Abstract
Measuring particle counts in water is a more sensitive method compared to turbidity. Particle counting gets an increasing importance for operational control in water works and for optimization of the treatment process. However, a general recommendation concerning particle size range and corresponding limit for the particle counts is not available.

The objective of the project was to identify particle sizes and corresponding particle counts suitable for an assessment of plant performance for particle removal in drinking water treatment. The project based on particle counts from 58 waterworks. Particle counters from different manufactures were employed for the measurements. The waterworks examined used dam, sea or ground water as well as bankfiltrate. Particle counting was conducted in effluents from conventional treatment steps, such as flocculation and filtration, as well as effluents from ultrafiltration membranes and samples from finished waters.

The results of the project yielded to a suitable interval for measuring particle counts and to a number of particle counts which should be met in an optimized water treatment plant.