A pilot scale examination of lead release in simulated premise plumbing systems

Lead in drinking water distribution systems is a cause for concern due to previously existing lead pipe infrastructure and the previous use of lead/tin solder within premise plumbing systems. Changes can be made to the water treatment process to curb lead corrosion but these changes may inevitably cause unintended consequences within the larger system. Levels of lead at the consumers tap can be used as an indication of corrosion within the distribution system. This research focused on changes to pH, disinfectant and the use of a corrosion inhibitor in pilot scale studies.;The pilot and full-scale experiments were conducted in Bridgewater Nova Scotia, with pilot scale studies being conducted in the town drinking water treatment facility. The pilot-scale experimental design included two primary phases, low and high pH, for each disinfectant treatment group as well as the addition or absence of a corrosion inhibitor within each phase. Full scale experimentation involved volunteer and profile sampling regimes.;The results of the pilot-scale experiments indicate that the greatest amounts of lead release occur under low pH conditions and in the presence of an ortho-poly blend corrosion inhibitor. Significantly greater amounts of lead are released from lead/tin soldered copper pipe under long stagnation times than short stagnation periods. The chlorine and high dosed chloramine systems had the greatest concentrations of lead release from their respective systems. These results verify the importance of pilot scale studies by utilities before the implementation of changes to the drinking water treatment train in the context of lead release from premise plumbing.;The pilot-scale experimentation consisted of six recirculating pipe loops with each having a corresponding copper pipe rack containing 24 50/50 lead tin solders. The test section in the Dalhousie Pipe. Loops(c) was Schedule 40 PVC pipe. Lead release was measured by chemical analysis at the influent and effluent of the pipe loop section as well as after a long and short stagnation time of the water within the copper pipe racks. There was no measurable lead concentration entering the copper pipe racks, indicating no lead contribution from the pipe loop sections. pH, disinfectant type and concentration, and the presence or absence of a phosphate based corrosion inhibitor were the test variables and were measured at all points within the system. Other water quality parameters including temperature, dissolved oxygen, turbidity, apparent colour, UV-254, and disinfection by-products were measured at all of the above mentioned locations within the system.