Wastewater Treatment Technologies Research Articles

Techno-economic feasibility of photovoltaic solar electrodialysis with bipolar membranes

Electrodialysis with bipolar membranes (EDBM) can transform concentrated brines into acids and bases through the application of an electric field. Nevertheless, the widespread use of EDBM is limited by its high energy consumption, typically based on fossil fuels. Yet, the integration of EDBM with renewable energy sources, like solar photovoltaic (PV), remains unexplored. This study presents a techno-economic analysis of PV-EDBM to produce NaOH and HCl from seawater reverse osmosis (SWRO) brines. An integrated PV-EDBM model was developed and applied to a hypothetical PV-EDBM plant located in the SWRO facility of Lampedusa (Italy). Results revealed that PV has no negative impact on the performance in terms of product concentration, specific energy consumption and current efficiency. Meanwhile, the levelized cost of NaOH for PV-EDBM was reduced by 20 % in comparison to the electrical grid mix, achieving 210 €·ton−1 NaOH on an annual average for PV-EDBM. Therefore, the investment associated with PV is offset by the benefits of reduced electricity costs from the grid. Consequently, EDBM emerges as a feasible solution to address resource scarcity, representing a significant step towards integrating renewable energies with advanced wastewater treatment technologies, thus paving the path to a greener future.

B, S co-doped mesoporous carbon as an efficient catalyst for H2O2 electrosynthesis in natural seawater

The small-scale electrochemical synthesis of hydrogen peroxide (H2O2) in marine environments is of great significance for environmental wastewater treatment, and the design of electrocatalysts for complicated marine conditions is the key for this technology. Although B-doped carbon materials have been demonstrated to be resistant to Cl− poisoning, the deposition of Ca2+ on the surface of catalyst in seawater and the sluggish reaction kinetics of non-metallic catalysts remain to be solved. Herein, B, S co-doped mesoporous carbon materials were synthesized by a simple NaCl template method. The H2O2 yield of the as-prepared sample was up to 3.66 mol/(gcat h) with a Faradaic Efficiency (FE) of 97.98 % at 100 mA/cm2 in natural seawater, and achieved 100 % inactivation of bacteria and Chlorella within 5 min at a low current density. Based on the structural characterization and electrochemical results, the S-containing structure on the carbon matrix suppresses Ca2+ deposition due to its excellent proton adsorption activity. Furthermore, the electron transfer process between the reactant and BC3 was enhanced by the abundant mesoporous structure, so as to optimize the sluggish oxygen reduction reaction (ORR) kinetics on BC3. This work offers a strategy for inactivation of marine microorganisms and the degradation of organic pollutants, which promotes the advancement of marine wastewater treatment technology, and also provides reference for the design of metal free catalysts used in marine environments.

Photocatalytic Activity and Antibacterial Properties of ZnO/CNTs Composites

Photocatalytic technology is one of the promising technologies for wastewater treatment. Herein, zinc oxide/multi-walled carbon nanotubes (ZnO/CNTs) photocatalyst was successfully prepared by hydrothermal method with combining in-situ synthesis technology. The micro-morphology, crystalline structure, surface chemical elements, and optical properties were characterized by SEM, TEM, XRD, FTIR, UV-Vis, and DRS technologies. The ZnO/CNTs photo-catalyst exhibited enhancement photo activity for degradation of organic pollutants under simulated light irradiation. Specifically, the photo-catalytic activity of the ZnO/CNTs catalysts improved with the rise of CNTs content in the composites. Investigation on the photo-degradation mechanism verified that the presence of CNTs in the catalyst not only optimized the band structure of ZnO semiconductor but also contributed to the transfer of photo-generated electrons and reducing the recombination of electron-hole pairs due to its excellent conductivity. Moreover, the active radical groups such as superoxide radical (O-2), hole (h+), and hydroxyl radical (·OH) played the dominated role for the pollutants degradation under the simulated sunlight irradiation. In addition, ZCT20 catalysts and light irradiation had synergistic effects on antibacterial activity, whose antibacterial rates against E. coli and S. aureus were up to 99.96% and 99.94%, respectively. Investigation on antibacterial mechanisms revealed that the existence of ROS and the continuous release of Zn2+ played an important role for improving the antibacterial activity of the ZCT20 catalyst under the simulated sunlight irradiation.

Enhanced peroxymonosulfate activation for degradation of iodinated contrast media by microwave-induced bimetallic carbon-based catalysts: Insight into the synergistic mechanism between microwaves and bimetallic sites

Microwave-assisted catalytic oxidation process was a promising wastewater treatment technology for the disposal of refractory organic contaminants. Nevertheless, its practical implementation was limited by the high energy consumption of microwaves and the poor sustainable reactivity of catalysts. To address these issues, the microwave-assisted dielectric-activation double-responsive Co/Fe carbon-based catalyst (CoFe/NC-3) was used to activate peroxymonosulfate (PMS) for oxidative degradation of refractory diatrizoate (DTZ). The results showed that the DTZ was completely degraded within 6 min in the MW/CoFe/NC-3/PMS reaction system, and the degradation efficiency increased by 82.38% compared with the MW/Fe/NC/PMS system. It was attributed to the enriched active sites and prolonged redox cycling capability of the bimetallic catalysts. Moreover, microwave enhanced electron migration ability to accelerate the circulation of Fe3+/Fe2+/Fe0 and Co3+/Co2+ and generate more reactive oxygen species (ROSs) for the high-efficiency degradation of DTZ. The degradation pathways of DTZ were elucidated by LC-MS in combination with DFT calculation and the product toxicity was evaluated using ecological structure-activity relationship software (ECOSAR). The results showed that the majority of intermediate degradation products were not acute or chronic toxicity to fish, daphnia, and green algae. Overall, these results revealed that the MW/CoFe/NC-3/PMS system was a cost-effective and stable method for wastewater treatment.

Application of Pure and Modified Polyvinylidene Fluoride Materials for Wastewater Treatment Using UASB Reactor Technologies: A Review

Wastewater treatment is now required because of the problems caused by water constraints. Wastewater is anaerobically digested to produce biogas, which can be used as a source of energy for things like lighting and heating. The upflow anaerobic sludge blanket (UASB) reactor has been recognized as an important wastewater treatment technology among anaerobic treatment methods. Although their treated effluent typically does not meet most discharge criteria, UASB reactors are generally stated to have a chemical oxygen demand (COD) reduction ranging from 60 to 90% for most types of wastewater. In comparison to traditional anaerobic procedures, anaerobic municipal wastewater treatment using membranes can produce higher effluent quality in terms of COD, suspended solids (SSs) and pathogen counts, as well as a steady treatment performance to fulfill strict discharge regulations. The objective of this review was to perform a literature review on parameters to consider when selecting a membrane to include in a UASB reactor. Membranes that are available in the market were compared in terms of both physical and chemical properties. Polyvinylidene fluoride (PVDF) membranes were found be superior to the others, and their modification also reduced the fouling propensity. When comparing modified PVDF (PVDF/PVDF-g-PEGMA) to pristine PVDF (116 L·m−2 h−1), a higher pure water flux (5170 L·m−2 h−1) was noted. The main drawback of such modifications could significantly increase the final membrane production costs. Research is still lacking when it comes to research on comparing the membranes and PVDF and UASB reactor technology interaction, including effects of its modification as discussed (stability, longevity of improved flux, etc.

The construction of a microalgal-bacterial biofilm reactor for enhanced swine wastewater treatment

Traditional biological wastewater treatment methods face challenges in treating swine wastewater with a low carbon-to‑nitrogen ratio. Microalgae show great potential in low-cost swine wastewater treatment for nutrient recovery. This study investigated the effects of altering the carbon/nitrogen/phosphorus (C:N:P) ratio in swine wastewater and immobilizing microalgae for enhancing treatment using Desmodesmus sp. A C:N:P proportion of 106:16:1 was determined to be optimal for treatment. The implementation of an inclined plate bioreactor facilitated microalgal adherence, forming a biofilm that improved treatment efficiency. The biofilm exhibited removal rates of 92 % for ammonia nitrogen (NH4+-N), 98 % for total phosphorus (TP), and 99 % for chemical oxygen demand (COD). The harvested biomass from the biofilm was 7.6 times higher than that from the suspended system with a high content (63 %) of fatty acids (C16:0, C18:0, C18:1n9c and C18:2n6c) suitable for biodiesel production. Proteobacteria were dominant in the biofilm, while Firmicutes and Bacteroidetes contributed to effective organic matter and nitrogen removal. These findings present a promising technology for cost-effective swine wastewater treatment and resource recovery.

The effect of cadmium on a semi-self-sustaining microalgal-bacterial granular sludge process for wastewater treatment

Microalgal-bacterial granular sludge (MBGS) is an innovative and sustainable technology for wastewater treatment. This research investigated the effect of Cd2+ on the performance and characteristics of such semi-self-sustaining MBGS reactors (with additional intermittent aeration). After 30 days of exposure to 0, 2, and 10 mg·l−1 Cd2+, the three reactors consistently exhibited robust removal efficiencies, achieving 89 % removal for chemical oxygen demand (COD) and 99 % removal for NH4+-N. However, the MBGS in control exhibited better performance in T-N removal compared to MBGS exposed to 10 mg·l−1 Cd2+ (especially during the light phase), indicating a potential impact of Cd2+ on the N-assimilation process of microalgae. The high concentration of Cd2+ also negatively affected the MBGS structure and increased the production of extracellular polymeric substances. Further investigations of the dissolved oxygen profile were conducted under phototrophic conditions, the maximum oxygen production rate contributed to microalgae in the control group was 20.9 % and 46.4 % higher than that of groups with 2 and 10 mg·l−1 Cd2+. The results show that Cd2+ mainly impacts the microalgae in the outer layer of the structure, and additional aeration helps compensate for the decrease in oxygen production caused by Cd2+ in MBGS, thereby making the system more stable in removing COD and NH4+-N.

Removal of heavy metal ions from water using nanocellulose-based membranes derived from macroalgae Chara corallina

Chara corallina is a freshwater macroalgae found in aquatic-terrestrial boundary environments. Their cellulose fibers have a crystallinity and biosynthesis similar to those of terrestrial plants. The algal nanocellulose (NC) was prepared through a series of chemical treatments, including alkaline, bleaching, grinding, and acid hydrolysis. The X-ray diffraction (XRD) crystallinity index of nanocellulose was 85.64%. The cellulose nanocrystals are seen in the form of nanorods, and the specific surface area of the sample of NC found was 5.823 m2g-1. The study aimed to test the effectiveness of a nanocellulose composite membrane in removing heavy metal ions, specifically cadmium (Cd), nickel (Ni), and lead (Pb) ions, from an aqueous solution. A vacuum filtration unit was used for the experiment, where up to five filter layers of composite membranes were examined for their ability to remove heavy metal ions. The results showed that the highest removal rates of Cd2+, Ni2+, and Pb2+ ions were 98.20%, 95.15%, and 93.80%, respectively, when using five layers of membranes of NC with the adsorbent dose set at 20 ppm. Cellulose and its derivatives are essential in sustainable technology for wastewater treatment, as they demonstrate exceptional performance in removing various types of pollutants, including heavy metals, dyes, and other pollutants. Cellulose is preferred due to its low cost, biodegradability, eco-friendliness, and simple surface modification.

Performances of constructed wetland system to treat whey and dairy wastewater during a macrophytes life cycle

Constructed wetlands system (CWs) have been proposed as an economical, efficient and sustainable wastewater treatment technology. The aim of this paper was to provide the first published data on the efficiency of CWs for dairy wastewater treatment in Tunisia. In most CWs, good organic, total suspended solids (TSS) and nutrient removal was measured. In order to evaluate the efficiency of this process, hybrid small-scale wetland system was designed containing three horizontal subsurface flow (HSSF) and one free water surface flow (FWS). A mixture of Reeds (Phragmites australis), Cattails (Typha latifolia), and Papyrus (Cyperus papyrus) was planted. Several water quality parameters in both raw and treated wastewaters were monitored during the macrophytes life cycle. The average influent properties for 20 % of whey are: TSS (3040 mg/L), COD (5060 mg O2/L), BOD5 (3020 mg O2/L), TKN (79 mg N/L) and TP (32,2 mg P/L). Removal efficiencies of 99.6 % for TSS, 80 % for COD, 97 % for BOD5, 90.4 % for TKN and 99.6 % for TP were observed. The results reveal temporal variations in system performance according to macrophyte growth rates. Reeds, Cattails and Papyrus start their life cycle at the beginning of the winter and continue growing in summer. The effluent pH, TSS, COD,BOD5, TKN and TP concentrations were in compliance with both irrigation reuse and discharge regulations.

Algal Membrane Bioreactors for Efficient Removal of Emerging Contaminants and Resource Recovery: Current Advances and Future Outlook

Emerging contaminants (ECs), whether of synthetic or natural origin, pose a significant environmental concern, particularly in the context of industrial wastewater. The Algae Membrane Photobioreactor (AMBR) has emerged as a promising technology for ECs remediation. AMBRs effectively remove contaminants due to its considerable flexibility, scalability and a huge surface area for pollutant adsorption. The productivity and efficiency of biomass are increased when it operates in regulated conditions, which minimizes land footprint. AMBR hold immense appeal in favoring integrated circular economy approach and its implementation could achieve the goals for carbon-neutrality and resource recovery by producing value-added products like biofuels, bioplastics, biochemicals, animal feed, biofertilizers and waste re-uses. However, addressing scalability, harvesting efficiency, membrane fouling, algal strain optimization, economic viability, and regulatory approval are some of the challenges faced in order to the advancement of AMBR technology. Life cycle assessments (LCA) and techno-economic assessments (TEAs) are crucial area of future research in implementation of AMBR at pilot scale. LCA evaluates the sustainability of AMBRs with those of conventional techniques. In contrast, TEA examines economic viability parameters like cost-effectiveness, by-product market potential, and policy implications for AMBR implementation. This review emphasizes AMBR's advantages over conventional wastewater treatment technologies in detail, focusing on algal physiology responsible for ECs removal. The innovations related to the design and configuration of AMBRs are also discussed. Several benefits of this technology via integrated circular paradigm are highlighted. Noteworthy pilot case studies, LCA, TEA, challenges and future perspective are spotlighted to underscore the compelling promise of this technology.

The Aerobic Granules Process for Wastewater Treatment: From Theory to Engineering

Aerobic granules are small, dense aggregates of microbial cells that form naturally in aerobic wastewater treatment systems. They are characterized by their spherical shape, strong structural integrity, and ability to rapidly settle. These granules are formed through a self-immobilization process where different microbial species coalesce to degrade organic and inorganic compounds in wastewater. This study summarizes the development of aerobic granulation technology in wastewater treatment and the mechanism of aerobic granules’ formation, analyzes the characteristics and the factors affecting the aerobic granules’ formation, and presents practical engineering examples of its application from pilot-scale to full-scale operation.

Research progress of electrolytic treatment technology for organic wastewater

Research progress of electrolytic treatment technology for organic wastewater

Novel 2D/2D S-scheme heterojunction photocatalyst for peroxymonosulfate activation enables ciprofloxacin ultrafast degradation: High-efficiency photogenerated carrier transport

Organic pollutants, such as ciprofloxacin (CIP), are ubiquitously detected in wastewater. However, their removal remains a challenge for conventional wastewater treatment technologies. Photocatalysis and peroxymonosulfate activation coupling are considered a promising strategy for the removal of recalcitrant organic pollutants. However, identifying optimal photocatalysts that can effectively couple with peroxymonosulfate activation and induce synergistic degradation of organic pollutants remains a challenge to be addressed. In this work, a novel S-scheme inorganic–organic heterojunction BiVO4/Cu-TCPP (BC) was fabricated. In situ X-ray photoelectron spectrum showed that the strong internal electric field of the S-scheme heterojunctions enabled efficient carrier transport. The generated photogenerated electrons could activate the peroxymonosulfate, which further promoted the separation of the carriers. The BC-vis-peroxymonosulfate system achieved 93.1% ciprofloxacin removal in 10 min with apparent rate constants k of 0.2426 min−1, which is larger than most reported peroxymonosulfate systems. Electron paramagnetic resonance spectra and liquid chromatography mass spectrometry demonstrated that the synergistic coupling of S-scheme heterojunction with peroxymonosulfate activation significantly improved the catalytic activity of the reaction system and enabled rapid CIP removal via both radical and nonradical pathways. The BC-vis-peroxymonosulfate system demonstrated ultra-fast removal of other quinolone antibiotics and organic pollutants and strong environmental adaptability under various conditions, suggesting its great potential for practical application. This study provides new insights for the design of efficient S-scheme heterojunction coupled peroxymonosulfate activation for environmental remediation.

Advancing wastewater treatment technologies: The role of chemical engineering simulations in environmental sustainability

Wastewater treatment stands as a critical component in mitigating environmental pollution and safeguarding public health. This review delves into the pivotal role of chemical engineering simulations in advancing wastewater treatment technologies towards enhanced environmental sustainability. The modernization of wastewater treatment processes necessitates a comprehensive understanding of the complex physical, chemical, and biological interactions involved. Chemical engineering simulations offer a powerful toolset for modeling and optimizing these processes with a focus on efficiency, effectiveness, and sustainability. Firstly, simulations enable the prediction and analysis of pollutant removal mechanisms within treatment systems. By simulating various operating conditions and configurations, engineers can optimize treatment processes to achieve higher removal efficiencies while minimizing resource consumption and waste generation. Secondly, simulations aid in the design and development of innovative treatment technologies, such as membrane filtration, advanced oxidation processes, and biological nutrient removal systems. Through computational modeling, engineers can assess the performance and feasibility of these technologies under different scenarios, facilitating informed decision-making and accelerating their implementation. Furthermore, chemical engineering simulations play a crucial role in addressing emerging challenges in wastewater treatment, including the removal of emerging contaminants such as pharmaceuticals, microplastics, and endocrine-disrupting chemicals. By simulating the behavior of these contaminants within treatment systems, engineers can devise targeted strategies for their removal, thus mitigating their adverse environmental and public health impacts. Chemical engineering simulations serve as indispensable tools for advancing wastewater treatment technologies towards greater environmental sustainability. By facilitating the optimization, design, and innovation of treatment processes, simulations contribute to the development of more efficient, cost-effective, and environmentally friendly solutions for managing wastewater and protecting our ecosystems. Embracing these simulation-driven approaches is essential for achieving the ambitious goals of sustainable development and ensuring a cleaner, healthier future for generations to come.

Investigation of shear stress behavior on membrane surfaces in reciprocating membrane bioreactors using fluid-structure interaction simulations

Although reciprocating membrane bioreactors (rMBRs) have been developed as energy-efficient wastewater treatment technologies, fouling removal mechanisms are yet to be elucidated. This study conducted simulations of fluid-structure interaction and experiments using particle image velocimetry to investigate the behavior of shear stress on the membrane surface in rMBRs. Simulations were performed on the three-dimensional model, varying parameters such as average reciprocating velocity (ARV), moving distance (MD), and membrane slack ratio (MSR). The results found that fluid advection can hinder foulant adhesion to the membranes. Increasing the ARV from 4 to 12 cm/s under shear stress resulted in higher fluid resistance and inertial forces, leading to elevated shear stress. The effect of MD on shear stress was negligible within the range of 4–12 cm. An intermediate level of MSR from 0 to 3% promoted turbulence around the membrane, thereby increasing shear stress. The response surface suggested that it may be desirable to simultaneously increase the ARV and MSR to maximize shear stress. However, this increase can also lead to stability failure by increasing the principal stress in the membrane potting area. This study provides insights into fouling removal mechanisms to improve the efficiency of rMBRs.

Improved hydrodynamic properties and enhanced resistance to particle deposition and membrane fouling by millimeter-scale patterned membranes

Membrane fouling is considered a persistent challenge in membrane technology for water and wastewater treatment. Membrane surface patterning is a chemical-free means of controlling membrane fouling. Previous studies mainly focused on nano- and micro-scale patterns, with little attention paid on millimeter-scale patterns on the membrane surface. In this study, the millimeter-scale patterned microfiltration membranes with different pattern heights (PM50, PM55 and PM60) were fabricated, the performances in resisting particle deposition and membrane fouling with synthetic wastewater were examined compared with flat-sheet membrane (FM), and the underlying hydrodynamic mechanism was unveiled using computational fluid dynamics (CFD). CFD simulation results reveal that compared to micro- and nano-scale patterns, millimeter-scale patterns exert a notable increase in maximum velocity, average shear stress and maximum shear stress. All the three millimeter-scale patterned membranes exhibit superior resistance to both particle deposition and membrane fouling than FM, owing to the improvement of hydrodynamic properties instead of enlarged membrane area. PM55 shows the lowest flux decline ratios and least particle/foulant deposition among the three millimeter-scale patterned membranes in both particle deposition and membrane fouling experiments. Pattern height plays a crucial role, as small pattern height cannot generate significant vortices, while high pattern height leads to flow separation. For PM55, the vortices form in the valley regions and locate close to bulk flow, which help transport the deposited particles or foulants back to the bulk flow. The design of pattern configuration is suggested to be tailored based on particle size. Future research can focus on the pilot testing of millimeter-scale patterned membranes, as well as the long-term stability with actual influent.

Degradation of brilliant crocein using the halotolerant bacterial consortium DAS

Technologies for removing azo dyes from textile wastewater have attracted increasing attention. In this study, a biological method was developed using the halotolerant bacterial consortium DAS, which was isolated from an activated sludge sample. Under optimal conditions (i.e., 40℃, pH 6.0, 15% salinity and 400 mg·L−1 peptone), the degradation rate of Brilliant Crocein (BC) (500 mg·L−1 initial concentration) was 70.67 mg·L−1·h−1, with a removal percentage of 97.43±0.15% after an incubation period of 3 days. Growth-based characterizations showed that the addition of peptone as a cosubstrate facilitated degradation by enhancing metabolic activity and increasing the total bacterial biomass. 16 S rRNA-based gene analysis showed that the addition of peptone did not increase the abundance of degrading functional bacteria in the halotolerant bacterial community DAS. The degradation could be carried out in mediums with high salinity (up to 25%), enabling direct treatment of textile wastewater without the need for the dilution step. This biological method is promising for constructing an efficient and environmentally friendly technology for textile wastewater treatment.

Floating La modified g-C3N4 photocatalytic sponge mesh for sustainable dye degradation under sunlight irradiation

The excellent photocatalyst, g-C3N4, presents separation and regeneration challenges due to its tendency to aggregate in aqueous solutions, which not only increases the cost of practical applications but also represents a significant research hurdle. In this study, we report a simple method to use polyurethane sponge as a carrier to support photocatalyst (La modified g-C3N4, LACN) to form a floating photocatalytic mesh (PS-LACN). The PS-LACN shows an excellent methylene blue (MB) degradation performance in an outdoor reactor under sunlight irradiation. The tests also showed that the PS-LACN was stable and reusable over four cycle times without significant loss of efficiency. Monte Carlo simulations demonstrated the low cost of PS-LACN. Taken together, this study provides a simple, economical and sustainable technology for dye wastewater treatment.

Scientific and technological innovations of wastewater treatment in China

The “dual-carbon” strategy promotes the development of the wastewater treatment sector and is an important tool for leading science and technology innovations. Based on the global climate change and the new policies introduced by China, this paper described the new needs for the development of wastewater treatment science and technology. It offered a retrospective analysis of the historical trajectory of scientific and technological advancements in this field. Utilizing bibliometrics, it delineated the research hotspots within wastewater treatment, notably highlighting materials genomics, artificial intelligence, and synthetic biology. Furthermore, it posited that, in the future, the field of wastewater treatment should follow the paths of technological innovations with multi-dimensional needs, such as carbon reduction, pollution reduction, health, standardisation, and intellectualisation. The purpose of this paper was to provide references and suggestions for scientific and technological innovations in the field of wastewater treatment, and to contribute to the common endeavor of moving toward a Pollution-Free Planet.

Performance of a Solar-Driven Photocatalytic Membrane Reactor for Municipal Wastewater Treatment

The increasing demand for efficient wastewater treatment technologies, driven by global population growth and industrialisation, highlights the necessity for advanced, reliable solutions. This study investigated the efficacy of a slurry photocatalytic membrane reactor (PMR) for the advanced removal of organic pollutants, quantified via chemical oxygen demand (COD), under natural and simulated solar light irradiation. Employing two variants of iron-doped titania as photocatalysts and a polysulfone-based polymeric membrane for the separation process, the investigation showcased COD removal efficiencies ranging from 66–85% under simulated solar light to 52–81% under natural sunlight over a 7 h irradiation period. The overall PMR system demonstrated COD removal efficiencies of 84–95%. The results confirmed the enhanced photocatalytic activity afforded by iron doping and establish solar-powered slurry PMRs as an effective, low-energy, and environmentally friendly alternative for the advanced treatment of municipal wastewater, with the research providing valuable insights into sustainable water management practices.