A Sensitive Monitor for Particles in Liquids
A new technique for monitoring low concentrations of particulate impurities in flowing liquids is introduced. The method is based on measurements of fluctuations in the intensity of light transmitted through the flowing sample. These fluctuations arise from variations in the number of particles in the probe volume and follow Poisson statistics, so that the root mean square value of the fluctuating signal depends on the square root of the particle concentration. Simple analysis indicates that, for particle sizes of around 1 μm or greater, the fluctuating signal provides a much more sensitive measure of particulate contamination than turbidity measurements (either by light scattering or transmission). A practical device based on the new technique is described, which provides a very simple means for continuous, flow-through monitoring of relatively clean liquids.
KeywordsLatex Particle Fluctuate Signal Particle Number Concentration Turbidity Measurement Polystyrene Latex
Unable to display preview. Download preview PDF.
- 1).E.R. Baumann, Water, its quality and YOU!, Filtration & Separation, 26(3). 204–211 (1989).Google Scholar
- 2).G.F. Craun, Surface water supplies and health, J. Amer. Water Works Assoc., 80(2). 40–52 (1988).Google Scholar
- 3).J.B. Rose, Occurrence and significance of Cryptosporidium in water, J. Amer. Water Works Assoc., 80(2), 53–58 (1988).Google Scholar
- 4).G.P. Treweek, Optimization of flocculation time prior to direct filtration, J. Amer. Water works Assoc, 71(2). 96–101 (1979).Google Scholar
- 6).N.G. Van Kampen, “Stochastic Processes in Physics and Chemistry”, North Holland, Amsterdam, 1981.Google Scholar
- 7).M. Kerker, “The Scattering of Light and Other Electromagnetic Radiation”, Academic Press, New York, 1969.Google Scholar
- 9).J. Gregory, A simple particle monitor for low-turbidity waters, Proc. Amer. Water Works Assoc. Water Quality Technology Conference, St. Louis, pp. 563-575, November 1988.Google Scholar