In its purest form, water is one of the most aggressive solvents known and will dissolve a material until the solution reaches saturation. Pure water is also a critical ingredient in many business ventures; manufacturing, power generation, health care, pharmaceuticals, research, food production and processing, etc. Each of these business sectors has a different but specific use for high purity water. Water purity is relative to its use.
Different industries have different critical levels or types of impurities; microelectronics—TOCs (total organic compounds); power—silica; pharmaceutical—bacteria; research—conductivity/resistivity. The specific purity needs, along with the analysis of the source water, form the basis of treatment to produce high purity water.
While purity requirements are paramount, another critical selection criterion is the quantity. It would seem obvious that higher volumes of pure water are directly related to equipment selection, redundancy, and, serviceability.
For example, a system with low-volume demand might effectively accomplish some of the pretreatment filtration functions using cartridge-type filters and closed-loop piping distribution with little or no storage. At the other end of the spectrum, where pure water is fundamental to the process or where extremely high volume demands are normal, a system may be developed with redundant vessels, filters, and pumps to allow for service and/or replacement of components without interrupting either the production or purification processes.
From: “Pure Water: A Drop by Drop Process For Selection of Your System”