| dc.description.abstract | Lead service lines (LSLs) can represent a significant health and economic issue for utilities that find elevated lead levels in tap water samples collected under the requirements of the Lead and Copper Rule (LCR). Full LSL replacement can be expensive if trenching is required. Additionally, the LCR does not require replacement of the homeowner-owned portion of the LSL. When utilities replace only their portion (partial replacement), the remaining disturbed LSL can contribute significant spikes in lead levels and continuing lead release. Application of a lining or coating may provide a more effective and less expensive alternative than partial LSL replacement, both for reducing corrosion and for increasing homeowner participation. However, it would be wise to first evaluate the impact the product itself will have on water quality through chemical leaching and chlorine consumption. Fill-and-dump experiments were performed to determine the impact of a commercially available epoxy coating and poly(ethylene terephthalate) (PET) liner on water quality in lead and copper pipes. Forty-five-inch-long pipe sections, including both LSL sections obtained from Rochester, N.Y. and sections of commercially available soft (annealed) Type L copper tubing were either coated with epoxy or lined with PET. These pipe sections were then tested using three types of extraction water: dechlorinated tap water and chlorinated extraction water (both at pH 8), and extraction water at pH 6.5. The chlorinated pH 8 extraction water and the pH 6.5 extraction water were prepared by dosing reagent water with NaCl, CaCl2, and NaHCO3, and were similar to waters outlined in NSF International 61 testing protocols. Holding times were varied to represent a range of detention times experienced by LSLs in use. Unlined lead and copper pipe sections were used as controls. In addition to lead and copper, the extraction waters were analyzed for chlorine demand, total organic carbon (TOC) concentration, and also for antimony in samples exposed to PET liner, which was found to contain ~130 mg Sb/kg PET. Partially digested epoxy was found to contain 8 mg Cu/kg. Extraction water exposed to the uncoated and unlined (control) lead and copper pipes contained 1,200 - 25,000 ìg/L lead, and 270 - 910 ìg/L copper, respectively. Extraction water exposed to epoxy-coated pipes had significantly less lead, with most samples below the detection level of 0.5 ìg/L. Only one pipe specimen yielded a lead concentration above the action limit (AL) of 15 ìg/L, and two subsequent extractions of the same pipe specimen yielded lead levels below the detection limit. All extraction waters exposed to epoxy-coated lead and copper pipes contained increased levels of copper (0.4 - 22 ìg/L), although significantly less than those from the uncoated control and far below the AL of 1300 ìg/L. This may be due to leaching of trace amounts of copper from the epoxy itself. Epoxy-coated pipes exerted significant free and combined chlorine demand, with nearly all chlorine consumed after 6 hours when exposed to an initial free chlorine or monochloramine concentration of 2 mg/L as Cl2, a demand similar to that of the uncoated control specimens. After repeated exposure, the free chlorine demand stabilized at approximately 10% of the initial free chlorine concentration in pipe specimens exposed to either 2 mg/L as Cl2 for 1 hour or 100 mg/L as Cl2 for 3 hours. Pipe specimens freshly coated with epoxy leached a statistically significant amount of TOC (an average of 0.65 mg/L) into the chlorinated pH 8 and pH 6.5 extraction waters, but there was, on average, no measureable increase in TOC in samples exposed to dechlorinated tap water. A statistically significant increase in antimony concentration was observed over time in PET-lined pipe specimens. Antimony concentrations in samples of extraction waters exposed to PET-lined specimens increased by an average of 0.09 and 0.33 ìg/L in specimens exposed for 6 - 24 hours and 4 days, respectively, but the antimony increases remained more than an order of magnitude below the maximum contaminant level (MCL) of 6 ìg/L. Free chlorine levels decreased only by half over 4 days when PET-lined pipes were exposed to an initial concentration of 2 mg/L as Cl2. When the same PET-lined pipes were again exposed to free chlorine for two or three 24-hour periods, the 24-hour chlorine demand was only about 5 percent of the initial chlorine concentration, approximately the same as in control samples of the chlorinated pH 8 extraction water. Thus, the PET liner exhibited no significant long-term chlorine demand. Lead and copper data collected from PET-lined pipe specimens were compromised by use of incompatible end fittings that failed to seal water flow during flushing, highlighting the importance of proper preparation of pipes for effective lining or coating installation. PET-lined pipe specimens leached an average of 0.15 mg/L TOC into chlorinated pH 8 extraction water. This small but statistically significant increase may have been associated with sample handling or small variations in instrument response rather than leaching, and no statistically significant increase in TOC was observed using the other extraction waters, including dechlorinated tap water.  | |
