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NOW YOU SEE IT David L. Russell, Senior Environmental Engineer Specialty Chemicals Division Allied Chemical Corporation Marcus Hook, Pennsylvania 19061 . James J. Tiede, Statistical Scientist Buffalo Research Laboratory Allied Chemical Corporation Buffalo, New York 14240 INTRODUCTION No matter how carefully we make a measurement, there will be some inaccuracy in it. The magnitude of those inaccuracies takes on greater importance when the measurements are used to determine compliance with a regulation or a permit. Frequently, the sampling method used to collect data may contribute additional uncertainty to the measurement. Occasionally, the combined uncertainty associated with sampling technique, flow measurement method and the chemical analyses employed may be larger than the value determined. In the latter case, one wonders what is being reported—is it an actual value or accumulated error? The identification of the variability in some water pollution analyses may appear to be akin to looking for the pea under the walnut shells at a carnival side show—sometimes you see it, and sometimes you don't. When decreasing pollution control permit limits are anticipated, and when the magnitude of the measurement errors cannot be proportionally reduced, the need to examine what is measured and reported becomes much greater. PERMITS, MONITORING AND REPORTING In the NPDES Permit System, the USEPA does not address the inherent inaccuracies in data measurement. During the development of the Effluent Guidelines, industrial efforts were directed toward the statistical evaluation of plant performance data with respect to these Guidelines; and little attention was given to the overall accuracy of the measurements being made. Guideline estimates of plant performance have become "absolute" rules in NPDES permit negotiations, and this situation has caused hardship on many industries. In one specific case, a plant was required to control their net discharge of a particular pollutant at one half part per million when the analytical accuracy of the chemical test method was around one fourth ppm. This example was one where guidelines were strictly followed. The situation just described might not have existed if the limits of accuracy on the measurements made had been examined at the appropriate time. To comply with the existing and proposed effluent permit limitations, we need to (a) determine and state the limits on our ability to measure effluent data, (b) use that information as a basis for action in setting internal performance standards for our control efforts, and (c) attempt to gain recognition of the magnitude of measurement uncertainties in current and future permit negotiations. 211
Object Description
Purdue Identification Number | ETRIWC1978023 |
Title | Now you see it |
Author |
Russell, David L. Tiede, James J. |
Date of Original | 1978 |
Conference Title | Proceedings of the 33rd Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,27312 |
Extent of Original | p. 211-217 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University LIbraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Date Digitized | 2009-06-22 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page0211 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | NOW YOU SEE IT David L. Russell, Senior Environmental Engineer Specialty Chemicals Division Allied Chemical Corporation Marcus Hook, Pennsylvania 19061 . James J. Tiede, Statistical Scientist Buffalo Research Laboratory Allied Chemical Corporation Buffalo, New York 14240 INTRODUCTION No matter how carefully we make a measurement, there will be some inaccuracy in it. The magnitude of those inaccuracies takes on greater importance when the measurements are used to determine compliance with a regulation or a permit. Frequently, the sampling method used to collect data may contribute additional uncertainty to the measurement. Occasionally, the combined uncertainty associated with sampling technique, flow measurement method and the chemical analyses employed may be larger than the value determined. In the latter case, one wonders what is being reported—is it an actual value or accumulated error? The identification of the variability in some water pollution analyses may appear to be akin to looking for the pea under the walnut shells at a carnival side show—sometimes you see it, and sometimes you don't. When decreasing pollution control permit limits are anticipated, and when the magnitude of the measurement errors cannot be proportionally reduced, the need to examine what is measured and reported becomes much greater. PERMITS, MONITORING AND REPORTING In the NPDES Permit System, the USEPA does not address the inherent inaccuracies in data measurement. During the development of the Effluent Guidelines, industrial efforts were directed toward the statistical evaluation of plant performance data with respect to these Guidelines; and little attention was given to the overall accuracy of the measurements being made. Guideline estimates of plant performance have become "absolute" rules in NPDES permit negotiations, and this situation has caused hardship on many industries. In one specific case, a plant was required to control their net discharge of a particular pollutant at one half part per million when the analytical accuracy of the chemical test method was around one fourth ppm. This example was one where guidelines were strictly followed. The situation just described might not have existed if the limits of accuracy on the measurements made had been examined at the appropriate time. To comply with the existing and proposed effluent permit limitations, we need to (a) determine and state the limits on our ability to measure effluent data, (b) use that information as a basis for action in setting internal performance standards for our control efforts, and (c) attempt to gain recognition of the magnitude of measurement uncertainties in current and future permit negotiations. 211 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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