Effects of varying temperatures and alkalinities on the corrosion and heavy metal release from low-lead galvanized steel

Impact of Lead Pollution from Vehicular Traffic on Highway-Side Grazing Areas: Challenges and Mitigation Policies

One major environmental concern is the lead (Pb) pollution from automobile traffic, especially in highway-side grazing areas. Sheep grazing in Pb-contaminated areas are particularly vulnerable because Pb exposure from soil, water, and feed can have harmful effects that impair their general health, reproductive capability, and immune systems. Long-term hazards to cattle from persistent Pb exposure include neurotoxicity, hematological abnormalities, reproductive health problems, and immunosuppression. These can have serious consequences, such as reduced productivity and even mortality. Additionally, through the food chain, Pb bioaccumulation in lamb tissues directly endangers human health. Pb poisoning is caused by a variety of intricate mechanisms, including disturbances in calcium-dependent processes, oxidative stress, and enzyme inhibition. To mitigate these risks, an interdisciplinary approach is essential, combining expertise in environmental science, toxicology, animal husbandry, and public health. Effective strategies include rotational grazing, alternative foraging options, mineral supplementation, and soil remediation techniques like phytoremediation. Additionally, the implementation of stringent regulatory measures, continuous monitoring, and community-based initiatives are vital. This review emphasizes the need for comprehensive and multidisciplinary methodologies to address the ecological, agricultural, and public health impacts of Pb pollution. By integrating scientific expertise and policy measures, it is possible to ensure the long-term sustainability of grazing systems, protect livestock and human health, and maintain ecosystem integrity.

Effects of polystyrene microplastics on the distribution behaviors and mechanisms of metalloid As(III) and As(V) on pipe scales in drinking water distribution systems

Pipe scales have long been considered the primary adsorption medium for trace heavy metals in drinking water distribution systems (DWDSs). Microplastics (MPs) potentially affect the distribution of metalloid arsenic (As) pollutants in DWDSs. Herein, the accumulation behaviors of As(Ⅲ) and As(V) on pipe scales and polystyrene microplastics (PSMPs) under different water conditions were studied. Additionally, As(Ⅲ) and As(V) accumulation behaviors on pipe scales coexisting with PSMPs were investigated. Results showed that pipe scales played a key role in the accumulation of As (pipe scales = 1.08-4.80 mg/g > PSMPs = 0.02-3.38 mg/g). The adsorption amount of As(Ⅲ) on PSMPs was higher than that of As(V). The addition of PSMPs promoted the accumulation of As(Ⅲ) on pipe scales at pH = 3-8 while inhibiting the accumulation of As(V) on pipe scales at pH = 3-10 due to the competitive adsorption. The oxidation of As(III) and the reduction of As(V) occurred during the accumulation of As(Ⅲ) and As(V) on pipe scales. Notably, PSMPs accumulated on pipe scales were beneficial to the oxidation of As(Ⅲ), potentially reducing the As-related risks. Overall, our results provide new insights into the hazards posed by MPs in DWDSs.

It's getting hot in here: Effects of heat on temperature, disinfection, and opportunistic pathogens in drinking water distribution systems

As global temperatures rise with climate change, the negative effects of heat on drinking water distribution systems (DWDS) are of increasing concern. High DWDS temperatures are associated with degradation of water quality through physical, chemical and microbial mechanisms. Perhaps the most pressing concern is proliferation of thermotolerant opportunistic pathogens (OPs) like Legionella pneumophila and Naegleria Fowleri. Many OPs can be controlled in DWDS by residual disinfectants such as chlorine or chloramine, but maintaining protective residuals can be challenging at high temperatures. This critical review evaluates the literature on DWDS temperature, residual disinfectant decay, and OP survival and growth with respect to high temperatures. The findings are synthesized to determine the state of knowledge and future research priorities regarding OP proliferation and control at high DWDS temperatures. Temperatures above 40 °C were reported from multiple DWDS, with a maximum of 52 °C. Substantial diurnal temperature swings from ∼30-50 °C occurred in one DWDS. Many OPs can survive or even replicate at these temperatures. However, most studies focused on just a few OP species, and substantial knowledge gaps remain regarding persistence, infectivity, and shifts in microbial community structure at high temperatures relative to lower water temperatures. Chlorine decay rates substantially increase with temperature in some waters but not in others, for reasons that are not well understood. Decay rates within real DWDS are difficult to accurately characterize, presenting practical limitations for application of temperature-dependent decay models at full scale. Chloramine decay is slower than chlorine except in the presence of nitrifiers, which are especially known to grow in DWDS in warmer seasons and climates, though the high temperature range for nitrification is unknown. Lack of knowledge about DWDS nitrifier communities may hinder development of solutions. Fundamental knowledge gaps remain which prevent understanding even the occurrence of high temperatures in DWDS, much less the overall effect on exposure risk. Potential solutions to minimize DWDS temperatures or mitigate the impacts of heat were identified, many which could be aided by proven models for predicting DWDS temperature. Industry leadership and collaboration is needed to generate practical knowledge for protecting DWDS water quality as temperatures rise.

Tap water microbiome shifts in secondary water supply for high-rise buildings

In high-rise buildings, secondary water supply systems (SWSSs) are pivotal yet provide a conducive milieu for microbial proliferation due to intermittent flow, low disinfectant residual, and high specific pipe-surface area, raising concerns about tap water quality deterioration. Despite their ubiquity, a comprehensive understanding of bacterial community dynamics within SWSSs remains elusive. Here we show how intrinsic SWSS variables critically shape the tap water microbiome at distal ends. In an office setting, distinct from residential complexes, the diversity in piping materials instigates a noticeable bacterial community shift, exemplified by a transition from α-Proteobacteria to γ-Proteobacteria dominance, alongside an upsurge in bacterial diversity and microbial propagation potential. Extended water retention within SWSSs invariably escalates microbial regrowth propensities and modulates bacterial consortia, yet secondary disinfection emerges as a robust strategy for preserving water quality integrity. Additionally, the regularity of water usage modulates proximal flow dynamics, thereby influencing tap water's microbial landscape. Insights garnered from this investigation lay the groundwork for devising effective interventions aimed at safeguarding microbiological standards at the consumer's endpoint.

Effects of chloride on corrosion scale compositions and heavy metal release in drinking water distribution systems

Variations in water chemistry may lead to the release of harmful heavy metals in drinking water distribution systems (DWDSs). In this study, the effects of chloride on the release of heavy metals such as Fe, Mn, As, Cr, Mo, V, Sr, and Co were examined using steel and cast iron pipe loops. After chloride was added, the relative contents of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and siderite (FeCO3) in pipe scales increased, but the contents of magnetite (Fe3O4) decreased. The most prevalent compounds were α-FeOOH and γ-FeOOH. When the chloride levels were increased, the effluent concentrations of Fe, Mn, As, Cr, Mo, V, Sr, and Co significantly increased. These heavy metals were released presumably because of the destabilization and dissolution of corrosion scales induced by chloride and adsorption site competition. Strong positive correlations were also observed between Fe&Mn, Fe/Mn&As, Fe/Mn&Cr, Fe/Mn&Mo, Fe/Mn&V, Fe/Mn&Sr, and Fe/Mn&Co, indicating the co-release of Fe, Mn, and other metals. This study may be helpful for the potential strategies on avoidance of heavy metal release and improvement of water supply security.

Reductions in Children's Blood Lead Levels from a Drinking-Water Intervention in Madagascar, Sub-Saharan Africa

One in three children globally is estimated to have blood lead levels (BLL) at or above the BLL reference value of 5 μg/dL with increased burden falling on low- and middle-income countries (LMIC). Within developed countries, aqueous lead is the predominant exposure route. However, aqueous lead exposure is rarely examined in the LMIC, leaving a gap in the literature that ignores a potentially significant route of exposure. Furthermore, limited lead-based remediation efforts around consumer products have been examined. This study investigates the importance of lead exposure from the water supply through a case study in Toamasina, Madagascar. The project measured aqueous lead and BLL of children pre- and postremediation efforts (i.e., removal of leaded pump components in hand pumps) to verify the impact of aqueous lead exposure within this community. Removal of the leaded pump components (i.e., piston and foot valves) and replacement with nonleaded components decreased aqueous lead levels below the World Health Organization provisional guideline of 10 μg/L in all but 4% of pumps tested. Measured BLL concentrations indicated a statistically significant decrease in BLL from pre- to postremediation. Furthermore, the remediation resulted in a decrease in BLL for 87% of children with the greatest changes in BLL observed for children with the highest preremediation concentrations. These findings point to a need for greater consideration of lead in drinking and cooking waters as an important exposure route in LMIC.

Study on release and occurrence of typical metals in corrosion products of drinking water distribution systems under stagnation conditions

Metal contaminants in corrosion products of drinking water distribution systems (DWDS) can be released into potable water under specific conditions, thereby polluting drinking water and posing a health risk. Under stagnation conditions, the release characteristics, occurring forms, and environmental risks of ten metals were determined in loose and tubercle scale solids of an unlined cast iron pipe with a long service history, before and after immersion. Most Al, As, Cr, Fe, and V in corrosion scales existed in the residual fraction, with the released concentration and pollution risk being low. Since more than 59% of Ca in pipe scales existed in the exchangeable fraction, Ca release was high. Although the Pb and Cd content of corrosion solids was low, a high proportion of Pb and Cd was present in non-residual fractions with high mobility. Sudden severe Pb or Cd pollution events in DWDS could result in high pollution and environmental risk levels. The total content and released amount of Mn and Zn in corrosion scales were both high. Therefore, while special attention should be paid to Mn and Zn, Pb and Cd also present a high risk in pipe scales, despite their low concentrations. During stagnation immersion, metal release from powdered pipe scales occurred via the processes of mass release, re-adsorption into scales, and slow release until equilibrium was reached. The levels of metal re-adsorption into scales were much higher than the concentrations dissolved into bulk water. However, the amount of metal re-adsorption into tubercle scale blocks was less. Importantly, these findings highlight that during DWDS operation, the sudden release of metal pollutants caused by pipe scale breakage should be avoided.

Elevated water lead levels in schools using water from on-site wells

Only 8% of US public schools operate their own community water systems, and thus are subject to the federal Lead and Copper Rule's regulation of water lead levels (WLLs). To date, the absence of parallel water testing data for all other schools has prevented the comparison of WLLs with schools that do not face federal regulation. This study compiled and analyzed newly available school-level WLL data that included water source (on-site well water or public utility) and pipe material data for public schools in New York State located outside of New York City. Despite direct federal regulation, schools that used water from on-site wells had a substantially higher percentage of water fixtures with elevated WLLs. Schools that used both on-site well water and iron pipes in their water distribution system had the highest percentage of elevated fixtures. Variation in water treatment practices was identified as a potential contributing mechanism, as schools that used on-site well water were less likely to implement corrosion control. The study concluded that information about water source and premise plumbing material may be useful to policymakers targeting schools for testing and remediation.

Iron release and characteristics of corrosion scales and bacterial communities in drinking water supply pipes of different materials with varied nitrate concentrations

Changes of drinking water quality can lead to iron release in drinking water distribution systems (DWDSs), which is one of the most important reasons for the deterioration of tap water quality. The objective of this study was to investigate the effects of nitrate on the iron release and characteristics of corrosion scales and bacterial communities in DWDSs using simplified pipe section reactors. With nitrate addition, the percentages of goethite (α-FeOOH), hematite (Fe₂O₃), and lepidocrocite (γ-FeOOH) in scales were decreased, whereas those of magnetite (Fe₃O₄) were increased. The growth of nitrate-reducing bacteria (NRB) was promoted significantly, with the fractions of 25.70% and 23.79% in the steel and cast iron pipes, respectively. Approximately 3.40% of iron-reducing bacteria (IRB) were reduced in both pipes. Moreover, under higher nitrate levels, iron release was inhibited obviously. The maximum decreased percentages of total iron in the steel and cast iron pipes were 44.90% (with 10.00 mg/L NO₃^--N) and 88.29% (with 30.00 mg/L NO₃^--N), respectively. This study may be helpful for improving drinking water supply safety.

Cr release after Cr(III) and Cr(VI) enrichment from different layers of cast iron corrosion scales in drinking water distribution systems: the impact of pH, temperature, sulfate, and chloride

Chromium accumulated from source water and pipeline lining materials in corrosion scales could potentially be released into bulk water in drinking water distribution systems (DWDS). This study examined the influence of pH (pH 4, pH 5.5, pH 7, pH 8.5, pH 10), temperature (5 °C, 15 °C, 25 °C), sulfate (50 mg/L, 150 mg/L, 250 mg/L), and chloride (50 mg/L, 150 mg/L, 250 mg/L) on chromium accumulation and release between iron corrosion scale phase and the surrounding water phase. For the first time, the accumulation and release behaviors of chromium were assessed and compared in two distinct layers of iron corrosion scales based on the speciation distributions of heavy metals. Results showed that in the outer and inner layers of corrosion scales, chromium exhibited an almost similar trend but significant differences in quantity, with the outer layer accumulating less and releasing more. In particular, the average difference of chromium released after Cr(VI) enrichment from the outer and inner layers was 50.53 μg/L under the same conditions. Further studies conclusively showed that in Cr(VI) accumulation process, a portion of Cr(VI) would be reduced to Cr(III) by Fe(II) in iron corrosion scales. The mechanisms of chromium retention based on different iron (oxyhydr)oxides were discussed.

Review on the Use of Heavy Metal Deposits from Water Treatment Waste towards Catalytic Chemical Syntheses

The toxicity and persistence of heavy metals has become a serious problem for humans. These heavy metals accumulate mainly in wastewater from various industries' discharged effluents. The recent trends in research are now focused not only on the removal efficiency of toxic metal particles, but also on their effective reuse as catalysts. This review discusses the types of heavy metals obtained from wastewater and their recovery through commonly practiced physico-chemical pathways. In addition, it covers the advantages of the new system for capturing heavy metals from wastewater, as compared to older conventional technologies. The discussion also includes the various structural aspects of trapping systems and their hypothesized mechanistic approaches to immobilization and further rejuvenation of catalysts. Finally, it concludes with the challenges and future prospects of this research to help protect the ecosystem.

Accumulation of vanadium and arsenic by cast iron pipe scales under drinking water conditions: A batch study

Metal pollutants accumulation in the scales of drinking water distribution systems presents a potential threat to water quality. Therefore, a study was carried out on the accumulation of V(V) and As(V) by cast iron pipe scales. The accumulation of V(V) and As(V) by scales and the effects of scale dosage, pH, temperature, and anion content on the accumulation process were assessed. Results showed that scales could rapidly accumulate V(V) and As(V), with maximum accumulation amounts of 3.94 mg/g and 3.90 mg/g, respectively. An increase in pH (from 3.0 to 9.0) and sulfate concentration (from 0 to 250 mg/L) decreased V(V) and As(V) accumulation by scales. Increased chloride ion concentrations (from 0 to 250 mg/L) reduced the amount of As(V) accumulated, while increasing the amount of V(V) accumulated. The V(V) and As(V) accumulation kinetics were well described by the Elovich model, with thermodynamic and accumulation isotherms showing that the accumulation process occurred via an entropic endothermic reaction. The mechanisms of accumulation of V(V) and As(V) by the scales include surface complexation, ligand exchange, electrostatic attraction and repulsion, and competitive adsorption.

Large-scale pattern of resistance genes and bacterial community in the tap water along the middle and low reaches of the Yangtze River

Antibiotic and metal resistance genes (ARGs and MRGs) in tap water are of great public health concern. However, very fewer studies focused on the relationship between resistance genes and opportunistic pathogens in tap water. In this study, the diversity and abundance of resistance genes and bacterial community from tap water at a large-scale along the middle and lower reaches of the Yangtze River were investigated. The total relative abundances of ARGs and MRGs were 2.95 × 10^-3-1.22 × 10^-1 and 1.93 × 10^-3-1.20 × 10^-1 copies/16S rRNA, respectively. The bla_TEM and merP detected were major ARG and MRG subtypes, respectively. Mobile genetic elements (Intl1 and tnpA) showed significant correlations with the abundance of ARGs. Heavy metals also played a vital role in the co-selection of ARGs. Surprisingly, there were still eight opportunistic pathogens in tap water, among which Escherichia coli, Helicobacter pylori, Mycoplasma pneumoniae, and Porphyromonas gingivalis were the potential host of ARGs and MRGs. Escherichia coli had the highest abundance, while Bacillus anthracis had the highest detected frequency (100%), a widespread opportunistic pathogen in tap water.

Manganese release from corrosion products of cast iron pipes in drinking water distribution systems: Effect of water temperature, pH, alkalinity, SO42- concentration and disinfectants

Manganese accumulated in corrosion scales on drinking water distribution systems (DWDSs) can be released into bulk water, causing discolouration and thereby leading to customer concerns about drinking water quality. A static release experiment was conducted on iron pipe scales under three different temperatures, pH values, alkalinity values, sulfate (SO₄^2-) concentrations, and disinfectants to study the separate effect of these factors on Mn release from pipe scales under stagnant conditions. Results showed that more Mn was released from corrosion scales under the conditions of lower pH, lower alkalinity, higher temperature, and higher SO₄^2- concentrations. Three commonly used disinfectants, sodium hypochlorite (NaClO), chlorine dioxide (ClO₂), and monochloramine (NH₂Cl) were found to inhibit the release of Mn from iron corrosion scales, with the ranked order of inhibitory effect of ClO₂≈NaClO > NH₂Cl under the same CT (product of disinfectant concentration and contact time) value. The orthogonal experimental results indicated that SO₄^2- and alkalinity had extremely significant effects on the release of Mn from pipe scales, while pH and disinfectant type had a significant impact on the release of Mn from pipe scales. Thus, the SO₄^2- concentration and alkalinity of the bulk water should be determined to avoid excessive release of Mn into drinking water. However, further investigation of the effect of disinfectants on Mn release in DWDSs is necessary. This research helps establish a systematic understanding of the influential factors in Mn release from pipe scales into bulk water, as well as their significant relationships.

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.