Ultrafiltration Equipment

Ultrafiltration equipment suppHers derive K empirically for their equipment on specific process fluids. Flux J is plotted versus log for a set of operation conditions in Figure 6 K is the slope, and is found by extrapolating to zero flux. Operating at different hydrodynamic conditions yields differently sloped curves through C. ... 

Commercial industrial ultrafiltration equipment first became available in the late 1960s. Since that time, the industry has focused on five different configurations. 

Poly(vinyl alcohol) can be recovered from the desizing Hquid by means of commercial ultrafiltration equipment. Recovery rates and effluent losses ate inversely proportional to the PVA solution viscosity and independent of the degree of hydrolysis. 

Ultrafiltration equipment are combined with other unit operations. The unique combination of unit operations depends on the wastewater characteristics and desired effluent quality, and cost considerations. 

Commercially available plate- and frame- type ultrafiltration equipment are used for exopolysaccharide concentration. The membranes are polysulphone or polyvinylidine fluoride with molecular weight cut-off between 20-60,000. There is a relatively low eneigy requirement (1-2 kWh m 3) for pumping the fluid through the filtration unit at the desired pressure. Pressure difference across the membrane is of the order 2-14 atmospheres. 

Because of the broad differences between ultrafiltration equipment, the performance of one device cannot be used to predict the performance of another. Comparisons can only be made on an economic basis and only when the performance of each is known,... 

Because of the glamour of biotechnology, these applications have received a disproportionate interest by academic researchers. However, this is not a major market for ultrafiltration equipment, and many of the plants use little more than bench-scale equipment. 

The authors would like to thank Dr. Randall Swartz, Biotechnology Engineering Center, Tufts University for helpful discussions and the Amicon Corporation for providing ultrafiltration equipment. 

The development of commercial ultrafiltration equipment has made recovery of the whey proteins economically feasible, and a number of uses for the remaining lactose (the principal BOD source)... 

In recent years, developing technology has led to the use of ultrafiltration and microfiltration membranes for juice clarification (1,4-13). The use of membranes has several advantages. Lower labor costs may be possible due to automation possibilities of membrane filtration (8). Filter aids such as diatomaceous earth (DE) aren t needed (9) so that product that would have been discarded with DE is saved, and DE acquisition and disposal costs are eliminated. Enzymes may be rejected by ultrafiltration membranes (4,12) causing the ultrafiltration equipment to act as an enzyme reactor (12), although some odor-active volatiles may be retained, resulting in some loss or change in flavor (8). 

For synthesis on a preparative scale, repetitive batch processing has proved to be an effective and easy-to-handle method1128. The repeated use of the enzyme is possible after concentration of the solution by means of commercially available ultrafiltration equipment and adding fresh substrate solution. Some of the advantages given for the Enzyme Membrane Reactor (see below) are also valid for the repetitive batch technique. 

For effective ultrafiltration, equipment must be optimized to promote the highest transmembrane flow and selectivity. A major problem which must be overcome is concentration polarization, the accumulation of a gradient of retained macrosolute above the membrane. The extent of polarization is determined by the macrosolute concentration and diffusivity, temperature effects on solution viscosity and system geometry. If left undisturbed, concentration polarization restricts solvent and solute transport through the membrane and can even alter membrane selectivity by forming a gel layer on the membrane surface—in effect, a secondary membrane — increasing rejection of normally permeating species. 

Ultrafiltration equipment (DC 30 P, Amicon, Grace) with an MWCO of 3000 was used to concentrate the 360 L of X1+X2 solutions to 80 L. This solution was dia-filtered under steady state conditions for 2 days to exchange 98% of the water. The 80 L were reduced to 22 L after two days. 

The wastewater used in the experiments was obtained from a printing company in China. The samples were withdrawn from the end of the ultrafiltration equipment, after concentrated by the ultrafiltration membrane and the effluents were used directly without any dilution. The wastewater samples were analyzed and the characteristics were given in Table 1. The parameters were measured based on the Standard Methods for the Examination of Water and Wastewater. 

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