Membrane and Desalination Technologies - TCE Moodle Website

Treatment of Food Industry Foods and Wastes by Membrane Filtration 245
for comparatively clean feed streams with low concentrations of suspended solids and
macromolecules (19). Most food materials in the food processing feed streams, however,
contain macromolecules displaying non-Newtonian behavior. Their viscosity will increase
dramatically above certain concentrations, making pumping difficult and reducing the masstransfer
rate within the boundary layer. This will eliminate most hollow fiber/capillary
modules because they cannot withstand high-pressure drops.
Membrane modules utilizing flat sheets (spiral-wound, plate and pleated sheet modules)
usually have a mesh-like spacer between sheets of membrane. This restricts their use to clear
feed streams containing only fine suspended solids. Feed streams containing large suspended
solids would be poorly treated in spiral-wound modules, owing to the spacers in their feed
channels. On the other hand, spiral-wound membrane modules (Fig. 6.7) are the lowest in
capital costs and energy consumption. The trend in the food and beverage industries seems to
be away from plate modules (Fig. 6.6) and toward spiral-wound modules (Fig. 6.7), with
ceramic tubular modules (Fig. 6.4) holding their own (19).
2.3. Cost of Membrane Filtration
The cost of a given membrane filtration installation is determined by two parts, the capital
cost and the operational cost. The capital cost can be further divided into three parts: membrane
modules; cost of piping, pumps, electronics, vessels; pretreatment and posttreatment.
The prices mentioned in here are prices for complete systems, which mean complete
systems, typically skid mounted, with membrane elements, internal piping and tubing, valves,
pumps, and control equipment. The prices mentioned do not include buildings, installation of
the system or auxiliary facilities like water, drain, electric power, and pressurized air. From
mid 1970s to 1989, prices for membrane systems in the USA were declining. In 1989, spiralwound
elements were massively introduced into the dairy industry, which reduced the price
Membrane
FEED
Support Plate
Permeate Spacer
Fig. 6.6. Schematic of plate membrane module.
Permeate
RETENTATE
Permeate