Water Purification

What is the Relevance of Water Purification?

Reagent quality is critical to the accuracy and repeatability of results.  Ultimately the success of laboratory or clinical endeavors depends on the quality, accessibility and reliability of the pure water supply.

Understanding Water Purification

In order to produce pure water suitable for use in scientific applications, water must pass through a series of technologies which remove impurities.  Various laboratory applications require the removal of different impurities and therefore a range of technologies are utilized.

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Water Purification Technologies:


Depth filters are commonly used as pre-treatment. Raw water passes through a series of winding fibers and carbon, which attract and trap impurities. This offers protection to the RO membrane and other purification technologies that follow. Membrane sub-micron filters are traditionally used as the final step to remove bacteria and other particles which have not been dealt with by the preceding technologies.


This is the most economical method of removing up to 99% of feed water contaminants. During natural osmosis, water flows from a less concentrated solution through a semipermeable membrane to a more concentrated solution until concentration and pressure on both sides of the membrane are equal. In water purification, external pressure is applied to the more concentrated side of the membrane to reverse the natural osmotic flow. This forces the feed water through the semipermeable membrane. The impurities are deposited on the membrane surface and flushed to drain. 


This process removes ions from water, usually RO water, with the use of synthetic resins. The ions are removed from the water through a series of chemical reactions. These reactions occur as the water passes through the ion exchange resin beads. Gradually, all unwanted ions are replaced by hydrogen and hydroxyl ions which combine to form pure water.



Ultraviolet (UV)photooxidationat254nm and 185nm

Photochemical oxidation and ultraviolet light eliminate trace organics and inactivate microorganisms in the feedwater. The 254nm light reacts with bacterial DNA resulting in denaturation. The 185nm light breaks up long-chain organics which can then be removed from the water by ion exchange.


Ultrafiltration is used to remove pyrogens (bacterial endotoxins) and nucleases. This process is critical when producing water for use in tissue or cell culture and media preparation. Ultrafilters use size exclusion to remove particles and macromolecules. Ultrafilters are usually employed at the end of the system to ensure near total removal of macromolecular impurities like pyrogens, nucleases, and particulates.


Water Quality is too Important to be Overlooked
Avidity has collaborated with a certified testing laboratory to develop a custom water test package designed specifically for animal research facilities. Avidity will provide results in an easy-to-read color-coded format with comparison to EPA safe drinking water standards along with recommendations to improve water quality in your facility.

Pre-treatment: Avidity offers several options for feed water treatment prior to RO membrane processing, which are largely intended to preserve the life of the RO membrane and the long-term system stability and operation. These options include carbon filtration, chlorination, pH adjustment, and on-line filtration. Source feed water quality and membrane type largely dictate the appropriate pre-filtration options.

RO Unit: The heart of the system is the RO membrane. Pre-treated water is forced through the membrane, separating out the purified permeate from the concentrate which contains the majority of contaminants found in the original feed water. From the RO, the permeate is funneled from the membrane to storage tanks for distribution to animals. Throughout this process, the system continuously monitors the water-making process and the permeate quality, ensuring that only the highest quality water passes into the storage tank.

Post-Chlorination: While chlorine must be removed from the inlet (feed) water before it enters the membranes, post-treatment water chlorination can be used to prevent bacteria growth in the storage tank. The permeate can be chlorinated up to 10 ppm. Avidity recommends chlorinating at a level of 2 to 3 ppm. Chlorination is accomplished with a chlorine injection pump and a solution tank filled with diluted bleach. The chlorine injection pump automatically operates when water is flowing into the storage tank. Post chlorine is injected between the machine’s permeate water outlet and the storage tank inlet.

Storage and Distribution: The permeate passes to a sealed storage tank where it is stored until it is distributed through rooms for animal consumption. These tanks may range from 90-1,500 gallons in size and, depending on water consumption patterns, some facilities may have multiple storage tanks connected to a single RO. The system is equipped with two distribution pumps that repressurize stored water for distribution throughout the facility.