New EPA Method to Determine Monochloramine Concentration in Drinking Water
Matthew T. Alexander, P.E., Thomas E. Waters, P.E., and Glynda A. Smith, Ph. D. Office of Ground Water and Drinking Water Standards and Risk Management Division Technical Support Center, Cincinnati, OH David G. Wahman, Ph.D., P.E. Office of Research and Development Center for Environmental Solutions & Emergency Response Water Infrastructure Division Drinking Water Management Branch Cincinnati, OH The information in this presentation has been reviewed and approved for public dissemination in accordance with U.S. Environmental Protection Agency (EPA). The views expressed in this presentation are those of the author(s) Disclaimer and do not necessarily represent the views or policies of the Agency. Any mention of trade names or commercial products does not constitute EPA endorsement or recommendation for use.
U.S. Environmental Protection Agency 2 Overview
Background Rationale Method Development Method Procedure Next Steps
U.S. Environmental Protection Agency 3 Background - Microbial and Disinfection Byproduct Rule Requirements
The Surface Water Treatment Rule (SWTR) requires a detectable disinfectant residual in the distribution system (DS), measured as total chlorine, combined chlorine, or chlorine dioxide (40 CRF 141.72).
Total chlorine = free chlorine + combined chlorine
Combined chlorine = monochloramine + dichloramine + trichloramine The Stage 1 Disinfectants & Disinfection Byproducts Rule (DBPR) established Maximum Residual Disinfectant Levels (MRDLs) for chlorine and chloramines at 4.0
mg/L (measured as Cl2) (40 CFR 141.65). Monochloramine predominates at the pH of most drinking waters (7 – 9) and is more effective and stable for disinfection, compared to di- and trichloramine.
U.S. Environmental Protection Agency 4 Background - Total Chlorine Analysis
Free and total chlorine are most commonly measured by public water systems (PWS) with N,N-diethyl-p- phenylenediamine (DPD) colorimetric methods published by Standard Methods. PWSs that use chloramines as a secondary disinfectant typically measure total chlorine to comply with the SWTR and Stage 1 DBPR. DPD reagent will readily react with chlorine and a variety of other oxidants.
Its undiscerning reactivity can result in overestimation of total chlorine residual in the presence of other oxidants
Organochloramines and oxidized manganese commonly interfere.
U.S. Environmental Protection Agency 5 Background - Organochloramines
Forms when chlorine reacts with dissolved DS Sample Results – October 6, 2010 organic nitrogen and have little to no Total Chlorine Monochloramine Difference disinfection efficacy. Location (mg/L as Cl2) (mg/L as Cl2) (mg/L as Cl2) Known to interfere with the total chlorine WTP DPD method and may result in 3.60 3.16 0.44 overestimation of the effective disinfectant. Effluent Issue was noted by AWWA in its Disinfection Residual Strategy Panel memo to EPA Site #1 0.70 0.28 0.42 OGWDW Director (dated July 31, 2015), the SYR3 DBP support document, and in various Site #2 0.43 0.13 0.30 peer-reviewed publications.
Lee, W., Westerhoff, P., Yang, X., & Shang, C. (2007). Comparison of colorimetric and membrane introduction mass spectrometry techniques for chloramine analysis. Water Research, 41, 3097-3102.
Wahman, D. G., & Pressman, J. G. (2015, August). Distribution System Residuals - Is "Detectable" Still Acceptable for Chloramines? Journal of the American Water Works Association, 107(8), 53-63.
U.S. Environmental Protection Agency 6 Background - Hach Monochloramine Method
Specifically measures monochloramine and is not affected by the presence of organochloramines or other oxidants. This commercially-available method was not available when EPA promulgated the SWTR and EPA has no requirements for the measurement of chloramine concentrations. The patent on the Hach MonochlorF reagent was filed on September 4, 1998 and expired 20 years after filing the patent application (i.e., September 4, 2018).
U.S. Environmental Protection Agency 7 Rationale – Benefits of EPA-Developed Method
Ensured that additional, important quality control measures were incorporated into the method. Validation study discovered sample reaction time discrepancy in existing commercially-available method: Can lead to low bias Issue at ≤ 15°C EPA Method includes updated, corrected sample reaction times
U.S. Environmental Protection Agency 8 Would allow PWSs an alternative compliance monitoring method that quantifies the effective disinfectant Rationale – (versus oxidants with little disinfectant efficacy), which is significant in a regulatory construct where systems Benefits of must only maintain a “detectable” residual. Many chloraminated PWSs already use a Method monochloramine method for process control or as part of a nitrification control plan. Method approval would Approval reduce the number of parameters that some PWSs would analyze, which would save time and money.
U.S. Environmental Protection Agency 9 Rationale – Regulatory Framework
Would be listed as an optional alternative testing method for total chlorine residual in 40 CFR 141.74(a)(2). If approved by the primacy agency, may be used by PWSs to better manage disinfectant residuals by obtaining a more accurate understanding of the level of chemical disinfectant in their distribution systems and still comply with the SWTR. This approach does not require a change to the SWTR, since monochloramine is a component of total and combined chlorine. A detectable monochloramine residual indicates a detectable total and combined chlorine residual. While this is separate from ongoing efforts related to potentially revising the MDBP rules, it would likely provide additional benefits to PWSs that chloraminate and are seeking to improve control of Legionella and other pathogens.
U.S. Environmental Protection Agency 10 Method Development
Validation Study Experiments
Standard Curve
Method Detection Limit (MDL)
Initial Precision & Recovery (IPR)
Matrix Spike
Interferences
Reaction and Hold Tim Notable Findings – Temperature/Color Development Method Summary & QC Requirements
U.S. Environmental Protection Agency 11 Standard Curve
U.S. Environmental Protection Agency 12 Initial Precision & Recovery (IPR)
U.S. Environmental Protection Agency 13 Matrix Spike
U.S. Environmental Protection Agency 14 pH
U.S. Environmental Protection Agency 15 Interferences Evaluated Non-Interfering Level Substance
Free Chlorine < 4 mg/L as Cl2 Free Ammonia < 5 mg/L as N
Phosphate < 500 mg/L as PO4 Iron (III) < 10 mg/L as Fe3+ Nitrite < 50 mg/L as N Nitrate < 100 mg/L as N
Evaluated Effect Interfering Level Substance
Magnesium Positive > 400 mg/L as CaCO3 Manganese (VII) Negative > 3 mg/L Ozone Negative > 1 mg/L Sulfide Positive > 0.5 mg/L, a “rust” color develops Thiocyanate Negative > 50 mg/L U.S. Environmental Protection Agency 16 Hold Time
U.S. Environmental Protection Agency 17 Reaction Time
U.S. Environmental Protection Agency 18 Reagent Color Development Time
Reagent Color Sample Sample Development Time Temperature (°C) Temperature (°F) (minutes) 5 41 28 7 45 22 9 47 17 10 50 15 12 54 12 14 57 10 16 61 8 18 64 6 20 68 5 23 73 4 ≥25 ≥77 3
U.S. Environmental Protection Agency 19 Method Summary & QC Requirements
MDL Application Range Instrument (mg/L as Cl2) (mg/L as Cl2) Laboratory Spectrophotometer 0.07 0.07 - 4.50 Portable Colorimeter 0.08 0.08 - 4.50 PPA 0.06 0.06 - 4.60
Sample Collection:
10 mL for colorimeters or laboratory spectrophotometer
120 mL for PPA Quality Control:
Initial Ongoing Instrument calibration Calibration verification: • Quarterly QCS with primary standard • Continuing calibration check with secondary standards with each instrument use Precision & recovery demonstration Laboratory reagent blanks (LRB) U.S. Environmental Protection Agency 20 Method Detection Limit (MDL) Grab sample duplicates Method Procedure for Colorimeters
Set up instrument (610 nm for colorimeters, 655 nm for spectrophotometers using analyst-generated calibration curve) Rinse and fill sample cell with prescribed volume Clean outside of sample cell with lint-free paper fiber optic cleaning wipe or delicate task wipe to remove fingerprints and condensation Check sample cell for air bubbles. If present, gently invert the capped sample cell until bubbles are eliminated. Insert sample cell into instrument cell holder and zero the instrument. Remove the sample cell, measure and record sample temperature, then add reagent. Cap sample cell and shake for approximately 20 seconds to dissolve reagent. Determine appropriate reaction time based on the measured sample temperature, and allow sample to react for that amount of time. When timer expires, clean the cell again and check for air bubbles. Place the cell into the instrument’s cell holder and read the sample. Sample color is stable for at least 15 minutes after the specified reaction time.
U.S. Environmental Protection Agency 21 Next Steps
Publish method and assign EPA document number. Create a memo for the record describing our rationale for allowing the method as an optional compliance monitoring method. The memo will be reviewed by OGC as part of their review of the expedited approval action. Include method in the Federal Register action for the next set of expedited method approvals.
U.S. Environmental Protection Agency 22 Questions? Acknowledgements Will Adams, Ph.D., Chris Frebis, and Steve Wendelken, Ph.D. EPA-OGWDW Taylor Rosenhagen and Chris Bobay, Louisville Water Company (Louisville, KY) John Consolvo, Joseph Mockus, Alexandra Rosario-Arocho, and, Philadelphia Water Department (Philadelphia, PA) Julian Fairey, PhD, University of Arkansas (Fayetteville, AR) City of Hamilton Water (Hamilton, OH) Greater Cincinnati Water Works (Cincinnati, OH) Augusta Regional Water Treatment Plant (Augusta, KY) City of Falmouth Water and Wastewater Department (Falmouth, KY) Justin Blashaw and Paul Handke, Pennsylvania DEP (New Stanton, PA) Kayla Quinter, former U.S. EPA intern
Contact Information Matthew Alexander: [email protected] Tom Waters: [email protected]