Hollow fiber nanofiltration (NF) membranes have gained increased attention in recent years, partly driven by the availability of alternatives to polyamide-based dense separation layers. Moreover, the global market for NF has been growing steadily in recent years and is expected to grow even faster. Compared to the traditional spiral-wound configuration, the hollow fiber geometry provides advantages such as low fouling tendencies and effective hydraulic cleaning possibilities. The alternatives to polyamide layers are typically chemically more stable and thus allow operation and cleaning at more extreme conditions. Therefore, these new NF membranes are of interest for use in a variety of applications. In this review, we provide an overview of the applications and emerging opportunities for these membranes. Next to municipal wastewater and drinking water processes, we have put special focus on industrial applications where hollow fiber NF membranes are employed under more strenuous conditions or used to recover specific resources or solutes.

Under UV irradiation, titanium dioxide (TiO 2 ) exhibits a strong bactericidal activity through the generation of hydroxyl radicals (•OH). Silver (Ag) sensitization is an effective way to enhance photocatalytic activity of TiO 2 . In the present study, Micrococcus lylae was used as a model bacterium to compare the bactericidal activity of Agsensitized TiO 2 (in two different Ag/TiO 2 molar ratios) and pure TiO 2 (P25). When the concentration of photocatalysts was fixed on 0.2 mg/ml with 300 rpm stirring, no obvious difference observed among the three photocatalysts. However, the Ag-sensitized photocatalysts with higher Ag/TiO 2 ratio showed better bactericidal efficiency when their concentration decreased (0.1 mg/ml) or the stirring speed increased (380 rpm). The results indicated that optimizing the phosico-chemical conditions of reaction promoted the efficiency of photocatalyst. Moreover, transmission electron microscopy (TEM) was used to observe the sub-cellular structural changes of M. lylae during photocatalytic oxidation (PCO). According to the TEM images, the disruption of cell wall occurred at a relatively long time after the cell death. The cause of cell death was the destruction of plasma membrane induced by membrane permeable •OH. These results supported that both modification on photocatalyst properties and optimization on reaction conditions enhanced the bactericidal efficiency of PCO.

Fast-growing water demand, population growth, global climate change, and water quality deterioration all drive scientists to apply novel approaches to water resource management. Nanotechnology is one of the state-of-the-art tools in scientists’ hands which they can use to meet human water needs via reuse of water and utilizing unconventional water resources. Additionally, monitoring water supply systems using new nanomaterials provides more efficient water distribution networks. In this chapter, we consider the generic concepts of nanotechnology and its effects on water resources management strategies. A wide range of nanomaterials and nanotechnologies, including nano-adsorbents, nano-photocatalysts, and nano-membranes, are introduced to explain the role of nanotechnology in providing new water resources to meet growing demand. Also, nanomaterial application as a water alternative in industry, reducing water demand in the industrial sector, is presented. Another revolution made by nanomaterials, also discussed in this chapter, is their use in water supply systems for monitoring probable leakage and leakage reduction. Finally, we present case studies that clarify the influence of nanotechnology on water resources and their management strategies. These case studies prove the importance and inevitable application of nanotechnology to satisfy the rising water demand in the modern world, and show the necessity of nanotechnology awareness for today's water experts.