Impacts of blending advanced treated water and traditional groundwater supply on lead and copper concentrations and microbial diversity in premise plumbing

In response to stresses on water demands, some regions augment conventional drinking water sources with alternative water supplies such as desalinated seawater and reclaimed wastewater. The advanced treatment of wastewater by reverse osmosis, microfiltration, and advanced oxidation processes can produce high quality water for potable uses. However, if not appropriately stabilized, the resulting water can be corrosive to metal-based distribution pipes and plumbing materials. We conducted long-term premise plumbing pipe loop experiments with copper pipes containing lead solder to test the impact of the introduction of advanced treated water on the water quality. Advanced treated water (ATW) originally at low pH (<7) and low alkalinity (<10 mg/L as CaCO3) was stabilized with a calcite contactor before being blended with baseline ground water (BLW). The effects of percentages of ATW on the release of lead and copper and on the changes in the microbial diversity were monitored. Experiments monitored metal release from pipes receiving (1) only BLW, (2) a series of blends of BLW and ATW that gradually increased from 25 % to 100 % ATW, and (3) an abrupt switch from BLW to 100 % ATW. Introducing 100 % ATW dramatically increased lead release and simultaneously decreased copper release. Pipe scale analysis showed that the introduction of ATW had destabilized sulfate-containing pipe scales, which exposed the copper pipe surface to galvanic corrosion. The dissolution of scale material was associated with a significant decrease in sulfate concentration in the 100 % ATW which was in agreement with theoretical solubility calculations. The impact of blending ATW on microbial diversity was studied via 16S rRNA gene amplicon sequencing. The composition of the microbial communities changed significantly after water was in contact with the copper pipes in experiments with both BLW and ATW. The type of water recirculating in the pipes affected the structure of the microbial community. The results from this study can be useful for water utilities that are considering potable reuse as they develop strategies to mitigate any adverse impacts of water quality changes.

Release of lead, copper, zinc from the initial corrosion of brass water meter in drinking water: Influences of solution composition and electrochemical characterization

Corrosion of brass plumbing materials may lead to metal release and deteriorate the drinking water quality. In this study, the initial corrosion of brass coupon cut from commercially available water meter was investigated. High rates of Pb, Cu and Zn release from the brass coupon were found during the early stage of corrosion (0-5 d) due to general corrosion and galvanic corrosion. The corrosion current density (Icorr) increased and resistance (RF) decreased during this period indicating that severe corrosion had occurred. In a later stage (5-30 d), a decreased Icorr and an increased RF were observed due to the development of a denser layer of Pb and Cu corrosion products which regulated the release of soluble Pb and Cu. The release of Zn continued and no significant Zn precipitation was found. Overall, particulate Pb, particulate Cu and soluble Zn dominated in the metal release during the initial corrosion of brass. The release of Pb, Cu and Zn was enhanced by a lower pH. Free chlorine was found to slightly reduce the release of Pb but promote the release of Cu and Zn. The presence of Pb on the brass surfaces was found to alleviate the dezincification process. A conceptual model based on metal release profile and electrochemical characterization was proposed to describe the initial corrosion of brass in typical drinking water.

Early phase effects of silicate and orthophosphate on lead (Pb) corrosion scale development and Pb release

Orthophosphate is widely used to control lead (Pb) release in drinking water distribution systems, but phosphorus addition is not sustainable. Alternative corrosion control treatments are needed, and sodium silicate is one possibility. Here, pre-corroded Pb coupons-with and without free chlorine-were used to examine early-phase corrosion scale development after silicate addition, with orthophosphate as a reference corrosion inhibitor. Scale development was evaluated in terms of total Pb release, phase transformation, electrochemical impedance, morphological changes, Pb dissolution kinetics, and short-term Pb-Cu galvanic corrosion. Elevated Pb release occurred for approximately one month after silicate addition, and total Pb release peaked at 1968.1 μg/L and 1176.9 μg/L from systems with and without free chlorine, respectively. In contrast, orthophosphate-treated coupons exhibited fewer, less pronounced spikes in Pb release. By day 354, the median total Pb release from orthophosphate-treated coupons with and without free chlorine had decreased to 3.7 and 5.0 μg/L, respectively, while the median total Pb release from corresponding silicate-treated coupons was much higher, at 44.9 μg/L and 34.3 μg/L. Calcium lead apatite (Ca_0.56Pb_3.77(PO₄)₃OH_0.67) was identified in orthophosphate-treated scales, with hydroxylpyromorphite (Pb₅(PO₄)₃OH) present in the absence of free chlorine. Plattnerite occurred on coupons in all chlorinated systems. Pb silicate compounds were not detected, but Ca₂SiO₄ and Na₂Ca₂(SiO₃)₃ were identified by X-ray powder diffraction. The charge transfer: film resistance ratio characterizing the orthophosphate-treated coupons decreased slowly while that of the silicate-treated coupons increased after silicate was added. These variations suggest orthophosphate provided better corrosion control than silicate did. Silicate treatment generally caused degradation of the top Pb scale layer, resulting in elevated Pb release, while orthophosphate encouraged the growth of more structured, generally thicker, corrosion scales that were effective in limiting Pb release.

Prediction of lead leaching from galvanic corrosion of lead-containing components in copper pipe drinking water supply systems

Galvanic corrosion is one of the main reasons for pipe degradation and lead contamination in drinking water systems. The electrical connection of dissimilar metals in corrosive tap water accelerates the dissolution rate of lead from leaded materials. This paper reports an electrochemistry based model to predict lead leaching from a copper pipe fitted with leaded connections. The corrosion of lead at the metal-electrolyte interface depends on the charge transfer and the electric field across the interface. The electric potential field and the mass transport process are dynamically coupled for corrosion propagation in stagnant water; they are respectively governed by the conservation of charge and reactant mass. Using polarization parameters for the electrodes as a function of concentration of oxidizing agents, a dynamic electrochemical model is developed to predict lead leaching from galvanic corrosion. The predicted lead and copper leaching curves are in good agreement with the experimental data for a lead-soldered coupled copper pipe, a brass valve coupled copper pipe, and a pure copper pipe. The findings offer a quantitative understanding on galvanic corrosion in drinking water supply systems and a practical modeling framework for prediction of lead leaching in tap water as a function of stagnation time.

Unraveling the Causes of Excess Lead in Drinking Water Supply Systems of Densely Populated High-Rise Buildings in Hong Kong

Excess concentrations of lead (Pb) were found in tap water from drinking water supply systems of high-rise buildings in 11 public rental housing (PRH) estates in Hong Kong, posing threats to public health. The copper supply lines are fitted with lead-soldered connections and brass fixtures and faucets. The causes of excess lead are studied through field sampling on occupied households, experiments on prototype supply chains, and 3D numerical modeling. The tap water lead concentration of 129 households in the PRH estates was sampled using a specially designed protocol, revealing the highly variable lead concentration variations induced by sources along the supply chain. Lead concentration variation at consumer tap and its relation with various lead sources are studied in a full-scale test rig. A 3D computational fluid dynamics (CFD) model is successfully developed to interpret the time variation of lead concentrations at the consumer tap. Model predictions of the complex variation of dissolved lead are in good agreement with data and confirm lead solder in copper pipe connections as a major cause of the "lead water" episode in Hong Kong. The CFD calculations demonstrate the importance of turbulent diffusion and shear flow dispersion in the modeling of lead; the use of a "plug flow" approximation can result in significant overestimation of lead concentration. The findings provide a basis for lead risk assessment of different water sampling strategies in densely populated high-rise buildings in Megacities.

Effect of Aluminum on Lead Release to Drinking Water from Scales of Corrosion Products

The occurrence of aluminum in scales on lead pipes is common. This study aimed to identify factors that influence Al accumulation on oxidized lead surfaces and to determine whether the presence of Al impacts Pb release from corrosion products to water. Al accumulation and Pb release were monitored both with and without the addition of phosphate as a corrosion inhibitor. Pb coupons with corrosion scales were exposed to chlorinated water for up to 198 days to investigate Al accumulation and Pb release. Al accumulation was facilitated by Pb corrosion products, but its accumulation was inhibited by phosphate addition. During the study period, the formation of Al deposits did not affect Pb release when phosphate was absent. In an Al-free system, the addition of 1.0 mg/L phosphate (as P) lowered the dissolved Pb concentration below 1.0 μg/L. In a system containing 200 μg/L Al, the emergence of phosphate's effect on Pb control was delayed, and the dissolved Pb concentration decreased but stabilized at a higher value (10-12 μg/L) than in the Al-free system. Phosphohedyphane (Ca₂Pb₃(PO₄)₃Cl) was formed in all phosphate-containing systems, and PbO₂ was formed independent of phosphate addition. The effect of Al on Pb release was probably related to its influence on the composition and morphology of Pb-containing minerals on coupon surfaces. The laboratory study has unavoidable limitations in its ability to simulate all conditions in real lead service lines, but this study still highlights the importance of considering the influence of Al when designing Pb corrosion control strategies.

Microelectrode Investigation on the Corrosion Initiation at Lead-Brass Galvanic Interfaces in Chlorinated Drinking Water

In this study, the effects of pH, dissolved inorganic carbon (DIC), and flow on changes in surface chemistry (pH, dissolved oxygen, and free chlorine) of lead-brass joints at initial stages of corrosion were investigated using microelectrodes. Surface measurements showed that the water chemistry at the metal surfaces was highly heterogeneous. At pH 7 and during water stagnation, local pH difference between anodic (leaded-solder) and cathodic (brass) regions differed by as much as 7.5 pH units. High DIC water under the water flowing condition showed minimal pH changes on the surface, whereas in low DIC water, a pH range of 7.6-5.4 (ΔpH 2.2) was observed over the surface. Free chlorine consumption near the lead-brass surface was greater under stagnation, regardless of bulk pH. It was also found that flow can move the low pH plume that originated at the anode. Overall, this study provides direct evidence for highly localized galvanic corrosion in a chlorinated drinking water environment.

Public Health Consequences of Lead in Drinking Water

PURPOSE OF REVIEW

Lead can enter drinking water from lead service lines and lead-containing plumbing, particularly in the presence of corrosive water. We review the current evidence on the role of drinking water as a source of lead exposure and its potential impacts on health, with an emphasis on children. Drinking water guidelines and mitigation strategies are also presented.

RECENT FINDINGS

The impact of lead on neurodevelopmental effects in children even at low levels of exposure is well established. Population and toxicokinetic modeling studies have found a clear relationship between water lead levels and blood lead levels in children at low levels of lead in drinking water. Various mitigation strategies can lower lead levels in water. The importance of drinking water as a contributor to total lead exposure depends on water lead levels and the amount consumed, as well as the relative contribution of other sources. Efforts should be made to reduce lead exposure for all sources, including drinking water, considering that no threshold level of exposure exists for the neurodevelopmental effects of lead in children.

Manganese Increases Lead Release to Drinking Water

Lead and manganese are regulated in drinking water due to their neurotoxicity. These elements have been reported to co-occur in drinking water systems, in accordance with the metal-scavenging properties of MnO₂. To the extent that manganese is a driver of lead release, controlling it during water treatment may reduce lead levels. We investigated transport of lead and manganese at the tap in a full-scale distribution system: consistent with a cotransport phenomenon, the two metals were detected in the same colloidal size fraction by size-exclusion chromatography with multielement detection. We also studied the effect of manganese on lead release using a model distribution system: increasing manganese from 4 to 215 μg L^-1 nearly doubled lead release. This effect was attributed primarily to deposition corrosion of lead by oxidized phases of manganese, and we used 16S rRNA sequencing to identify bacteria that may be relevant to this process. We explored the deposition corrosion mechanism by coupling pure lead with either MnO₂-coated lead or pure lead exposed to MnO₂ in suspension; we observed galvanic currents in both cases. We attributed these to reduction of Mn(IV) under anaerobic conditions, and we attributed the additional current under aerobic conditions to oxygen reduction catalyzed by MnO₂.

Lead and copper release from full and partially replaced harvested lead service lines: Impact of stagnation time prior to sampling and water quality

Partial lead service line replacement (PLSLR) results in the addition of a new galvanic connection and can increase lead concentrations at the tap. Focus has been given to minimizing lead release after PLSLR, but little information is available on the impact of lead remedial actions on copper concentrations, especially before passivation occurs. The impact of water quality (decreased chloride-to-sulfate mass ratio from 0.9 to 0.3; addition of orthoP; pH increase to 8.3) on lead and copper concentrations was investigated after stagnation (30 min-336 h) in a pipe rig comparing full lead service line (LSL), and two configurations of partial LSLs (Cu-Pb and Pb-Cu). Results show different trends for lead and copper: maximum lead concentrations were reached in 16 h while copper concentrations continued to increase over 336 h. Lead release rates were also the highest in the first 16 h of stagnation and were strongly impacted by water quality and the configuration of PLSLR (Cu-Pb vs Pb-Cu). Increasing the sampling flow rate from 5 to 15 LPM drastically increased the particulate lead release (78-fold) in Pb-Cu configurations; this effect was however not observed in 100% Pb or Cu-Pb configurations. High velocity flushing prior to 16 h stagnation decreased total Pb release by a factor of 12-fold for Cu-Pb, 1.6-fold for Pb-Cu and 2.0-fold for 100% Pb. Results support the definition of sampling protocols targeted for the detection of lead and copper sources and the proscription of flushing prior to sampling.

Study of the long-term impacts of treatments on lead release from full and partially replaced harvested lead service lines

Long-term (155 weeks) Pb concentrations, following partial lead service lines replacements (PLSLR), were measured in a flow through pilot made of harvested lead service lines (LSL) from the distribution system of the City of Montreal. The present study also investigates how release of Pb from full and partial LSLs is influenced by: pipe diameter, decrease in chloride-to-sulfate mass ratio (CSMR) from 0.9 to 0.3, addition of orthophosphate (1 mg P/L), and increase in pH to 8.3. Pb concentrations were measured after 16 h of stagnation and under flow conditions. In this study, Pb concentrations did not decrease, in the long term, after partial LSL replacement. Moreover, the most effective corrosion control treatment in full LSLs was the addition of orthoP. In contrast, the decrease of the CSMR best reduced lead release from partial LSLs. The impact of pipe configuration therefore influenced the effectiveness of corrosion control treatments. It is noteworthy that the increase in Pb concentrations following PLSLR were attributed to particulate Pb release from the galvanic section of the pipe. The occurrence of galvanic corrosion, caused by the connection between Pb and copper pipes, adds a new source of Pb in the partial LSL. At least, this new source of lead has to be offset by the removal of a long enough section of LSL during PLSLR. Full LSL replacements may be warranted to minimize the exposure of consumers to elevated Pb levels caused by galvanic corrosion in LSLs.

A new scenario of lead contamination in potable water distribution systems: Galvanic corrosion between lead and stainless steel

Lead pipe has been banned for distributing drinking water in the 1980s and partial replacement of lead pipes with stainless steel pipes has been practiced in many Asian countries. Due to the different potentials of lead and stainless steel, galvanic corrosion may take place. The extent of lead release and effects of water chemistry on this process, however, are largely unknown. The objectives of this study are to characterize lead release resulting from galvanic connection between lead and stainless steel, the effects of pH, chloride and sulfate concentrations on this process, and the effectiveness of using orthophosphate to mitigate this problem. The experiments were conducted by connecting aged lead pipes to stainless steel fittings and placing the couple in different water conditions. The results of this study demonstrated that lead release significantly accelerated when lead and stainless steel were galvanically connected and the rate of lead release accelerated with decreasing pH and increasing chloride-to-sulfate mass ratio (CSMR). Orthophosphate could effectively reduce lead release but CSMR needs to be considered since water with a higher CSMR still caused more lead release when galvanic corrosion took place.

Mineralogical Evidence of Galvanic Corrosion in Drinking Water Lead Pipe Joints

Galvanic corrosion as a mechanism of toxic lead release into drinking water has been under scientific debate in the U.S. for over 30 years. Visual and mineralogical analysis of 28 lead pipe joints, excavated after 60+ years from eight U.S. water utilities, provided the first direct view of three distinct galvanic corrosion patterns in practice: (1) no evidence of galvanic corrosion; (2) galvanic corrosion with lead cathode; (3) galvanic corrosion with lead anode. Pattern 3 is consistent with empirical galvanic series (lead → brass → copper in order of increasing nobility) and poses the greatest risk of Pb exposure. Pattern 2 is consistent with galvanic battery reversion. The identification of copper-sulfate minerals (Pattern 2), and lead-sulfate and lead-chloride minerals (Pattern 3) in galvanic zones illustrated the migration of chloride and sulfate toward the anode. Geochemical modeling confirmed the required pH drop from the bulk water level to at least pH 3.0-4.0 (Pattern 2) and pH < 5.5 (Pattern 3) in order to form these minerals. Despite joints being over 60 years old, galvanic zones in Pattern 3 were active and possibly posed an important source of lead to drinking water. Importantly, Pattern 3 was not observed in samples from systems representing water qualities favoring PbO2 formation.

Short- and Long-Term Lead Release after Partial Lead Service Line Replacements in a Metropolitan Water Distribution System

Thirty-three households were monitored in a full-scale water distribution system, to investigate the impact of recent (<2 yr) or old partial lead service line replacements (PLSLRs). Total and particulate lead concentrations were measured using repeat sampling over a period of 1-20 months. Point-of-entry filters were installed to capture sporadic release of particulate lead from the lead service lines (LSLs). Mean concentrations increased immediately after PLSLRs and erratic particulate lead spikes were observed over the 18 month post-PLSLR monitoring period. The mass of lead released during this time frame indicates the occurrence of galvanic corrosion and scale destabilization. System-wide, lead concentrations were however lower in households with PLSLRs as compared to those with no replacement, especially for old PLSLRs. Nonetheless, 61% of PLSLR samples still exceeded 10 μg/L, reflecting the importance of implementing full LSL replacement and efficient risk communication. Acute concentrations measured immediately after PLSLRs demonstrate the need for appropriate flushing procedures to prevent lead poisoning.

Galvanic Corrosion of Lead by Iron (Oxyhydr)Oxides: Potential Impacts on Drinking Water Quality

Lead exposure via drinking water remains a significant public health risk; this study explored the potential effects of upstream iron corrosion on lead mobility in water distribution systems. Specifically, galvanic corrosion of lead by iron (oxyhydr)oxides was investigated. Coupling an iron mineral cathode with metallic lead in a galvanic cell increased lead release by 531 μg L^-1 on average-a 9-fold increase over uniform corrosion in the absence of iron. Cathodes were composed of spark plasma sintered Fe₃O₄ or α-Fe₂O₃ or field-extracted Fe₃O₄ and α-FeOOH. Orthophosphate immobilized oxidized lead as insoluble hydroxypyromorphite, while humic acid enhanced lead mobility. Addition of a humic isolate increased lead release due to uniform corrosion by 81 μg L^-1 and-upon coupling lead to a mineral cathode-release due to galvanic corrosion by 990 μg L^-1. Elevated lead in the presence of humic acid appeared to be driven by complexation, with ²⁰⁸Pb and UV₂₅₄ size-exclusion chromatograms exhibiting strong correlation under these conditions (R²_average = 0.87). A significant iron corrosion effect was consistent with field data: lead levels after lead service line replacement were greater by factors of 2.3-4.7 at sites supplied by unlined cast iron distribution mains compared with the alternative, lined ductile iron.

Comparison of three corrosion inhibitors in simulated partial lead service line replacements

Partial lead service line replacements (PLSLR) were simulated using five recirculating pipe loops treated with either zinc orthophosphate (1mg/L as P), orthophosphate (1mg/L as P) or sodium silicate (10mg/L). Two pipe loops served as ⿿inhibitor-free⿿ (Pb-Cu) and ⿿galvanic free⿿ (Pb-PVC) controls. Changes in water quality (CSMR [0.2 or 1], conductivity [⿿330mS/cm or ⿿560mS/cm], chlorine [1.4mg/L]) were not observed to provide a significant impact on lead or copper release, although galvanic corrosion was shown to be a driving factor. Generally, both orthophosphate and zinc orthophosphate provided better corrosion control for both total and dissolved lead (30min, 6h, 65h) and copper (30min, 6h), when compared to either the inhibitor-free control or the sodium silicate treated system. This work highlights the importance of understanding the complex interplay of corrosion inhibitors on particulate and dissolved species when considering both lead and copper.

Modeling Soluble and Particulate Lead Release into Drinking Water from Full and Partially Replaced Lead Service Lines

Partial replacement of lead service lines (LSLs) often results in the excessive long-term release of lead particulates due to the disturbance of pipe scale and galvanic corrosion. In this study, a modeling approach to simulate the release and transport of particulate and dissolved lead from full and partially replaced LSLs is developed. A mass-transfer model is coupled with a stochastic residential water demand generator to investigate the effect of normal household usage flow patterns on lead exposure. The model is calibrated by comparing simulation results against experimental measurements from pilot-scale setups where lead release under different flow rates and water chemistry scenarios was reported. Applying the model within a Monte Carlo simulation framework, partial replacement of the LSL was predicted to result in releasing spikes with significantly high concentrations of particulate lead (1011.9 ± 290.3 μg/L) that were five times higher than those released from the simulated full LSL. Sensitivity analysis revealed that the intensity of flow demands significantly affects particulate lead release, while dissolved lead levels are more dependent on the lengths of the stagnation periods. Preflushing of the LSL prior to regulatory sampling was found to underestimate the maximum monthly exposure to dissolved lead by 19%, while sampling at low flow rates (<5.2 LPM) was found to consistently suppress the high spikes induced by particulate lead mobilization.

In-situ 2D maps of pH shifts across brass-lead galvanic joints using microelectrodes

Galvanic corrosion in drinking water distribution systems, such as conditions following partial lead (Pb) service line replacement, has received recent attention. In order to better understand conditions at galvanic connections that lead to enhanced metal release and provide remedial strategies, the water-metal and anodic-cathodic interfaces at these locations must be better understood. In this paper, a pH microelectrode system was used to create in-situ 2D spatial images of the pH of water across two brass coupons connected by a leaded solder joint at 100 μm above the metal's surface under flowing and stagnation conditions. Water stagnation resulted in significant pH changes across the surfaces compared to flow condition. Under stagnation, the pH above the anode (leaded solder) was 1.5 pH units below the bulk water and as much as 2.5 units below the cathode (brass). These conditions can enhance lead release at the anode, which reflects different anodic-cathodic relationships of coupled metals primarily controlled by water flow. Most importantly, this work has demonstrated the ability to make real pH measurement at the surface of corroding metals using a novel microelectrode approach.

Understanding the Role of Particulate Iron in Lead Release to Drinking Water

Lead service lines (LSLs) are a major source of drinking water lead, and high iron levels are frequently observed along with elevated lead release. A model distribution system, dosed with orthophosphate, was used to evaluate the effect of corroded iron distribution mains on lead release from recovered LSLs. Lead release was higher by 96 μg L(-1), on average, from LSLs supplied by corroded iron compared to the inert reference material (PVC). This effect may be explained by deposition of semiconducting iron oxide particles within LSLs. When galvanic cells with lead and magnetite (Fe3O4) electrodes were short-circuited, lead release increased 8-fold and a current averaging 26 μA was observed. In effluent from LSLs with an upstream iron main, colloidal lead and iron occurred in the same size fraction-possibly due to release of colloidal particles from LSL corrosion scale enriched with iron. Under these circumstances, high molecular weight (>669 kDa) (208)Pb and (56)Fe elution profiles, observed via size-exclusion chromatography, were highly correlated (average R(2) = 0.97). Increasing orthophosphate from 0.5 to 1.0 mg L(-1) (as PO4(3-)) accompanied an average reduction in lead release of 6 μg L(-1) month(-1) but did not significantly reduce the effect of an upstream iron main.

Long-Term Behavior of Simulated Partial Lead Service Line Replacements

In this 48-month pilot study, long-term impacts of copper:lead galvanic connections on lead release to water were assessed without confounding differences in pipe exposure prehistory or disturbances arising from cutting lead pipe. Lead release was tracked from three lead service line configurations, including (1) 100% lead, (2) traditional partial replacement with 50% copper upstream of 50% lead, and (3) 50% lead upstream of 50% copper as a function of flow rate, connection types, and sampling methodologies. Elevated lead from galvanic corrosion worsened with time, with 140% more lead release from configurations representing traditional partial replacement configurations at 14 months compared to earlier data in the first 8 months. Even when sampled consistently at moderate flow rate (8 LPM) and collecting all water passing through service lines, conditions representing traditional partial service line configurations were significantly worse (≈40%) when compared to 100% lead pipe. If sampled at a high flow rate (32 LPM) and collecting 2 L samples from service lines, 100% of samples collected from traditional partial replacement configurations exceeded thresholds posing an acute health risk versus a 0% risk for samples from 100% lead pipe. Temporary removal of lead accumulations near Pb:Cu junctions and lead deposits from other downstream plastic pipes reduced risk of partial replacements relative to that observed for 100% lead. When typical brass compression couplings were used to connect prepassivated lead pipes, lead release spiked up to 10 times higher, confirming prior concerns raised at bench and field scale regarding adverse impacts of crevices and service line disturbances on lead release. To quantify semirandom particulate lead release from service lines in future research, whole-house filters have many advantages compared to other approaches.

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

Bench-scale experiments investigated the role of iron and aluminum residuals in lead release in a low alkalinity and high (> 0.5) chloride-to-sulfate mass ratio (CSMR) in water. Lead leaching was examined for two lead-bearing plumbing materials, including harvested lead pipe and new lead: tin solder, after exposure to water with simulated aluminum sulfate, polyaluminum chloride and ferric sulfate coagulation treatments with 1-25-μM levels of iron or aluminum residuals in the water. The release of lead from systems with harvested lead pipe was highly correlated with levels of residual aluminum or iron present in samples (R(2) = 0.66-0.88), consistent with sorption of lead onto the aluminum and iron hydroxides during stagnation. The results indicate that aluminum and iron coagulant residuals, at levels complying with recommended guidelines, can sometimes play a significant role in lead mobilization from premise plumbing.

Profile sampling to characterize particulate lead risks in potable water

Traditional lead (Pb) profiling, or collecting sequential liters of water that flow from a consumer tap after a stagnation event, has recently received widespread use in understanding sources of Pb in drinking water and risks to consumer health, but has limitations in quantifying particulate Pb risks. A new profiling protocol was developed in which a series of traditional profiles are collected from the same tap at escalating flow rates. The results revealed marked differences in risks of Pb exposure from one consumer home to another as a function of flow rate, with homes grouped into four risk categories with differing flushing requirements and public education to protect consumers. On average, Pb concentrations detected in water at high flow without stagnation were at least three to four times higher than in first draw samples collected at low flow with stagnation, demonstrating a new "worst case" lead release scenario, contrary to the original regulatory assumption that stagnant, first draw samples contain the highest lead concentrations. Testing also revealed that in some cases water samples with visible particulates had much higher Pb than samples without visible particulates, and tests of different sample handling protocols confirmed that some EPA-allowed methods would not quantify as much as 99.9% of the Pb actually present (avg. 27% of Pb not quantified).

Effect of water chemistry on the dissolution rate of the lead corrosion product hydrocerussite

Hydrocerussite (Pb3(CO3)2(OH)2) is widely observed as a corrosion product in drinking water distribution systems. Its equilibrium solubility and dissolution rate can control lead concentrations in drinking water. The dissolution rate of hydrocerussite was investigated as a function of pH, dissolved inorganic carbon (DIC), and orthophosphate concentrations at conditions relevant to drinking water distribution using continuously stirred tank reactors (CSTRs). In the absence of DIC and orthophosphate, the dissolution rate decreased with increasing pH. Addition of DIC inhibited the dissolution of hydrocerussite. The addition of orthophosphate significantly decreased the dissolution rate of hydrocerussite. At conditions with orthophosphate and without DIC, a lead(II) phosphate solid hydroxylpyromorphite (Pb5(PO4)3OH) was observed after reaction, and orthophosphate's inhibitory effect can be attributed to the formation of this low-solubility lead(II) phosphate solid. In the presence of both orthophosphate and DIC, no lead(II) phosphate solid was observed, but the rate was still lowered by the presence of orthophosphate, which might be due to the adsorption of orthophosphate to block reactive sites on the hydrocerussite surface. For systems in which hydroxylpyromorphite was present, the steady-state effluent lead concentrations from the CSTRs were close to the predicted equilibrium solubility of hydroxylpyromorphite. In the absence of orthophosphate rapid equilibration of hydrocerussite was observed.