scada
~ refereed paper
Table 3. Disinfectant residual online monitor selection chart (parameters in italics refer to our testing program). Parameler Measuring range. mg/I.
Accuracy (COV), "
According to Trial Testing
According lo Manulacturer
A·1
A·2
A·1
0·5
0·5
0·5
A·Z
0·5
Equal
Equal
Equal
Equal
O.o35mg/Lor5%
0.05 mg/Lor
7
28
Equal
6%FS
1st
2nd
No data
3% of lull range
0.07
0.23
No data
0.01 mg/L
l
Equal Repeatability (DDRep/,
1st
mg/I.
Sensft,v,ty/MDL (LOO),
o,i-
%
mg/l.
1st
2nd
0.06
0.02
2nd
1st
Response Time (+I· Response Time), sec
Output Signal (4-20 mA)
National Institute of Standards and Technology, Gaithersburg, Maryland.
1.5
109
2nd
tst
90% <2 mlns
90% <5 mlns
128.81128.4
41.51472
99% < s min
2nd
2nd
1st
precision) of measurement method s and results. Part 1: General principles and definitions. The International Organization for
Standardization, Geneva. International Standard ISO 8466-1. 1990 Water quality - Calibration
rr.
48"
1S1
1st
2nd
4·6
4·10
3"
186.3
Equal
Equal
1st
2nd
No data
10·2500 µSiem
Yes Equal
Decision
Guenther, F. R., Dorko, W. D., Miller, W.R. & Rhoderick, G. C. 1996
3
lnterlerence) pH Range (pH lntertemnce/. "
American Public Health Association, American Water Works Association & Water Pollution Control Federation. 1998 Standard Methods for the Examination of Water and Wastewater. American Public Health Association, Washington D.C.
1st
No data
1st Conductivity Range (conductivity
References
The NIST traceable reference material program for gas standards.
1st Stablllty/Dntt (ShTD/, "
Adjunct Associate Professor, SA Water Centre for Water Management and Reuse, University of South Australia. Dammika Vitanage is t he Science and Technology Program Manager (Treatment and Infrastructure), Sydney Water Corporation and was the Program Leader, Dist ribution, CRC for Water Quality and Treatment.
No
II
4
Yes
Yes
Yes
Equal
Equal
Equal
, _Yes
-
-
Yes
No
ch lorine monitors in simulated field cond itions, where this monitor is intended to be used, is a very important st ep. Sometimes, a manufacturer mistakenly supplies a val ue of one met rological performance characteristic, whereas in reality t his parameter has a different meaning. To avoid the ambiguity in interpretation of laboratory testing results, the operator should strictly follow procedures outlined in respective standards (such as the ISO Standards 15839:2003 and 8466-1 :1990 used in the present study). The monitor evaluation and selection protocol outlined in t his paper was successful in the identification of the most appropriate residual disinfectant monitor for a specific applicat ion. More importantly though , the princi ples app lied are sound for any on line instrumentat ion and will resu lt in better and more confident decision making in inst rument selection.
International Standard ISO 5725-1 . 1994 Accuracy (trueness and
and evaluation of analytical methods and estimation of performance characteristics. Part 1: Statistical evaluation of the linear calibration function. The International Organization for
Standardization, Geneva. International Standard ISO 15839. 2003 Water quality - Online sensors/analysing equipment for water - Specifications and performance tests. The International Organization for
Standardization, Geneva
Acknowledgment The authors wish to thank CRC for Wat er Quality and Treatment, Fiona Fitzgerald and Joach im Buff. The Authors
Dr Alexander Badalyan works as research assistant at the Sansom Inst itute (University of South Australia). He has a Bachelor Degree in Instrumentation and Process Control, and a PhD in Thermal Properties of Liquid and Gases. His research interests are broad but include development of computerbased systems for real-time process monitoring and control in research and industrial applications. Mike Holmes is a Research Scientist at United Water International. Dr Christopher W K Chow - correspond ing author (emai l: Chris.Chow@sawater. com.au) is a Senior Research Chemist, Wat er Treat ment Unit, Australian Water Quality Cent re and
water SEPTEMBER 2009 73