Cartridge filtration

They are, necessarily, dead-end fibers and because of this have only limited capacity for the removal of suspended sohds, a typical 10 in cartridge nominally rated at 10 pm may be able to remove up to 20 g of suspended material before the pressure drop across the fiber becomes unacceptable. This limits their application to clarification, but it is common to find fibers using many such cartridges in parallel. This allows larger dirt 

Depth Filters. All the mechanisms for particle collection provided in Section 6.1, except surfece straining, are relevant in cartridge depth filtration. Metal fibers are preferred to 

Sur ce charged filters, negatively or positively, are also available to enhance particle capture during filtration. This is usefiil when filtering charged suspended mat ial fi-om liquids of low ionic strength or conductivity, such as deionised water. 

Inhomogeneous fibers using metal medm are also avai ble, the size of sintered bead changing within the depth of the filter to again provide a prefiheting effect for the finest filtration sur ce. Combinations of a very fine filtering sur ce formed firom sintered beads on top of coarse fibres or a woven metal support are also possible, providing fine 

Synthetic or natural fibres are formed into a thick waU and then impregnated with resin to fix them in position. A light porous structure which is self-supporting and relatively cheap results. The pore size of these filters is restricted by both the method of construction and structural liinitations. 

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Rgure 4-69. Pleated radial-fan filter cartridge. Filtration is from outside to Inside. Courtesy of Dollinger Corp. 

Treatment technology Cartridge filtration, activated carbon (oil removal), activated sludge sedimentation. 

A typical in-line cartridge filtration application is illustrated in Figure 7.13. A pump forces liquid through the filter, and the pressure across the filter is measured by a pressure gauge. Initially, the pressure difference measured by the gauge is small, but as retained particles block the filter, the pressure difference increases until a predetermined limiting pressure is reached, and the filter is changed. 

Traditional pretreatments make an extensive use of chemicals (NaCIO as disinfection, FeCl3 as flocculants, H2S04 as antiscaling agent) and mechanical filtration units (sand filtration, media filtration, cartridge filtration). 

Examples of depth filtration are sand and cartridge filtration. Solids are trapped in the interstices of the medium. As solids accumulate, flow approaches zero and the pressure drop across the bed increases. The bed must then be regenerated or the cartridge changed. For this reason, this method is not viable for high solids concentration streams as it becomes cost prohibitive. Cartridge filtration is often used as a secondary filtration in conjunction with a primary, such as the more widely used cake filtration. 

Cross-flow filtration as a processing alternative for separation and concentration of soluble or dissolved components competes with traditional equipment such as dead end cartridge filtration, pre-coat filtration and centrifugation. The specific merits and weaknesses of each of these filtration alternatives are summarized in Table 3. In addition to the ability to handle wide variations in processing conditions, other considerations may need to be addressed for economical viability of cross-flow filtration. These are briefly discussed below. A more detailed discussion on process design aspects, capital and operating cost considerations is presented in Sec. 6.7. 

A variety of hybrid processes can also be used, such as pretreatment of powdered activated carbon (PAC), coagulation, conventional treatment, resin or cartridge filtration followed by ion exchange, adsorption, or membranes. 

Muro et al. [80] showed the beneficial effects of hybrid processes in wastewater treatment in the food industry. These mixed systems included traditional techniques as centrifugation, cartridge filtration, disinfection, and different membrane techniques resulting in a cascade design, which could be applied in a variety of the applications. They argued that the risk of membrane damage due to the contact with particles, salt conglomerates, chemicals, or others substances must be minimized to prevent short membrane life. Operation... 

Cartridge filtration using 5.0 pm pore size cartridges are too large for removing bacteria. 

Seawater supply is from an intake 20 m below the water surface, about 1.5 km offshore and 2.2 km from the RO plant. The supply tunnel is about 70 m below the ground surface. The pre-treatment train includes chlorination, polyelectrolyte and ferrous sulphate coagulation/flocculation, acid dosage, dual-media filtration, anti-sealant addition, acid, cartridge filtration and sodium metabisulphite (e.g. see Figures 3.31 and 3.32]. The RO system is a two-pass unit. Post-treatment includes CO2 and lime treatment and chlorination with sodium hypochlorite. The desalinated product water TDS is 220 mg/1 with maximum boron concentration of 1 mg/1. 

Standard blocking has been reported to be an appropriate filtration model for cartridge filtration of liquids and a form of the standard blocking equations shown in Table 2.3 has been used to correlate the filtration of viscose and cellulose acetate [Grace, 1956]. The model assumed in the derivation of the standard blocking equations is that... 

The usual objective of clarifying filtration is to separate solids at a very low concentration fi om a liquid stream. The liquid may be drinking (potable) water, wine, beer, oil, etc. and it is usually the liquid which is the valuable product. The techniques used in clarification processes include deep-bed, precoat, candle and cartridge filtration all of which involve capture of particles inside the porous mass of the filter. Such techniques produce clearer filtrates than those obtained in clarification by sedimentation. The filtration techniques listed are ofiioa complementary they are eirqrloyed for similar duties, but usually operate over different conditions of feed flow rate, feed concentration and process economics. These operating conditions are summarised in Table 6.1. 

This chapter is concerned primarily with process scale membrane fihratinn and phenomena or effects that are relevant to such filtration. Cartridge filtration has already been discussed in Chapter 6, hence most of the following work refers to membrane filtration under crossflow conditions. Hiis technique is applicable to both microfiltration... 

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