What is Water Purification?
Water purification is the process of removing biological pollutants, unwanted chemicals, suspended solids and gases from water. In water purification, purification is done to produce water suitable for certain purposes. Water purification is carried out in a variety of fields, including drinking water as well as medical, pharmacological, chemical and industrial applications. water purification; physical processes such as filtration, distillation and precipitation; biological processes such as biological activated carbon, slow sand filters; chemical processes such as chlorination and flocculation; It is carried out by processes using electromagnetic radiation such as ultraviolet (UV) light and processes such as reverse osmosis, continuous deionization, ion exchange.
Although tap water can be considered highly purified, there are 5 classes of contaminants that can pose a problem in laboratory operations. These are organics, inorganic ions, gases, particles/colloids and bacteria.
Water systems are classified as Type I, Type II and Type III for technical and intended use and help to identify different water quality levels. Classification allows the user to select the correct water quality for a particular process.
- Type I pure water device (ultra pure water systems) is the highest purity level of water according to ASTM D1193 with 18.2 MΩ.cm resistance at 25 ºC. Sensitive analytical and biological applications such as liquid chromatography (HPLC), gas chromatography (GC) critically depend on Type 1 ultrapure water to eliminate costly risks of instrument damage and false research data due to contaminants.
- Type II water purification systems, pure water with a resistivity of >1 Mohm-cm at 25ºC, are classified as Type 2 according to ASTM D1193 and are suitable for general laboratory use such as buffer, media and reagent preparation, cell culture studies, pH solutions glassware rinsing and supply equipment. widely used for applications. Type 2 water can also be used as a feed to Type 1 water treatment systems.
- Purified water with >98% rejection at 25ºC is classified as Type III reverse osmosis water and is commonly used for general equipment such as water baths, window washers, humidifiers and autoclaves. Type 3 water can also be used as a feed to a Type 1 water treatment system.
What is Reverse Osmosis?
Reverse osmosis is the most economical method of removing up to 99% of feedwater contaminants.
To understand reverse osmosis, you must first understand osmosis. During natural osmosis, water flows from a less concentrated solution through a semipermeable membrane to a denser solution until the concentration and pressure on both sides of the membrane are equal.
In water purification systems, external pressure is applied to the more concentrated (feedwater) side of the membrane to reverse the natural osmotic flow. This forces the feedwater to pass through the semipermeable membrane.
The impurities accumulate on the membrane surface and are sent to the drain, and the water that passes through the membrane as product water is often freed from impurities.
The reverse osmosis membrane has a fine microporous surface that rejects impurities but allows water to pass through. The membrane rejects bacteria, pyrogens and 90-95% of inorganic solids. Multivalent ions are more easily rejected than monovalent ions. Organic solids with molecular weight greater than 200 Dalton are rejected by the membrane, but dissolved gases are not effectively removed.