio rerio)

The ever-increasing production and processing of textiles will lead to greater risks of releasing pollutants into the environment. Textile wastewater treatment plants (TWTPs) effluent are an important source of persistent toxic pollutants in receiving water bodies. The effects of specific pollutants on organisms are usually studied under laboratory conditions, and therefore, comprehensive results are not obtained regarding the chronic combined effects of pollutants under aquatic environmental conditions. Thus, this study aimed to determine the combined effects of TWTP effluents on the growth performance, oxidative stress, inflammatory response, and intestinal microbiota of adult zebrafish (Danio rerio). Exposure to TWTP effluents significantly inhibited growth, exacerbated the condition factor, and increased the mortality of adult zebrafish. Moreover, markedly decreases were observed in the activities of antioxidant enzymes, such as CAT, GSH, GSH-Px, MDA, SOD, and T-AOC, mostly in the intestine and muscle tissues of zebrafish after 1 and 4 months of exposure. In addition, the results demonstrated that TWTP effluent exposure affected the intestinal microbial community composition and decreased community diversity. Slight changes were found in the relative abundance of probiotic Lactobacillus, Akkermansia, and Lactococcus in zebrafish guts after chronic TWTP effluent exposure. The chronic toxic effects of slight increases in opportunistic pathogens, such as Mycoplasma, Stenotrophomonas, and Vibrio, deserve further attention. Our results reveal that TWTP effluent exposure poses potential health risks to aquatic organisms through growth inhibition, oxidative stress impairment of the intestine and muscles, and intestinal microbial community alterations.

Integrated loose nanofiltration-electrodialysis process for sustainable resource extraction from high-salinity textile wastewater

Effective extraction of useful resources from high-salinity textile wastewater is a critical pathway for sustainable wastewater management. In this study, an integrated loose nanofiltration-electrodialysis process was explored for simultaneous recovery of dyes, NaCl and pure water from high-salinity textile wastewater, thus closing the material loop and minimizing waste emission. Specifically, a loose nanofiltration membrane (molecular weight cutoff of ~800 Da) was proposed to fractionate the dye and NaCl in the high-salinity textile wastewater. Through a nanofiltration-diafiltration unit, including a pre-concentration stage and a constant-volume diafiltration stage, the dye could be recovered from the high-salinity textile wastewater, being enriched at a factor of ~9.0, i.e., from 2.01 to 17.9 g·L^-1 with 98.4% purity. Assisted with the subsequent implementation of electrodialysis, the NaCl concentrate and pure water were effectively reclaimed from the salt-containing permeate coming from the loose nanofiltration-diafiltration. Simultaneously, the produced pure water was further recycled to the nanofiltration-diafiltration unit. This study shows the potential of the integration of loose nanofiltation-diafiltration with electrodialysis for sufficient resource extraction from high-salinity textile wastewater.

Phthalate esters in surface sediments from fishing ports in Circum-Bohai-Sea region, China

The concentration, composition, distribution, and possible sources of phthalate esters (PAEs) in surface sediments from fishing ports in the Circum-Bohai-Sea region were investigated. The potential ecological risks of PAEs on three sensitive aquatic organisms (algae, crustacean, and fish) were assessed based on the risk quotient. The concentrations of 16 PAEs were in the range of 8.53-86.13 μg/g. Six PAEs, which were considered as priority pollutants by the United States Environmental Protection Agency, were main congeners. Fishing ports with high PAE concentration were located near the eastern area of the Shandong Peninsula, the southern area of the Liaodong Peninsula, and the estuary of the Yellow River. Wastewater, atmospheric deposition, plastic, and rubber products were possible sources of PAEs. The PAEs showed medium to high ecological risks on the three aquatic organisms, and the ecological risks were attributed to four PAEs, including dimethyl phthalate, diethyl phthalate, dibutyl phthalate, and benzylbutyl phthalate.

Seasonal distribution and ecological risks of phthalic acid esters in surface water of Taihu Lake, China

Phthalic acid esters (PAEs) are endocrine-disrupting compounds that are ubiquitous in surface water. However, early studies on PAEs only focused on six species on the priority contaminant list, and the seasonal variation in the PAE distribution in Taihu Lake, China is unclear. The present study investigated the occurrence, spatial distribution, and ecological risks of 16 PAEs in Taihu Lake during the dry, normal, and wet seasons. The results showed that dibutyl phthalate, diethylhexyl phthalate (DEHP), and diisobutyl phthalate (DIBP) were the major species detected in the surface water of Taihu Lake. The summed concentration of the six priority PAEs accounted for less than 50% of the total, indicating that the contamination of the other PAE congeners was non-negligible. Significant seasonal effects were observed that the total PAE concentration was higher in the wet season than in the dry season, and there were significant positive correlations between the total PAE concentration and rainfall, the water reserve, and the water level. In the dry season, a relatively high PAE level was detected in the area close to the inflow river estuary and the tourist island in the lake. The concentrations of PAEs in the lakeshore area were higher than those in the lake center in the normal season, and were generally high in the wet season. DEHP posed high risks for fish regardless of the season, while butyl benzyl phthalate, DIBP, dihexyl phthalate, and diphenyl phthalate also showed high risks in the normal and wet seasons. These results suggest that the contamination and risks of congeners other than the priority PAEs are also of necessary concern, and seasonal variation should be considered for a comprehensive understanding of PAE contamination in surface water.

Fluidized-bed Fenton technologies for recalcitrant industrial wastewater treatment-Recent advances, challenges and perspective

In recent years, fluidized-bed Fenton (FBR-Fenton) process has gained more attention in treating recalcitrant industrial wastewater. FBR-Fenton combines the effectiveness of homogeneous Fenton and sludge reduction of heterogeneous Fenton. Comparing to other modified Fenton processes, FBR-Fenton has greater economical and scaling up potential. However, large consumption of Fenton reagents and strict pH control are still the bottlenecks hampering the full-scale application of FBR-Fenton. While prior reviews mainly focused on the operation and performance of FBR-Fenton process, the present study critically discussed the challenges and bottlenecks for its full-scale industrial application. This study also comprehensively reviewed the development strategies for tackling these drawbacks, mainly over the recent five years. Homogeneous FBR-Fenton, heterogeneous FBR-Fenton and heterogeneous FBR-photo-Fenton processes were classified for the first time according to their reaction mechanisms and system designs. Important operational and design parameters affecting the cost-effectiveness of all FBR-Fenton technologies were reviewed, including the fundamentals, common practices and even innovative steps for enhancing the process performance. Up-to-date applications of FBR-Fenton technologies in recalcitrant wastewater/compounds treatment were also summarized, and it was found that upscaling of heterogeneous FBR-Fenton and heterogeneous FBR-photo-Fenton processes was still very challenging. Strategies to overcome the key technical limitations and enhance process cost-effectiveness were discussed in the future perspective part. Furthermore, modelling techniques such as computational fluid dynamics model and artificial neural network were suggested to be promising modelling techniques for speeding up the full-scale applications of FBR-Fenton technologies.

Preparation of Ag Nanoclusters-Modified Non-Sintered Silica Ceramic-Like Nanosheet for Removing Dyes and Bacteria from Water

PURPOSE

Worldwide water contamination treatment and water security are essential for all living organisms. Among various water contaminants, dye, and bacteria pollution needs to be solved urgently.

METHODS AND RESULTS

In this work, a ceramic sheet from monodisperse, porous silica nanospheres (SiO2 NSs) with an average diameter of 220 was prepared. The prepared SiO2 ceramic sheets were investigated as a "filtration" material in removing dyes (alcian blue, AB; and methylene blue, MB) and bacteria (E. coli and S. aureus). The obtained sheets had efficient adsorption efficiency of 98.72% (for AB) and 97.35% (for MB), and a high adsorption capacity for AB is 220 (mg/g), for MB is 176 (mg/g). Furthermore, these SiO2 ceramic sheets had a high recycling capability for removing dyes by calcination. Being modified by Ag nanoclusters, the ceramic sheets present a strong bactericidal function.

CONCLUSION

Our results demonstrated that the obtained SiO2 non-sintered ceramic sheets is rapid and efficient in the filtration of dyes and bacteria from polluted water.

The Application of Modified Natural Polymers in Toxicant Dye Compounds Wastewater: A Review

The utilization of various types of natural and modified polymers for removing toxicant dyes in wastewater generated by the dye industry is reviewed in this article. Dye wastewater contains large amounts of metals, surfactants, and organic matter, which have adverse effects on human health, potentially causing skin diseases and respiratory problems. The removal of dyes from wastewaters through chemical and physical processes has been addressed by many researchers. Currently, the use of natural and modified polymers for the removal of dyes from wastewater is becoming more common. Although modified polymers are preferred for the removal of dyes, due to their biodegradability and non-toxic nature, large amounts of polymers are required, resulting in higher costs. Surface-modified polymers are more effective for the removal of dyes from the wastewater. A survey of 80 recently published papers demonstrates that modified polymers have outstanding dye removal capabilities, and thus have a high applicability in industrial wastewater treatment.

Chemical Characterization of Specific Micropollutants from Textile Industry Effluents in Fez City, Morocco

Textile industry is one of the most polluting industries in the world. It has a high importance in terms of its environment impact, since it consumes a considerably large amount of water and produces highly polluted discharge water. In this work, characterization of toxic organic compounds is proposed. Based on gas chromatography coupled to mass spectrometry (GC/MS) screening analysis, organic micropollutant diversity of textile effluents from a local textile processing factory was investigated. In the present work, physicochemical characterization of the studied textile effluents showed considerably high values of principal pollution parameters above the prescribed discharge water limits. Heavy metals like zinc (Zn), copper (Cu), iron (Fe), nickel (Ni), cadmium (Cd), chromium (Cr), and lead (Pb) were found to be present within the permissible limits. The results of GC/MS revealed the presence of various organic compounds belonging to a wide range of chemical classes. Main groups of chemical compounds detected in these effluents were aromatic carboxylic acids, alkanes, aromatic amines, phthalates, aliphatic carboxylic acids, and linear aliphatic alcohols. The results of this study allowed significant contributions to the chemical characterization of textile industry contaminants and identification of indicators that can be considered an important tool for assessment of the potential impact of textile activities to the contamination of aquatic environment and health hazard.

Algal toxicity induced by effluents from textile-dyeing wastewater treatment plants

This research aimed to evaluate the alga Scenedesmus obliquus toxicity induced by textile-dyeing effluents (TDE). The toxicity indicator of TDE in alga at the physiological (algal growth), biochemical (chlorophyll-a (Chl-a) synthesis and superoxide dismutase (SOD) activity) and structural (cell membrane integrity) level were investigated. Then we further study the relationship among toxicity indicators at physiological and biochemical level, and supplemented by research on algal biomacromolecules. According to the analysis of various endpoints of the alga, the general sensitivity sequence of toxicity endpoints of Scenedesmus obliquus was: SOD activity > Chl-a synthesis > algal growth. The stimulation rate of SOD activity increased from day 3 (57.25%~83.02%) to day 6 (57.25%~103.81%), and then decreased on day 15 (-4.23%~-32.96%), which indicated that the antioxidant balance system of the algal cells was destroyed. The rate of Chl-a synthesis inhibition increased gradually, reaching 19.70%~79.39% on day 15, while the rate of growth inhibition increased from day 3 (-12.90%~10.16%) to day 15 (-21.27%~72.46%). Moreover, the algal growth inhibition rate was positively correlated with the inhibition rate of SOD activity or Chl-a synthesis, with the correlation coefficients were 0.6713 and 0.5217, respectively. Algal cells would be stimulating to produce excessive reactive oxygen species, which would cause peroxidation in the cells, thereby destroying chloroplasts, inhibiting chlorophyll synthesis and reducing photosynthesis. With increasing exposure time, irreversible damage to algae can lead to death. This study is expected to enhance our understanding of the ecological risks through algal tests caused by TDE.

Chlorobenzene levels, component distribution, and ambient severity in wastewater from five textile dyeing wastewater treatment plants

Chlorobenzenes (CBs) present in synthetic dyes are discharged into natural waters during the treatment of textile dyeing wastewater, which may have adverse effects on human and environment. In this study, the existence and removal of 12 CBs in different units of five treatment plants were examined. The ecological risk of CBs in textile dyeing wastewater was assessed by ambient severity (AS) and risk quotients (RQs). The results showed that trichlorobenzene, tetrachlorobenzene, pentachlorobenzene and hexachlorobenzene were ubiquitous in textile dyeing wastewater, and their distribution was similar. In one of the plants, the content of hexachlorobenzene was found to be as high as 9.277 μg/L in the raw water, which was an oil-water mixture. In other plants, there was no significant difference in the content and composition of CBs among influent and effluent suggesting that the conventional wastewater treatment plants cannot improve the existence of them. Monochlorobenzene and dichlorobenzene were not detected, which may have been related to strong volatility, biochemical properties, and weak instrument sensitivity. In the treatment process and effluent, trichlorobenzene is the main pollutant and accounted for 39.51% of all CB. CB removal was found only in the anaerobic system, while the aerobic system did not have the corresponding removal effect on CB and total organic carbon. According to ecological risk assessment, CBs in effluent has not been found the significant potential harm to human health (AS < 1), but posed moderate ecological risk to aquatic ecosystem (RQs > 0.1).

Phthalates in preschool children's clothing manufactured in seven Asian countries: Occurrence, profiles and potential health risks

Phthalates could be introduced into clothing as chemical additives or impurities, becoming a potential source of human exposure. We measured the concentrations of 15 phthalates in new preschool children's clothing manufactured in seven Asian countries. Phthalates were prevalent in all samples, and total concentrations were 2.92-223 μg/g, indicating a moderate contamination level. Bis(2-ethylhexyl) phthalate, di(isobutyl) phthalate and di-n-butyl phthalate were the most abundant phthalates measured, representing a median of 48.5 %, 13.6 % and 13.4 % of the total concentrations, respectively. Total concentrations did not differ significantly by country of manufacture, while the concentrations of individual phthalates and their composition profiles varied widely. We also found differing phthalate levels by item type, fabric composition, and color. Under the assumed two exposure scenarios, the median of summed dermal exposure doses of six phthalate were 539 and 950 ng/kg of body weight per day, respectively. When children wore trousers, long-sleeved shirts, briefs and socks at the same time, the reproductive risks exceeded acceptable level, although the carcinogenic risk of DEHP was low. Our results suggested that new clothing is an important route of phthalate exposure to preschool children. More research is required to investigate the contaminations and associated with risks in child clothing.

Enzyme mimics based on self-assembled peptides for di(2-ethylhexyl)phthalate degradation

Enzyme mimics inspired by serine proteases are developed through self-assembled peptides to degrade di(2-ethylhexyl)phthalate (DEHP).

Inhibiting effect of textile wastewater on the activity of sludge from the biological treatment process of the activated sludge plant

Textile industry represents an important source of toxic substances rejected in environment. Indeed, effluent of these industries contains dyes and chemicals. They are rejected in environment without any treatment. The aim of this work is to evaluate ecotoxicological effect of industrial textile effluents on the sludge harvested from activated sludge treatment plant of Marrakech city (Morocco). For this, we are interested in determining the inhibition condition that corresponds to 50% decrease of bacterial activity in sludge. Obtained results showed that inhibition percentage of bacterial activity depends narrowly on contact time and on added effluent volume, until a limit concentration where there is no degradation of substratum. In fact, substratum degradation speed shows about 65 times decrease when 80% (v/v) of textile wastewater is added, in comparison with the controlled one. Consequently the inhibition constant (Ki) that corresponds to 50% of bacterial inhibition activity is estimated to 0.65 mg l^-1 of dye. These studies confirm a real ecotoxicological risk of these effluents. Therefore, a treatment is mandatory before their rejection in environment.

Textile finishing dyes and their impact on aquatic environs

In the present review, we have been able to describe the different families of dyes and pigments used in textile finishing processes (Yarns, fabrics, nonwovens, knits and rugs) such as dyeing and printing. These dyes are reactive, direct, dispersed, indigo, sulphur and vats. Such that their presence in the liquid effluents resulting from the textile washing constitutes a serious risk, in the absence of their purification, for the quality of receiving aquatic environments. Indeed, the presence of these dyes and pigments can cause a significant alteration in the ecological conditions of the aquatic fauna and flora, because of the lack of their biodegradability. This has a negative impact on the equilibrium of the aquatic environment by causing serious dangers, namely the obvious dangers (Eutrophication, under-oxygenation, color, turbidity and odor), the long-term dangers (Persistence, bioaccumulation of carcinogenic aromatic products and formation of by-products of chlorination), mutagenicity and carcinogenicity.

Enhanced photocatalytic degradation of methyl orange by porous graphene/ZnO nanocomposite

Degrading aquatic organic pollutants efficiently is very important but strongly relied on the design of photocatalysts. Porous graphene could increase photocatalytic performance of ZnO nanoparticles by promoting the effective charge separation of electron-hole pairs if they can be composited. Herein, porous graphene, ZnO nanoparticles and porous graphene/ZnO nanocomposite were prepared by fine tuning of partial combustion, which graphene oxide imperfectly covered by the layered Zn salt was combusted under muffle furnace within few minutes. Resulting ZnO nanoparticles (32-72 nm) are dispersed uniformly on the surface of graphene sheets, the pore sizes of porous graphene are in the range from ∼3 to ∼52 nm. The synthesized porous graphene/ZnO nanocomposite was confirmed to show enhanced efficiency under natural sunlight irradiation compared with pure ZnO nanoparticles. Using porous graphene/ZnO nanocomposite, 100% degradation of methyl orange can be achieved within 150 min. The synergetic effect of photocatalysis and adsorption is main reason for excellent MO degradation of PG/ZnO nanocomposite. This work may offer a new route to accurately prepare porous graphene-based nanocomposite and open a door of their applications.

Adsorption Thermodynamics and Dynamics of Three Typical Dyes onto Bio-adsorbent Spent Substrate of Pleurotus eryngii

Dyeing wastewater is very hard to treat, and adsorption could be a good choice. Spent substrate of Pleurotus eryngii (SSPE) was first used to adsorb malachite green, safranine T and methylene blue from aqueous solutions, and the corresponding adsorption isotherm, thermodynamics and dynamics models were simulated. More than 93% of the dyes were removed with solutions with 100 mg/L of initial dye concentration, 1 g of SSPE and pH of 6.0 after adsorption for 4 h. Freundlich isotherm models fit better the adsorption data than Langmuir models. Adsorption of the dyes onto SSPE was a spontaneous exothermic process based on an adsorption thermodynamics model. SSPE could adsorb the dyes rapidly, and a second-order kinetics model fit better with the adsorption data than a pseudo first-order kinetics model. Accordingly, SSPE could be a good bio-adsorbent for the removal of malachite green, safranine T and methylene blue from the aqueous solution.

Treatment of a simulated sludge by ultrasonic zero-valent iron/EDTA/Air process: Interferences of inorganic salts in polyaromatic hydrocarbon removal

Understanding the occurrence states of persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) in textile dyeing sludge is the key to their further treatment and disposal. Here, the effects of inorganic salts (silicate, sulfate, phosphate, hydroxide, and iron salts) that were typically rich in textile dyeing sludge on PAH adsorption by sludge and PAH degradation by an ultrasound (US) combined zero-valent iron/EDTA/Air (ZEA) system were studied in a simulated sludge system. The results showed that the simulated sludge containing inorganic salts had a larger specific surface area, which was beneficial for the adsorption of PAHs. More low-ring PAHs were adsorbed on the surface of the particles in the simulated sludge because of the inorganic salts, which was conducive to low-ring PAHs degradation by US/ZEA. The PAH removal rates were increased by 15.37% and 11.19%, respectively, in the presence of SiO₃^2- and HPO₄^2-. The yield of hydroxyl radicals (OH) was increased by 42.39% and 66.25% by SiO₃^2- and HPO₄^2-, respectively. The reason was that the oxidation of the ligand ([Fe^Ⅱ(EDTA)]) formed by ethylenediaminetetraacetic acid (EDTA) and divalent iron was promoted by SiO₃^2- and HPO₄^2-. The formation of OH in the US/ZEA system was inhibited by the corrosion inhibition of SO₄^2- on zero-valent iron (ZVI), the reaction of ferric salt with EDTA, and the reaction of Mg(OH)₂ with the ligand ([Fe^III(EDTA)]). This work provides an essential theoretical insight into the role of the inorganic components of sludge in the removal of PAHs by advanced oxidation processes.

Degradation of phthalic acid esters (PAEs) by an enzyme mimic and its application in the degradation of intracellular DEHP

An enzyme mimic inspired by serine proteases was developed for the degradation of PAEs and applied in the hydrolysis of intracellular DEHP.

Toxicity evaluation of textile dyeing effluent and its possible relationship with chemical oxygen demand

Textile dyeing wastewater was the focus of much research because of its adverse effect on aquatic biota. In the present research, textile dyeing influent and effluent samples were collected from four textile dyeing wastewater treatment plants (TDPs) in Guangdong province, China, and their conventional indicators and toxicity were examined to reveal relationships. The relationship between toxicity and chemical oxygen demand (COD) was clearly established at individual TDPs. Results indicated the highest removal efficiencies of 94.4%, 90.6%, 91.9%, 94.6%, 92.8% and 97.5% for TOC, mixed-liquor volatile suspended solids (MLVSS), COD, ammonia nitrogen (NH₃-N), total phosphorus (TP) and colour, respectively. The primary clarifier used in TDP3 and TDP4 was beneficial for removing macromolecular organic substances, and membrane filtration and sedimentation basin employed at TDP1 and TDP2, respectively, helped to remove toxic substances. Toxicity to V. fischeri or D. subspicatus was found to be related to certain conventional indicators such as TOC, COD, TP, colour, and MLVSS, and was positively correlated with COD in different textile dyeing effluents (R² > 0.84). It was recommended that the relationship between toxicity and COD in wastewater should be established individually at each plant. Therefore, this study could be useful in providing suggestions for guiding effluent management when no toxicity experiments were conducted.

Discrimination of typical cyclic compounds and selection of toxicity evaluation bioassays for coal gasification wastewater (CGW) based on toxicity mechanism of actions (MOAs)

This paper originally investigated toxicity discrimination of typical cyclic compounds and bioassays selection on toxicity evaluation for coal gasification wastewater (CGW) effluent with mechanism-oriented investigation. Initially, representative cyclic toxicants were selected and classified with quantitative structure-toxicity relationship (QSTR). Nitrogen heterocyclic compounds (NHCs) and polycyclic aromatic hydrocarbons (PAHs) were basically discriminated as nonpolar narcotics with significant correlation to hydrophobicity (p < 0.05, R² = 0.8668-0.9635), while phenols were regarded as polar narcotics and reactive compounds due to slight correlation to hydrophobicity (p > 0.05, R² < 0.5). Furthermore, specific mechanism of actions (MOAs) to various organisms revealed that phenols were discriminated as critical source of acute toxicity in CGW, with short-term visible and irreversible damage. However, NHCs and PAHs, which exerted accumulation toxicity rather than acute toxicity, might result in potential mutagenicity and unpredictable risk along the food chain. Afterwards, based on species sensitivity to typical toxicants and application in real CGW effluent, non-applicability of Chlorella vulgaris (C. vulgaris) was validated in toxicity evaluation. While Daphnia magna (D. magna) was suggested as a toxicity bioassay in entire effluent due to the highest sensitivity and applicability. Tetrahymena thermophile (T. pyriformis) might be applicable in effluent with low biodegradability due to similar evaluation results (TU = 8.90) to D. magna (TU = 6.67) in aerobic effluent. Finally, the relationship between toxicity and bioavailability based on typical pollutants and model species illustrated necessity for dualism toxicity-biodegradability investigation on CGW.

The model binary/ternary mixtures for actual EPS solution extracted from the activated sludge in MBR using dead-end membrane filtration cell

In order to find a model solution to simulate actual extracellular polymeric substances (EPS) solution in terms of filterability behavior, a series of experiments were conducted in a dead-end unstirred cell with 0.1 μm polyvinylidene fluoride membranes using binary/ternary mixtures consisting of sodium alginate (SA), bovine serum albumin (BSA) and humic acid (HA). Three target parameters (cumulative filtrate volume (CFV), specific cake resistance (α_c) and rejection (R)) were compared and the roles of mixture components were investigated. The order of degree of influence on CFV, α_c and R in ternary mixture was SA (94.5%, 85.6% and 88.2%, respectively) > BSA (5.2%, 10.3% and 8.0%) > HA (0.3%, 4.1% and 3.8%). Meanwhile, when the composition of ternary mixture was SA/BSA/HA = 285.1/150.1/10.2 mg·L^-1, the deviation for CFV, α_c and R was 7.65%, 19.6% and 7.27%, respectively, while the corresponding values for the most suitable binary solution (SA/BSA = 140.4/50.35 mg·L^-1) were -12%, 1% and 164% respectively. This indicated that the ternary solution demonstrated a more accurate estimation than the binary solution for imitating the filterability of actual EPS solution. Therefore, the ternary mixture could be employed efficiently to replace the actual EPS solution in terms of three target parameters in practice applications.