TOC ANALYSIS IN DRINKING WATER continued
Table 1 – Results of raw and finished drinking water TOC analysis
Potable Watr quality control standard (OI Analytical)
9210p (mg TOC/L) 8.68 (1.03)* 8.75 (0.82) 8.76 (0.75) 8.73 (0.86)
Suwannee River NOM Reference Material (1R101N)
1030W (mg TOC/L) 9210p (mg TOC/L) 7.92 (0.20) 8.67 (0.06) 8.56 (0.63) 8.41 (3.62)
1.19 (1.15) 4.55 (0.85)
*%RSD in parentheses; n = 3.
1030W (mg TOC/L) 1.13 (1.38) 4.34 (1.55)
Figure 1 – The 9210p on-line TOC analyzer can be used as an on-line instrument throughout the drinking water treatment process, or in the laboratory, with streams coming off the pro- cess for intermittent analysis.
alarm closure or as a 4–20 mA analog signal. The user-friendly analyzer is adaptable to most processes and plant environments.
Results and discussion Test methods for U.S. EPA regulatory com-
pliance reporting are currently based on laboratory TOC analysis. On-line TOC analyz- ers are generally used for process control and need not operate under the quality assurance requirements specified in U.S. EPA methods.
The raw and finished drinking water results shown in Table 1 were run on an OI Analytical Aurora 1030W laboratory TOC analyzer and 9210p on-line TOC analyzer employing the heated sodium persulfate oxidation technique in U.S. EPA-approved methods 415.3 and SM 5310C.
Use of benchtop and on-line TOC analyzers in tandem is optimal, since on-line analyzers must be calibrated periodically to ensure accuracy, minimize drift and verify oxidation efficiency.
As shown in Figure 2, the correlation of 0.99747 demonstrates that the results between the two instruments are statistically the same.
Figure 2 – Correlation of results obtained on unknown samples using the 9210p on-line TOC analyzer and Aurora 1030W TOC analyzer.
Thus, tandem use of benchtop and on-line TOC analyzers provides water processing facilities with a very efficient, cost-effective tool for the monitoring and optimization of influent and effluent process streams.
References 1. Peyton, G.R. The free-radical chemistry of persulfate-based total organic carbon ana- lyzers. Marine Chemistry 1993, 41, 91–103.
AMERICAN LABORATORY • 22 • AUGUST 2015
2. Hargesheimer, E.; Conio, O. et al. Online monitoring for drinking water utilities. American Water Works Association, 2002;
http://www.waterrf.org/ExecutiveSumma- ryLibrary/90829_2545_profile.pdf
John Welsh, Jr., Ph.D., is TOC product manager at OI Analytical, P.O. Box 9010, College Sta- tion, Texas 77842, U.S.A.; e-mail: john.welsh@
xyleminc.com;
www.xyleminc.com
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