The effect of suction velocity on concentration polarization in microfiltration membranes under turbulent flow conditions

Membrane-Based Processes Used in Municipal Wastewater Treatment for Water Reuse: State-Of-The-Art and Performance Analysis

Wastewater reuse as a sustainable, reliable and energy recovery concept is a promising approach to alleviate worldwide water scarcity. However, the water reuse market needs to be developed with long-term efforts because only less than 4% of the total wastewater worldwide has been treated for water reuse at present. In addition, the reclaimed water should fulfill the criteria of health safety, appearance, environmental acceptance and economic feasibility based on their local water reuse guidelines. Moreover, municipal wastewater as an alternative water resource for non-potable or potable reuse, has been widely treated by various membrane-based treatment processes for reuse applications. By collecting lab-scale and pilot-scale reuse cases as much as possible, this review aims to provide a comprehensive summary of the membrane-based treatment processes, mainly focused on the hydraulic filtration performance, contaminants removal capacity, reuse purpose, fouling resistance potential, resource recovery and energy consumption. The advances and limitations of different membrane-based processes alone or coupled with other possible processes such as disinfection processes and advanced oxidation processes, are also highlighted. Challenges still facing membrane-based technologies for water reuse applications, including institutional barriers, financial allocation and public perception, are stated as areas in need of further research and development.

Improvement of virus removal using ultrafiltration membranes modified with grafted zwitterionic polymer hydrogels

Potable water reuse has been adopted by cities suffering water scarcity in recent years. The microbial safety in water reuse, especially with respect to pathogenic viruses, is still a concern for water consumers. Membrane filtration can achieve sufficient removal of pathogenic viruses without disinfection byproducts, but the required energy is intensive. In this study, we graft-polymerized zwitterionic SPP ([3-(methacryloylamino) propyl] dimethyl (3-sulfopropyl) ammonium hydroxide) on a 150 kDa ultrafiltration polyethersulfone membrane to achieve a significantly higher virus removal. The redox-initiated graft-polymerization was performed in an aqueous solution during filtration of the monomer and initiators, allowing for functionalizing the membrane pores with hydrophilic polySPP. Bacteriophage MS2 and human adenovirus type 2 (HAdV-2) were used as surrogates for pathogenic human norovirus and human adenovirus. The grafting resulted in ∼18% loss of the membrane permeability but an increase of 4 log₁₀ in HAdV-2 removal and 3 log₁₀ in MS2 removal. The pristine and the grafted membranes were both conditioned with soluble microbial products (SMP) extracted from a full-scale membrane bioreactor (MBR) in order to test the virus removal after fouling the membranes. After fouling, the HAdV-2 removal by the grafted membrane was 1 log₁₀ higher than that of the pristine membrane. For MS2, the grafted membrane after fouling with SMP achieved an additional 5 log₁₀ removal compared to the unmodified membrane. The simple graft-polymerization functionalization of commercialized membrane achieving enhanced virus removal efficiency highlights the promise of membrane filtration for pathogen control in potable water reuse.

Comparison of behaviors of two surrogates for pathogenic waterborne viruses, bacteriophages Qbeta and MS2, during the aluminum coagulation process

Differences in the behaviors of two surrogates for pathogenic waterborne viruses, F-specific RNA bacteriophages Qbeta and MS2, were investigated during the coagulation process by using river water spiked with these bacteriophages. The particle size and electrophoretic mobility of Qbeta and MS2 were similar, but the removal performances of infectious Qbeta and MS2, as measured by a plaque forming unit (PFU) method, differed markedly during the coagulation process. The removal ratio of the infectious Qbeta concentration was approximately 2log higher than that of the infectious MS2 concentration at all coagulant doses tested. The total Qbeta and MS2 bacteriophage concentrations, which were measured by a real-time reverse transcription-polymerase chain reaction (RT-PCR) method and represented the total number of bacteriophages regardless of their infectivity, were similar after the coagulation process, suggesting that the behaviors of Qbeta and MS2 as particles were similar during the coagulation process. The difference between total concentration and infectious concentration indicated that some of the bacteriophages were probably inactivated during the coagulation process. This difference was larger for Qbeta than MS2, meaning that Qbeta was more sensitive to the virucidal activity of the aluminum coagulant. Analysis of the PFU and real-time RT-PCR findings together suggested that the difference in removal performances of Qbeta and MS2 during the coagulation process was probably caused by differences not in the extent of bacteriophage entrapment in the aluminum floc particles but in the sensitivity to virucidal activity of the aluminum coagulant.