NEW INSIGHTS INTO LEAD AND COPPER CORROSION AND IMPLICATIONS FOR REGULATORY REVISIONS

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1 NEW INSIGHTS INTO LEAD AND COPPER CORROSION AND IMPLICATIONS FOR REGULATORY REVISIONS Roger B. Arnold, ARCADIS ABSTRACT The Lead and Copper Rule (LCR) was established to instigate monitoring and mitigation of lead and copper release from premise plumbing materials into drinking water. However, recent research has demonstrated that the monitoring protocol of the current LCR may underestimate peak lead and copper levels in drinking water. Upcoming regulatory revisions are expected to re-define high-risk sites and update the sampling procedure based on an evolved understanding of premise plumbing corrosion. Based on a review of Safe Drinking Water records, North Carolina had a disproportionally high number of LCR violations over the period from The results indicate that these violations stemmed largely from a failure to evaluate and recommend corrosion control treatment per LCR requirements following an Action Level exceedance. Considering North Carolina s history of LCR violations, it is important for utilities to understand the drivers for the upcoming LCR revisions in order to proactively protect public health from lead and copper release to drinking water. KEYWORDS: Lead and Copper Rule, corrosion, lead service lines, corrosion control treatment, drinking water, distribution system INTRODUCTION While finished water leaving the treatment plant is typically devoid of lead and copper, premise plumbing materials release these metals into drinking water at concentrations that can sometimes pose an acute public health risk. Since the 1991 promulgation of the Lead and Copper Rule (LCR), corrosion in premise plumbing systems has been a topic of active research. As a result, our understanding of lead and copper release into drinking water has evolved, and significant upcoming long-term revisions to the Lead and Copper Rule are intended to address growing concerns that LCR monitoring does not accurately reflect public health risk. While observed lead levels in LCR compliance samples have generally decreased since the release of the regulation due to heightened focus on corrosion control, the current monitoring protocol may fundamentally miss or underestimate the highest lead concentrations (Sandvig et al, 2008; Del Toral et al, 2013). This paper will review the current LCR regulations and discuss scientific drivers for regulatory revisions in the Long Term Lead and Copper Rule (LT-LCR). Furthermore, a review of historical regulatory data will be used to evaluate the status of LCR compliance in North Carolina. Lead in drinking water is a significant source of lead exposure and has been shown to contribute to elevated blood lead levels (Edwards et al, 2009; Lambrinidou et al, 2010) that cause health problems due to brain and kidney damage, especially among children. Under the current regulation, the established Action Level is exceeded if the 90 th Percentile concentration of the sample group is above 15 µg/l for lead or 1.3 mg/l for copper. The required sample size per monitoring period is based on water system population, and sample site selection must be conducted according to the established tier structure (Table 1) that is intended to target sites with high risk of lead and copper exposure according. Systems demonstrating consistently low lead and copper levels may quality for reduced triennial monitoring. In order to evaluate fluctuation of water quality throughout the distribution system, water systems must also

2 monitor water quality parameters at the tap throughout the distribution system as a surrogate measure of corrosion, including: ph, alkalinity, calcium, conductivity, orthophosphate, silica, and temperature. Table 1. Summary of Current LCR Sample Site Selection Tier Criteria Tier Site Selection Criteria Single family structures that: Contain copper pipes with lead solder installed after 1982 or contain lead pipes; and/or Are served by a lead service line Buildings, including Multi-family residences, that: Contain copper pipes with lead solder installed after 1982 or contain lead pipes; and/or Are served by a lead service line. Single family structures that contain copper pipes with lead solder installed before Compliance sampling is typically completed by the homeowner in coordination with the local water utility. Instructions are provided to homeowners by the utility, and a 6 hour stagnation period is required prior to sampling during which no water use at the home is permitted. There has been little standardization among individual utilities sampling instructions for some other factors that affect observed lead and copper levels, such as flow rate (Cartier et al, 2012), aerator removal, and pre-flushing prior to stagnation. Exceeding the Action Level during a specific monitoring period triggers a number of Treatment Technique requirements, such as corrosion control treatment, public education, and lead service line replacement, but does not necessarily result in a violation of the Lead and Copper Rule. A recent study noted that Community Water Systems in North Carolina had the highest number of LCR violations in 2011 of any state (Rubin, 2013), so the LT-LCR revisions may have a significant impact on NC drinking water utilities of all sizes. Three primary areas have been the subjects of recent research that may impact the LCR revisions: (1) Lead Service Line Monitoring, (2) Lead Service Line Replacement, and (3) Targeted Copper Monitoring, According to a 1990 estimate, there are about 3.3 million lead service lines in existence in the United States (Weston, 1990). The service line typically connects the water main to the structure s premise plumbing system. Lead pipe was commonly used as a service line material during the early 1900 s and was primarily installed in urban areas in the Northeast and Midwest. Due to the age of installations, location records for LSL s are often based on record drawings, historic construction practices, or building age and location, and anecdotal evidence suggests that LSL location records may often be inaccurate or incomplete. As the current LCR targets a 50:50 split of LSL and non-lsl sites, the sample tier structure does not currently focus primarily on LSL sites with high risk of lead in drinking water. First-draw 1 Liter samples required in the current LCR typically only capture water that has been stagnant in the faucet and premise plumbing system and therefore do not systematically monitor lead release from service lines. Leaded materials in the premise plumbing system that would be monitored by a first-draw sample include leaded brass fixtures and lead-tin solder, which can contribute significant concentrations of lead into drinking water (Schock, 1990; Triantafyllidou et al, 2012; Cartier et al, 2011). However, field research on sources of lead at the tap has concluded that LSL s are the primary contributors to total lead at tap, and reported premise plumbing volumes from field investigations range from 0.9L to 5.4L (Sandvig et al, 2008). Sequential sampling is generally accepted as the most reliable method of LSL sampling (Giani et al, 2004; Estes-Smargiassi et al, 2006; Sandvig et al, 2008; Toral et al, 2013), in which a profile of consecutive samples is collected that comprises the entire volume of water from the tap to the main.

3 Based on this research, the sampling procedure in the LT-LCR would need to be fundamentally restructured in order to effectively monitor lead release from service lines. Lead Service Line Replacement is a required Treatment Technique under the current LCR. A system that continues to exceed the Action Level after implementing corrosion control treatment may be required to replace LSL s at a rate of 7% per year. The regulation is intended to reduce lead exposure by elimination of leaded material from the distribution system. However, as the LSL connects the private plumbing system to the public water main, often only a portion of the LSL is owned by the utility. As a result, utilities are only required to replace the portion beyond the property line, resulting in a partial lead service line replacement (PLSLR). PLSLR sometimes also occurs voluntarily in conjunction with distribution system repair or upgrade when an existing service line is re-connected to a new water main. Copper pipe is typically substituted for the replaced portion of lead pipe, and galvanic corrosion can occur as a result of dissimilar metal contact. Physical disturbance of the lead pipe caused by excavation and cutting can also cause a temporary elevation of lead release due to scale disruption (Sandvig et al, 2008). Bench and pilot scale laboratory studies have demonstrated that galvanic corrosion can cause a localized acceleration of lead release into drinking water (Britton and Richards, 1981; Gregory, 1990; DeSantis et al, 2009; Arnold et al, 2011; Arnold et al, 2012a), and despite reducing the length of lead pipe in contact with drinking water, PLSLR does not effectively reduced lead levels at the tap (Cartier et al, 2012; Triantafyllidou et al, 2011; Clark et al, 2011; Wang et al, 2013). Based on review of available field and laboratory data, a 2011 report from the EPA Science Advisory Board concluded that PLSLR has not been shown to reliably reduce drinking water lead levels. As a result, the LT-LCR is expected to revise lead service line replacement requirements to address concerns about the prudence of the approach, especially considering the high cost of undertaking a pipe replacement program. Despite equal monitoring of lead and copper as part of the LCR, occurrence of elevated copper release in excess of the Action Level is generally isolated to a small proportion of systems. However, elevated copper release into drinking water has caused instances of blue water, blue ice cubes, or blue staining. Water quality factors such as low ph, high alkalinity, and high organic content can contribute to elevated copper release (Schock et al, 1995; Edwards et al, 1996). In circumstances in which a system is compliance with the copper Action Level overall, isolated instances of elevated copper release can occur in new construction. Due to the process of copper pipe aging, copper release in new pipes is typically high, but over time, a passivated interior surface scale (such as malachite) can form and lead to diminished copper solubility. In the presence of water with low ph or high organic content, the copper aging process is hindered, and elevated copper release can persist indefinitely (Edwards et al, 2001; Turek et al, 2011; Arnold et al, 2012b). As the current LCR focuses on older homes, the LCR sample tier would need to be restructured in order to target new sites with high risk of copper release. As lead and copper release is elevated at low ph, and low alkalinity contributes to lead corrosion (Korshin et al, 1999; Arnold et al, 2011), adjustment of ph and/or alkalinity is a common corrosion control method. Orthophosphate is often used as a corrosion inhibitor, but despite generally positive results from utility experience (Brown et al, 2013), addition of orthophosphate is not a corrosion panacea (Nguyen et al, 2011; Arnold et al, 2011) and is associated with other negative consequences such as the potential to fuel microbial growth and increased nutrient load at the wastewater treatment plant (Morton et al, 2005; Volk et al, 2000). If revisions in the LT-LCR were to cause an increase in observed lead levels in compliance monitoring, there would likely be renewed focus on implementing optimized corrosion control treatment (OCCT) and increasing treatment efficiency with emerging strategies. METHODOLOGY In order to elucidate the trends and causes of North Carolina s historical LCR violations, the Safe Drinking Water Information System (SDWIS) database was used to gather and analyze regulatory violation information over the period of 2010 to The SDWIS database contains records of health-based Treatment Technique violations that occur when the Action Level is exceeded and required follow-up steps such as lead service line replacement or addition of optimized corrosion control treatment are not

4 completed as specified. For each state and compliance year, SDWIS contains data on system size, source water type, violation type, and violation cause. A system that exceeds the Action Level but successfully completes Treatment Technique requirements would not be listed in the SDWIS database. In order to identify state-specific trends for North Carolina, state violation data was compared to the national baseline of LCR violations, and by evaluating recent compliance data, the potential local effects of the LT-LCR can be better predicted. RESULTS Nationally, the largest number of LCR violations occurs in very small systems, but the population impacted by these violations is relatively low (Figure 1). At the standard monitoring frequency in systems serving a population of people, the utility is required to collect only 10 samples per monitoring period, and the Action Level would be exceeded with only two samples over 15ppb of 1.3ppm for lead and copper, respectively. The population affected tends to increase as the system size increases, and the largest population affected is in the very large category. Number of Viola'ons 1,200 1, ,600,000 1,400,000 1,200,000 1,000, , , , ,000 0 Popula'on in Viola'on Total Number of Viola7ons Average Popula7on in Viola7on Figure 1. LCR Violations in the United States from 2010 to To compare LCR violations in NC and the US, the number of NC violations in each category was divided by total national violations (Figure 2). Overall, violations in NC accounted for 27% of national violations, which would be proportionally equivalent to about 13 states if violations were equally divided among states. In NC, the highest percentage of violations occurred in the very small category, which accounted for over 30% of violations nationally. In the very small category, about 94% of violations occurred in groundwater systems. In NC, the highest population in violation occurred in the Large

5 category, in which the percentage of national violations was about 28%. In Large systems, about 55% of violations occurred in surface water systems. Due to the high population affected, the results suggest that the Large category is a focus area for LCR compliance in North Carolina. Percentage of Total Viola'ons Occuring in NC 35% 30% 25% 20% 15% 10% 5% 0% 180, , , , ,000 80,000 60,000 40,000 20,000 0 Popula'on in Viola'on Percentage of Na7onal Viola7ons Average Popula7on in Viola7on Figure 2. LCR Violations in North Carolina from 2010 to Percentage represents fraction of national violations occurring in NC for each size category. In order to determine the causes for the disproportionally high number of violations in North Carolina, the types of violations in NC were compared to the national distribution of violation types. As shown in Figure 3, the types of Treatment Technique violations that may occur following an Action Level exceedance are: Lead service line replacement (LSLR), Maximum Permissible Level (MPL) non-compliance (referring to the concentrations of lead and copper in source water), OCCT installation/demonstration, OCCT study recommendation, Public Education, and water quality parameter (WQP) non-compliance at the entry point. In NC, all LCR violations were caused by either OCCT study or public education. The percentage of violation types was not strongly affected by system size and was roughly equal for all size categories. Public Education required following an Action Level exceedance includes mandatory language about lead and copper risk to be distributed through notices in the water bill, information to newspapers, pamphlet distribution, and TV/radio broadcast. Considering the numerous procedural requirements of public education, it is not surprising that it is the second leading cause of LCR violations in NC and nationally. In comparison to the national distribution of violation types, NC had an especially high percentage of OCCT Study Recommendation violations. This result indicates that NC utilities have been challenged by planning and implementation of OCCT following an Action Level exceedance, either due to not completing a study within the required timeframe of 18 months or not receiving state approval of the OCCT plan.

6 Percentage of Viola'on Type 80% 70% 60% 50% 40% 30% 20% United States North Carolina 10% 0% LSLR MPL OCCT OCCT Study Public Installa7on Educa7on WQP Figure 3. Comparison of Violation Types in NC and the US. As shown in Figure 4, a significant number of violations in NC occurred in consecutive systems with purchased water. The percentage of violations in consecutive systems in NC was markedly higher than the national average for small, medium, and large systems. EPA has specified that each state is responsible for defining relationships between water suppliers and consecutive systems, including responsible parties for enforcement actions following an Action Level exceedance. According to EPA, in general, consecutive systems are responsible for public education and lead service line replacement requirements, while the wholesaler is responsible for is responsible for treatment and source water monitoring.

7 70% Percentage of Total Viola'ons 60% 50% 40% 30% 20% 10% 0% Public Educa7on - North Carolina OCCT Study - North Carolina Na7onal Percentage of Viola7ons in Consecu7ve Systems Figure 4. Comparison of Violations in Consecutive Systems (Purchased Water) in NC and the US Despite the disproportionally high number of violations in NC, examination of trends over the period of 2010 to 2012 indicates that compliance in NC has improved (Figure 5). While the total number of national violations has decreased by about 60%, the percentage of total violations occurring in NC has decreased from 30% to 20%, indicating that compliance in NC has improved faster than the national trend. This may be a result of two possible causes: (1) improved corrosion control has resulted in lower observed Pb/Cu levels and fewer Action Level exceedances, or (2) improved understanding of Treatment Technique requirements has decreased the number of violations resulting from an equal number of Action Level exceedances.

8 Number of Viola'ons % 30% 25% 20% 15% 10% 5% 0% Percentage of Viola'ons in NC United States North Carolina Percentage of Total in NC Figure 5. LCR Compliance Trend in North Carolina and the US from 2010 to DISCUSSION While the intent of the tier structure is to target sites with the highest risk of lead exposure, based on examples in the literature, the current tier structure would need to be revised in order capture the highest risk. Furthermore, the sampling protocol would need to be changed in order to monitor lead release from service lines. If changes to the tier structure and sampling protocol lead to an increase in observed lead levels, systems currently practicing corrosion control as required by the LCR may be triggered to reevaluate corrosion control. Other systems exceeding the Action Level may be challenged to implement optimized corrosion control for the first time. Research has shown that simplistic water quality parameters used in the past (such as Ryznar or Langelier index) do not adequately reflect lead and copper behavior, and a variety of water quality parameters must be considered. Given NC s history of high LCR violations associated with OCCT implementation, LT-LCR revisions could cause renewed emphasis on OCCT planning and installation. Emerging strategies for corrosion control include improved distribution system management as well as water quality optimization at the treatment plant. Distribution system modeling and monitoring may be useful to improve understanding of water quality in the system, and through strategic upgrade and renewal of distribution infrastructure, detrimental water quality fluctuations can be reduced. Alkalinity adjustment serves to improve buffer capacity and stabilize the ph throughout the distribution system, as unstable ph can contribute to corrosion problems. Lead and copper corrosion can also be aggravated by microbially-induced corrosion, which can be minimized by management of microbial regrowth and nitrification in the distribution system. To improve corrosion control without increasing the inhibitor dose, orthophosphate treatment can be optimized by ph adjustment to a target range in the mid sevens, which can be evaluated through bench scale treatment testing. Furthermore, source water with a higher level of TOC has also been shown to require a greater orthophosphate dose for effective corrosion control (Arnold et al, 2012; Li et al, 2004), and the orthophosphate dose can be optimized by improving TOC removal at the treatment plant. Moreover, addition of orthophosphate is not a panacea for lead and copper corrosion, and water treatment process alterations (such as switching disinfectant or coagulant) can have unintended consequences for lead and copper release.

9 A comprehensive approach including a thorough understanding of the drivers for the LCR revisions will be required to ensure compliance and proactively protect public health. Due to the important interplay of water treatment and distribution system quality management, simultaneous compliance with the LT-LCR, Revised Total Coliform Rule, and DBP regulations requires a holistic approach for distribution system management. CONCLUSIONS Based on results of recent research, the current LCR may underestimate actual lead and copper levels in drinking water, and upcoming regulatory revisions for the LT-LCR are expected to restructure the targeted monitoring of high-risk sites. North Carolina has a disproportionally high number LCR violations, especially among Very Small and Large systems, and accounted for about 27% of health-based LCR violations from , although the percentage of total violations occurring in NC decreased over the same period. North Carolina had a higher than average number of violations associated with OCCT Study Recommendations and a higher than average percentage of violations occurring in consecutive systems. LT-LCR revisions have the potential to increase observed lead levels for some systems and retrigger Treatment Technique requirements such as corrosion control treatment. Considering NC s history of violations associated with OCCT study, corrosion control planning may garner renewed focus in the state.

10 REFERENCES Arnold, R.B., Raetz, M., Edwards, M., Effects of Alkalinity, NOM, and Orthophosphate on Galvanic Corrosion. Proc AWWA Annual Conference, Washington, D.C. Arnold, R.B., Edwards, M., 2012a. Potential Reversal and the Effects of Flow Pattern on Galvanic Corrosion of Lead. Environmental Science & Technology, 46:20. Arnold, R.B., Griffin, A., Edwards, M., 2012b. Controlling Copper Corrosion in New Construction by Organic Matter Removal. Journal AWWA, 104:5, E310- E317. Brown, R., McTigue, N., Cornwell, D., Strategies for assessing optimized corrosion control treatment of lead and copper. Journal AWWA, 105:5, Cartier, C., Laroche, L., Deshommes, E., Nour, S., Richard, G., Edwards, M., Prevost, M., Investigating dissolved lead at the tap using various sampling protocols. Journal AWWA, 103:3, Cartier, C., Arnold, R. B., Triantafyllidou, S., Prevost, M., Edwards, M., Effect of Flow Rate and Lead/Copper Pipe Sequence on Lead Release from Service Lines. Water Research, 46:13, Clark, B., Cartier, C., Clair, J.S., Triantafyllidou, S., Prevost, M., Edwards, M., Lead Contamination of Drinking Water After Partial Lead Service Line Replacement With Copper Pipe: Bench Scale Testing of Galvanic Impacts. Proceedings 2011 AWWA Annual Conference, Washington, D.C. Del Toral, M.A., Porter, A., Schock, M.R., Detection and Evaluation of Elevated Lead Release from Service Lines: A Field Study. Environmental Science and Technology, 47:16, DeSantis, M.K., Welch, M., Schock, M., Mineralogical Evidence of Galvanic Corrosion in Domestic Drinking Water Pipes. Proceedings 2009 AWWA Water Quality Technology Conference, Seattle, Washington. Edwards, M., Triantafyllidou, S., Best, D., Elevated Blood Lead in Young Children Due to Lead-Contaminated Drinking Water: Washington, DC, Environmental Science and Technology, 43:5, Edwards, M., Schock, M., Meyer, T., Alkalinity, ph, and Copper Corrosion By-product Release. Journal AWWA, 88(3), Edwards, M., Sprague, Organic Matter and Copper Corrosion By-Product Release: A Mechanistic Study. Corrosion Science, V. 43, No. 1, Estes-Smargiassi, Cantor, Lead Service Line Contributions to Lead Levels at the Tap. Proc AWWA WQTC, Denver, CO. Giani, R., M. Edwards, C. Chung, J. Wujek Use of Lead Profiles to Determine Source of Action Level Exceedances from Residential Homes in Washington, D.C. Proceedings AWWA Water Quality Technical Conference. Gregory, R Galvanic Corrosion of Lead Solder in Copper Pipework. Water and Environment Journal, 4: Korshin, Gregory V., Ferguson, J. F., Lancaster, A. N., Wu, H, Corrosion and Metal Release for Lead-Containing Materials: Influence of NOM. AWWA Research Foundation Report. Lambrinidou, Y., Triantafyllidou, S.., Edwards, M., Failing Our Children: Lead in U.S. School Drinking Water. New Solutions, 20(1), Li, S., Ni, L., Sun, C., Wang, L., Influence of organic matter on orthophosphate corrosion inhibition for copper pipe in soft water. Corrosion Science, 46. Morton, S.C.; Zhang, Y.; & Edwards, M., Implications of Nutrient Release From Iron Metal for Microbial Regrowth in Water Distribution Systems. Water Research, 39:13:2883. Rubin, S. J., Evaluating violations of drinking water regulations. Journal AWWA, E Sandvig, A., Kwan, P., Kirmeyer, G., Maynard, B., Mast, D., Trussel, R. R., Trussel, S., Cantor, A., Prescott, A., Contribution of Service Line and Plumbing Fixtures to Lead and Copper Rule Compliance Issues. Report Water Research Foundation, Denver. Schock, M.R., Causes of Temporal Variability of Lead in Domestic Plumbing Systems. Environmental Monitoring and Assessment, 15: Schock, M.R., Lytle, D.A., Clement, J.A., Effect of ph, DIC, Orthophosphate, and Sulfate on Drinking Water Cuprosolvency. US EPA Report, Office of Research and Development. Swertfeger, J., Hartman, D.J., Shrive, C., Metz, D.H. and DeMarco, J. (2006) Water quality effects of partial lead line replacement. AWWA Annual Conference, San Antonio, TX. Triantafyllidou, S., Edwards, M., Galvanic corrosion after simulated small-scale partial lead service line replacements. Journal AWWA, 103(9). Triantafyllidou, S., Raetz, M., Parks, J., Edwards, M., Understanding how brass ball valves passing certification testing can cause elevated lead in water when installed. Water Research, 46(10), Turek, N., Kasten, L., Lytle, D., Goltz, M., Impact of Plumbing Age on Copper Levels in Drinking Water. Journal of Water Supply: Research and Technology, 60:1. Volk, Dundore, Schiermann, Lechevallier, Practical Evaluation of Iron Corrosion Control in a Drinking Water Distribution System. Water Research. 34, Wang, Y., Mehta, V., Welter, G. J., Giammar, D. E., Effect of connection methods on lead release from galvanic corrosion. Journal AWWA, E337-E351 Weston, R.F., and Economic and Engineering Services, Inc Lead Service Line Replacement: A Benefit-to-Cost Analysis. AWWA Report.