Surface Water Treatment Research Articles

Crosslinked chitosan-modified ultrafiltration membranes for efficient surface water treatment and enhanced anti-fouling performances

Graphic abstract

Turbidity removal from surface water using Cactus opuntia

Coagulation and flocculation are critical processes in water treatment facilities and typically precede the more intricate secondary and tertiary treatment stages. Currently, the most commonly used coagulants in water treatment are aluminum sulfate (alum) and ferric chloride. In developing countries, synthetic coagulants can be neither economical nor health-friendly. Consequently, natural coagulants have garnered significant research attention over the past decade. This study explored the use of cactus as a natural coagulant to decrease turbidity in surface water from the Sekak dam in Tlemcen, Algeria. Various jar tests were performed to optimize parameters such as coagulant and flocculant dosages, mixing speed, rapid mixing duration, and the pH of the water. The initial turbidity level of 5.45 NTU was reduced by up to 84.03%. The turbidity removal capacity observed in this study suggests that Opuntia cactus has considerable potential for application in surface water treatment.

Nano-Fe3O4/FeCO3 modified red soil-based biofilter for simultaneous removal of nitrate, phosphate and heavy metals: Optimization, microbial community and possible mechanism

The pollution of nitrogen, phosphorus and heavy metals in surface water is becoming more and more serious, affecting the safety of water quality. In this study, three biofilters were constructed using iron-modified red soil-based filler carriers (RSC, nano-Fe3O4@RSC, and FeCO3@RSC) combined with strain Zoogloea sp. ZP7 to simultaneously remove nitrate (NO3--N), phosphate (PO43--P), copper (Cu2+), and zinc (Zn2+). The long-term operation results showed that the three groups of biofilters could remove 85.0 %, 90.0 %, and 89.8 % of NO3--N, respectively. Furthermore, the addition of iron compounds enhanced the removal of PO43--P and the resistance to the stress of Cu2+ and Zn2+ in the biofilter. The analysis illustrated that iron modification improved the redox activity and zeta potential of RSC surface. The secondary structure analysis of the protein showed that the microbial secreted proteins were more compact on the surface of the iron-modified RSC, which facilitated the formation of biofilm on the carrier surface. In addition, the iron-modified RSC-based biofilter also showed excellent NO3--N and PO43--P removal efficiency in the treatment of actual surface water. The microbial community analysis results showed that Zoogloea became the dominant species in the biofilter. On the other hand, the presence of iron-reducing bacteria and the expression iron cycle-related genes may contribute to denitrification under low nutrient conditions.

Electro-assisted carbon nanotube dual catalytic membrane system for high-efficiency and energy-efficient water treatment

Improving performance of peroxymonosulfate (PMS) catalytic membrane via electrochemical assistance renders an effective way for water decontamination. However, the current cathodic or anodic membrane based electro-assisted PMS catalytic single-membrane systems (EPSM) usually suffer from their inherent deficiencies. Herein, a novel electro-assisted PMS catalytic dual-membrane system (EPDM) was constructed by employing two electro-conductive carbon nanotube membranes as the anodic and cathodic membranes, in order to couple the advantages of anodic and cathodic catalytic membranes for enhanced water treatment. Moreover, the filtration sequence (anode–cathode (A-C) or cathode–anode (C-A)) was varied to explore its effect on EPDM performance. Results showed the EPDM operated in C-A mode achieved ultrafast (0.95 s−1) and energy-efficient (0.008 kWh m−3) removal towards sulfamethoxazole (SMX), and its SMX mineralization rate was 1.7 times higher than that of EPDM operated in A-C mode and 5.1 or 2.4 times higher than that of cathodic or anodic membrane based EPSM. Meanwhile, the EPDM also displayed efficient fouling mitigation on both membrane surface and pores. Furthermore, EPDM can maintain high performance and good stability in long-term actual surface water treatment. The outstanding performance of EPDM operated in C-A mode was attributed to the collaboration of cathodic and anodic membranes: For one thing, cathodic and anodic membranes sequentially activated PMS to produce radicals (OH and SO4−) and non-radicals (1O2 and electron transfer) for enhanced pollutant oxidation; for another, both membranes in C-A mode effectively resisted coexisting interferents in real water.

Catalytic membrane with dual-layer structure for ultrafast degradation of emerging contaminants in surface water treatment

The catalytic membrane-based oxidation-filtration process integrates physical separation and chemical oxidation, offering a highly efficient water purification strategy. However, the oxidation-filtration process is limited in practical applications due to the short residence time of milliseconds within the catalytic layer and the interference of coexisting organic pollutants in real water. Herein, a dual-layer membrane containing a top selective layer and a bottom catalytic layer was fabricated using an in situ co-casting method with a double-blade knife. Experimental results demonstrated that the selective layer rejected macromolecular organic pollutants, thereby alleviating their interference with bisphenol A (BPA) degradation. Concurrently, the catalytic layer activated peracetic acid oxidant and achieved a high BPA degradation exceeding 90 % in milliseconds with reactive oxygen species (especially •OH). The finite-element analysis confirmed a high-concentration reaction field occupying the pore cavity of the catalytic layer, enhancing collision probability between reactive oxygen species and BPA, i.e., the nano-confinement effect. Additionally, the dual-layer membrane achieved a long-term stable performance for emerging contaminant degradation in surface water treatment. This work underscores a novel catalytic membrane structure design for high-performance oxidation-filtration processes and elucidates its mechanisms underlying ultrafast degradation.

Simultaneous degradation of cyanobacteria and cyanotoxins by catalytic wet peroxide oxidation: Impact of morphology and growth stage

The widespread proliferation of potentially toxic cyanobacteria in source waters for drinking water treatment plants (DWTPs) presents a pressing contemporary challenge. Although catalytic wet peroxide oxidation (CWPO) has been recognized as a highly effective and environmentally friendly technology for removing cyanotoxins from water, the simultaneous degradation of cyanobacteria and cyanotoxins has been scarcely investigated. Considering their great morphological diversity, in this work, the impact of the presence of pure strains of several species of toxic and non-toxic cyanobacteria on the degradation of relevant cyanotoxins has been evaluated considering also the main stages of their life cycle. In each studied scenario, achieving a full eradication of the cyanobacteria also led to the complete elimination of the cyanotoxin, including both intra and extracellular fractions. Morphological factors, including filament and cell sizes, play a crucial role in the efficiency of the process. Small cells and long filaments entail a higher presence of particulate organic matter, which consumes hydroxyl radicals considerably in competence with the cyanotoxin degradation. Moreover, the growth stage emerges as a pivotal factor in understanding the CWPO process performance, with cyanobacteria in their early life stages, exhibiting more pronounced interference compared to later stages, probably due to their higher cell viability and accelerated metabolism. All these understandings are essential for the successful implementation of the technology in treating surface waters affected by toxic cyanobacterial blooms.

Surface water removal of Aluminum(III), Iron(III) and Manganese(II) using sustainable natural serpentinite mining tailings, proof of concept

To remediate surface water as the Doce River and spring waters from Minas Gerais, Brazil, this study examined the possibility of natural serpentinite mining tailings as a sustainable alternative for removing aluminum (III), iron (III), and manganese (II). The study used a Box-Behnken experimental design to examine how initial metal concentration, adsorbate dosage, and adsorption time affect metal removal effectiveness. Results demonstrated impressive performance, with removal rates exceeding 80 % for Al(III) and Fe(III) within the initial 5 min, and 60 % for Mn(II) within 30 min. This study delves deeper into the removal mechanisms, kinetics, adsorption isotherms and characterization identify physisorption and chemisorption pathways in which complex formation with released OH− groups and ion exchange with Mg(II) from serpentinite emerged as key contributors to the removal process. Furthermore, ion metal adsorption and regeneration cycles were assessed, exhibit sustained removal efficacy without notable capacity reduction. Each cycle shows an average metal adsorption capacity of 0.32 mg g−1 and an average Mg(II) release capacity of 0.98 mg g−1. Remarkably, the application of serpentinite successfully lowered the metals content of the Doce River and spring water to drinkable standards. A batch and continuous process is proposed for scaling-up serpentinite's metal adsorption. Overall, this study shows serpentinite's potential as a foundation for sustainable and cost-effective methods to treat surface water contamination with Al(III), Fe(III), and Mn(II).

Surface water quality assessment and probable health threats of metal exposure in the Tano South Municipality, Ahafo, Ghana

The prime goal of this study was to assess the surface water quality and the associated health risks for residents in the Tano South Municipality, Ghana. The WHO drinking water criteria were compared with the findings of an analysis of eight surface waters for parameters such as physiochemical parameters, nutrient levels, and concentrations of selected metals. An evaluation was performed regarding the potential non-carcinogenic and carcinogenic risks associated with metal exposure by oral and dermal absorption. The estimated water quality index indicated that seven water samples were deemed unsuitable for human consumption, while one sample indicated very low water quality. The fluoride levels in all water samples were below the limit of detection, although it guards against dental caries. All of the water samples had mean concentrations of Cd and Fe above WHO guideline values, while one water sample had a Pb concentration that was higher than recommended. Principal component analysis showed that aside from the natural source, human-induced sources such as runoff of excess chemicals and soil erosion from adjacent farm soils were responsible for the substantial levels of contaminants in surface water samples. There was a possibility of non-carcinogenic consequences for children in seven out of eight water samples. However, cancer risk for Cd and Pb was not likely for adults and children in the study area. Findings serve as a representative case study for other districts and call on water managers to treat surface waters to guard against harmful health consequences and safeguard the designated buffer zones.

Reduction of organic matter and disinfection by products formation at surface water treatment plants in Egypt

ABSTRACT Although the removal of colloidal particles continues to be an important reason for using coagulation, currently a newer approach, the removal of organic matter to reduce the formation of disinfection byproducts (DBPs) such as trihalomethanes (THMs) are suspected carcinogens. Inefficient removal of total organic carbon (TOC) leads to the formation of carcinogenic THMs. This motivates the research efforts to find a way to reduce them in potable water. The first objective of this research is monitoring the water quality (raw and produced) for selected three water treatment plants within Giza Governorate to reveal the most polluted site (high TOC in the raw water and THMs in the treated water) in the study areas. The second objective of this study is enhancing coagulation to reduce TOC and THMs from surface water treating. In this study, two different coagulants aluminum sulfate (alum), and ferric chloride were tested under different conditions of pH and coagulant concentration to determine their effectiveness for removal of TOC, THMs and turbidity. Optimum values for the mentioned conditions were used to achieve the maximum reduction for TOC and THMs in Al-Ayat drinking water treatment plant (DWTP) which recorded the highest concentration of TOC and THMs. Ferric chloride as a coagulant achieved the maximum removal percentage % of TOC, THMs and turbidity as 79%, 82% and 94%, respectively, at ferric chloride dose 100 mg/L, while alum as a coagulant recorded the maximum removal percentage % of TOC, THMs and turbidity as 46%, 52% and 91%, respectively, at alum dose 100 mg/L. The results indicated that ferric chloride as a coagulant has the highest efficiency reduction of TOC, THMs and turbidity if compared to alum with the same dose added.

Pressure-induced piezoelectric response for mitigating membrane fouling in surface water treatment: Insights from continuous operation and biofouling characterization

Organic fouling and biofouling represents a critical challenge encountered by the membrane-based water treatment process. Herein, a piezoelectric PVDF membrane (PEM), capable of generating electrical responses to hydraulic pressure stimuli, was synthesized and employed for mitigating the fouling in surface water treatment. The surface-hydrophobilized PEM demonstrated sensitive and enhanced underwater output performance in response to increasing transmembrane pressure (TMP) during constant-flux filtration, with signals reaching up to ∼800 mV at a TMP of ∼80 kPa. This in-situ piezoelectric response significantly reduced TMP growth in both short-term (1 h) and long-term (15 days) filtration trials, demonstrating a strong capability to mitigate membrane fouling. Moreover, continuous piezoelectric stimulation effectively inhibited microbial activity and the accumulation of extracellular polymeric substances (EPS) on PEM surface, surpassing the dominant electrokinetic repulsion mechanisms observed in short-term trials. Microbial community analysis suggests that this evolution is primarily due to the targeted impact of piezoelectric stimulation on microbial metabolic behavior. The piezoelectric-induced electrical microenvironment inhibited the growth of microbes associated with high EPS production while promoting the proliferation of electrically active microbes involved in biopolymer digestion. In addition, the PEM demonstrated enhanced permeate quality throughout the filtration process, with DOC and UV254 removal rates increasing from 11.7 % and 15.6 % initially to 28.6 % and 19.5 % by the 15th day, respectively. Given the performance and self-powered capability of PEM compared to current electrified antifouling methods that require an external power supply, these attributes are anticipated to hold practical significance in developing innovative and energy-efficient strategies for mitigating both organic fouling and biofouling.

Bridging the Technology Gap for Cost‐Effective and Sustainable Treatment of Per‐ and Polyfluoroalkyl Substances in Surface Water and Stormwater

ABSTRACTThis article addresses the urgent need for cost‐effective and sustainable methods to mitigate per‐ and polyfluoroalkyl substances (PFAS) contamination in surface water and stormwater. Although the majority of PFAS research and development to date has focused on groundwater and soil treatment technologies, in some cases there may be a greater risk posed by the high mobility and potential for direct contact with PFAS in surface water and stormwater. Based on the evolving regulatory landscape and the elevated PFAS concentrations observed in available stormwater data near some fire training facilities, additional attention to this topic is needed to support the development of effective and practical treatment technologies for PFAS in surface water and stormwater. We propose addressing the need to bridge the current technology gap between (1) expensive mechanical and/or construction‐intensive technologies and (2) the development of cost‐effective and sustainable surface water and stormwater PFAS treatment options. We envision a future where nature‐based approaches could be employed for stand‐alone PFAS treatment. Alternatively, nature‐based approaches could be used for initial PFAS mass removal as a pretreatment step within a treatment train followed by engineered adsorbents or other technologies, if needed to achieve low concentration cleanup thresholds. We provide an example of a potential nature‐based treatment train that would rely on the natural propensity of PFAS to accumulate in surface water foams using foam‐enhancing weirs and flumes (FWFs), combined with the demonstrated treatment potential of constructed floating wetlands (CFWs). Additional research into the validation, optimization, and site‐specific design factors of nature‐based treatment trains, such as the FWF+CFW approach, warrants future research and development.

Assessment of poly(diallyl dimethyl ammonium chloride) and lime for surface water treatment (pond, river, and canal water): seasonal variations and correlation analyses.

The present study deals with the assessment of different physicochemical parameters (pH, electrical conductivity (E.C.), turbidity, total dissolved solids (TDS), and dissolved oxygen) in different surface water such as pond, river, and canal water in four different seasons, viz. March, June, September, and December 2023. The research endeavors to assess the impact of a cationic polyelectrolyte, specifically poly(diallyl dimethyl ammonium chloride) (PDADMAC), utilized as a coagulation aid in conjunction with lime for water treatment. Employing a conventional jar test apparatus, turbidity removal from diverse water samples is examined. Furthermore, the samples undergo characterization utilizing X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The study also conducts correlation analyses on various parameters such as electrical conductivity (EC), pH, total dissolved solids (TDS), turbidity of raw water, polyelectrolyte dosage, and percentage of turbidity removal across different water sources. Utilizing the Statistical Package for Social Science (SPSS) software, these analyses aim to establish robust relationships among initial turbidity, temperature, percentage of turbidity removal, dosage of coagulant aid, electrical conductivity, and total dissolved solids (TDS) in pond water, river water, and canal water. A strong positive correlation could be found between the percentage of turbidity removal and the value of initial turbidity of all surface water. However, a negative correlation could be observed between the polyelectrolyte dosage and raw water's turbidity. By elucidating these correlations, the study contributes to a deeper understanding of the effectiveness of PDADMAC and lime in water treatment processes across diverse environmental conditions. This research enhances our comprehension of surface water treatment methodologies and provides valuable insights for optimizing water treatment strategies to address the challenges posed by varying water sources and seasonal fluctuations.

Feasibility Research on Surface Water Reinjection into the Sandstone Geothermal Reservoir of the Guantao Formation in Tianjin Based on Laboratory Experiments

Tianjin possesses abundant geothermal resources, and geothermal reinjection is an effective strategy for maintaining the sustainable development and utilization of these resources. However, several issues have arisen in the reinjection of sandstone geothermal reservoirs in the Tianjin area, including a mismatch between the reinjection capacity and effluent capacity, as well as challenges related to continuous reinjection. Therefore, it is crucial to investigate the reinjection of exogenous water into sandstone pore-type geothermal reservoirs. This study focuses on the geothermal reservoir of the Guantao Formation in the Binhai New Area. The surface water treatment process for reinjection into sandstone geothermal reservoirs was determined through water treatment simulation experiments. Additionally, experiments examining the interaction between the reinjected water and reservoir rock were conducted to assess the feasibility of using treated surface water for reinjection into sandstone geothermal reservoirs. The hydrogeochemical response mechanisms and the impact on the reservoir under reinjection conditions were also investigated. The results indicate that a nanofiltration module and tubular microfiltration membrane are essential to ensure the stability of the system. The pH and TDS of water samples decreased after reinjecting mixed water (HHS) into the sandstone reservoir. The hydrochemical type consistently remained Cl-Na. The conventional water chemistry components and trace elements were influenced by the corresponding water–rock reactions. The reservoir minerals exhibited minimal precipitation, primarily consisting of K-feldspar and Fe-dolomite. The minerals produced during the experiment accounted for only 0.08% of the total cuttings’ mass, indicating a negligible impact on the reservoir structure. PHREEQC was employed to simulate the changes in mineral saturation index before and after the reinjection of mixed water and geothermal water, respectively. Notably, similar hydrogeochemical changes were observed in the geothermal fluids. Thus, this study demonstrates the feasibility of reinjecting treated surface water into sandstone geothermal reservoirs from a hydrogeochemical perspective. This research provides valuable insights for the development of external water reinjection projects in hot spring health care units, contributing effectively to the achievement of carbon peaking and carbon neutrality goals.

Enhancing Rural Surface Water Remediation with Iron–Carbon Microelectrolysis-Strengthened Ecological Floating Beds

Ecological floating beds, with their compact footprint and mobility, offer a promising solution for sustainable surface water remediation in rural areas. However, low removal efficiency and instability still limit its application. In this study, iron–carbon-based fillers were integrated into ecological floating beds to investigate their impact and mechanisms in removing pollutants, including carbon, nitrogen, phosphorus, and heavy metals. Results indicate that all five fillers (activated carbon, iron–carbon fillers, sponge iron, activated carbon + iron–carbon fillers, and activated carbon + sponge iron) can completely remove orthophosphate, and the sponge iron filler system can completely remove nitrate. Then, fillers were applied to ecological floating beds, and the iron–carbon microelectrolysis (activated carbon + sponge iron filler)-enhanced ecological floating bed showed superior removal efficiency for pollutants. It achieved 95% removal of NH4+-N, 85% removal of NO3−-N, 75% removal of total phosphorus, 90% removal of chemical oxygen demand, and 90% removal of heavy metals. Typical nitrifying bacteria Nitrospira, denitrifying bacteria Denitratisoma, and a variety of bacterial genera with denitrification functions (e.g., Rhodobacter, Dechloromonas, Sediminibacterium, and Novosphingobium) coexisted in the system, ensuring efficient and robust nitrogen removal performance. These findings will provide support for the sustainable treatment of surface water in rural areas.

A membrane fouling control strategy based on a combination of pre-treatment mitigation and in-situ membrane surface regulation using a composite coagulant

Ultrafiltration technology (UF) is efficient in surface water treatment, but its development and widespread application are limited by membrane fouling. Herein, an efficient and stable polymerized ferric titanium coagulant (PFTC) was synthesized and used as a UF pretreatment agent in actual lake water treatment. The control mechanism of PFTC on membrane fouling was investigated from the perspective of organic removal efficiency and in-situ membrane surface regulation. PFTC demonstrated a remarkable affinity for soluble metabolic intermediates and hydrophilic proteins through complexation and hydrogen bonding force, achieving removal efficiencies of 66.4 % for UV254 and 81.3 % for DOC, respectively. The hydrophilic pollutants with high molecular weight and non-saturated structure could be preferentially removed by PFTC due to its diverse hydrolysates including positively charged Fe-based hydrolysates, amorphous Ti-based hydrolysates, and highly polymerized Fe-Ti copolymers. The flocs generated by PFTC exhibited strong hydrophilicity, allowing for the formation of a loose porous cake layer on the ultrafiltration membrane, which acted as a hydrophilic layer to enhance the anti-fouling performance of ultrafiltration membrane. With its dual function of contaminant removal and in-situ membrane surface regulation, PFTC alleviated 98.9 % of membrane fouling. This study provides new insights into membrane fouling control by coagulation pretreatment and efficient treatment of surface water.

Formation, speciation, and temporal variability of DBPs in drinking water distribution systems in the context of ASR operations and extended storage periods

As climate change induces changes in water quality and available water quantity of drinking water supply sources, the final product water quality changes in terms of trace organics including disinfection byproducts (DBPs) formed during water treatment. In this study, the seasonal variability and speciation of DBPs across nine sample sites within a drinking water distribution system serving ∼400k people over a one-year period was investigated considering the governing parameters of water quality and treatment/transport/storage of finished water. The system considered treats surface water from a river and practices aquifer storage and recovery to address seasons water availability changes. Eighty-eight (88) sample sets were collected and held for 6-months in the laboratory to simulate extended storage scenarios associated with ASR operations, and each was analyzed at 9 different timesteps for concentration and speciation of chlorinated DBPs. Samples from groundwater influenced sites exhibited significantly lower total organic carbon (TOC) compared to other sites from the river source, and also were observed to have the lowest DBP formation. Three sites exceeded the Maximum Contaminant Level (MCL) for four total trihalomethanes (THM4) within 30–60 days of storage. Chloroform was the predominant THM4 species, even in groundwater-influenced locations, whereas di- and tri-chloroacetic acid (DCA and TCA) were the most prevalent haloacetic acids (HAA5). Extended water age at one site, coupled with low initial chlorine concentrations exhibited higher initial THM4 concentrations and flat DBP formation curves. The study results provide new insights into DBP occurrence and fate in drinking water distribution systems which consider water storage such as in ASR.

Genetic determinants of increased sodium hypochlorite and ciprofloxacin susceptibility in Pseudomonas aeruginosa PA14 biofilms

Reactive chlorine species (RCS) like sodium hypochlorite (NaOCl) are potent oxidizing agents and widely used biocides in surface disinfection, water treatment, and biofilm elimination. Moreover, RCS are also produced by the human immune system to kill invading pathogens. However, bacteria have developed mechanisms to survive the damage caused by RCS. Using the comprehensive Pseudomonas aeruginosa PA14 transposon mutant library in a genetic screen, we identified a total of 28 P. aeruginosa PA14 mutants whose biofilms showed increased susceptibility to NaOCl in comparison to PA14 WT biofilms. Of these, ten PA14 mutants with a disrupted apaH, PA0793, acsA, PA1506, PA1547, PA3728, yajC, queA, PA3869, or PA14_32840 gene presented a 4-fold increase in NaOCl susceptibility compared to wild-type biofilms. While none of these mutants showed a defect in biofilm formation or attenuated susceptibility of biofilms toward the oxidant hydrogen peroxide (H2O2), all but PA14_32840 also exhibited a 2–4-fold increase in susceptibility toward the antibiotic ciprofloxacin. Further analyses revealed attenuated levels of intracellular ROS and catalase activity only for the apaH and PA1547 mutant, providing insights into the oxidative stress response in P. aeruginosa biofilms. The findings of this paper highlight the complexity of biofilm resistance and the intricate interplay between different mechanisms to survive oxidative stress. Understanding resistance strategies adopted by biofilms is crucial for developing more effective ways to fight resistant bacteria, ultimately contributing to better management of bacterial growth and resistance in clinical and environmental settings.

Color, COD, and turbidity removal from surface water by using linseed and alum coagulants: optimization through response surface methodology

This study examined the treatment of surface water using a mixed natural (linseed) and chemical (alum)-based coagulant in terms of color, turbidity, and chemical oxygen demand (COD) (%) removal in a laboratory jar test. Experimental results showed that using a combined coagulant has shown higher removal of color (99.72%) and turbidity (97.76%) at pH values of 3.5 using a 1.5 g/L dosage and a stirring time of 38.58 min. Similarly, at the same pH value and 2.5 g/L dosage, the COD removal was 96%. To determine the optimum value with the highest percent removal efficiency of the coagulation–flocculation process, several experimental parameters including blended dosage, pH, COD concentration, and initial turbidity have been studied in terms of the percent of color, chemical oxygen demand, and turbidity removal. The optimum value was found for the highest removal of color-97.75%, turbidity-96.86%, and COD-90.33% with the pH values of 7.0, at a dosage of 2.5 g/L and a stirring time of 40 min, respectively. Statistical techniques of response surface methodology were used in experimental design and optimization, in order to calculate the confidence intervals to assess population parameter precision. An ANOVA-95% confidence interval ensures that the high reliability optimizes the result. The findings proved the excellent adsorption potential and high performance of the blended coagulant in the removal of contaminants from surface water.

Innovative composite fluidized hydrogel GAC particles for effective membrane fouling mitigation and membrane integrity protection

Membrane filtration is recognized as an environmentally friendly and cost-efficient technology for water treatment, but membrane fouling is still a significant challenge that increases maintenance costs and reduces membrane lifespan. Particle scouring can effectively mitigate fouling with lower energy consumption. This study investigates the use of fluidized granular activated carbon (GAC) particles encapsulated with hydrogel layers to enhance fouling mitigation in microfiltration systems treating surface water. The proposed hydrogel-modified GAC particles aim to balance scouring efficiency with membrane integrity. The results demonstrate that optimizing hydrogel preparation conditions significantly enhanced the mechanical strength and surface hydrophilicity of GAC particles. The incorporation of hydrogel layers notably improved membrane fouling mitigation, reducing transmembrane pressure (TMP) by 19.3 %, 27.1 %, and 34.3 % for layer thicknesses of 0.5 mm, 1.0 mm, and 1.5 mm, respectively. The hydrodynamic behavior of fluidized GAC particles was significantly improved, enhancing the effectiveness of fouling mitigation in water treatment processes. Additionally, the hydrogel layer effectively protected membrane integrity and inhibited carbon release, ensuring minimal damage and stable permeability. This study underscores the pivotal role of hydrogel layers in improving the performance and longevity of membrane filtration systems, when fluidized GAC particles are used for membrane fouling control.

Biomimetic interlayer brought unexpected enhancement in permeability and rejection of polyamide nanofiltration membrane

Construction of interlayer between porous substrate and polyamide (PA) layer has been proved to be an effective way in improving membrane separation performance by the regulation of membrane structure and chemical properties. In present study, biomimetic material—1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) lipid bilayer was selected to serve as the interlayer prepared by suction filtration due to its unique advantages such as smooth, continuous, uniform and hydrophilic surface. The results showed that DOPE interlayer effectively lowered the diffusion rate of piperazine (PIP) from membrane surface to organic phase and thus contributing to the thinner and smoother PA layer. The permeability of the interlayer-based PA membrane reached 35.9 L/m2·h·bar, which was 190 % higher than pure PA NF membranes. More important, the interlayer-based PA membrane exhibited excellent Na2SO4 rejection about 99.8 % accompanied by a good separation selectivity between univalent and bivalent ions. Besides, the interlayer-based PA membrane possessed good stability to the changes of operating pressure, concentration and pH of feed solution, and the long-term NF test. Meanwhile, it performed well in removing NTU, TOC, Mg2+ and SO42− in the treatment of surface water and showed its potential in the practical application. In all, the present work brought new interlayer material in fabricating high-performance NF membrane.