Plumbosolvency Effects and Control in Hard Waters

Abstract

A laboratory lead‐pipe rig has been used to support Anglian Water's successful orthophosphate dosing programme to reduce plumbosolvency. The hard waters in the region generally fall into low or high plumbosolvency categories according to the types of crystalline deposit formed. To improve the cost‐effectiveness of plumbosolvency control, the effects of temperature, phosphate doses, blending and alternation of these waters were investigated. Initial phosphate concentrations must be above 0.6 mg P/l (as phosphorus) to establish plumbosolvency control. Subsequently, phosphate doses may be reduced, provided that dosing is continuous and sufficient phosphate reaches the extremities of the distribution system. When high and low plumbosolvency waters are blended before distribution, both (or the mixture) must be phosphate dosed. However, where waters alternate in distribution, laboratory studies have shown that low plumbosolvency deposits are more stable, resulting in low lead concentrations. The high plumbsolvency of some hard waters may be due to the presence of low concentrations of humic substances.

Impact of treatment on Pb release from full and partially replaced harvested Lead Service Lines (LSLs)

“…OrthoP treatment significantly reduced (64%) lead release from a mean of 72 AE 14 to 26 AE 9 mg/L ( Fig. 3b) within 8 days after the onset of treatment (mean: 24 AE 4 mg/L) consistent with observations by others (Xie and Giammar, 2011;Colling et al, 1992). The concentrations then remained relatively stable for 100 days (Fig.…”

Experience in Wales (UK) of the optimisation of ortho-phosphate dosing for controlling lead in drinking water

“…Laboratory plumbosolvency testing was undertaken by the standard method developed by Colling et al (1987Colling et al ( , 1992 for the major works requiring ortho-phosphate dosing and for a representative selection of the minor works requiring ortho-phosphate dosing. Testing involves pumping test water through sections of new lead piping at 258C with a water-pipe contact time of 30 minutes and measuring the lead emissions over a four week period.…”

Role of iron and aluminum coagulant metal residuals and lead release from drinking water pipe materials

“…[2][3][4][5][6][7][8][9] It is also accepted that the removal of natural organic matter (NOM) via coagulation and other water treatment steps can strongly influence lead release and metal corrosion through a variety of mechanisms. [10][11][12][13][14] One prior research article also attempted to quantify possible secondary benefits of aluminum from coagulation passing through water treatment (i.e., residual aluminum) in reducing lead release, but instead demonstrated that the aluminum tended to increase mobilization of lead. [1] It was speculated that the aluminum deposits sorbed lead from the plumbing material, causing excess lead to slough or dissolve into the water.…”