Ultrafiltration system design

In a study of the bioaccumulation of metals as colloid complexes and free ions by the marine brown shrimp, Penaeus aztecus [29] the colloids were isolated and concentrated from water obtained from Dickinson Bayou, an inlet of Galveston Bay, Texas, using various filtration and ultrafiltration systems equipped with a spiral-wound 1 kDa cutoff cartridge. The total colloidal organic carbon in the concentrate was found to be 78 lmgdm 3. The shrimps were exposed to metals (Mn, Fe, Co, Zn, Cd, Ag, Sn, Ba and Hg) as radiolabelled colloid complexes, and free-ionic radiotracers using ultrafiltered seawater without radiotracers as controls. The experiments were designed so that the animals were exposed to environmentally realistic metal and colloid concentrations. 

It is proposed that the apparatus of Figure 2 would be a useful tool in monitoring ultrafiltration of latex and electrophoretic paints and in systems design (11). 

Figure 3.40 Typical tubular ultrafiltration module design. The membrane is usually cast on a porous fiberglass or paper support, which is then nested inside a plastic or steel support tube. In the past, each plastic housing contained a single 2- to 3-cm-diameter tube. More recently, several 0.5- to 1.0-cm-diameter tubes, nested inside single housings, have been introduced. (Courtesy of Koch Membrane Systems)...

The current ultrafiltration market is approximately US 200 million/year but because the market is very fragmented, no individual segment is more than about US 10-30 million/year. Also, each of the diverse applications uses membranes, modules, and system designs tailored to the particular industry served. The result is little product standardization, many custom-built systems, and high costs compared to reverse osmosis. The first large successful application was the recovery... 

In this chapter, we will introduce fundamental concepts of the membrane and membrane-separation processes, such as membrane definition, membrane classification, membrane formation, module configuration, transport mechanism, system design, and cost evaluation. Four widely used membrane separation processes in water and wastewater treatment, namely, microfiltration (MF), ultrafiltration (UF), nanofiltrafion (NF), and reverse osmosis (RO), will be discussed in detail. The issue of membrane foufing together with its solutions will be addressed. Several examples will be given to illustrate the processes. 

An integrated membrane approach in UPW systems consists of four major membrane-based water treatment components ultrafiltration (UF), reverse osmosis (RO), electrodeionization (EDI), and membrane degasification. Each process is unique and contributes particular advantages to the system design. As the need increases and the costs become more acceptable, these technologies will become lynchpins of UPW systems. 

A system based on microdialysis coupled with flow-injection chemiluminescence detection allows for direct sampling of unbound drug without extractive sample preparation [72], A similar approach based on continuous ultrafiltration has also been reported [73]. Modifications designed to overcome challenges of low solubility and high-non-specific binding in the ultrafiltration approach have also been described [74]. 

Water supplied to industry has to meet stringent specifications. For example, process water for the chemical and biotechnology industries is routinely purified beyond potable water standards. Boiler feed water for steam generation must contain a minimum of silica. Reverse osmosis units designed specifically for these purposes are in widespread use today. For example, reverse osmosis/distillation hybrid systems have been designed to separate organic liquids. For semiconductor manufacture, reverse osmosis is combined with ultrafiltration, ion exchange, and activated carbon adsorption to produce the extremely clean water required. 

Ole Jentoft Olsen (DSS Danish Separation Systems) presented a large-scale industrial example on using ultrafiltration for the production of antibiotics. Within 15 hr, a volume of 100 metric tons of biomass was processed. The design of membrane module, operational conditions, and the overall plant were presented, along with detailed cost considerations for this process. 

Brine Staging Velocity past the membrane is important. If too low, polarization is excessive, local O rises, and rejection declines. Fouling occurs faster. If too high, pressure losses are higher than they need be, and the osmotic pinch is premature. Since the volume of feed declines continuously, the hydraulic design needs periodic rearrangement. This is commonly done as shown in Fig. 22-64, sometimes known as a Christmas tree. This design is commonly used where the fluid is pumped once, as in RO, NF, and gas-separation systems, but not where recirculation is practiced, as in ultrafiltration. 

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