Glossary
The technical terms used in this site and the general terms of water treatment are explained on this page. The terms are listed in alphabetic order. Select the term you are looking for from the index on the left.
- Semipermeable membrane
- This is a membrane type whose velocity of passing the dissolved matter largely varies depending on the size and the characteristics of the dissolved matter. The characteristics above are used to separate, purify or concentrate solutions. The solvent retention quantity is incomparably larger than the films made of the same material, and it has porous structure in general.
- Shear rate
- If the fluid flows along a wall, the flow velocity significantly becomes smaller as it is closer to the wall surface caused by the frictional resistance between the fluid and the wall. The change in flow velocity per position in the perpendicular direction to the wall surface is the shear rate. Normally, it becomes maximum on the wall surface, and decreases as it is away from it. It becomes larger as the watercourse is narrower, and larger as the flow velocity is higher. Since the force applied to each other between the flow and the wall surface or the adjacent parts in the flow becomes stronger as the shear rate becomes higher, there is an effect to make the concentration polarization layer and the gel layer thinner.
- Spiral type module
- This is a membrane module which contains a cylindrical membrane element formed as below; two pieces of flat membrane are bonded to form a long, tube-like envelope, filled with packing material, connected to the water collecting pipe at the open end, and wound around a core pipe along with the spacer where the feed water flows. Its feature is that it is possible to contain a large-size membrane in relatively compact space. However, since the watercourse for the raw water is narrow, clogging occurs easily, and it is not suitable for solutions which contain solid components.
- Sterile purified water
- This is one of water standards of the Japanese Pharmacopoeia. It indicates high-quality water acquired by sterilizing purified water.
- Suspended solid (SS)
- This is an abbreviation of the amount of suspended matter. It indicates solid suspended matter which does not dissolve in water such as clay particles and microbes. It is used as an indicator of water pollution. The substances which causes turbidity in water is filtered with filter, and its measured weight is the amount of SS.
- Tubular module
- A module that tubular membrane is attached inside or outside of its hanger tube whose inner diameter is approx. 0.5 to 1 inch. There are holes on the hanger tube to pass the permeate. In general, most of the modules are the internal pressure type which contains the membrane inside. There is a demerit that the module is bulky, but since the watercourse is not blocked by suspended substances, etc., and it is possible to clean the membrane surface by rubbing with sponge balls, it is very effective for treatment of a liquid which contains solid matter.
- Turbidity
- It is degree of muddiness of water indicated with values. The turbidity when 1mg of standard kaolin is included in 1L of purified water is 1 degree of turbidity.
- Ultrafiltration membrane (UF membrane)
- Its mesh is yet smaller than microfiltration membrane (MF membrane), and separation is performed by pushing water out by applying pressure to the membrane. The pore size on the surface of membrane is 0.01µm, and the molecular cutoff, which expresses the size of the substances that can be separated in molecular mass, is 1,000 to 300,000.
- Ultrapure water
- High-purity water which impurities such as inorganic ions, organic matter and fine particles are removed from to an extremely low level.
- Ultraviolet sterilization
- Sterilization which makes microbes extinct by generating ultraviolet rays. The ultraviolet ray of 253.7nm wavelength is often used because it is easy to generate and has strong sterilizing power. Two types of ultraviolet sterilization are used: the method which sterilizes the air of the work environment and the method which sterilizes water. Running water type and immersion type germicidal lamps are used on the drinking water, medical water and ultrapure water manufacturing systems and others, but they are not effective in the shade, and also their efficacy of sterilization decreases by the dirt on the tubular lamp caused by adhesion of deposits. Therefore, complete sterilization like heat sterilization cannot be realized.