Integrating sphere tests water quality

In a drinking-water treatment plant, it is important to measure both particles and dissolved materials to ensure that the water meets quality standards. Many dissolved materials can be detected by their optical absorption; however, absorption measurement is made difficult by interference from scattering caused by particles. In addition, the cuvette windows of a standard measurement system are often fouled, which reduces instrument reliability.

Researchers at North West Water (Warrington, England) have developed a new method that overcomes both problems. In the technique, the water flows in an unconstrained stream through an integrating sphere. Within the sphere, optical absorption is measured independent of scattering, and this combination of window-free and scattering-independent absorption measurement offers a highly reliable industrial instrument.