Alkalinity, pH, and copper corrosion by-product release

Application of water safety planning to improve drinking water safety in an Arctic community - a case study in Cambridge Bay, Nunavut

Water safety planning is a risk management approach that accounts for quantitative and qualitative drinking water hazards and includes ongoing input from stakeholders. This approach has been applied in jurisdictions across the world including Canada. Rural and remote communities in Canada, impacted by water safety, stand to benefit most from holistic approaches to water safety risk management such as water safety planning. Unfortunately, these communities typically have limited resources to engage in this approach. Additionally, most remote communities rely on truck and cistern water systems, which have less understood hazards than communities in Canada with piped service. In this study, we report the results of an initial water safety planning case study in Cambridge Bay, Nunavut. We identified numerous water quality hazards including disinfection byproducts in trucks, manganese in the source water, and copper in tap water, as well as operational challenges that increase the risk of water emergencies in the community. We conclude that water safety planning has the potential to substantially improve water safety in Nunavut but current information gaps as well as complex stakeholder interactions are likely to hinder top-down attempts. A dynamic and inclusive approach is recommended that incorporates a targeted exploration of water safety hazards.

Freshwater faces a warmer and saltier future from headwaters to coasts: climate risks, saltwater intrusion, and biogeochemical chain reactions

Alongside global climate change, many freshwater ecosystems are experiencing substantial shifts in the concentrations and compositions of salt ions coming from both land and sea. We synthesize a risk framework for anticipating how climate change and increasing salt pollution coming from both land and saltwater intrusion will trigger chain reactions extending from headwaters to tidal waters. Salt ions trigger 'chain reactions,' where chemical products from one biogeochemical reaction influence subsequent reactions and ecosystem responses. Different chain reactions impact drinking water quality, ecosystems, infrastructure, and energy and food production. Risk factors for chain reactions include shifts in salinity sources due to global climate change and amplification of salinity pulses due to the interaction of precipitation variability and human activities. Depending on climate and other factors, salt retention can range from 2 to 90% across watersheds globally. Salt retained in ecosystems interacts with many global biogeochemical cycles along flowpaths and contributes to 'fast' and 'slow' chain reactions associated with temporary acidification and long-term alkalinization of freshwaters, impacts on nutrient cycling, CO2, CH4, N2O, and greenhouse gases, corrosion, fouling, and scaling of infrastructure, deoxygenation, and contaminant mobilization along the freshwater-marine continuum. Salt also impacts the carbon cycle and the quantity and quality of organic matter transported from headwaters to coasts. We identify the double impact of salt pollution from land and saltwater intrusion on a wide range of ecosystem services. Our salinization risk framework is based on analyses of: (1) increasing temporal trends in salinization of tributaries and tidal freshwaters of the Chesapeake Bay and freshening of the Chesapeake Bay mainstem over 40 years due to changes in streamflow, sea level rise, and watershed salt pollution; (2) increasing long-term trends in concentrations and loads of major ions in rivers along the Eastern U.S. and increased riverine exports of major ions to coastal waters sometimes over 100-fold greater than forest reference conditions; (3) varying salt ion concentration-discharge relationships at U.S. Geological Survey (USGS) sites across the U.S.; (4) empirical relationships between specific conductance and Na+, Cl-, SO4 2-, Ca2+, Mg2+, K+, and N at USGS sites across the U.S.; (5) changes in relationships between concentrations of dissolved organic carbon (DOC) and different salt ions at USGS sites across the U.S.; and (6) original salinization experiments demonstrating changes in organic matter composition, mobilization of nutrients and metals, acidification and alkalinization, changes in oxidation-reduction potentials, and deoxygenation in non-tidal and tidal waters. The interaction of human activities and climate change is altering sources, transport, storage, and reactivity of salt ions and chain reactions along the entire freshwater-marine continuum. Our salinization risk framework helps anticipate, prevent, and manage the growing double impact of salt ions from both land and sea on drinking water, human health, ecosystems, aquatic life, infrastructure, agriculture, and energy production.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10533-025-01219-6.

Guidance for Residents Addressing Copper Problems in Drinking Water: Opportunities and Challenges

Residents and their pets may experience aesthetic or health concerns resulting from elevated copper in their drinking water. The United States Environmental Protection Agency Lead and Copper Rule focuses on addressing systemwide corrosion issues, but gaps in the rule leave some municipal water consumers and residents with private well water vulnerable to high cuprosolvency. We developed guidance to aid residents in understanding, detecting, and addressing cuprosolvency issues in their drinking water. Three types of at-home test kits for copper and one for pH were determined to be accurate enough (R 2 > 0.9 (lab, based on average values from n = 5 replicates each) and >0.7 (field)) to detect concerns related to high cuprosolvency and inform selection of intervention options. Case study results indicate that, although water treatments such as increasing pH on-site may be effective, long-term treatment (>36 weeks or permanently) may be needed to maintain reductions in cuprosolvency. A decision tree is provided to help residents and citizen scientists navigate these concerns for both public water systems and private wells.

Considering a Utility-Centric Framework Based on "Minimum Orthophosphate" Criteria for Mitigation of Elevated Cuprosolvency in Drinking Water

Gaps in the United States Environmental Protection Agency (US EPA) Lead and Copper Rule (LCR) leave some consumers and their pets vulnerable to high cuprosolvency in drinking water. This study seeks to help proactive utilities who wish to mitigate cuprosolvency problems through the addition of orthophosphate corrosion inhibitors. The minimum doses of orthophosphate necessary to achieve acceptable cuprosolvency in relatively new copper pipe were estimated as a function of alkalinity via linear regressions for the 90th, 95th, and 100th percentile copper tube segments (R2 > 0.98, n = 4). Orthophosphate was very effective at reducing cuprosolvency in the short term but, in some cases, resulted in higher long-term copper concentrations than the corresponding condition without orthophosphate. Alternatives to predicting "long-term" results for copper tubes using simpler bench tests starting with fresh Cu(OH)2 solids showed promise but would require further vetting to overcome limitations such as maintaining water chemistry and orthophosphate residuals and to ensure comparability to results using copper tube.

The influence of calcium on copper corrosion and its by-product release in drinking water

Copper is a high-quality material commonly used in drinking water supply pipes. Calcium is a prevalent cation found in drinking water. However, the effects of calcium on copper corrosion and its by-product release remain unclear. This study discusses the influences of Ca²⁺ on copper corrosion and its by-product release in drinking water under different conditions of Cl^-, SO₄^2-, and Cl^-/SO₄^2-, using electrochemical and scanning electron microscopy techniques. The results indicate that Ca²⁺ slows down the corrosion reaction of copper to some extent in comparison with Cl^-, and the E_corr shifts positively by 0.022 V, while I_corr decreases by 0.235 μA cm^-2. However, the by-product release rate increases by 0.5 μg cm^-2. The addition of Ca²⁺ causes the anodic process to become the controlling factor for corrosion, with an increase in resistance observed in both the inner and outer layers of the corrosion product film through SEM analysis. The corrosion product film becomes denser due to the reaction between Ca²⁺ and Cl^-, forming a product that inhibits the entry of Cl^- into the passive film on the copper surface. Adding Ca²⁺ promotes copper corrosion with the help of SO₄^2- and the release of corrosion by-products. The anodic reaction resistance decreases while the cathodic reaction resistance increases, resulting in a small potential difference of only 10 mV between the anode and cathode. The resistance of the inner layer film decreases, while that of the outer layer film increases. SEM analysis shows that the surface becomes rougher with the addition of Ca²⁺, and 1-4 mm granular corrosion products are formed. This is due to the fact that Cu₄(OH)₆SO₄ has low solubility and forms a relatively dense passive film that inhibits the corrosion reaction. The added Ca²⁺ also reacts with SO₄^2- to form CaSO₄, which reduces the amount of Cu₄(OH)₆SO₄ generated at the interface, thus damaging the integrity of the passive film. Adding Ca²⁺ promotes the corrosion of copper by Cl^- and SO₄^2- and enhances the release of corrosion by-products, with the highest corrosion rate observed under the Cl^-/SO₄^2-/Ca²⁺ conditions. The resistance of the inner layer membrane decreases, while the mass transfer resistance of the outer layer membrane increases. Under the Cl^-/SO₄^2- conditions, the SEM surface of the Cu₂O particles is uniform in size, arranged in an orderly and compact manner. After adding Ca²⁺, the size of the particles becomes uneven, and the surface becomes rough and uneven. This is because Ca²⁺ firstly combines with SO₄^2-, thus promoting corrosion. And then the remaining Ca²⁺ combines with Cl^-, which inhibits corrosion. Despite the amount of remaining Ca²⁺ being small, it still promotes corrosion. The amount of released corrosion by-products is mainly controlled by the redeposition reaction that occurs in the outer layer membrane, determining the amount of Cu₂O to which the copper ions are converted. The increase in resistance of the outer layer membrane means that the charge transfer resistance of the redeposition reaction increases, and the reaction rate slows down. Consequently, the amount of Cu(ii) converted to Cu₂O decreases, leading to an increase in Cu(ii) in the solution. Therefore, adding Ca²⁺ in all three conditions results in an increase in the release of corrosion by-products.

A national survey of lead and other metal(loids) in residential drinking water in the United States

BACKGROUND

Exposure to lead (Pb), arsenic (As) and copper (Cu) may cause significant health issues including harmful neurological effects, cancer or organ damage. Determination of human exposure-relevant concentrations of these metal(loids) in drinking water, therefore, is critical.

OBJECTIVE

We sought to characterize exposure-relevant Pb, As, and Cu concentrations in drinking water collected from homes participating in the American Healthy Homes Survey II, a national survey that monitors the prevalence of Pb and related hazards in United States homes.

METHODS

Drinking water samples were collected from a national survey of 678 U.S. homes where children may live using an exposure-based composite sampling protocol. Relationships between metal(loid) concentration, water source and house age were evaluated.

RESULTS

18 of 678 (2.6%) of samples analyzed exceeded 5 µg Pb L-1 (Mean = 1.0 µg L-1). 1.5% of samples exceeded 10 µg As L-1 (Mean = 1.7 µg L-1) and 1,300 µg Cu L-1 (Mean = 125 µg L-1). Private well samples were more likely to exceed metal(loid) concentration thresholds than public water samples. Pb concentrations were correlated with Cu and Zn, indicative of brass as a common Pb source is samples analyzed.

SIGNIFICANCE

Results represent the largest national-scale effort to date to inform exposure risks to Pb, As, and Cu in drinking water in U.S. homes using an exposure-based composite sampling approach.

IMPACT STATEMENT

To date, there are no national-level estimates of Pb, As and Cu in US drinking water collected from household taps using an exposure-based sampling protocol. Therefore, assessing public health impacts from metal(loids) in drinking water remains challenging. Results presented in this study represent the largest effort to date to test for exposure-relevant concentrations of Pb, As and Cu in US household drinking water, providing a critical step toward improved understanding of metal(loid) exposure risk.

School and childcare center drinking water: Copper chemistry, health effects, occurrence, and remediation

The study goal was to better understand the risks of elevated copper levels at US schools and childcare centers. Copper health effects, chemistry, occurrence, and remediation actions were reviewed. Of the more than 98,000 schools and 500,000 childcare centers, only 0.2% had copper water testing data in the federal Safe Drinking Water Information System database. Of the facilities designated public water systems, about 13% had reported an exceedance. Schools that were not designated a public water system (PWS) also had exceedances. Few studies document levels in schools and childcare centers. Widely different sampling and remedial actions were reported. Flushing contaminated water was the most evaluated remedial action but was unreliable because copper quickly rebounded when flushing stopped. Building water treatment systems have been used, but some were not capable of making the water safe. The health risk was difficult to determine due to the limited occurrence data and lack of best management practice studies. A national drinking water testing campaign and field studies are recommended.

Impact of physical and chemical parameters on square wave anodic stripping voltammetry for trace Pb2+ detection in water

Exposure to lead, a toxic heavy metal, in drinking water is a worldwide problem.

Evaluation and comparison of centralized drinking water softening technologies: Effects on water quality indicators

Drinking water softening is often implemented to increase consumer convenience e.g. by reducing lime scaling and soap use. Softening reduces hardness, but changes also the overall mineral composition of the water, depending on the technology. A broad spectrum of effects from softening has to be considered in relation to e.g. health and corrosion when selecting softening technology and design, otherwise adverse effects may be overlooked in the attempt to increase consumer convenience. We here provided a framework for evaluating softening technologies using water quality indicators for lime scaling, soap use, corrosion, human health, taste and removal of contaminants. None of the evaluated softening technologies scored positive on all the included water quality indicators. Precipitation technologies (lime/soda-ash softening and pellet softening) reduce the predicted copper and lead release, but negatively affect stainless steel corrosion expressed by the Larson Ratio. Pellet softening does not remove magnesium, which may limit the achievable softening depth, but maintains a protective effect against cardio-vascular diseases. Strong-acid cation exchange is not expected to affect the included corrosion indicators, whereas the effects from membrane separation (nanofiltration and reverse osmosis) and weak-acid cation exchange depend on the specific source water and process design. All the evaluated technologies reduce hardness, calcium carbonate precipitation potential (CCPP) and atopic eczema, but have potential adverse effects on dental carries (expressed by DMF-S). Our framework provides a better understanding of softening and can prepare water utility planners and managers for better decisions that balance the positive and adverse effects from drinking water softening.

Quartz Crystal Microbalance with Dissipation: A New Approach of Examining Corrosion of New Copper Surfaces in Drinking Water

Corrosion of copper material in drinking water systems causes public health concerns and plumbing failures. This study investigated the early corrosion of new copper surfaces in situ using a novel technique: quartz crystal microbalance with dissipation (QCMD). The QCMD results showed that increasing the water pH from 6.5 to 9.0 and the addition of 6 mg/L orthophosphate at pH 6.5 and 9.0 slowed down the copper surface mass changes as indicated by the reduced changes in frequency (Δf5) at 51-89% and total copper release at 29-72%. The water pH 9.0 without orthophosphate was the most likely to induce localized corrosion relative to other conditions at pH 6.5 and pH 9.0 with orthophosphate. Based on the changes in dissipation values (ΔD5) from QCMD and the morphology, microstructure, and composition of the deposited copper corrosion byproducts, digital microscopy, field-emission scanning electron microscopy with energy dispersive spectroscopy, and X-ray photoelectron spectrometry analyses confirmed that the pH and orthophosphate inhibited copper corrosion with different mechanisms. QCMD provided sensitive, rapid, and continuous responses to mass and surface changes and can be useful for evaluating early water corrosivity to new copper.

Natural Organic Matter, Orthophosphate, pH, and Growth Phase Can Limit Copper Antimicrobial Efficacy for Legionella in Drinking Water

Copper (Cu) is a promising antimicrobial for premise plumbing, where ions can be dosed directly via copper silver ionization or released naturally via corrosion of Cu pipes, but Cu sometimes inhibits and other times stimulates Legionella growth. Our overarching hypothesis was that water chemistry and growth phase control the net effect of Cu on Legionella. The combined effects of pH, phosphate concentration, and natural organic matter (NOM) were comprehensively examined over a range of conditions relevant to drinking water in bench-scale pure culture experiments, illuminating the effects of Cu speciation and precipitation. It was found that cupric ions (Cu²⁺) were drastically reduced at pH > 7.0 or in the presence of ligand-forming phosphates or NOM. Further, exponential phase L. pneumophila were 2.5× more susceptible to Cu toxicity relative to early stationary phase cultures. While Cu²⁺ ion was the most effective biocidal form of Cu, other inorganic ligands also had some biocidal impacts. A comparison of 33 large drinking water utilities' field-data from 1990 and 2018 showed that Cu²⁺ levels likely decreased more dramatically (>10×) than did the total or soluble Cu (2×) over recent decades. The overall findings aid in improving the efficacy of Cu as an actively dosed or passively released antimicrobial against L. pneumophila.

Impacts of Municipal Water-Rainwater Source Transitions on Microbial and Chemical Water Quality Dynamics at the Tap

When rainwater harvesting is utilized as an alternative water resource in buildings, a combination of municipal water and rainwater is typically required to meet water demands. Altering source water chemistry can disrupt pipe scale and biofilm and negatively impact water quality at the distribution level. Still, it is unknown if similar reactions occur within building plumbing following a transition in source water quality. The goal of this study was to investigate changes in water chemistry and microbiology at a green building following a transition between municipal water and rainwater. We monitored water chemistry (metals, alkalinity, and disinfectant byproducts) and microbiology (total cell counts, plate counts, and opportunistic pathogen gene markers) throughout two source water transitions. Several constituents including alkalinity and disinfectant byproducts served as indicators of municipal water remaining in the system since the rainwater source does not contain these constituents. In the treated rainwater, microbial proliferation and Legionella spp. gene copy numbers were often three logs higher than those in municipal water. Because of differences in source water chemistry, rainwater and municipal water uniquely interacted with building plumbing and generated distinctively different drinking water chemical and microbial quality profiles.

Using Compliance Data to Understand Uncertainty in Drinking Water Lead Levels in Southwestern Pennsylvania

The historical use of lead in potable water plumbing systems has caused significant public health challenges. The Lead and Copper Rule requires utilities to take action if the 90^th percentile lead concentration exceeds the action level (AL) of 15 ppb. Assessment of the AL is based on a sample of homes representing a relatively small fraction of connections. Due to the intentional nonrepresentative sampling approach, the full set of conditions influencing lead concentrations in a large distribution system may be poorly characterized. Further, there is uncertainty in assessing statistical parameters such as the 90^th percentile concentration. This work demonstrates methods to compute the uncertainty in the 90^th percentile statistic and assesses the associated effect on compliance outcomes. The method is demonstrated on four utilities in southwest Pennsylvania (referred to as A, B, C, and D). For Utility A, evaluation of the 90^th percentile showed an increase over time in observed and estimated values and the value's uncertainty. This type of change in the uncertainty might have served as an early warning of the exceedance that followed. This could have triggered more timely review of operational changes in order to avoid the effects of noncompliance on utility costs and consumer confidence.

Metal-release potential from iron corrosion scales under stagnant and active flow, and varying water quality conditions

The release of potentially toxic metal ions from corrosion scales formed on pipe surfaces is of great concern for water quality in drinking water distribution systems (DWDS). This study examined the effects of alkalinity, chloride, and sulfate on metal release from corrosion scales sampled from a corroded iron pipe. Jar tests and recirculation pipe systems were used to investigate the metal-release potential during stagnant and active flow conditions. The experimental data show that both the ambient water chemistry and hydraulic conditions exerted complex influences on metal release from the exposed corrosion scales. Fe, Mn, and Ni were more labile to be released during a 132-h period of stagnation, while the release of Al, Zn, and Cu was an order of magnitude higher under flow conditions compared to stagnant conditions. Increasing concentrations of chloride (from 5 mg/L to 60 mg/L) and sulfate (from 20 mg/L to 100 mg/L) resulted in the increased release of Fe, Al, and Zn, especially under active flow conditions. This effect could be effectively mitigated by increasing alkalinity from 50 mg/L to 200 mg/L as CaCO₃. While increasing alkalinity suppressed the release of Fe and stimulated the release of Al and Cu under stagnant conditions, this contradictory effect was not observed under active flow conditions.

Source Water Characteristics and Building-specific Factors Influence Corrosion and Point of Use Water Quality in a Decentralized Arctic Drinking Water System

Access to clean and safe drinking water is a perpetual concern in Arctic communities because of challenging climatic conditions, limited options for the transportation of equipment and process chemicals, and the ongoing effects of colonialism. Water samples were gathered from multiple locations in a decentralized trucked drinking water system in Nunavut, Canada, over the course of one year. The results indicate that point of use drinking water quality was impacted by conditions in the source water and in individual buildings and strongly suggest that lead and copper measured at the tap were related to corrosion of onsite premise plumbing components. Humic-like substances were the dominant organic fraction in all samples, as determined by regional integration of fluorescence data. Iron and manganese levels in the source water and throughout the water system were higher in the winter and lower in the summer months. Elevated concentrations of copper (>2000 μg L^-1) and lead (>5 μg L^-1) were detected in tap water from some buildings. Field flow fractionation coupled with inductively coupled plasma mass spectrometry and ultraviolet-visible spectrometry was used to demonstrate the link between source water characteristics (high organics, iron and manganese) and lead and copper in point of use drinking water.

Chlorine Reduction Kinetics and its Mass Balance in Copper Premise Plumbing Systems During Corrosion Events

Hypochlorous acid has been reported as the main oxidant agent responsible for the corrosion of copper plumbing systems in chlorinated water supplies. However, there is little information about chlorine consumption kinetics in a combined system (i.e., with dissolved oxygen (DO) and free chlorine), as well as its complete mass balance within a copper pipe during stagnation. The results of our experiments using copper pipes filled with synthetic drinking water, with a moderate alkalinity (pH = 7.2; dissolved inorganic carbon = 80 mg as CaCO₃ /L), and tested under chlorine concentrations from 0 to 8 mg/L, show that chlorine depletion is associated with pipe wall reactions (i.e., copper oxidation and scale formation processes). Free chlorine was depleted after 4 h of stagnation and its kinetic constant depend on the initial concentration, probably due to diffusion processes. Surface analysis including scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and total reflection X-ray fluorescence (T-XRF) suggest chlorine precipitation, probably as CuCl. The obtained kinetics of chlorine and DO reduction would be critical for modeling and prediction of corrosion events of copper premise plumbing systems. In addition, our results indicate that the pipe's surface reactions due to corrosion induces a loss of free chlorine in the bulk water, decreasing chlorine added for disinfection and the subsequent effect on water quality.

The effect of salinity and alkalinity on growth and the accumulation of copper and zinc in the Chlorophyta Ulva fasciata

Copper and zinc accumulation in macroalgae is a complex issue. While these metals exist as micronutrients and can serve to add nutritional value to the macroalgae when consumed by both plants and animals, elevated levels of the metals can reduce growth or even kill the algae. Many water parameters can influence the toxicity of the metals, though past studies have rarely isolated individual water parameters. This study aimed to independently determine the effects that salinity and alkalinity have on the growth and accumulation of these two metals on the macroalgae Ulva fasciata, distinguishing the effects of salinity and alkalinity as whole parameters from the collective effects of the water different constituents. The effect of salinity was determined using sodium chloride additions rather than seawater dilution, as performed in past studies, while alkalinity was tested using sodium bicarbonate additions to artificial seawater. The results of the study reinforce previous findings that copper is very toxic to macroalgae, even at low concentrations (50 µg L^-1) though the effects of zinc remain inconclusive at 50 µg L^-1, since the experiment was conducted over only a two-week trial period. The research suggests that salinity and alkalinity have no significant effect on the toxicity of copper to the growth of the macroalgae, but alkalinity significantly reduced copper and increased zinc accumulation in U. fasciata. The results of this study warrant further research in the field to investigate which other components of seawater and macroalgae reduce metal toxicity in the macroalgae. Additionally, these findings suggest the need for further refinement of toxicity models when adapted to macroalgae.

Copper Corrosion and Biocorrosion Events in Premise Plumbing

Corrosion of copper pipes may release high amounts of copper into the water, exceeding the maximum concentration of copper for drinking water standards. Typically, the events with the highest release of copper into drinking water are related to the presence of biofilms. This article reviews this phenomenon, focusing on copper ingestion and its health impacts, the physicochemical mechanisms and the microbial involvement on copper release, the techniques used to describe and understand this phenomenon, and the hydrodynamic effects. A conceptual model is proposed and the mathematical models are reviewed.

Effect of Corrosion Inhibitors on In Situ Leak Repair by Precipitation of Calcium Carbonate in Potable Water Pipelines

Corrosion inhibitors can affect calcium carbonate precipitation and associated in situ and in-service water distribution pipeline leak repair via clogging. Clogging of 150 μm diameter leak holes represented by glass capillary tubes, in recirculating solutions that are supersaturated with calcite (Ω_calcite = 13), demonstrated that Zn, orthophosphate, tripolyphosphate, and hexametaphosphate corrosion/scaling inhibitors hinder clogging but natural organic matter (NOM) has relatively little impact. Critical concentrations of phosphates that could inhibit leak repair over the short-term in one water tested were: tripolyphophate (0.05 mg/L as P) < hexametaphosphate (0.1 mg/L) < orthophosphate (0.3 mg/L). Inhibitor blends (Zn+orthophosphate and Zn+NOM+orthophosphate) had stronger inhibitory effects compared to each inhibitor (Zn, orthophosphate or NOM) alone, whereas Zn+NOM showed a lesser inhibitory effect than its individual component (NOM) alone due to formation of smaller CaCO₃ particles with a much more negative zeta-potential. Overall, increased dosing of corrosion inhibitors is probably reducing the likelihood of scaling and in-service leak repair via clogging with calcium carbonate solids in potable water systems.

Distribution system water age can create premise plumbing corrosion hotspots

Cumulative changes in chemical and biological properties associated with higher "water age" in distribution systems may impact water corrosivity and regulatory compliance with lead and copper action levels. The purpose of this study was to examine the effects of water age and chemistry on corrosivity of various downstream premise plumbing pipe materials and configurations using a combination of controlled laboratory studies and a field survey. Examination of lead pipe, copper pipe with lead solder, and leaded brass materials in a replicated lab rig simulating premise plumbing stagnation events indicated that lead or copper release could increase as much as ∼440 % or decrease as much as 98 % relative to water treatment plant effluent. In field studies at five utilities, trends in lead and copper release were highly dependent on circumstance; for example, lead release increased with water age in 13 % of cases and decreased with water age in 33 % of conditions tested. Levels of copper in the distribution system were up to 50 % lower and as much as 30 % higher relative to levels at the treatment plant. In many cases, high-risks of elevated lead and copper did not co-occur, demonstrating that these contaminants will have to be sampled separately to identify "worst case" conditions for human exposure and monitoring.

Modeling MIC copper release from drinking water pipes

Copper is used for household drinking water distribution systems given its physical and chemical properties that make it resistant to corrosion. However, there is evidence that, under certain conditions, it can corrode and release unsafe concentrations of copper to the water. Research on drinking water copper pipes has developed conceptual models that include several physical-chemical mechanisms. Nevertheless, there is still a necessity for the development of mathematical models of this phenomenon, which consider the interaction among physical-chemical processes at different spatial scales. We developed a conceptual and a mathematical model that reproduces the main processes in copper release from copper pipes subject to stagnation and flow cycles, and corrosion is associated with biofilm growth on the surface of the pipes. We discuss the influence of the reactive surface and the copper release curves observed. The modeling and experimental observations indicated that after 10h stagnation, the main concentration of copper is located close to the surface of the pipe. This copper is associated with the reactive surface, which acts as a reservoir of labile copper. Thus, for pipes with the presence of biofilm the complexation of copper with the biomass and the hydrodynamics are the main mechanisms for copper release.

Nitrification and potential control mechanisms in simulated premises plumbing

Indigenous drinking water organisms were used to establish nitrification in glass reactors containing copper or polyvinyl chloride (PVC) surfaces. The reactors were fed soil-derived humics as the organic carbon source and ammonium sulfate as the nitrogen source in biologically treated tap water. Water in the reactors was stagnant for 8 h and then flowed for 5 min to simulate conditions in household plumbing. Following the establishment of complete nitrification (conversion of ammonia to nitrate) in both reactor types, various inhibitors of nitrification were tested followed by a period where recovery of nitrification was observed. In one PVC reactor, copper was gradually introduced up to 1.3 ppm. To ensure that most of the copper was in the ionic form, the pH of the influent was then gradually lowered to 6.6. No significant change in nitrification was observed in the presence of copper. Chlorite was introduced into copper and PVC reactors at doses increasing from 0.2 ppm to 20 ppm. There was limited effect on the PVC system and inhibition in the copper reactor only at 20 ppm. Chloramine was tested at chlorine to ammonia ratios ranging from 0.5:1 to 5:1. Nitrification activity was impacted significantly at a 5:1 ratio and ultimately stopped, with the fastest response being in the copper system. Whenever a control mechanism was tested, there was increased release of copper from the reactors with copper coupons. In all cases, nitrification recovered when inhibitors were removed but the rates of recovery differed depending on the treatment method and coupon surface.

Rapid free chlorine decay in the presence of Cu(OH)2: chemistry and practical implications

A rapid reaction between free chlorine and the cupric hydroxide [Cu(OH)2] solids commonly found on pipe walls in premise plumbing can convert free chlorine to chloride and rapidly age Cu(OH)2 to tenorite (CuO). This reaction has important practical implications for maintaining free chlorine residuals in premise plumbing, commissioning of new copper pipe systems, and maintaining low levels of copper in potable water. The reaction stoichiometry between chlorine and Cu(OH)2 is consistent with formation of CuO through a metastable Cu(III) intermediate, although definitive mechanistic understanding requires future research. Natural levels of silica in water (0-30 mg/L), orthophosphate, and higher pH interfere with the rate of this reaction.

Designing water supplies: Optimizing drinking water composition for maximum economic benefit

It is possible to optimize drinking water composition based on a valuation of the impacts of changed water quality. This paper introduces a method for assessing the potential for designing an optimum drinking water composition by the use of membrane desalination and remineralization. The method includes modeling of possible water quality blends and an evaluation of corrosion indices. Based on concentration-response relationships a range of impacts on public health, material lifetimes and consumption of soap have been valued for Perth, Western Australia and Copenhagen, Denmark. In addition to water quality aspects, costs of water production, fresh water abstraction and CO(2)-emissions are integrated into a holistic economic assessment of the optimum share of desalinated water in water supplies. Results show that carefully designed desalination post-treatment can have net benefits up to €0.3 ± 0.2 per delivered m(3) for Perth and €0.4(±0.2) for Copenhagen. Costs of remineralization and green house gas emission mitigation are minor when compared to the potential benefits of an optimum water composition. Finally, a set of optimum water quality criteria is proposed for the guidance of water supply planning and management.

Copper release in low and high alkaline water

Copper release in drinking water, caused by electrochemical corrosion of household distribution systems, was investigated. Experiments were developed testing both low and high alkaline water in stagnant conditions. The effect of varying stagnation time was investigated also. Both soluble and insoluble copper compounds, produced by corrosion processes are quantified, using appropriate experimental procedures. On the basis of obtained results, copper concentration in stagnant water is defined as a function of water alkalinity, while total metal release is defined as a function of stagnation length, and is not dependent on water alkalinity.

Chemical characterization of blue stains in domestic fixtures in contact with drinking water

Bluish green staining in domestic fixtures was observed in three to 9-year-old houses in the city of Talca, located 256 km. south of Santiago, the capital of Chile. The houses contained copper pipes which were exposed to soft well water, with low pH and low buffer capacity. The aim of this paper is to establish the chemical composition of the stains and to determine the conditions by which they were formed. X-ray diffraction analysis of the stains revealed the presence of malachite, a copper compound that caused green coloring in kettles and water boilers. Dioptase, which is deep green in coloring, was identified in a bathtub tile. In one house, where blue stains were found in a toilet bowl, the presence of chrysocolla was suggested by means of X-ray fluorescence. In the field conditions studied it was concluded that the bluish green stains in bathroom home appliances were generated by the precipitation of copper compounds in places were leakages occur.

Enhanced copper release from pipes by alternating stagnation and flow events

Traditional studies of copper release in plumbing systems assume that the water extracted from a pipe follows a plug-type flow and that the pipe surface does not interact with the bulk water under flow conditions. We characterized actual stagnation-flushing cycles in a household pipe undergoing corrosion in the presence of a microbial biofilm. The mass of copper released in 10 experiments was on average 8 times the value estimated by using the plug-flow assumption. The experimental copper release pattern was explained by an advection-diffusion model only if a high copper concentration occurs near the pipe surface after stagnation. Microscopic examination of the pipe surface showed a complex assemblage of biotic and abiotic features. X-ray diffraction analyses identified only malachite, while X-ray absorption spectroscopy also revealed cupric hydroxide and cuprite. These results indicate that the surface serves as a storage compartment of labile copper that may be released under flow conditions. Thus, the diffusive transport from the pipe surface to the bulk during stagnation is not the only control of the flux of copper to the tap water when porous reactive microstructures cover the pipe. Our results highlight the need for models that consider the interaction between the hydrodynamics, chemistry, and structure at the solid-water interface to predict the release of corrosion byproducts into drinking water.

Effects of fluoridation and disinfection agent combinations on lead leaching from leaded-brass parts

This study concerns effects on water-borne lead from combinations of chlorine (CL) or chloramines (CA) with fluosilicic acid (FSA) or sodium fluoride (NaF). CL is known to corrode brass, releasing lead from plumbing devices. It is known that CA and CL in different ratios with ammonia (NH) mobilize copper from brass, which we have found also enhances elution of lead from leaded brass alloys. Phase I involved leaded-brass 1/4 in. elbows pre-conditioned in DI water and soaked in static solutions containing various combinations of CL, CA, FSA, NaF, and ammonium fluosilicate. In Phase II 20 leaded-brass alloy water meters were installed in pipe loops. After pre-conditioning the meters with 200 flushings with 1.0 ppm CL water, seven different solutions were pumped for a period of 6 weeks. Water samples were taken for lead analysis three times per week after a 16-h stagnation period. In the static testing with brass elbows, exposure to the waters with CA+50% excess NH3+FSA, with CA and ammonium fluosilicate, and with CA+FSA resulted in the highest estimated lead concentrations. In the flow-through brass meter tests, waters with CL+FSA, with CL+NaF, and with CL alone produced the highest average lead concentration for the first 3-week period. Over the last 3 weeks the highest lead concentrations were produced by CL+NaF, followed by CL alone and CA+NH3+FSA. Over the first test week (after CL flushing concentrations were increased from 1.0 to 2.0 ppm) lead concentrations nearly doubled (from about 100 to nearly 200 ppb), but when FSA was also included, lead concentrations spiked to over 900 ppb. Lead concentrations from the CL-based waters appeared to be decreasing over the study period, while for the CA+NH3+FSA combination, lead concentrations seemed to be increasing with time.

Monitoring of distribution water qualities under various source water blending

The main goal of this large-scale pilot distribution study was to systematically investigate the impacts of blending different source waters on distribution water qualities. The principal source waters investigated were conventionally treated ground water (G1), surface water processed by enhanced treatment (S1), and desalted seawater by reverse osmosis membranes (RO). Due to the nature of raw water quality and associated treatment processes, G1 water had high alkalinity, while S1 and RO sources were characterized as high sulfate and high chloride waters, respectively. One year of pilot pipe study demonstrated that water quality was significantly deteriorated by increased color when source water blends with characteristics different from historic groundwater were introduced to pipe distribution systems. Elevated color was associated with release of iron corrosion products, mainly from aged unlined cast iron pipes. Iron release increased significantly when exposed to RO and S1 waters: that is, the greater iron release was experienced with alkalinity reduced below the background of G1 water. Lead and copper release to water, on the other hand, enhanced with the application of RO and G1 waters, respectively.

Influences of water treatment process on iron and copper release in distribution system

A pilot study was conducted to assess the effect of water quality changes on iron and copper release in distribution systems. Three finished waters were prepared from groundwater source by conventional treatment, lime softening and reverse osmosis (RO). To mimic desalinated seawater, sea salts were added to RO treated water. Both lime softening and RO treatment significantly decreased the calcium concentration and alkalinity of groundwater. During a yearlong investigation, the impact of seasonal changes on iron and copper release was also evaluated. The results showed that groundwater after lime softening slightly increased iron release potential but significantly decreased copper release. Desalination water caused much higher iron release but lower copper release than conventionally treated groundwater. Blended water with conventional groundwater and desalination water resulted in intermediate iron release but much high copper release. Both iron and copper release could be accelerated by temperature increase.

Role of temperature, chlorine, and organic matter in copper corrosion by-product release in soft water

Soft, low alkalinity drinking waters tend to cause relatively high copper corrosion by-product release in plumbing systems. Long-term tests (6-8 months) in a synthetic, microbially stable soft tap water confirmed that lower pHs and higher temperatures increased copper release to water. Soluble copper release increased at lower temperature and lower pH. Low levels of free chlorine (0.7 mg/L) slightly increased copper release at pH 9.5, in marked contrast to the dramatic reductions in copper release that have been observed in soft waters in which Type III pitting corrosion is occurring. Gum xanthan and sodium alginate produced a microbially unstable water that reduced the pH and DO during stagnation in pipes--these indirect effects far outweighed their possible role in chelation or other modes of direct attack on copper surfaces.