Uf technology   

Ultra-filtration (UF) is a kind of membrane filtration. Process principle of UF can be described as that hydrostatic pressure forces a liquid against a semi-permeable membrane. Suspended solids and solutes of high molecular weight are retained, while water and low molecular weight solutes pass through the membrane. Particles, colloids, dissolved molecules and biological contaminants from fluids under a feed pressure are separated by UF process. On the other hand, nano-filtration (NF) and reverse osmosis (RO) systems have been used to purify tap water to distilled water quality in which salts and small molecules are separated from low molecular weight solutes. Among these methods, UF is the most frequently used for waste-water treatment owing to the fact that it can be controlled and maintained easily and cost of it is relatively lower than NF and RO systems.

UF membranes removes particles colloids, proteins, macro-molecules, bacteria and viruses from a feed solution. Schematic illustration of membrane filtration spectrum is shown in Figure 1. The molecular weight cut-off (MWCO) value is a minimum molecular weight of a solute to obtain a rejection of 90% in a membrane separation process. MWCO is expressed by Daltons (Da) and determined by molecular weights of materials with different molecular weights e.g. albumin and dextrans.

The advantages of UF membrane processes compared with conventional water treatment techniques can be listed as:

· No need for chemicals (coagulants, flocculants, disinfectants, pH adjustment)

· Since the basic principal of hollow fibers is filtration, it does not have possibility to create any waste during operation except the undesired component in the feed stream

· Provides cost reduction in waste management · Low energy consumption

· Good and constant quality of the treated water in terms of particle and microbial removal

· Process and plant compactness