AWWA QTC98270

Microscopic counts of National Institute of Standards and Technology (NIST) traceable polystyrene latex spheres (PSL) from a scanning electron microscope (SEM) were used to determine the aperture size of a "standard" in-situ light obscuration sensor. The standard in-situ sensor was count correlated to all treatment facility process in-situ sensors at a 16 MGD treatment facility creating a SEM traceable count correlation procedure. The treatment facility process sensors were adjusted using a software accessible aperture factor to allow process particle counts to be considered as spherical equivalent microscopic counts. Determining the number of spheres injected was performed by: capturing the spheres after flow through two in-series sensors (capture technique); and, measuring a diluted aliquot of the stock sphere solution prior to placement into an injection syringe (stock technique). The results of five injection runs for two sensors showed mean aperture factors of .120 and .108 using the capture technique and of .092 and .082 using the SEM stock technique. The nominal aperture size was .12 and the factory matched aperture factor was .120 and .113 for the two sensors. The average percent recovery between the number of spheres theoretically injected as determined by the SEM determined stock solution prior to placement into the injection system compared to the SEM determined spheres captured after placement into and flow through the injection system was 75.8%. The SEM traceable count correlation procedure (SEM-traceable procedure) used the capture technique determined aperture factor for one of the standard in-situ sensor(s) to count correlate all of the treatment facility process in-situ sensors.

Product Details

Published:

01/01/1998

ISBN(s):

0898679796

Number of Pages:

15

File Size:

1 file , 130 KB