High Salinity Wastewater Treatment Research Articles

Hydrophobic C60-modified PVDF membrane with micro-nano structures for mitigating CaSO4 scaling in direct contact membrane distillation (DCMD)

Membrane scaling is a non-negligible problem for membrane distillation (MD) in the treatment of high-salinity wastewater (e.g., calcium sulfate and calcium carbonate). In this study, fullerene (C60) was adhered to a polyvinylidene fluoride (PVDF) membrane using a polydimethylsiloxane (PDMS) solution to create a micro-nano structure, fabricating the C60/PDMS-PVDF membrane. This membrane was then re-immersed in a PDMS solution to further reinforce the C60 nanoparticles on the surface, forming the PDMS/C60/PDMS-PVDF membrane. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the membrane surface morphology. Fourier transform infrared (FT-IR) was used to explore the membrane chemical composition. Liquid entry pressure (LEP) and water contact angle (WCA) measurements were employed to assess the membrane wettability. The results showed that C60-modification created the micro-nano structure on the membrane surface. The WCA of the PVDF membrane was 112.7 ± 2.4°, with a sliding angle far greater than 90°, whereas the PDMS/C60/PDMS-PVDF membrane exhibited a WCA of 147.9 ± 3.2° and a sliding angle of 6.3°. Compared to the virgin PVDF membrane, the LEP value of the PDMS/C60/PDMS-PVDF membrane increased from 68.4 ± 2.7 kPa to 87.2 ± 3.3 kPa. In direct contact membrane distillation (DCMD), a CaSO4 solution (2 g/L) was used to test the membrane performance. After 48 hours of operation, the flux of the PDMS/C60/PDMS-PVDF membrane remained at approximately 3.57 kg/(m2·h), and the salt rejection rate was over 99.96 %. This could be attributed to the C60 modification forming a micro-nano structure on the membrane surface, which trapped an air layer. This air layer could reduce the contact area between the crystal and the membrane, decrease nucleation probability, and shorten the residence time of liquid on the membrane surface. Additionally, the PDMS/C60/PDMS-PVDF membrane exhibited superior stability during the ultrasonic destruction experiment due to the encapsulation of PDMS. In summary, a novel hydrophobic membrane with a micro-nano structure was fabricated through C60 modification, offering superior anti-scaling properties and stability in treating high-salinity wastewater.

Impacts of high salinity on antifouling performance of hydrophilic polymer-modified reverse osmosis (RO) membrane

Reverse osmosis (RO) is a crucial process for treating waters across various salinity levels, but membrane fouling persists as an inherent challenge. While surface modification with hydrophilic polymers such as polyethylene glycol (PEG) and its derivatives is a prevailing strategy to alleviate fouling, its effectiveness has primarily been explored in low-salinity conditions, leaving a critical knowledge gap regarding the performance of such membranes in high-salinity environments and their susceptibility to feed salinity variations. We here investigated the antifouling characteristics of PEG-modified RO membranes for high-salinity wastewater and seawater treatment. Remarkably, our findings indicated a substantial decrease in fouling resistance under high-salinity conditions compared to low-salinity wastewaters used as control. The reduction in Lewis acid-base interactions, induced by decreased water structuring, was found to be a critical factor for the diminished fouling resistance based on the Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis. Complementary experimental and theoretical studies unveiled the disruptive role of high-concentration NaCl on PEG-water hydrogen bonds, causing PEG dehydration and configurational compression, which thus compromised the enthalpic barrier and entropic repulsion against fouling. Our study emphasizes the pivotal role of feed salinity in determining the fouling resistance of membranes modified with hydrophilic polymers, a factor often neglected in prior research.

Facile preparation of a novel basalt fiber fabric-based photothermal material for high salinity wastewater treatment and solar interface evaporation

Solar-driven interfacial evaporation (SIE) is a sustainable, efficient, and environmentally friendly desalination technology. It has great potential for solving the shortage of clean water and environmental pollution that humanity faces. Nevertheless, low strength, inadequate efficiency, and complicated preparation process of photothermal materials continue to be primary barriers to achieving the widespread application of SIE technology. Therefore, in the present work, a low-cost and eco-friendly photothermal material was prepared successfully by using multi-walled carbon nanotubes (MWCNTs), sodium alginate (SA) hydrogel, and basalt fiber (BF) fabric for obtaining purified/drinking water from seawater/brackish water. The results indicated that newly developed MWCNTs-SA/BF fabric had better wettability, evaporation performance, and purification capability. The evaporation rate of MWCNTs-SA/BF evaporator using simulated high salinity seawater could reach 1.48 kg m−2h−1 and 2.5 kg m−2h−1, under 1 and 2 suns illumination, respectively, and solar energy utilization efficiency is 91.6 % under 1 sun irradiation. Additionally, cyclic evaporation test results show that fabrics are highly durable for long-term solar evaporation. Furthermore, an excellent water purification performance of MWCNTs-SA/BF fabrics was also demonstrated by evaluating the purity of water samples and determining the changes in the four major ions (Na+, K+, Ca2+, and Mg2+) in seawater before and after evaporation experiments. This work provides a simple, practical, and economical approach to preparing a novel BF fabric-based evaporator that utilizes abundant solar energy potential for large-scale desalination and wastewater treatment.

Catalytic ozonation of reverse osmosis concentrate from coking wastewater reuse by surface oxidation over Mn-Ce/γ-Al2O3: Effluent organic matter transformation and its catalytic mechanism

Degradation of organics in high-salinity wastewater is beneficial to meeting the requirement of zero liquid discharge for coking wastewater treatment. Creating efficient and stable performance catalysts for high-salinity wastewater treatment is vital in catalytic ozonation process. Compared with ozonation alone, Mn and Ce co-doped γ-Al2O3 could remarkably enhance activities of catalytic ozonation for chemical oxygen demand (COD) removal (38.9%) of brine derived from a two-stage reverse osmosis treatment. Experimental and theoretical calculation results indicate that introducing Mn could increase the active points of catalyst surface, and introducing Ce could optimize d-band electronic structures and promote the electron transport capacity, enhancing HO• bound to the catalyst surface ([HO•]ads) generation. [HO•]ads plays key roles for degrading the intermediates and transfer them into low molecular weight organics, and further decrease COD, molecular weights and number of organics in reverse osmosis concentrate. Under the same reaction conditions, the presence of Mn/γ-Al2O3 catalyst can reduce ΔO3/ΔCOD by at least 37.6% compared to ozonation alone. Furthermore, Mn-Ce/γ-Al2O3 catalytic ozonation can reduce the ΔO3/ΔCOD from 2.6 of Mn/γ-Al2O3 catalytic ozonation to 0.9 in the case of achieving similar COD removal. Catalytic ozonation has the potential to treat reverse osmosis concentrate derived from bio-treated coking wastewater reclamation.

High performance bimetallic ZIF-CoZn@PVDF-HFP composite nanofiber membrane for membrane distillation based on coaxial electrospinning technology

Membrane Distillation (MD) technology stands out for its cost-effectiveness and sustainability in diverse applications, such as high-salinity wastewater treatment and seawater desalination. However, conventional MD membranes frequently encounter challenges associated with inadequate permeate flux and insufficient anti-wetting performance. In the present study, we fabricated a series of ZIF-CoZn@PVDF-HFP composite nanofiber membranes with a core–shell structure via coaxial electrospinning. Here, PVDF-HFP functions as the core, while a blend of bimetallic Zeolitic imidazolate framework ZIF-CoZn nanoparticles and PVDF-HFP constitutes the shell. Through the utilization of the coaxial technology, functional nanoparticles achieve uniform and stably dispersed on the nanofiber surface, leading to the creation of a secondary rough structure in addition to the inherent roughness of single-nozzle electrospinning. This results in a surface with a 3D-hierarchical structure. The significantly amplifies the evaporation area on the surface of the composite nanofiber membrane, thereby bolstering the permeate flux in the MD process. Additionally, the incorporation of bimetallic ZIF-CoZn nanoparticles, recognized for their superior hydrophobicity and low thermal conductivity, improves the anti-wetting and heat-insulating properties of the composite nanofiber membrane, further advancing permeate flux performance. Using a 35 g L−1 NaCl as the feed solution, the optimal 1 % ZIF-CoZn@PVDF-HFP composite nanofiber membrane demonstrated a permeate flux of 21.8 L m−2 h−1, coupled with a salt rejection rate exceeding 99.9 %. Even during long-term MD testing, it maintained excellent insulation and anti-wetting capabilities. Our research offers a convenient and effective approach for fabricating anti-wetting composite nanofiber membranes.

Fluid dynamics and energy efficiency of submerged combustion process for treating wastewater with high salinity and COD concentration

Focusing on submerged combustion technology for the treatment of high salinity and high chemical oxygen demand (COD) wastewater, this study explores the characteristics of gas-liquid two-phase flow and heat transfer during the submerged combustion process, employing both experimental and numerical simulation methods.Consequently, the impact of essential parameters on the efficacy of submerged combustion in treating wastewater was analyzed. The experimental results show that increasing the fuel flow rate and immersion depth is beneficial to improve the temperature rise rate and shorten the evaporation time. With the increase of the organic solution flow rate and the initial COD value of the organic solution, the COD removal rate decreased, and the effect of the organic solution flow rate on the COD removal efficiency was more obvious. The use of a flat orifice plate or tapered orifice plate immersed tube structure can improve the thermal efficiency by over 10%. However, it is not conducive to the stability of the pressure in the combustor, increasing the fluctuation of the liquid level. Compared with that of traditional single-effect evaporation crystallization, the energy consumption of the submerged combustion device is decreased, and the total operation cost is reduced by 22.5%.

Recovery mechanism of heterotrophic ammonia assimilation system under chromium hexavalent stress

Heterotrophic ammonia assimilation (HAA), an innovative technology for high-salinity wastewater treatment, demonstrates self-recovery capability following Cr (VI) stress. This study investigated the inhibitory effects and self-restoration mechanisms of Cr (VI) at various stress levels. The removal efficiencies of NH4+-N and Cr (VI) in the HAA gradually decreased with increasing influent Cr (VI) concentration. Exposure to Cr (VI) increased the amounts of high-molecular-weight proteins in soluble microbial products and stimulated the generation of extracellular polymeric substances. Heterotrophic functional microorganisms with Cr (VI) tolerance, such as Marinobacter and Planktosalinus, were enriched. An assimilation pathway gene (glnA) and a Cr (VI)-related gene (atoB) were also upregulated. After ceasing Cr (VI) addition, the HAA system demonstrated a 17.1 % increase in the removal efficiency of NH4+-N, which was attributable to its self-recovery ability. This study provides a scientific and theoretical foundation for the HAA process in resisting the impact of heavy-metal-containing wastewater and self-recovery.

Research Progress in the Treatment of High-Salinity Wastewater

The generation of high-salinity wastewater is closely associated with various industries, containing a plethora of dissolved salts such as chlorides, sulfates, and carbonates, which pose a significant threat to the environment and human health. Consequently, the treatment of high-salinity wastewater has emerged as a pivotal environmental challenge in contemporary society. This review aims to elucidate the sources and characteristics of high-salinity wastewater, as well as the current status and trends in the field of high-salinity wastewater treatment. First and foremost, we explore the means by which high-salinity wastewater is generated in different industries and the principal salt components it contains. We revisit conventional methods for high-salinity wastewater treatment, including chemical precipitation, ion exchange, evaporation-crystallization, and reverse osmosis, while emphasizing the application of biotechnological approaches. This includes the utilization of salt-tolerant microorganisms, biological adsorption, biodegradation processes, and various types of bioreactors. Advanced oxidation technologies also play a crucial role in high-salinity wastewater treatment. We introduce advanced oxidation techniques such as ozone oxidation, UV-catalyzed oxidation, and high-pressure water oxidation, emphasizing their potential in degrading organic compounds and reducing salt concentration. Furthermore, we discuss hybrid approaches, such as case studies combining biological treatment with advanced oxidation technologies, and the advantages and challenges associated with these integrated techniques. Finally, we provide an outlook on future trends, including research on novel and efficient biodegrading agents, advancements and innovations in advanced oxidation technologies, and the development of intelligent high-salinity wastewater treatment systems. Policy and industry trends will also influence the direction of high-salinity wastewater treatment field development. In summary, high-salinity wastewater treatment represents a complex and pressing environmental challenge. However, through the integration of diverse treatment technologies and ongoing research efforts, it is anticipated that more effective, cost-efficient, and environmentally friendly solutions can be developed to mitigate the impact of high-salinity wastewater on ecosystems and society.

Experimental Study on the Desalination of Waste Leachate Using the Combined Freezing Method

The current high-salinity wastewater treatment technology is complex, costly, and carries the risk of secondary contamination. As a traditional desalination technology, the combined method using frozen technology has broad development prospects in wastewater treatment. This study investigates the desalination effects of waste leachate using three different methods: the frozen–gravity method (FGM), frozen–centrifugal method (FCM), and frozen–blowing methods (FBMs), under various experimental conditions. The results showed that the salt rejection of all three methods could reach more than 75% under the conditions of a freezing time of 12 h, freezing temperature of −15 °C, and ice production rate of 40%; the salt rejection of FGM increased at higher ambient temperatures, but it was not conducive to the removal of organic pollutants; the salt rejection of FCM was sensitive to the centrifugal time and centrifugal speed, with a significant correlation (p < 0.05), the increase in centrifugal time and centrifugal speed can help to improve the salt rejection, and the increase in centrifugal speed in the range of 1000–2000 rpm can accelerate the discharge of concentrated brine more effectively; the frozen–crushed–blowing method (FCBM) in FBM has a salt rejection as high as 93.86% at an ice production rate of 25.80%, which reduces the salinity of the effluent from 4.07% to 0.25%, speeds up the desalination process, and improves the salt rejection compared to the other methods. This study provides a new perspective and reference for the treatment of high-saline wastewater.

Aminal-Linked Covalent Organic Framework Membranes Achieve Superior Ion Selectivity.

High-salinity wastewater treatment is perceived as a global water resource recycling challenge that must be addressed to achieve zero discharge. Monovalent/divalent salt separation using membrane technology provides a promising strategy for sulfate removal from chlor-alkali brine. However, existing desalination membranes often show low water permeance and insufficient ion selectivity. Herein, an aminal-linked covalent organic framework (COF) membrane featuring a regular long-range pore size of 7Å and achieving superior ion selectivity is reported, in which a uniform COF layer with subnanosized channels is assembled by the chemical splicing of 1,4-phthalaldehyde (TPA)-piperazine (PZ) COF through an amidation reaction with trimesoyl chloride (TMC). The chemically spliced TPA-PZ (sTPA-PZ) membrane maintains an inherent pore structure and exhibits a water permeance of 13.1Lm-2h-1bar-1, a Na2SO4 rejection of 99.1%, and a Cl-/SO4 2- separation factor of 66 for mixed-salt separation, which outperforms all state-of-the-art COF-based membranes reported. Furthermore, the single-stage treatment of NaCl/Na2SO4 mixed-salt separation achieves a high NaCl purity of above 95% and a recovery rate of ≈60%, offering great potential for industrial application in monovalent/divalent salt separation and wastewater resource utilization. Therefore, the aminal-linked COF membrane developed in this work provides a new research avenue for designing smart/advanced membrane materials for angstrom-scale separations.

Bioaugmentation using salt-tolerant bacteria in a dual-stage process for high-salinity wastewater treatment: Performance, microbial community, and salt-tolerance mechanism

To address the challenges of nitrogen removal and stability problems in biological treatment of high-salinity wastewater, a new technology based on salt-tolerant aerobic denitrifying (SAD) bacteria to strengthen the two-stage bio-contact oxidation reactor (TBOR) and moving bed biofilm reactor (MBBR) dual-stage process was proposed. The results showed that the NH4+-N removal rate of TBOR and TN removal rate of MBBR increased by 26.05 % and 15.90 %, respectively, after bioaugmentation with SAD bacteria at salinity of 5 %. The COD, NH4+-N and TN removal rates in real wastewater (at salinity of 4 ~ 5 %) treatment were 93.45 %, 97.57 % and 90.83 %, respectively. Microbial analysis showed that at salinity of 5 %, SAD bacteria Halomonas and Truepera were the main functional bacteria responsible for nitrogen removal. Microbial functional analysis and metabolic predictions further revealed that bioaugmentation enhanced the expression of the nir gene, thereby further promoting the process of dissimilatory nitrite reduction to ammonium (DNRA). Furthermore, bioaugmentation can also resist the external high-salinity environment by exporting Na+ extracellularly, promoting extracellular polymeric substances (EPS) secretion and amino acid metabolism. This study demonstrates that bioaugmentation with SAD bacteria is a suitable approach for nitrogen and carbon removal of high-salinity wastewater.

Particle emissions from submerged combustion evaporation of membrane-concentrated leachate

The submerged combustion evaporation process, which is extensively utilized in the treatment of high salinity wastewater, inevitably confronts the challenge of particle emissions. These emissions significantly impact the local environment and pose substantial health risks to on-site workers. Currently, the understanding of particle emissions' characteristics and their critical conditions during direct-contact heat and mass transfer processes is limited, which hampers the development of effective strategies for particle control. Here, particles emitted from three evaporation projects with different membrane-concentrated leachate sources were first characterized. Most of the particles were ultrafine particles (≤100 nm) in the range of 6–500 nm, most of which were in the range of 30 nm and constituted 75.37%–89.98% of the total mass. The particles were mainly composed of inorganic ions (80.86%–86.88%), humus (1.95%–3.66%) and insoluble carbon (2.57%–4.26%). The particle concentrations range from 1.64 to 218.35 mg/m3, depending on factors such as bubble temperature, evaporation capacity, and leachate composition within evaporators. A model assessing particle release capacities showed an increase with rising bubble temperature and humus concentration. A critical bubble temperature of 1390 K was identified for significant particle release, highlighting the need to keep the bubble temperature below this level to manage heat-induced particle release within 2 mg/m3. Additionally, the high humus migration capacity to particles underscores the need to prioritize humus removal before evaporation in particle control strategies. The application of these strategies can significantly decrease particle emissions, fostering cleaner production during submerged combustion evaporation and other direct-contact heat and mass transfer processes.

Microalgae biofilm photobioreactor and its combined process for long-term stable treatment of high-saline wastewater achieved high pollutant removal efficiency

High-saline wastewater treatment processes have a high energy demand, while microalgae-driven wastewater biotechnology is both economical and environmentally friendly, and the use of microalgae to treat high-saline wastewater can effectively reduce energy consumption. However, it is unclear whether the performance of microalgae reactor can be stable for a long time. In this study, an open continuous-flow biofilm photobioreactor using Dunaliella salina was innovatively constructed, and operated in combination with a membrane bioreactor (MBR) for high-saline wastewater treatment. The purpose of this study was to investigate the long-term performance of MBR, MBPBR alone and their combined operation for the removal of organic matter, phosphorus and nitrogen, explore the pathway and mechanism of nitrogen and phosphorus removal by MBPBR, and evaluate the feasibility of MBPBR-MBR integrated system for the treatment of saline wastewater. The MBR effectively removed most of the organic matter and converted ammonia nitrogen into nitrate nitrogen, which is a preferred nitrogen source for the growth of Dunaliella salina, thereby providing favorable water quality for Dunaliella salina in the subsequent MBPBR. The MBPBR, with a hydraulic retention time (HRT) of 72 h, achieved a NO3--N removal load of 74.9 g N/(m3∙d) and a removal efficiency of approximately 60 %, and the PO43--P removal load of 8.33 g P/(m3∙d) and removal efficiency of over 80 %. The MBR-MBPBR system demonstrated long-term stability, achieving removal efficiencies of 84.3 %, 81.6 %, and 91.0 % for COD, TN and PO43--P, respectively. Within the MBPBR, the growth of algae and their assimilation contributed 44.9 % and 38.7 % of the nitrogen and phosphorus removal, respectively. The abundance of Dunaliella salina in the MBPBR remained at approximately 90 % for over 40 days of operation, providing an opportunity for Dunaliella salina recovery. These findings provide valuable insights into the utilization of microalgae for the treatment of high-salinity wastewater, while also supporting the practical implementation of microalgae-based treatment methods for such wastewater.

Unraveling the role of NaCl on microfiltration fouling: Insights from In situ analysis of dynamic interfacial behaviors

Resolving the interfacial behaviors plays a pivotal role in elucidating the formation of membrane fouling. However, quantifying the short-term rapid changes in these processes remains challenging, particularly for complex solutions like food waste digestate. In this study, a poly (vinylidene fluoride) (PVDF) membrane was employed to filter food waste digestate; the dynamic membrane-foulant and foulant-foulant interactions during the initial filtration were in situ examined using optical coherence tomography (OCT) to ascertain the effects of varying concentrations of sodium chloride (NaCl). Results indicate that NaCl could alter the solution structure by disrupting the hydration bonds. The hydration repulsion caused by Na+ ions gave rise to a slower deposition of foulants, thereby delaying the transition from membrane-foulant to foulant-foulant interactions; the hydration-repulsion effect was intensified by increasing the salt concentration. On the other hand, when foulant-foulant interactions began to dominate, compression of the electric double layer could result from the elevated ionic strength and thereby contribute to a denser cake layer. Moreover, the hydrated layer could also be an effective inhibitor to the internal fouling that plagues the membrane cleaning. These mechanistic insights would be in favor of designing more efficient fouling-control strategies for membrane-based treatment of high salinity wastewater.

Performance analysis of microbial fuel cell - membrane bioreactor with reduced graphene oxide enhanced polypyrrole conductive ceramic membrane: Wastewater treatment, membrane fouling and microbial community under high salinity

The application of membrane bioreactor (MBR) in high salinity wastewater treatment was mainly hindered by membrane fouling. Microbial fuel cell (MFC)-MBR coupling system was established to alleviate membrane fouling and save energy. Reduced graphene oxide/polypyrrole ceramic membrane (rGO/PPy CM) with high conductivity and stability was innovatively placed in MFC-MBRs as both cathode and filter, with PPy CM, rGO/PPy CM and CM placed in other reactors. MFC-MBR (rGO/PPy) and MFC-MBR (PPy) achieved higher pollutant removal efficiencies (90.73 % and 90.45 % for TOC, 87.22 % and 86.56 % for NH4+-N, respectively) and superior anti-fouling performance (1.86 and 1.93 kPa/d for average membrane fouling rates) than both conventional MBRs (CMBRs). The stable voltage generation was around 287 and 242 mV, respectively. Through high throughput sequencing, electric field showed a positive correlation with the abundance and activity of most dominant phylum (Bacteroidetes, Chloroflexi, Actinobacteria, and Firmicutes) and functional genes (amoA, hao, narG, napA, nirK, norB, and nosZ), thereby improving pollutant removal efficiency. The higher conductivity of rGO/PPy CM resulted in enhanced electric field intensity, leading to superior performance of anti-fouling and pollutant removal. This study inventively explored the effects of conductive membrane property on electricity generation performance, microbial community, pollutant removal and membrane fouling, providing theoretical support for the selection of electrode materials in MFC-MBR.

Enhancing microbial salt tolerance through low-voltage stimulation for improved p-chloronitrobenzene (p-CNB) removal in high-salinity wastewater

As an important raw material for the synthesis of chemical and pharmaceutical, hazardous carcinogen p-chloronitrobenzene (p-CNB) has been widely found in high-salinity wastewater which need to be treated carefully. Due to the high-salinity shock on microorganisms, conventional microbial treatment technologies usually show poor effluent quality. This study initially investigated the p-CNB removal performance of microorganisms stimulated by 1.2 V low-voltage in high-salinity wastewater under facultative anaerobic conditions and further revealed the enhanced mechanisms. The results showed that the p-CNB removal kinetic parameter kp-CNB in the electrostimulating microorganism reactor (EMR) increased by 104.37 % to 155.30 % compared to the microorganism reactor (MR) as the control group under the varying salinities (0–45 g/L NaCl). The secretion of extracellular polymeric substances (EPS) in halotolerant microorganisms mainly enhanced by 1.2 V voltage stimulation ranging from 0 g/L NaCl to 30 g/L NaCl. Protein concentration ratio of EMR to MR in loosely bound EPS achieved maximum value of 1.77 at the salinity of 15 g/L NaCl, and the same ratio in tightly bound EPS also peaked at 1.39 under the salinity of 30 g/L NaCl. At the salinity of 45 g/L NaCl, 1.2 V voltage stimulation mainly enhanced salt-in strategy of halotolerant microorganisms, and the intracellular Na+ and K+ concentration ratio of EMR to MR reached maximum and minimum values of 0.65 and 1.92, respectively. Furthermore, the results of microbial metagenomic and metatranscriptomic analysis showed the halotolerant microorganisms Pseudomonas_A and Nitratireductor with p-CNB removal ability were enriched significantly under 1.2 V voltage stimulation. And the gene expression of p-CNB removal, salt-in strategy and betaine transporter were enhanced under voltage stimulation at varying salinities. Our investigation provided a new solution which combined with 1.2 V voltage stimulation and halotolerant microorganisms for the treatment of high-salinity wastewater.

Centrifugation forced ice-concentrate separation to enhance suspension freezing desalination performance

Suspension freeze desalination is a promising route for treatment of high salinity wastewater, but the poor ice-concentrate separation often generates decrease of desalination efficiency. In this work, it is demonstrated that centrifugation forced dewatering can assist in ice purification and enhance suspension freeze desalination performance. The positive correlation and good linear fitting relationship between ice purity and dewatering rate were identified at various centrifugation speeds, centrifugation time, and ice layer thickness. Changes of ice shape were recorded by low-temperature optical microscope observation system. The free water removal and ice floc destruction induced by centrifugal field have an important contribution to ice purification. Increasing centrifugation speed from 100 r/min to 500 r/min, the corresponding relative centrifugal force increased 27-fold, creating sharp increases in ice purity (rate constant k = 0.1605) and dewatering rate (rate constant D = 0.0563). Due to the strong binding characteristics and small portion of bound water, ice desalination efficiency per unit centrifugal force dropped when centrifugation speed increased from 1000 r/min to 3000 r/min. Besides, the multi-step dewatering and purification mechanism involved in ice centrifugation was depicted. The suspension freeze technology hybrid with centrifugation not only enhances desalination efficiency but also is beneficial to obtain high-purity ice.

Membrane flux response technology for early warning of initial surface scaling in membrane distillation

Membrane distillation (MD) is a promising green separation technology for the treatment of high salinity wastewater attributed to excellent salt rejection, which is significant in relevant environmental and chemical engineering application. However, membrane scaling is an inevitable issue during long-term membrane distillation process. Thus, we developed a membrane flux response technology with data processing method to in-situ monitor the membrane scaling according to the reduction of permeate flux. By real-time analyzing the derivative of deviation between theoretical and experimental fluxes, early warning of initial membrane surface scaling was observed at initial nucleation stage. Besides, such timely detection was also achieved under different temperatures and flow velocities of feed solution, even for the poor light transmittance aqueous solution (such as NiSO4 and CoSO4 solution), which exhibited wide application potential on diverse high salinity wastewater systems. In addition, the metastable zone width of salt solution within MD system was obtained for the efficient operation design. To sum up, membrane flux response technology provides an early warning at imminent membrane scaling, which will maintain the great separation effect for a fresh feed solution after a facile cleaning by pure water, indicating the extension of device lifetime.

Ingenious integration of Fe0 and multiphased MoS2 to activate peroxymonosulfate for carbamazepine removal at high salinity condition

To tackle high salinity challenge, differently from singlet oxygen-governed systems, extremely abundant and highly reactive sulfate radicals (SO4•─)-dominated systems might be also feasible. Ingenious integration of two active popular catalysts, and optimal selection of reaction parameters could sufficiently activate the added peroxymonosulfate (PMS) to efficiently degrade complicated pollutants within a short time so as to overlook the negative effects of inorganic anions. Herein, zero-valent iron decorated metallic 1T/semiconducting 2H hybrid phased molybdenum disulfide with different Mo/S feeding ratio (Fe0/Nx-MoS2) were constructed and compared to activate PMS for carbamazepine (CBZ) removal, where Fe0/N2-MoS2 (M(Mo):M(S) = 7:30) with ultrathin sheet morphology presented most charming decontamination performance. Optimal Fe0/N2-MoS2 dosage and PMS amount was respectively selected as 75 and 50 mg·L-1 in treating 10 mg·L-1 CBZ at pH = 3.00 via tailoring reaction parameters. CBZ could be completely removed in a short time of 10 min with a high pseudo-first-order kinetic rate constant of 0.939 ± 0.016 min−1. The system exhibits the promising anti-interference capacity toward Cl─, NO3─ and SO42─ of high concentration (even up to 3000 mg·L-1). Electron paramagnetic resonance and scavenging experiments of reactive species suggested that SO4•─ played a dominant function. Furthermore, Mo and Fe bimetallic cycles could efficiently promote PMS activation to produce rich reactive radicals. Degradation pathways and toxicity evolutions for CBZ in the (Fe0/N2-MoS2 + PMS) system were proposed via liquid chromatography time-of-flight mass spectrometer and Toxicity Estimation Software Tool, and we hope that the system would be applied in high salinity wastewater treatment in future.

Surface regeneration of templated PVDF membrane for efficient microalgae-rich high saline aquaculture wastewater treatment in membrane distillation

This study investigated the use of templated PVDF membranes with intermediate flushing to revive fouled membrane during membrane distillation (MD) for sustainable high saline seawater aquaculture wastewater treatment. Results showed that superhydrophobic templated membrane with intermediate physical flushing was highly effective in reducing fouling, even after 5 cleaning cycles, when treating microalgae-rich feed with algogenic organic matter and high salinity aquaculture wastewater. Specifically, the membrane restoring flux performance by up to 97.2 %, compared to only 75.6 % for pristine membranes. In this study, intermediate flushing effectively restored the advancing and reducing contact angles of fouled templated membranes, enhancing membrane regeneration and reducing surface adhesion properties. In long-term 82-h MD tests, the superhydrophobic templated membrane still demonstrated excellent separation, achieving 99.84 % rejection rate for all components and maintaining average water permeation flux of 21.4 kg/m2.h when treating microalgae-rich feed. The study suggests that the use of superhydrophobic templated membrane with surface reviving capability holds immense potential in overcoming the challenges of membrane fouling in MD, providing a sustainable treatment solution for microalgae-rich and high salinity wastewater treatment.