Ambient water quality criteria are the important basis for establishing water quality standards,and the significant part of scientific water quality management system.The Dianshan Lake is an important water resource located in the upstream of the Huangpu River.Its water quality directly affects the quality of the drinking water in Shanghai.Since the first algal bloom in 1985,the ecosystem in 1985—1992 is not a healthy but relatively stable compared with that other periods.To protect the lake and fulfill its designated uses,this research developed a water quality criteria based on the change of Chl.a in the recent 23 years.On inter-annual variation the concentration of Chl.a in the lake can be divided into four periods: relatively stable,slow rise,rapid increase and slow down.Analysis by the temporal reference state and the frequency distribution methods suggested that Chl.a should be divided into winter-spring and summer-autumn on season variation.The recommended criteria value of Chl.a in winter-spring time and summer-autumn time were 2.0 μg/L and 5.0 μg/L,respectively,which were validated using the input-response relationship referring to the TP criteria of Taihu lake.
Tissue vasculature efficiently distributes nutrients, removes metabolites, and possesses selective cellular permeability for tissue growth and function. Engineered tissue models have been limited by small volumes, low cell densities, and invasive cell extraction due to ineffective nutrient diffusion and cell-biomaterial attachment. Herein, we describe the fabrication and testing of ceramic hollow fibre membranes (HFs) able to separate red blood cells (RBCs) and mononuclear cells (MNCs) and be incorporated into 3D tissue models to improve nutrient and metabolite exchange. These HFs filtered RBCs from human umbilical cord blood (CB) suspensions of 20% RBCs to produce 90% RBC filtrate suspensions. When incorporated within 5 mL of 3D collagen-coated polyurethane porous scaffold, medium-perfused HFs maintained nontoxic glucose, lactate, pH levels, and higher cell densities over 21 days of culture in comparison to nonperfused 0.125 mL scaffolds. This hollow fibre bioreactor (HFBR) required a smaller per-cell medium requirement and operated at cell densities > 10-fold higher than current 2D methods whilst allowing for continuous cell harvest through HFs. Herein, we propose HFs to improve 3D cell culture nutrient and metabolite diffusion, increase culture volume and cell density, and continuously harvest products for translational cell therapy biomanufacturing protocols.
Perovskite oxides exhibit appreciable mixed oxygen ionic and electronic conductivity and have been paid much interests in the last three decades due to their potential applications as oxygen permeable membranes. The hollow fibre geometry can provide much larger areas per unit volume (500~9000 m<sup>2</sup>/m<sup>3</sup>) for oxygen permeation compared to the flat sheet or tubular membranes, making it possible to reduce the membrane system size and the operation cost remarkably. In this work, the progresses on the development of perovskite hollow fibre membranes and the application in oxygen production are summarized. The challenges associated with the commercialization of the technology are also presented and discussed.
Graphene oxide (GO)-based membranes have demonstrated great potential in water treatment. However, microdefects in the framework of GO membranes induced by the imperfect stacking of GO nanosheets undermine their size-sieving ability and structural stability in aqueous systems. This study proposes a targeted growth approach by growing zeolitic imidazolate framework-8 (ZIF-8) nanocrystals precisely to patch microdefects as well as to cross-link the porous graphene oxide (PGO) flakes coated on the outer surface of the hollow fiber (HF) alumina substrate (named the hybrid PGO/ZIF-8 membrane). This method simultaneously improves their structural stability and size-sieving performance without compromising their water permeance. Various structural and elemental analyses were used to elucidate the targeted growth of the ZIF-8 crystals. The X-ray photoelectron spectroscopy (XPS) analysis confirmed the targeted coordination interaction of oxygen moieties on the edges of PGO nanosheets with metal ions of ZIF-8 crystals, allowing for the precise growth of the ZIF-8 nanocrystals in the PGO membranes. The XPS depth profile analysis revealed the uniform distribution of the ZIF-8 precursor throughout the PGO/ZIF-8 membrane. The resultant membrane showed a water permeance of 4 L m–2 h–1 bar–1 and maintained a very stable performance under pressure and prolonged cross-flow operation. Notably, the molecular weight cutoff (MWCO) improved considerably from 570 to 320 g/mol without sacrificing any water permeance after the targeted growth of ZIF-8. This research paves the way for the preparation of highly selective and stable PGO-based membranes for applications in industrial wastewater treatment.
Assembly of atomic-scale thin two-dimensional (2D) graphene oxide (GO) nanosheets into a membrane with macroscopic three-dimensional (3D) laminar structure is accompanied by the formation of wrinkles. The size and pattern of wrinkles, which depend on the substrate curvature and the thickness of the 3D laminar structure, adversely affect the separation performance of the membrane. Therefore, smoothing the formed wrinkles is essential to boost the separation performance of GO-based membranes. For the first time, we proposed a new approach to prepare porous hollow fiber (HF) yttria-stabilized zirconia (YSZ) substrates with small-diameter (660–790 μm, outer diameter (OD)) by stretching the nascent HF using gravitational force. Also, using a delayed phase inversion, a plurality of radial micro-channels opening from the interior surface of HFs can be realized. The resultant HF substrates show promising permeation characteristics and good fracture strength owing to their open microstructure and the robustness of YSZ. Small-diameter HF substrates (OD = 660 μm) with higher surface curvature ensured the fabrication of porous GO (PGO) membranes with better dye separation performance. The rejection of methyl red (MR, MW = 269.3 g mol−1) dye molecule for small-diameter HF PGO membranes (OD 660 μm) was 10%–167% higher than that of membranes fabricated using large-diameters (OD 1250–2600 μm). This study shed light on the fabrication of high-performance thin film membranes by tailoring the geometric features of substrates.
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