This is the most common application of UV light in water treatment. A pharmaceutical water system could have several locations where UV equipment would be installed, including post-carbon filter and pre-RO (reverse osmosis). When installed downstream of the carbon bed and/or directly upstream of the RO unit, a UV system can significantly reduce the microbial counts by inactivating the microorganisms present in the influent stream. Inactivation is also recommended for the process distribution loop and pre storage tank.

UV using low-pressure lamps is a highly effective, versatile, and reliable method to address chloramine reduction. Studies have demonstrated conclusively that chloramine residuals up to 4 ppm can be successfully reduced to by the application of UV light. The breakdown products from treating monochloramine with UV are primarily non-hazardous ionic species and subsequently removed by the downstream RO system. At typical pH and dissolved oxygen levels in municipal treated waters, ammonia formation is negligible.

Ozone is commonly used in the pre-treatment area of a water system, as well as for sanitizing process and recirculating systems. Prior to the point-of-use, the residual ozone needs to be reduced to ensure the process water is not compromised. Because it is a fast-acting treatment, UV technology is the preferred method for this application. A properly sized UV unit can reduce the ozone to non-detectable limits, ensuring the integrity of the process and the product. A dosage of 90 mJ/cm² is recommended for reduction of ozone residuals of 1.0ppm.