Ultrafiltration, also known as UF, is a separation process, driven by pressure, that employs a membrane to separate solid matter from dissolved components in water. The pores in a UF membrane are usually in the range of 0.03 µm, which endows them with a high capability for removal of turbidity and pathogens.Most untreated water, such as the feed water in effluent treatment plants, contains particulates, including silt and colloids, as well as pathogens. These components impair the safety and mar the appearance of drinking water. Ultrafiltration is often used as the primary method of treatment in industrial filters in order to guarantee the potability and purity of water for drinking. Many industrial filtration plants also prefer ultrafiltration technologies as a means of protecting the elements used in reverse osmosis desalination systems.
Ultrafiltration removes practically all colloidal particles (classed as those between 0.001 and 1.0 microns) from the input water, together with most of the major soluble contaminants. The size of the membrane pores are the main mechanism for regulating the size and range of impurities removed. Membrane pores generally range between 0.005 and 0.1 microns. The manufacturers of ultrafiltration membranes for water treatment technologies tend to classify their products according to thecut-off point for molecular weight in Daltons. In other words, the approximate size of pollutants which would be sure to be removed when a given membrane is employed.
Membranes used in ultrafiltration for commercial water filters may have various geometries. A spiral design is intended to maximise the potential surface area while keeping to a minimum amount of space. This option tends to be cheaper but is also more likely to be sensitive to excess pollution as a result of the processes used in its manufacture. Plate frame designs may be used for situations where the input water is of poor quality and consist of membrane stacks interspersed with supporting plates. The tubular design is ideal for viscous liquids and does not require an extensive pre-treatment process for the input water. Due to the fact that the input solution flows through the core of the membrane, the tiny particles that manage to pass the membrane are collected within the tubular casing. This system has the drawback of being bulky and cost-heavy.