NDMA Concentrations within Two Water Supply Systems in Northeastern Oklahoma

Introduction

The Contaminant Candidate List (CCL) is a key provision of the 1996 Safe Drinking Water Act that is used to identify potentially harmful drinking water contaminants. Currently, CCL 3 consists of 104 chemicals or chemical groups and twelve (12) microbial contaminants. The CCL 3 was further distilled to thirty-eight (38) chemical contaminants in June 2011 and at that time EPA indicated that they would publish regulatory determinations on contaminants found on the short list by mid-2012. N-Nitroso-dimethylamine (NDMA)is listed on the Contaminant Candidate List (CCL) 3 and the short list. NDMAis classified as a B2 (sufficient evidence - probable human carcinogen) by the EPA. NDMA and four (4) other nitrosamines were also found on the short list. (EPA 2011a) The EPA drinking water unit risk for NDMA(established in 1987) is 0.7 ng/L for 1 person in 1,000,000 to develop cancer from the consumption of two (2) L of water for seventy (70) years. The NDMA drinking water unit risk is based on data extrapolated from female colworthrats oral exposure study. The dose-response study found that tumors developed on the liver of the rats. (EPA 2011c) The State of California has established a public notification level of 10 ng/L of NDMA. The World Health Organization has established 100 ng/L as a guidance value for 1 person in 100,000 from chronic exposure to drinking water. Currently, there is no European Union Standard for NDMA. (WHO 2011) NDMA forms when ammonia, free chlorine and precursors are combined in water. (EPA 2011a) Precursors for NDMA formation have been indicated as aliphatic amines, such as diethylamine, dimethylamine, ethylamine, methylethylamine and methylamine. (Bond et al. 2011) These aliphatic amines are commonly found in waters high in algae. (Fang et al. 2010)

As a part of the unregulated contaminant monitoring regulation (UMCR) 2, EPA required sampling fromlarge public water supplies for NDMA and five (5) other nitrosamines from 2008 to 2010. Test results from the UMCR 2 have indicated a high prevalence of NDMA in the sample set (17,900 samples from 1,200 Public Water Supplies). NDMA was to be found present (at least one detect greater than minimum recordable level of 2 ng/L) in 38.6 % of all surface water treatment plants tested that use chloramines. When water supply systems utilize free chlorineNDMA was found present (at least one detect greater than minimum recordable level of 2 ng/L) in 4.3 % of all surface water treatment plants tested that use free chlorine. Test results indicated that chloraminated drinking water contains between 5 to 30 ng/L of NDMA with levels as high as 140 ng/L. (EPA 2011a) (EPA 2011d) (WHO 2011)

Materials and Methods

An investigation was conducted to determine the presence ofNDMAin public water supplies in northeastern Oklahoma. Communities A and B were selected because they use the same source water. The source water comes from an impoundment containing466,352 acre-feet of water when the conservation pool is full. The drainage area is approximately 350 square miles containing mostly agricultural and residential land use. (USACOE 2012) This impoundment was also selected because it has no OPDES licensed discharges directly into the impoundment. It also only has two (2) small licensed discharges from a single community (<4,000 pop.) within its drainage basin. The impoundment experiences limited algae outbreaks and according to the 303d list only impairment is dissolved oxygen. (ODEQ 2012)

Although different sizes, the water treatment facilities for communities A and B also utilize the same process for treatment (ferric sulfate coagulant, anionic polymer (acrylamide), Degrmont Technologies Superpulsator™ flocculation/ sedimentation, mixed media filtration, and chlorination disinfection). Community BWTP is sized for a peak flow of eight (8) MGD, and the Community A is sized for three (3) MGD. The main difference between the facilities is that Community B WTP utilizes chloramines as a barrier in the distribution system, whereas Community A utilizes hypochlorite (chlorination). Sampling sites were chosen in the approximate geographical middle of the distribution system to obtain samples that could be used to represent an average NDMA concentration in the distribution system. Literature has stated that NDMA formation is similar to other disinfection byproducts, wherein the concentration increases with the increased detention time. (Knight et al. 2011)

The NDMA sampling was conducted on Monday, October 10, 2011. Water samples were taken from the distributions systems of communities A, B and C. The testing protocol was identical for both sample sites and followed the collection procedures as determined by EPA method 521. The water samples (2 – 1 L glass bottles provided by UL) were gathered from the bathroom hose bib that is found in a public park which is located approximately six (6) miles from the water treatment facility. In Community B, the sample site was a convenience store which is located 1 mile north of the water treatment facility. The water samples (2 – 1 L glass bottles provided by UL) were gathered from the bathroom faucet. All of the sample sites were flushed for ten (10) minutes prior to the gathering of the samples. All of the samples were immediately placed in an iced cooler. Unfortunately, the shipped samples were misplaced in transit by United Parcel Service of America, Inc. (UPS) and stored for eight (8) days; thus the October 10, 2011 sampling event was eliminated from sample set. Another round of NDMA sampling was conducted on Wednesday, November 2, 2011 and Tuesday, November 15, 2011. These water samples were successfully delivered to Underwriters Laboratory, Inc. in South Bend, IN. The November 2, 2011 samples arrived at the lab at 2.6 degrees C on November 4, 2011. The November 15, 2011 samples arrived at the lab at 2.6 degrees C on November 17, 2011. The November 30, 2011 sample arrived at the lab at 2.6 degrees C on December 2, 2011.

Underwriters Laboratory completed the sample analysis in accordance with EPA Method 521 determination of nitrosamines in drinking water by solid phase extraction and capillary column gas chromatography with large volume injection and chemical ionization tandem mass spectrometry (ms/ms).

Results and Discussions

The results of the NDMA concentration comparison between Community A and Community B found in northeastern Oklahoma is presented in Table 1.1.

Table 1.1 – NDMA Testing Results for Community A and Community B

Public Water Supply / Location / Sampling Date: 11/2/2011 / Sampling Date: 11/15/2011 / Units
Community A – (Chlorinated) / Six (6) miles from WTP in the Geographical Center of Distribution System - Bathroom Faucet / <2 / <2 / ng/L
Community B – (Chloraminated) / One (1) mile from WTP in the Geographical Center of Distribution System - Bathroom Faucet / 5.3 / 3.2 / ng/L

The results above indicate a strong correlation that using chloramines as a barrier in the distribution system can increase NDMA concentrations. These results are similar to the observations of UCMR 2.

Conclusions

Considering the prevalence and health effects associated with NDMA, it is expected that the contaminant (including other nitrosamines) will be regulated in the future. EPA is on record stating that “regulating nitrosamines could constrain chloramines use”. (EPA 2011a) This is in agreement with the Director of Federal Agencies, Alan Roberson of AWWA. (AWWA2011a) Recently, it was indicated that EPA is going to regulate nitrosamines with a likely final published regulation of 2017. (Roberson 2012) Given the small sample size, it is recommended that continued research be conducted into the production of NDMA from chloraminated water authorities in northeastern Oklahoma.

References

aAmerican Water Works Association. 2011. Impending Regulatory Proposals (AWWA Webcast W1125). Denver: American Water Works Association.

Bond, T. Huang, J. Templeton, M. Graham, N. 2011. Occurrence and control of nitrogenous disinfection by-products in drinking water – a review. Water Research, 45, 4341-4354.

aEnvironmental Protection Agency. 2011. Contaminant Candidate List and Regulatory Determination. Found at on December 4th, 2011.

cEnvironmental Protection Agency. 2011. Integrated Risk Information System (IRIS). Found at on February 4th, 2011.

dEnvironmental Protection Agency. 2011. Unregulated Contaminant Monitoring Program. Found at on February 4th, 2011.

Fang, J. Yang, X. Ma, J. Shang, C. Zhao, Q. 2010. Characterization of algal organic matter and formation of DBPs from chlor(am)ination. Water Research, 44, 5897-5906.

Knight, N. Watson, K. Jose Farre, M. Shaw, G. 2011. N-nitrosodimethylamine and trihalomethane formation and minimization in Southeast Queensland drinking water. Environmental Monitoring and Assessment, DOI 10.1007/s10661-011-2256-7.

aOklahoma Department of Environmental Quality. 2011. Public Water Supply Construction Standards. Found at on February 4th, 2011.

cOklahoma Department of Environmental Quality. 2011. Drinking Water Watch. Found at on February 14, 2011.

dOklahoma Department of Environmental Quality. 2011. Water Pollution Control Facility Construction Standards. Found at on February 4th, 2011.

Oklahoma Department of Environmental Quality. 2012. DEQ GIS Viewer. Found at on September 13th, 2012.

Roberson, J.A. 2012. Regulating Nitrosamines Now will be Controversial. American Water Works Association Journal, 104, 9, 10-13.

U.S. Army Corps of Engineers. 2012. Tulsa District Water Control Homepage. Found at on September 13th, 2012.

World Health Organization. 2011. Guidelines for Drinking-water Quality: Fourth Edition. Found at on February 4th, 2011.

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