Concentrate minimization and water recovery enhancement using pellet precipitator in a reverse osmosis process treating textile wastewater

Performance of sulfur-based autotrophic denitrification process for nitrate removal from permeate of an MBR treating textile wastewater and concentrate of a real scale reverse osmosis process

Textile is one of the industrial sectors generating the highest amount of wastewater with various polluting substances. Lately, water reuse in textile industries, especially, with the reverse osmosis (RO) process following membrane bioreactor (MBR) treatment has been applied more commonly. In this study, an autotrophic sulfur-based denitrifying column performance was evaluated, for the first time, for nitrate reduction from permeate of a lab-scale MBR receiving real textile wastewater and from the concentrate stream of a real scale-RO plant used for recovering water from textile wastewater. Nitrate concentration in the MBR effluent and RO concentrate averaged 35 ± 3 and 12 ± 2 mg-N/L, respectively. With the sulfur-based column bioreactor, quite high (≥90%) denitrification performances were attained both for MBR effluent and RO concentrate up to nitrate loadings of 0.432 and 0.12 g-N/(L.d), respectively. COD present in wastewater was not utilized in the column bioreactor, which illustrates no or minimal contribution of heterotrophic denitrification. Alkalinity concentration in the wastewater was enough to buffer the acid formation during autotrophic denitrification. Sulfate was generated accompanied by nitrate reduction and sulfide was formed at low nitrate loadings. In the batch tests, the denitrification rates for the MBR effluent and RO concentrate were 0.31 and 0.28 g-N/(g-VSS.d), respectively, which were relatively higher than the ones observed for the synthetic nitrate-contaminated groundwater. Autotrophic sulfur-based denitrification is a promising and robust process alternative even for textile RO concentrate with high concentrations of salinity, non-biodegradable COD, and color.

Efficiency of iron modified Pyrus pyrifolia peels biochar as a novel adsorbent for methylene blue dye abatement from aqueous phase: equilibrium and kinetic studies

Herein, a magnetic biochar adsorbent based on Pyrus pyrifolia discarded peels impregnated with precursor FeCl_3·6H₂O was fabricated and probed as a low-cost adsorbent for toxic cationic dye methylene blue (MB). The textural characterization of Pyrus pyrifolia magnetic biochar (PMBC) obtained from BET analysis exhibited its mesoporous nature with S_BET of 133.960 m²/g. The physicochemical characteristics of PMBC were elucidated using XRD, FTIR, SEM-EDX and TEM techniques. The impregnation of FeCl₃ has a significant impact on the microstructure of Pyrus pyrifolia based biochar which resulted in enhancement in adsorption efficiency of PMBC. The sorption parameters adsorbent dosage, time, initial MB concentration, and pH were thoroughly elucidated using a batch methodology which were found to be 0.8 g/L, 40 min, 90 mg/L and 6, respectively. Temkin and pseudo-second-order rate equation respectively appropriated the equilibrium data than the rest of the models. The maximum adsorption capacity determined by the Langmuir model was found to be 967.80 mg/g. The adsorbent exhibited better regeneration up to 3 cycles validating its practical usage. The facile synthesis, economic, and environmentally benign characteristic of Pyrus pyrifolia magnetic biochar corroborated it as a highly efficient adsorbent to sequester MB from an aqueous phase.

A study of inline chemical coagulation/precipitation-ceramic microfiltration and nanofiltration for reverse osmosis concentrate minimization and reuse in the textile industry

Reverse osmosis concentrate (ROC) is one of the major drawbacks in membrane treatment technologies specifically due to the scale-forming ions. It is important to remove these ions from ROC to enhance total water recovery and reuse in the textile industry that is the largest water-consumer and polluter industry. In this work, coagulation/high pH precipitation (CP) integrated with ceramic microfiltration (CMF) was studied as a pre-treatment method followed by nanofiltration (NF) to increase the efficiency of water recovery. To prevent organic fouling, ferric chloride (FeCl₃) was applied at a concentration of 3 mM, and ceramic membranes were used for the removal of non-precipitating crystals and/or suspended solids (at high pH) before the NF processes. The CP-CMF method successfully removed calcium (Ca²⁺), magnesium (Mg²⁺), silica (SiO₂), and TOC up to 97, 83, 92, and 87% respectively, which resulted in higher performance of the NF process. Moreover, this method provided higher flux at lower pressure that ultimately increased overall water recovery of the NF process to achieve near-zero liquid discharge (n-ZLD). A cost-benefit estimation showed that a high-quality effluent (COD<5 mg/L; conductivity 700<μS/cm; negligible residual color) can be generated and recycled in the textile industry at an economical cost (approximately 0.97 USD/m³). Therefore, ROC minimization and water recovery can help to achieve n-ZLD using the CP-CMF/NF method.

Reuse solution of hardness industrial circulating cooling water: Targeted ion-selective electro-adsorption by functionalized electrode

A low-cost, efficient and environmentally friendly hardness ion selective electro-adsorption system for high-hardness industrial circulating cooling water reuse was constructed to simultaneously realize a high salt removal rate and hardness ion (Ca²⁺ and Mg²⁺) selection. Multiply modified graphite carbon felt (GCF) materials for both negative and positive electrodes were proposed simply and economically, and an electro-adsorption system for hardness control was assembled. The multiple modified GCF (GCF_M) materials were characterized by SEM, BET and FT-IR and the electrochemical performance was tested by CV and EIS; surface properties were studied by Zeta potential; the hardness ion removal selectivity and operational stability of the electro-adsorption system were tested. Hydrophilic functional groups were introduced in GCF_M electrode, GCF_M exhibited a large microporosity and demonstrated stable electrochemical performance in aqueous with a specific capacitance. The hardness ion selective electro-adsorption system achieved an adsorption capacity of 58.05 mg/g per circle for calcium ions and 31.03 mg/g for magnesium ions, indicating the superior hardness ion selectivity. In the circulating cooling water at the electro-adsorption stage, the ion removal performance was over 42.1% and maintain in good stability, GCF_M electrode showed excellent deionization performance and demonstrated the application potential of hardness ion selective electro-adsorption system.

Sequential sulfur-based denitrification/denitritation and nanofiltration processes for drinking water treatment

Efficient and cost-effective solutions for nitrogen removal are necessary to ensure the availability of safe drinking water. This study proposes a combined treatment for nitrogen-contaminated groundwater by sequential autotrophic nitrogen removal in a sulfur-packed bed reactor (SPBR) and excess sulfate rejection via nanofiltration (NF). Autotrophic nitrogen removal in the SPBR was investigated under both denitrification and denitritation conditions under different NO₃^- and NO₂^- loading rates (LRs) and feeding strategies (NO₃^- only, NO₂^- only, or both NO₃^- and NO₂^- in the feed). Batch activity tests were carried out during SPBR operation to evaluate the effect of different feeding conditions on nitrogen removal activity by the SPBR biofilm. Bacteria responsible for nitrogen removal in the bioreactor were identified via Illumina sequencing. Dead-end filtration tests were performed with NF membranes to investigate the elimination of excess sulfate from the SPBR effluent. This study demonstrates that the combined process results in effective groundwater treatment and evidences that an adequately high nitrogen LR should be maintained to avoid the generation of excess sulfide.

Photocatalytic degradation of Reactive Blue 21 dye using ZnO nanoparticles: experiment, modelling, and sensitivity analysis

This paper presents the photocatalysis, adsorption, and photolysis of C.I. Reactive Blue 21 dye using synthesized zinc oxide nanoparticles. The density, mean particle diameter, surface area, and porosity of the catalyst were 5550 kg/m³, 1.19 × 10^-7, 16,830 m²/kg, and 0.08, respectively. The impact of catalyst mass per volume of solution (0.2-1.0 kg/m³) was experimentally investigated in terms of the percentage of dye degradation. Due to the small catalyst porosity, adsorption contributed little to overall degradation. However, the photolysis of the dye was around 12.5%, which occurred predominantly between 0 and 5 min. In the second part of the present study, the photocatalytic degradation of C.I. Reactive Blue 21 was modelled mathematically based on the mass conservation law in the solution and catalyst. The model had two adjustable variables: the convection mass transfer coefficient and the photocatalytic reaction rate constant. The model was solved numerically using the finite difference method and was validated with the experimental data. The validated model was employed to examine the impact of catalyst size and initial pollutant concentration on the photocatalytic degradation.

Ceramic membrane overview and applications in textile industry: a review

The importance of water recovery and reuse is increasing day by day. Therefore, the use of advanced technologies is applied for the treatment and recovery of textile wastewater. The fact that ceramic membranes are resistant to the challenging characteristics of textile wastewater makes the use of ceramic membranes useful. Within the scope of this review, general information about the textile industry and treatment techniques are mentioned, as well as the properties of ceramic membranes and textile wastewater treatment. In the literature review made in this study, recent studies on the production of ceramic membranes and laboratory applications have been compiled. However, it has been observed that although the real-scale studies are relatively higher in industries such as the food and petrochemical industry, it is rather limited in the textile industry.

Diversity of Synthetic Dyes from Textile Industries, Discharge Impacts and Treatment Methods

Natural dyes have been used from ancient times for multiple purposes, most importantly in the field of textile dying. The increasing demand and excessive costs of natural dye extraction engendered the discovery of synthetic dyes from petrochemical compounds. Nowadays, they are dominating the textile market, with nearly 8 × 105 tons produced per year due to their wide range of color pigments and consistent coloration. Textile industries consume huge amounts of water in the dyeing processes, making it hard to treat the enormous quantities of this hazardous wastewater. Thus, they have harmful impacts when discharged in non-treated or partially treated forms in the environment (air, soil, plants and water), causing several human diseases. In the present work we focused on synthetic dyes. We started by studying their classification which depended on the nature of the manufactured fiber (cellulose, protein and synthetic fiber dyes). Then, we mentioned the characteristics of synthetic dyes, however, we focused more on their negative impacts on the ecosystem (soil, plants, water and air) and on humans. Lastly, we discussed the applied physical, chemical and biological strategies solely or in combination for textile dye wastewater treatments. Additionally, we described the newly established nanotechnology which achieves complete discharge decontamination.

A Mini Review on Antiwetting Studies in Membrane Distillation for Textile Wastewater Treatment

The textile industry is an important contributor to the growth of the global economy. However, a huge quantity of wastewater is generated as a by-product during textile manufacturing, which hinders the ongoing development of textile industry in terms of environmental sustainability. Membrane distillation (MD), which is driven by thermal-induced vapor pressure difference, is being considered as an emerging economically viable technology to treat the textile wastewater for water reuse. So far, massive efforts have been put into new membrane material developments and modifications of the membrane surface. However, membrane wetting, direct feed solution transport through membrane pores leading to the failure of separation, remains as one of the main challenges for the success and potential commercialization of this separation process as textile wastewater contains membrane wetting inducing surfactants. Herein, this review presents current progress on the MD process for textile wastewater treatment with particular focuses on the fundamentals of membrane wetting, types of membranes applied as well as the fabrication or modification of membranes for anti-wetting properties. This article aims at providing insights in membrane design to enhance the MD separation performance towards commercial application of textile wastewater treatment.

Self-forming dynamic membrane bioreactor for textile industry wastewater treatment

The robustness of anaerobic dynamic membrane bioreactor (AnDMBR) for synthetic textile wastewater treatment was investigated. Textile wastewater may contain high concentrations of NaCl and sulfate, hence their impact on the AnDMBR performance was investigated in detail. A dynamic membrane was formed on a 20-μm pore sized nylon support layer at a constant flux of around 8 LMH. In the absence of sulfate addition, total and filtered (soluble) COD averaged 96 ± 49 mg/L (91% removal) and 75 ± 35 mg/L (93% removal), respectively. Sulfate addition increased total COD in the permeate to 222 ± 68 mg/L (79% removal). Average SS concentration was lower than 30 mg/L in the permeate although its concentration in the bioreactor reached 10 g/L. Throughout the AnDMBR operation dye removal averaged >97%. Sludge filterability, which was assessed by specific resistance to filtration, supernatant filtration, capillary suction time and viscosity, decreased after sulfate addition. Organic and inorganic matters in the dynamic layer were characterized by SEM-EDS and FTIR analyses.

Trimetallic composite nanofibers for antibacterial and photocatalytic dye degradation of mixed dye water

Membrane technology is an advanced approach to making a healthier and cleaner environment. Using such catalytic membrane technology to get clean, usable water by removal of dye impurities as well as pathogenic microbes is the main goal behind the research work. Here, we present the synthesis and efficacy study of polymethyl methacrylate (PMMA)-based Ag/ZnO/TiO₂ trimetallic bifunctional nanofibers with antibacterial and photocatalytic activity. The nanofibers have been proven to be effective for the degradation of methylene blue (MB 93.4%), rhodamine B (Rh 34.6%), auramine-O (Au 65.0%) and fuchsin basic (FB 69.8%) dyes individually within 90 min in daylight. The study is further extended in abating a mixture of these dyes from contaminated water using composite nanofibers. Also, in the case of a mixture of these dyes (3 ppm each), nanofibers show dye degradation efficiency (DDE) of 90.9% (MB), 62.4% (Au) and 90.3% (FB and Rh) in 60 min. The role of Ag nanoparticles with a synergic photocatalytic effect on ZnO and TiO₂ is also demonstrated. Also, PMMA/ZnO/TiO₂ composite fiber membrane in synergy with silver particles shows better antibacterial activity against Gram-negative bacteria E. coli, making PMMA/Ag/ZnO/TiO₂ fibers a promising candidate in water purification.

Evaluation of the efficiency of coagulation/flocculation and Fenton process in reduction of colour, turbidity and COD of a textile effluent

The present study investigated the efficiency of physicochemical processes of coagulation and flocculation and Fenton advanced oxidative process in reducing the parameters of colour, turbidity and Chemical Oxygen Demand (COD) of a real effluent from a textile industry. During the physicochemical process, the efficiencies of different coagulants (aluminium polychloride (Polifloc 18), ferric chloride (Acquafloc FC40), aluminium sulphate combined with organic coagulant (AST) and aluminium sulphate) and nonionic (FX NS2), cationic (FX CS6 and FX CS7) and anionic (FX AS6 and AN905) flocculants were tested. After the tests, 72.60% of COD, 36.25% of colour and 98.59% of turbidity were removed, using aluminium polychloride coagulant and AN 905 flocculant. It was also evaluated the effect of Fenton advanced oxidative process application in removal of colour, COD and turbidity of the effluent previously treated through the physicochemical process. Removals of these parameters were analysed in two different pH ranges (pH 6.0 and 7.0). In both pH 6.0 and pH 7.0, reductions were observed in all analysed parameters, obtaining 170.78 mg O₂/L of COD, 22.19 mg/L of colour and 0.80 NTU of turbidity (at pH 6.0) and 151.80 mg O₂/L of COD, 26.73 mg/L of colour, 0.94 NTU of turbidity (at pH 7.0), which demonstrates the efficiency of this process in the reduction of parameters analysed.

Performance of a pilot-scale reverse osmosis process for water recovery from biologically-treated textile wastewater

Textile industry generates a high volume of wastewater containing various type of pollutants. Although high color and chemical oxygen demand (COD) removals are achieved with the combination of biological and chemical treatment processes, reverse osmosis (RO) process is generally needed for water recovery due to high conductivity of the textile wastewater. In this study, a pilot scale RO process containing one spiral wound membrane element was operated under three different operational modes, i.e. concentrated, complete recycle and continuous, to collect more information for the prediction of a real-scale RO process performance. It was claimed that complete recycle mode of operation enabled mimicking the operational conditions exerted on the first membrane, whereas continuous mode of operation created conditions very similar to the ones exerted on the last membrane element in a real scale RO process train. In the concentrated and continuous mode of operation, water recovery and flux were around 70% and 19 L/m²/h (LMH). Permeate produced in the RO process can be safely reused in the dyeing process as the feed and permeate conductivities were around 5500 μS/cm and 150 μS/cm, respectively, at 70% water recovery. However, color concentration in the concentrate exceeded the discharge limits and would need further treatment. The RO performance was accurately predicted by ROSA simulations.

Water reclamation and reuse

Literature published in 2018 pertinent to water reclamation and reuse has been classified into five topics: safe reuse, treatment technologies, management, assessment, and case studies. Researches have been conducted to develop new technologies and improve conventional treatments for achieving sustainable wastewater reclamation, and increasing efforts have been made to facilitate safe water reuse. PRACTITIONER POINTS: The way of publicity greatly influences people's acceptance of water reuse and willingness to purchase produce irrigated with recycled water. Integrated process is the most commonly used treatment technology to reclaim water. There is a lack of local or regional regulatory and policy for sustainable water management.

A Review on Microbial Electrocatalysis Systems Coupled with Membrane Bioreactor to Improve Wastewater Treatment

Microbial electrocatalysis is an electro reaction that uses microorganisms as a biocatalyst, mainly including microbial electrolytic cells (MEC) and microbial fuel cells (MFC), which has been used for wastewater treatment. However, the low processing efficiency is the main drawback for its practical application and the additional energy input of MEC system results in high costs. Recently, MFC/MEC coupled with other treatment processes, especially membrane bioreactors (MBR), has been used for high efficiency and low-cost wastewater treatment. In these systems, the wastewater treatment efficiency can be improved after two units are operated and the membrane fouling of MBR can also be alleviated by the electric energy that was generated in the MFC. In addition, the power output of MFC can also reduce the energy consumption of microbial electrocatalysis systems. This review summarizes the recent studies about microbial electrocatalysis systems coupled with MBR, describing the combination types and microorganism distribution, the advantages and limitations of the systems, and also addresses several suggestions for the future development and practical applications.

Adsorption of Rhodamine B dye from aqueous solution onto acid treated banana peel: Response surface methodology, kinetics and isotherm studies

The adsorption of rhodamine B (RhB) using acid modified banana peels has been examined. Chemical characteristics of the adsorbents were observed in order to determine active functional groups. The major functional groups on the surface were OH, C = O, C = C and C-O-C. Interactions between operational parameters were studied using the central composite design (CCD) of response surface methodology (RSM). The predictions of the model output indicated that operational factors influenced responses at a confidence level of 95% (P<0.05). The optimum conditions for adsorption were pH 2 at a 0.2 g/L dose within 60 minutes of contact time. Isotherm studies were carried out using the optimized process variables. The data revealed that RhB adsorption fitted the Langmuir isotherm equation while the reduction of COD followed the Freundlich isotherm. Kinetic experiments fitted the pseudo second order model for RhB removal and COD reduction. The adsorption mechanism was not the only rate controlling step. Diffusion through the boundary layer described the pattern of adsorption.

Feasibility of industrial-scale treatment of dye wastewater via bio-adsorption technology

This review emphasizes the importance of costs in industrial-scale treatment of dye wastewater and provides a way to assess the cost-based feasibility of bio-adsorption technologies. Dye wastewater is one of the major contributors to environmental pollution. Bio-adsorption has attracted considerable attentions in dye wastewater treatment due to its technical feasibility, flexibility and operation simplicity. However, industrial-scale treatment of dye wastewater via bio-adsorption technologies remains stagnant, mainly due to high costs. So far, no review or research articles have systematically discussed the criteria for successful utilization of bio-adsorption technologies on a large scale. This review discusses the major factors affecting adsorption and desorption performance based on basic chemical and physical structures of bio-adsorbents available in literatures. A quantitative relationship has been summarized based on previous studies to assess the cost to utilize a bio-adsorption technology and serve as an access threshold for quality bio-adsorbents to be taken into real applications.