AWWA QTC97123

In 1995, the Philadelphia Water Department (PWD) purchased an on-line particle counting system with four sensors and a batch unit for each of its three water treatment plants and a fourth batch unit for distribution system studies. During the investigation of particle counting technology prior to purchase, the PWD had discovered that there did not exist any method to perform on-site particle count calibration by the user and that variations in particle counts were expected between the sensors. Most manufacturers felt that this count variation would range from 10 to 25% among their own sensors and that there could be even greater variations between different manufacturers' sensors. Initial testing of the sensors before they were installed revealed a range of 15 to 45% difference for the total number of particles greater than 2 microns with an average of approximately 30% difference between sensors. As this was unacceptable, the manufacturer showed the PWD how to count match its particle counters. Count matching is defined as a process of fine adjustments to the calibration curves of two or more sensors so that they yield essentially the same particle count value when challenged with a common source. This paper discusses the PWD's experience with count matching and describes some of the benefits and drawbacks of the process. The standard operating procedure developed by the PWD for the use of on-line particle counters is also presented.

Product Details

Published:

01/01/1997

ISBN(s):

0898679583

Number of Pages:

12

File Size:

1 file , 170 KB