Ultrapure water equipment is used to provide high-purity deionized water (DI water) to the semiconductor and pharmaceutical industries. It is also used in alloy metal fabrication, the manufacture of medical devices, laboratory applications, nanotechnology products, and by the electronics industry. Ultrapure water (UPW) is contaminant-free and contains only water, hydrogen ions, and hydroxyl ions. It has an electrical resistivity of 18.3 MegOhm-cm. Ultrapure water equipment is used to remove bacterial fragments (pyrogens), colloidal silica, metal ions, and other particles. The minimization or elimination of total organic carbon (TOC) is especially important in the semiconductor industry, and in the production of integrated circuits (ICs) and microelectronics.
Ultrapure water equipment features a modular design and contains a series of filters and purifiers. These water treatment modules provide pre-filtration, water softening, activated carbon filtration, reverse osmosis (RO), post-RO demineralization, RO/recirculation, storage, and distribution. Pre-filters are designed to remove large, suspended particles and solids. There are two basic types of UPW pre-filtration products: cartridge filters and multi-media filters. UPW water softeners are designed to remove calcium, magnesium, manganese, and iron. They increase membrane life and decrease system downtime. Ultrapure water equipment also uses activated carbon filters to remove chlorine and bacteria.
Reverse osmosis (RO) is central to the production of ultrapure water. In ultrapure water equipment, multiple RO membranes remove feedwater ions and provide a barrier against particulates. Because UPW applications require deionized water (DI water), the RO permeate line includes a deionization module that treats the water before it enters a loop/storage tank for recirculation, additional filtration, and storage. The recirculation loop provides a relatively constant flow rate while the storage tank holds ultrapure water to meet peak demand. The final module of an ultrapure water treatment system consists of a recirculation loop pump, several DI mixed-bed tanks, and an ultraviolet (UV) subsystem. Ultrapure water equipment also includes a final filter that is employed before the water exits the treatment system.
Ultrapure water equipment is specified according to continuous flow rate and control system type. Continuous flow rate describes UPW system performance while the equipment is running at an optimal, steady-state condition. Because UPW equipment often runs discontinuously, however, ultrapure water systems should be designed for the most efficient use and to account for periods of peak flow. There are two basic control systems for ultrapure water equipment: manual and automatic. Manual control systems require manual backwashing or periodic flushing to regenerate the exchange medium. Automatic control systems automatically backwash or flush the exchange medium based on parameters such as time, volumetric operation, and chemical sensing.