China 
Africa 
Explore chapters and articles related to this topic
Membrane Technologies for Water Purification
Published in P.K. Tewari, Advanced Water Technologies, 2020
UF separation technology can be designed in two configurations: dead-end filtration and cross-flow filtration. Dead-end filtration is the most basic form of filtration where the feed flow is forced through the membrane and the filtered matter gets accumulated on the surface of the membrane. In dead-end filtration, the accumulated matter on the filter decreases the filtration capacity due to clogging of pores. It requires removal of the accumulated matter. This filtration is a useful technique for concentrating compounds. In cross-flow filtration, a constant flow is maintained along the membrane surface, preventing the accumulation of matter on the surface. The feed flowing through the membrane is at higher pressure as a driving force for the filtration process and high velocity to create turbulence. This process is referred to as cross-flow, since the feed flow and filtration flow direction are perpendicular to each other. Cross-flow filtration is preferred for liquids having a high concentration of filterable matter.
Applications of Ceramic Membranes
Published in Mihir Kumar Purkait, Randeep Singh, Membrane Technology in Separation Science, 2018
Mihir Kumar Purkait, Randeep Singh
Microfiltration and ultrafiltration membrane processes are used for orange juice clarification by using either polymeric or ceramic membranes. Nowadays, due to the better operational properties of ceramic membranes, they are preferred for the orange juice clarification. Measures are taken to improve the membrane processes for the better orange juice clarification by using membranes with high membrane flux, which reduces the total membrane surface requirements. The fouling problem is dealt by using cross-flow filtration and membranes with better antifouling nature. The ceramic membranes used for orange juice clarification have pore sizes in the range of 20 and 200 nm, membrane flux of values ~500 L/m2h at 150 kPa, and cross-flow velocity of ~4.5 m/s.
Recovery of bioactive compounds in citrus wastewater by membrane operations
Published in Alberto Figoli, Jan Hoinkis, Sacide Alsoy Altinkaya, Jochen Bundschuh, Application of Nanotechnology in Membranes for Water Treatment, 2017
Alfredo Cassano, Carmela Conidi, René Ruby-Figueroa
Membranes can be operated in either dead-end or crossflow configurations. In the dead-end mode the feed flow is perpendicular to the membrane surface. It is forced through the membrane, which causes the retained particles to accumulate and form a type of cake layer at the membrane surface. The thickness of the cake layer increases with filtration time, and the permeation rate decreases as the thickness of the cake layer increases. Dead-end filtration is often used as a method to estimate the specific cake resistance for crossflow filtration and usually gives reasonable data for spherical- and ellipsoidal-shaped cells (Tanaka et al., 1994). On the other hand, in crossflow filtration the fluid flows in a direction parallel to the membrane surface and permeates through the membrane due to an imposed transmembrane pressure difference. Unlike dead-end filtration, rejected particles form a cake layer on the membrane surface which does not build up indefinitely, so the cake formed is of a limited thickness (Tiller and Cooper, 1962). The cake structure will be affected by different phenomena, such as the collapse of the pore structure, pore compression and pore distortion. This set of phenomena will affect to differing extents the porosity, the pore size and the pore tortuosity of the filtration cake (Mota et al., 2002).
Appropriate technologies for upgrading wastewater treatment plants: methods review and case studies in China
Published in Journal of Environmental Science and Health, Part A, 2018
Kai Hu, Qing L. Zhao, Wei Chen, Wei Wang, Feng Han, Xing H. Shen
Decreasing the pore size means that the applied pressures on the membranes increase considerably because of hydrodynamic resistance. The MF and UF operations are based on the convective pore-flow mechanism (i.e., Darcy’s law), whereas the RO membrane operation is based on the solution diffusion mechanism (i.e., Fick’s law).[26] The intrinsic membrane capability varies greatly from the actual membrane performance. This is mainly due to concentration polarization and membrane fouling. Therefore, in practice, it is the feed conditions, such as concentration polarization and fouling, which will determine membrane performance rather than its intrinsic properties. Consequently, the most important issue affecting membrane technology is contamination of the membranes, which is often called fouling. However, there are many ways of reducing fouling,[1] such as pre-treatment of WWTP effluent using in-line coagulation and/or deep-bed filtration; optimization of process configuration using cross-flow filtration and dead-end filtration; cleaning the membranes using back-flushing (sometimes combined with an oxidizing compound, such as sodium hypochlorite or hydrogen peroxide), forward flushing (sometimes combined with air), and ultrasonic cleaning.
Filtration of aerosol particles by parallel and staggered filter arrays
Published in Aerosol Science and Technology, 2022
Manabu Nishimura, Yajiao Liu, Masao Gen, Takafumi Seto, Yoshio Otani
The filtration conditions in the parallel and staggered filter arrays are comparable to cross flow filtration technology (Sibanda et al. 2010). Cross flow filtration technology utilizes a membrane (filter) array positioned parallel to a particle-laden flow. Similar to this study, particle filtration is realized by a pressure drop across the filter as the driving force (Wang et al. 2017; Kim and Zydney 2006; Bailey, Warf, and Maigetter 1990). The permeation flux passing through the filter for particle filtration is high when the pressure drop between the filters is large and the flow resistance of the filter is small. The filtration rate in cross flow technology increases with Ff (Kim et al. 2019; Sibanda et al. 2010). In addition, the accumulation of particles collected in the filters leads to an increase in the flow resistance of the filters, reducing the permeation flux (i.e., Ff) (Kyllönen et al. 2006; Baker et al. 1985). Dancy’s law (Kim et al. 2019; Li, H-Kittikun, and Youravong 2008) is given by: where ΔP(L) and R(L) are the pressure drop (ΔP(L)), and the filter flow resistance (R(L)), respectively; µ the fluid viscosity. The only difference between this study and the cross flow filtration technology is the medium type (i.e., gas or liquid). Fundamental processes governing particle filtration are comparable. Therefore, we assume that Equation (2) is applicable to our study. Rearranging Equation (2), the pressure drop, ΔP(L), in this study can be related to a flow perpendicular to the filter material, Ff(L), and the flow resistance across the filter material, R(L). Note that Ff(L) and R(L) are a function of filter array length, L, and particle accumulation in the filter material alters Ff(L) and R(L). As particles accumulate in the filter material, R(L) increases, and hence, ΔP(L) increases (Kanaoka 2019; Thomas et al. 2019; Saleh and Vahedi Tafreshi 2014). Evidently, the flow resistance of the filter material used in this study increases as the dust loading increases (Figure S2 in SI). Ff(L) is expected to be large in the initial stage for a small R(L), and Ff(L) decreases as R(L) increases. In this study, ΔP(L) and R(L) are critical parameters for determining the filter performance. The following sections will discuss the three filter arrays in terms of ΔP(L) and R(L).