Selecting Particle Counters for Process Monitoring

Abstract

Instruments that simultaneously count and size individual particles can be used for analyzing raw‐water particulates, optimizing chemical dosages, measuring particulates in filter effluent, determining filter efficiency in terms of percent removal of particles, and many other applications. A single particle counter will not, however, be universally applicable to all of these circumstances. The type of particle counter required will be determined by the types of water samples to be analyzed and the ultimate use of the data. Commercially available particle counters differ in terms of operational principles as well as complexity, particle size range capabilities, concentration limits, resolution, data‐processing power, and physical installation requirements. Basic features of particle counters and a step‐by‐step approach for evaluating particle counter capabilities are discussed, along with installation considerations for water quality monitoring in discrete and on‐line sampling configurations.

Water Environment Quality Assessment for the Water Park

“…In terms of effective disinfection, a useful but not absolute, upper-limit guideline for turbidity is 0.5 NTU (ISO, 1999). Particle counters can be more sensitive to changes in water quality (Gregory, 1994;Hunt, 1995;Lewis, et al, 1992). The light obscuration of each particle is proportional to its size, and particle counters measure a change in light intensity as particles pass through a laser beam to report the particle size distribution in water, usually 1 µm and larger (Hunt, 1995;Lewis, et al, 1992).…”

“…Particle counters can be more sensitive to changes in water quality (Gregory, 1994;Hunt, 1995;Lewis, et al, 1992). The light obscuration of each particle is proportional to its size, and particle counters measure a change in light intensity as particles pass through a laser beam to report the particle size distribution in water, usually 1 µm and larger (Hunt, 1995;Lewis, et al, 1992). In many instances, turbidity and particle count trends correlate strongly with each other (Gregory, 1994;Hunt, 1993;Hunt, 1995;ISO, 1999;Lewis, et al, 1992).…”

Particle count and online turbidity interference from bubble formation

“…In terms of quality assurance and quality control (QA/QC), particle counters and turbidimeters are among the few standard analytical devices for which possible matrix effects are not explicitly tested. Several factors preclude the testing: (1) some turbidity and particle count signals are found in all dilution water; (2) sometimes salts must be added to samples to allow for the analysis (i.e., electrical zone sensing); (3) the devices work only within fairly narrow concentration ranges; and (4) industry‐accepted performance standards are unavailable for particle counters (e.g., Van Gelder et al, 1999; Lewis et al, 1992). Because instruments are calibrated at the factory, running sample “blanks” with particle‐free water is the only routine check.…”

Evaluation of optical detection methods for waterborne suspensions

“…Turbidimeters respond to a “cloud” of particles in a sample view volume, whereas OPCs count and size individual particles as they pass through a view volume. Comparative studies in performance evaluation show that because of their higher sensitivity, OPCs respond to particle breakthroughs much sooner than turbidimeters 9 – 11 . Ideally, given an OPC‐measured size distribution, it should be possible to obtain turbidity as a sum of the scattered light signal response from each particle in a suspension, 12 provided particle characteristics such as size, shape, structure, and refractive index are known.…”