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To establish a database to determine whether selected chemicals, not included in the NCCLS standards, could be detected in point-of-use water treatment systems (POUs), we analyzed water samples collected from 50 POUs following service maintenance. These samples were first analyzed for compliance with NCCLS standards for reagent grade water. A spectrophotometer was then used to analyze product water samples for detectable levels of free and total Cl, ClO2, Cr, Cu, Fe, Mn, NO3, SO4 and Si. The following percentages of water systems had detectable levels chemicals (according to water type). For Type I water, free Cl was found in 89%, total Cl, 50%; ClO2, 11%; Cr, 28%; Cu, 78%; Fe, 33%; Mn, 22%; NO3, 89%, Si, 83%; and SO4, 17%. For Type II water, free Cl was found in 71 %, total Cl, 50%; ClO2, 21%; Cr, 29%; Cu, 63%; Fe, 25%; Mn, 4%; NO3, 54%; and Si, 75%.

Results of recent studies conducted to evaluate 4 water-treatment systems (including pre-filter, reverse osmosis, carbon absorption, deionization, and membrane filtration) showed inconsistent performance among the generic components. In addition, a wide range of values were observed for contaminants such as microorganisms, bacterial endotoxin, total oxidizable carbons, chlorine residual, conductivity, temperature, and pH. Results demonstrate the need for careful attention to system component selection and placement in order to provide required water quality. Water treatment and product technology application have undergone vast changes over the last 5 years. While more efficient and compact components for water treatment have been modified or designed, precision means for measuring water quality have not advanced as rapidly. The design and operation of a water system contribute greatly to the quality of water.

Municipal water was purified by an electrodeionization (ED) process for use in the research and diagnostic laboratory. Except for elevated silica levels electrodeionization product water met NCCLS Type II water specifications. An extensive battery of physical, microbiologic, and chemical tests were performed to determine the effect of this technology on water quality and to demonstrate the interaction with the other components of a typical water purification system.