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Forward osmosis (FO) technology is an emerging technology in wastewater treatment, benefiting from its 'zero' energy consumption and 'zero' pollution. Draw solute (DS) selection is a key challenge for FO technology. Recently, increasing studies were focus on the regenerated and recoverable DS, with the aiming of finding a simple, energy-efficient and low-cost way to reuse it for subsequent cycle-to-cycle of the FO process. The responsive DS have been great concerned for their ability to change their speciation, conformation, morphology or properties under different stimulus conditions. The water molecules are separated from the responsive DS with desired simple stimulation procedure. The modified materials and modification methods has been extensively studied to improve the characteristics of responsive DS, such as stimulus sensitivity, water drawing capacity and low transmembrane penetration. This paper systematically summarized the responsive mechanism, modified materials, modification methods, responsive capacity, FO performance, commercial feasibility of responsive DS, including magnetism-responsive DS, CO 2 -responsive DS, thermo-responsive DS, pH-responsive DS, electric-responsive DS, and solar energy-responsive DS. The characteristics of all types of responsive DS were comprehensively analyzed and comparison. This review aims to fully clarify the current development of responsive DS and lay the foundation for the future development of FO technology. • The responsive mechanism of responsive DS was summarized. • The FO performances and stability of responsive DS was evaluated. • The modified materials and modification methods were exhibited. • The application, feasibility and commerciality of responsive DS were analyzed. • The influence of responsive DS on environment was discussed. [ABSTRACT FROM AUTHOR]

• The maximum treatment capacity of 1167.44 g is achieved in Mode 1 systems. • Optimization of operating conditions enhances energy efficiency and reduces costs. • Systems in Mode 2 exhibit higher energy efficiency but a lower COD removal value. • Switching modes maximize energy utilization across different application scenarios. A multi-stage reverse electrodialysis reactor (MSREDR) wastewater treatment system with an independent strategy is researched theoretically in this paper. The influences of operating conditions on the system performance and levelized costs are explored. Results illustrate that reducing the number of membrane pairs not only enhances the system performance but also decreases the levelized cost of wastewater treatment. A high concentration of concentrated solution facilitates enhancing the total COD removal value and reducing the levelized cost, but it adversely affects the energy conversion efficiency of the system. The optimal total COD removal value and energy efficiency are respectively 1164.77 g and 3.58 % under the given conditions. However, when the wastewater discharge rate from the plant is lower than the maximum treatment capacity, it transitions from a wastewater treatment mode to a combined power generation and wastewater treatment mode. Compared to the system operating in the wastewater treatment mode, the system operating in the combined power generation and wastewater treatment mode exhibits higher effective energy and energy efficiency but a lower COD removal value. This research successfully achieves the flexible adjustment of operating modes based on real-world applications, thereby maximizing energy efficiency and establishing a theoretical foundation for practical implementations. [ABSTRACT FROM AUTHOR]

Textile and cosmetic industries generate large amounts of dye effluents requiring treatment before discharge. This wastewater contains high levels of reactive dyes, low to none-biodegradable materials and chemical residues. Technically, dye wastewater is characterised by high chemical and biological oxygen demand. Biological, physical and pressure-driven membrane processes have been extensively used in textile wastewater treatment plants. However, these technologies are characterised by process complexity and are often costly. Also, process efficiency is not achieved in cost-effective biochemical and physical treatment processes. Membrane distillation (MD) emerged as a promising technology harnessing challenges faced by pressure-driven membrane processes. To ensure high cost-effectiveness, the MD can be operated by solar energy or low-grade waste heat. Herein, the MD purification of dye wastewater is comprehensively and yet concisely discussed. This involved research advancement in MD processes towards removal of dyes from industrial effluents. Also, challenges faced by this process with a specific focus on fouling are reviewed. Current literature mainly tested MD setups in the laboratory scale suggesting a deep need of further optimization of membrane and module designs in near future, especially for textile wastewater treatment. There is a need to deliver customized high-porosity hydrophobic membrane design with the appropriate thickness and module configuration to reduce concentration and temperature polarization (CP and TP). Also, energy loss should be minimized while increasing dye rejection and permeate flux. Although laboratory experiments remain pivotal in optimizing the MD process for treating dye wastewater, the nature of their time intensity poses a challenge. Given the multitude of parameters involved in MD process optimization, artificial intelligence (AI) methodologies present a promising avenue for assistance. Thus, AI-driven algorithms have the potential to enhance overall process efficiency, cutting down on time, fine-tuning parameters, and driving cost reductions. However, achieving an optimal balance between efficiency enhancements and financial outlays is a complex process. Finally, this paper suggests a research direction for the development of effective synthetic and natural dye removal from industrially discharged wastewater. [Display omitted] • Discharge of dye effluent requires robust and cost-effective treatment processes. • Membrane distillation emerged as a promising tool towards dye remediation. • The current study reviewed research advancement towards environmental dye remediation. • However, fouling and thermal efficiency of MD remain a major challenge. • The reviewed study suggested optimization of membrane and module designs for effective dye remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Application of membrane technology to textile wastewater treatment is summarized. • Trends and research hotspots are analyzed using bibliometric tools. • Comparison of pollutants removal by membrane technologies is shown by Circos. • Characteristics and improvements of different membrane technologies are discussed. • Membrane material and integrated process are explored to ease membrane fouling. The textile industries hold an important role in the world, while a large amount of textile wastewater is generated every year. It is important to develop effective technologies for textile wastewater treatment, and membrane technologies showed great promising applications in this field. This review focused on membrane technologies for the treatment of textile wastewater. Firstly, the quantity and chemical composition of textile wastewater were discussed. The change in research hotspot and co-occurrence analysis from 2000 to 2021 were analyzed using bibliometric tools. Following this, the removals of primary pollutants using typical membrane technologies were compared. Then, current research on state-of-the-art membrane technologies for textile wastewater treatment was systematically evaluated. The performance of a range of membranes is evaluated, and the primary characteristics and influencing factors of these technologies were discussed. In terms of factors that reduce treatment efficiency, membrane fouling has the largest and broadest impact. This paper discussed mitigation measures for membrane fouling, such as membrane modification and addition of pretreatment. Performance optimization and energy consumption reduction measures for the combinations of multiple membrane processes were analyzed. Membrane modification, process optimization, and the use of clean energy were proposed as the future research directions of membrane processes in textile wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • A comparative study of advanced oxidation-based hybrid technologies. • TN decrease through hybrid systems was 10 times more than that by the ECO process. • Assessing the performance of calcium-based coagulation flocculation/ECO process. • The significant role of pH in reducing energy consumption and TN removal. • Investigation of factors affecting ECO and advanced oxidation-based hybrid systems. In this paper, several advanced oxidation-based hybrid technologies were employed to efficiently remove organic pollutants from industrial wastewater. First, the efficiency of hybrid treatment systems composed of coagulation-flocculation, electrochemical oxidation (ECO), and ozone oxidation for removal of several landfill leachates were investigated and the effects of coagulation-flocculation with different chemicals, including polyaluminum chloride, anionic polymers, calcium-based compounds, and sodium carbonate were studied. Coagulation-flocculation/ECO/Ozone oxidation hybrid system achieved the best performance (90.65% removal rate) for fluoride removal, compared with ECO alone and coagulation-flocculation/ECO systems. With a 92.2% fluoride removal rate, Ca(OH) 2 achieved the best performance among all calcium-based hybrid treatment technologies. Then, the role of Fenton oxidation/adsorption hybrid technologies in industrial wastewater treatment were also investigated and compared with adsorption and Fenton oxidation alone. Fenton oxidation-adsorption technology achieved a high TOC removal rate of 97%, which was 2.42 times higher than that obtained by activated carbon alone (41.4%) and 1.56 times higher than that achieved by the homogeneous FO process alone (63%). Finally, factors influencing the efficiency of pollutant degradation, including initial pH value, pollutant concentration, and current density were evaluated. [ABSTRACT FROM AUTHOR]

Increasing energy demands combined with local scarcities and rising prices make the valorisation of energy from domestic wastewater seen as a valuable resource. Chemically enhanced primary treatment (CEPT) enables an increased redirection of organic compounds into sludge in the primary stage of a wastewater treatment for a transformation into biogas (carbon capture). Traditionally used coagulants consist of metallic salts, but in the last two decades, the development of polymers, based on petroleum or synthesized from renewable sources such as plants, has been intensified. However, a direct comparison of the effectiveness of these products is missing. In this paper, we analysed data of peer-reviewed research from jar tests to full-scale studies, highlighting key parameters for successful carbon capture. More than 100 studies were identified, with a majority presenting results from tests under static conditions (jar tests), while data on full-scale applications are scarce. Overall, for TSS and COD, a clear correlation between inflow concentration and removal efficiency was found, irrespective of the product used. Comparison between the effectiveness of the different types of products is difficult, but bio-based coagulants need to be generally added in higher product concentrations for a considerable removal efficiency. While CEPT seems to increase the general sludge and biogas output, future studies should focus on harmonising laboratory analysis to make results comparable. Another important issue that should be addressed is the provision of experimental details, especially for full-scale trials, to enable for reliable conclusions. [Display omitted] • Studies on chemically enhanced primary treated domestic wastewater were evaluated. • Removal efficiencies for metal salts, petro- and bio-based coagulants were compared. • COD and TSS removal is strongly correlated to the inflow concentration. • Removal of COD increases up to 45% and TSS up to 30% compared to primary settling. • Future studies should focus on harmonising experimental conditions. [ABSTRACT FROM AUTHOR]

Wastewater treatment plants (WWTPs) play a pivotal role in natural water recycling and safeguarding the water security of approximately 42% of the world's population, yet they confront challenges posed by escalating energy consumption and regional energy constraints. In this study, we developed an evaluation framework that integrated regional energy scarcity with the operation conditions of WWTPs to quantify their energy efficiencies by applying multiregional input–output (MRIO) analysis and data envelopment analysis (DEA). A case study using this framework was conducted on 3776 WWTPs in 30 provinces in China. The results showed that the average scarcity-based energy efficiency level of WWTPs in China was low, of which those in northern provinces were higher compared to southeastern provinces. Furthermore, only 24 WWTPs in China attained the highest efficiency levels, while the rest had different degrees of input redundancy, indicating an energy-saving potential of 9.05 × 109 kWh. This paper enables the development of optimal efficiency strategies for WWTPs in different provinces considering the potential energy scarcity risks caused by trading activities. • The DEA and MRIO analyses were combined for 3776 WWTPs in China. • Efficiency evaluation index was modified considering energy scarcity levels. • Scarcity-based energy efficiency assessment framework for WWTPs was developed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Feasibility of using organic wastewater as renewable energy source is verified. • ＞99% COD, TOC removal rate in the experimental platform. • Up to 78.75% of the energy recovery efficiency of the SCWO system. The degradation of high concentration organic wastewater and the recovery of energy using supercritical water oxidation (SCWO) technology have the potential to become viable in the future. High concentration organic wastewater contains a significant amount of energy. This paper focuses on utilizing high concentrated wastewater as a renewable energy source, from an energy system perspective, an experimental rig was designed to determine the optimal working conditions. The experiments were conducted with an oxidation coefficient of 1.1, a flow rate of high concentration organic wastewater of 9 ml/min, a heating temperature of 400 °C, and a reaction pressure of 25 MPa. Under these conditions, the COD and TOC removal rates of the high concentration organic wastewater were found to be 99.383 % and 99.876 % respectively. Additionally, the phenomenon of "Abnormalities in pressure sensitivity" observed during high concentration organic wastewater the experiment was further explained through additional experiments. Finally, by comparing the experimental energy recovery with the simulation results, an energy recovery efficiency of 78.95 % was achieved. The feasibility of the simulated energy recovery in practice was verified, confirming the potential to convert the previous energy-consuming wastewater treatment process into a productive one. This study provides a theoretical and experimental foundation for further related research. [ABSTRACT FROM AUTHOR]

This paper focuses on the comparative study of vertical and horizontal vacuum membrane distillation (VMD) modules coupled with mechanical vapor recompression (MVR) system to obtain the optimal system layout structure and further improve operation stability and energy efficiency in the wastewater treatment. Firstly, freshwater accumulation characteristic in the vertical VMD module was explored under different working conditions. Then, comparative experiments of vertical and horizontal VMD-MVR systems were conducted. Finally, comprehensive performance of horizontal VMD-MVR system were evaluated. The obtained results showed that freshwater production in the distilling tank and freshwater accumulation in the VMD module were affected by operation time, feed temperature, feed flow rate, feed concentration and vacuum side pressure. Furthermore, the horizontal VMD-MVR system was proved to be a better choice due to lower freshwater accumulation in the VMD module and energy consumption in comparison to the vertical VMD-MVR system. Finally, long term operation experiment of 240 h indicated evaporation rate dropped to 55 kg/h as operation time reached to 180 h owing to membrane fouling. After membrane cleaning, evaporation rate recovered from 55 to 62 kg/h with a higher recovery efficiency of 95.1 %. Compared to conventional wastewater treatment systems, the horizontal VMD-MVR system exhibited excellent comprehensive performance. [Display omitted] • Performance comparison of vertical and horizontal VMD-MVR were conducted. • Freshwater accumulation in the VMD module affected the evaporation rate. • Vertical VMD-MVR system had higher energy consumption than horizontal system. • Separation efficiency of horizontal VMD-MVR system was 99.9 %. • Evaporation rate recovered from 55 kg/h to 62 kg/h after membrane cleaning. [ABSTRACT FROM AUTHOR]