Real-time on-line monitoring of process water for low concentrations of bacteria

Naturally occurring outbreaks of bacteria have the potential to contaminate process water used in semiconductor manufacturing. Bacteria are normally filtered out in the water treatment process, however contamination can still occur from biofilm growth, filter or media break-through, and air vectors. Because there is seldom a residual disinfectant and system sanitation is intermittent, the manufacturer must rely on point of use filters to prevent contamination at critical points in the process. Particle counters in the distribution system can tell when the number of particles is increasing but cannot discriminate bacteria from small silica particles and often are unable to detect smaller gram-negative particles. If an on-line multi-angle light scattering system is used in place of particle counters or in conjunction with them, then the discrimination between silica particles and bacteria can be made and the proper action taken in the distribution system to help identify the contamination source, improve preventative maintenance, and ultimately increase yields. This paper describes the multi-angle light scattering method of detecting bacteria with the BioSentry (TM) system to provide an effective real-time on-line water monitoring sensor.