INTRODUCTION TO ULTRAFILTRATION

Ultrafiltration (UF) is a low-pressure operation at transmembrane pressures of, typically, 0.5 to 5 bars. This is not only allows nonpositive displacement pumps to be used, but also the membrane installation can be constructed from synthetic components, which has cost advantage.

UF membranes can be fabricated essentially in one of two forms: tubular or flat sheet. Membranes of these designs are normally produced on a porous substrate material. The single operational unit into which membranes are engineered for use is referred to as a module. This operational unit consists of the membranes, pressure support structures, feed inlet, concentrate outlet ports, and permeate draw-off points. Two major types of UF modules can be found in the market, i.e., hollow fibers (capillary), and spiral wound. Other modules are plate and frame, tubular, rotary modules, vibrating modules, and Dean vortices.

Operation of UF membrane can be performed in two different service modes, i.e., dead-end flow and cross-flow. The dead-end flow mode of operation is similar to that of a cartridge filter where there is only a feed flow and filtrate flow.

The dead-end flow approach typically allows optimal recovery of feed water on the 95 to 98% range, but is typically limited to feed streams of low suspended solids (<1 NTU). The cross-flow mode different with dead-end mode in which there is an additional flow aside from feed flow and filtrate flow (permeate), i.e., the concentrate. The cross-flow mode of operation typically results in lower recovery of feed water, i.e., 90 to 95% range [Bates, 1999].

Hollow fiber membrane

Benefits of Ultrafiltration Membrane

• Removal of bacteria, viruses with turbidity of < 0.1 NTU, 95% recovery rate
• Removal of total suspended solids > 0.1 micron
• Consistent permeate water quality
• Concentrate and recovery of valuable salts

Application

  • Dialysis and other blood treatments
  • Concentration of milk before making cheese
  • Fractionation of proteins
  • Clarification of fruit juice
  • Recovery of vaccines and antibiotics from fermentation broth
  • Laboratory grade water purification
  • Wastewater treatment
  • Drinking water disinfection (including removal of viruses)
  • Removal of endocrines and pesticides combined with Suspended Activated Carbon pretreatment