AWWA JAW46260

Since promulgation of the Surface Water Treatment Rule (SWTR) and confirmed outbreaks of cryptosporidiosis and giardiasis, interest in particle counters as a process monitoring device for water treatment facilities has increased. In this article, particle counting methods for use in a water treatment facility were analyzed to compare counts made by a particle counter with a forward-angle light scatter (FALS) sensor with counts made with a scanning electron microscope and by microscopic particulate analysis. A separate study compared a FALS sensor with a light obscuration sensor when challenged with latex spheres and cultured microorganisms and when performing continuous in-line counts of the facility's filter effluent. Log removal values were comparable among the particle counting methods and did not vary significantly across various size ranges of a FALS sensor. Microorganisms were undersized by both sensor types compared with sizes determined with an optical microscope. These results suggest counters accurately indicate facility particle removal efficiency. However, counts made by a particle counter within a specific size range should be interpreted after characterizing the nature of the particles in the source. Includes 22 references, tables, figures.