Bacterial Anti-Adhesion of Coated and Uncoated Thin-Film-Composite (TFC) Polyamide (PA) Membranes

This study investigates the bacterial anti-adhesion performance of uncoated and coated reverse osmosis (RO) membranes. All the membranes were commercially available fully-aromatic thin-film-composite (TFC) polyamide (PA) membranes. Two of the TFC PA membranes (SW30 and BW30) were coated using polyvinyl alcohol (PVA) coating, while the other three membranes (LE, XLE and NF90) were uncoated. Among the characterised TFC PA membranes, the PVA coated were more hydrophilic and their surface energy was higher in comparison to uncoated. In addition, the PVA coated membranes had lower surface roughness. AFM interaction force measurement demonstrated higher repellence performance for the more polar surface. Bacteria attachment test showed differences between the coated and the uncoated membranes. Indeed, the increase in hydrophilicity and surface polarity showed decrease in the attachment of Pseudomonas aeruginosa cells. Moreover, the results demonstrated that the surface polarity showed better correlation with the attachment of the bacteria. In addition, the type of the surface roughness may somehow contribute to the bacteria repellence

Membrane module design and dynamic shear-induced techniques to enhance liquid separation by hollow fiber modules: a review

Membrane-based separation processes have found numerous applications in various industries over the past decades. However, higher energy consumption, lower productivity, and shorter membrane lifespan due to polarization and membrane fouling continue to present severe technical challenges to membrane-based separation. Improved membrane module design and novel hydrodynamics offer strategies to address these challenges. This review focuses on hollow fiber membrane modules which are well suited to membrane contactor separation processes. Attempts to improve membrane module design should begin with a better understanding of the mass transfer in the hollow fiber module; therefore, this review provides a summary of prior studies on the mass transfer models related to both the shell-side and tube-side fluid dynamics. Based on the mass transfer analysis, two types of technique to enhance hollow fiber membrane module performance are discussed: (1) passive enhancement techniques that involve the design and fabrication of effective modules with optimized flow geometry or (2) active enhancement techniques that uses external energy to induce a high shear regime to suppress the undesirable fouling and concentration polarization phenomena. This review covers the progress over the past five years on the most commonly proposed techniques such as bubbling, vibrations, and ultrasound. Both enhancement modes have their advantages and drawbacks. Generally, the passive enhancement techniques offer modest improvement of the system performance, while the active techniques, including bubbling, vibrating, and ultrasound, are capable of providing as high as 3–15 times enhancement of the permeation flux. Fundamentally, the objectives of module design should include the minimization of the cost per amount of mass transferred (energy consumption and module production cost) and the maximization of the system performance through optimizing the flow geometry and operating conditions of the module, scale-up potential, and expansion of niche applications. It is expected that this review can provide inspiration for novel module development

Corporate social responsibility: Mapping its social meaning

Purpose – The purpose of this paper is to address the social meaning of corporate social responsibility (CSR) and improve understanding of this concept. Design/methodology/approach – A free association task was completed by a sample of 275 individuals, mostly employees from different industries, who were given “socially responsible corporation” as the stimulus. Findings – The results elicit three distinct views of a socially responsible corporation. Some individuals consider a socially responsible corporation to be one that undertakes its business operations in an efficient and ethical manner. Others see it as an organisation that takes an active role in contributing to the well being of society and behaves in an ecologically friendly way and acts in the field of social solidarity. For yet another set of participants a socially responsible corporation is one that adopts human resources practices that demonstrate respect and concern for the well being of employees and their families. Research limitations/implications – The social meaning of CSR includes ideas that to some extent mirror the conceptualisation introduced by previous theoretical models. However, this paper suggests that the translation of the theoretical models into instruments addressing stakeholders’ perceptions of CSR requires closer scrutiny and validation through contextual (e.g. national) adaptations. Originality/value – The paper contributes by providing additional knowledge on the social meaning of CSR in a European country, Portugal, and not only on Anglo-Saxon countries, therefore, introducing specific situational challenges

Stability of layer-by-layer nanofiltration membranes in highly saline streams

Layer-by-layer (LBL) assembly is an essential method for the preparation of nanofiltration (NF) membranes, offering tunable charge and pore size, high water permeability, and good anti-fouling properties, making them highly suitable for resource recovery, seawater desalination, and other fields. Despite their advantages, LBL NF membranes suffer from salinity instability, limiting their use in highly saline streams. This perspective review provides a summary of the fundamental physical and chemical principles of LBL assembly related to the salinity stability of LBL NF membranes. We critically analyze the driving force of LBL assembly, the binding strength of polyelectrolyte (PE) pairs, and the overcompensation of LBL membranes. We also discuss the factors affecting overcompensation level with respect to two different time scales. Furthermore, we examine the relationship between overcompensation level and salinity stability of LBL membranes, considering physical (osmotic pressure) and chemical (Le Chatelier's principle) aspects. Our analysis demonstrates that the salinity stability of LBL NF membranes in highly saline solutions can be improved by selecting PEs with stronger binding strength, increasing the overcompensation level, and chemical crosslinking. These methods not only enhance the salinity stability of LBL NF membranes but also offer greater potential for their future application in highly saline streams

Potable Water Reuse through Advanced Membrane Technology

© 2018 American Chemical Society. Recycling water from municipal wastewater offers a reliable and sustainable solution to cities and regions facing shortage of water supply. Places including California and Singapore have developed advanced water reuse programs as an integral part of their water management strategy. Membrane technology, particularly reverse osmosis, has been playing a key role in producing high quality recycled water. This feature paper highlights the current status and future perspectives of advanced membrane processes to meet potable water reuse. Recent advances in membrane materials and process configurations are presented and opportunities and challenges are identified in the context of water reuse

Contracepção: Conhecimentos e atitudes em jovens universitários

O aumento da percentagem de gravidez na adolescência (Portugal regista 19/1000 na faixa etária dos 15 aos 19 anos), juntando-se a outros riscos ligados à actividade sexual, tornam os jovens um grupo vulnerável em termos de saúde sexual e reprodutiva. Esta investigação avaliou os conhecimentos e atitudes sobre os métodos contraceptivos em jovens estudantes universitários. Administraram-se 436 questioná - rios a 113 rapazes e 323 raparigas, entre os 18 e os 24 anos. Aplicaram-se medidas de conhecimento (CKI; Delcampo e Delcampo, 1976) e de atitudes (CAS; Kyes, 1987) acerca dos métodos contraceptivos. Os resultados obtidos demonstram que a maioria tem pouco conhecimento acerca dos métodos contraceptivos mas revelou uma forte atitude preventiva face a uma gravidez indesejada. Encontraram-se diferenças estatis - tica mente signficativas entre indivíduos de sexo diferentes: as raparigas apresent am mais conhecimentos e preocupação preventiva face à contracepção. ------ ABSTRACT ------The increase in unplanned pregnancies (the rate in Portugal is 19/1000 in 15-19 year-olds), is responsible for ranking young people as an important target group in terms of sexual health prevention. This study tested knowledge and attitude towards contraceptive methods in 18-24 year old college students. Structured selfreported questionnaires were responded by 436 participants (113 college men and 323 college women). Questionnaires assessed knowledge (CKI; Delcampo e Delcampo, 1976) and attitude (CAS; Kyes, 1987) towards contraceptive methods. The findings show the majority has insufficient contraceptive knowledge although they have a strong preventive attitude towards unwanted pregnancy. The results reveal significant variation in responses by gender: college women demonstra ted better knowledge and preventive attitude in relation to contraception

Gypsum scaling during forward osmosis process : a direct microscopic observation study

This study investigated the effect of supersaturation index (SI), ionic strength, membrane orientation, and antiscalant (AS) addition on gypsum scaling during forward osmosis (FO) desalination. Scaling tests were performed in a cross-flow FO system, and the development of gypsum scalants on FO membrane was directly observed using an optical microscope integrated with the FO filtration cell. Greater surface coverage by gypsum crystals and larger crystal sizes occurred on the scaled FO membranes for feed solutions (FS) with higher SI values accompanying with more severe flux reduction. At fixed Ca2+ and SO_4^(2-) concentrations, reducing the ionic strength of the FS from 0.55 to 0.15 M resulted in longer induction time. Nevertheless, more flux loss and surface coverage by scalants occurred at longer filtration duration for 0.15 M FS due to its greater ion activities and thus higher SI. The active layer facing (AL)-draw solution membrane orientation was found to be prone to internal scaling, which is likely as a result of unfavorable internal concentration polarization of scaling precursors inside the FO membrane support layer. On contrary, the AL-FS orientation had much more stable flux behavior. The current study also demonstrated the effectiveness of AS addition and rinsing under cross-flow conditions for FO scaling control.Published versio

Making waves: Why do we need ultra-permeable nanofiltration membranes for water treatment?

Over the last few decades, developing ultra-permeable nanofiltration (UPNF) membranes has been a focus research area to support NF-based water treatment. Nevertheless, there have been ongoing debates and doubts on the need for UPNF membranes. In this work, we share our perspectives on why UPNF membranes are desired for water treatment. We analyze the specific energy consumption (SEC) of NF processes under various application scenarios, which reveals the potential of UPNF membranes for reducing SEC by 1/3 to 2/3 depending on the prevailing transmembrane osmotic pressure difference. Furthermore, UPNF membranes could potentially enable new process opportunities. Vacuum-driven submerged NF-modules could be retrofitted to existing water/wastewater treatment plants, offering lower SEC and lower cost compared to conventional NF systems. Their use in submerged membrane bioreactors (NF-MBR) can recycle wastewater into high-quality permeate water, which enables energy-efficient water reuse in a single treatment step. The ability for retaining soluble organics may further extend the application of NF-MBR for anaerobic treatment of dilute municipal wastewater. Critical analysis of membrane development reveals huge rooms for UPNF membranes to attain improved selectivity and antifouling performance. Our perspective paper offers important insights for the future development of NF-based water treatment technology, which could potentially lead to a paradigm shift in this burgeoning field

The agile hour in a virtual world: Teaching agile methods with Open Wonderland

Multi-User Virtual Environments (MUVEs) are the subject of increasing interest for educators and trainers. In the context of software development, they are beginning to see increasing use both as learning spaces and as a richer means of collaboration for virtual teams. This chapter reflects on a project that developed and evaluated a virtual agile software development workshop hosted in the Open Wonderland MUVE, designed to help learners to understand the basic principles of some core agile software development techniques. The work took a design-based research approach, following a reflective path of development through two major iterations. The authors trace the research process from a real world implementation of the 'agile hour' workshop to its virtual incarnation, describing the design philosophy and the constructed virtual artifacts. They conclude by reflecting on the insights into learner perceptions and practical implementations gained from building and evaluating the Open Wonderland workshop