Identifying effects of pipe material, hydraulic condition, and water composition on elemental accumulation in pipe corrosion scales

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.

Multidimensional Profiling of Human Body Hairs Using Qualitative and Semi-Quantitative Approaches with SR-XRF, ATR-FTIR, DSC, and SEM-EDX

This study aimed to assess the potential of a multidimensional approach to differentiate body hairs based on their physico-chemical properties and whether body hairs can replace the use of scalp hair in studies linked to forensic and systemic intoxication. This is the first case report controlling for confounding variables to explore the utility of multidimensional profiling of body hair using synchrotron synchrotron microbeam X-ray fluorescence (SR-XRF) for longitudinal and hair morphological region mapping) and benchtop methods, including attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) (complemented with chemometrics analysis), energy dispersive X-ray analysis (EDX) (complemented with heatmap analysis), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) analysis (complemented by descriptive statistics) to profile different body hairs in terms of their elemental, biochemical, thermal, and cuticle properties. This multidimensional approach provided supportive information to emphasize the intricate and rather complex interplay between the organization and levels of elements and biomolecules within the crystalline and amorphous matrix of different body hairs responsible for the differences in physico-chemical properties between body hairs that are predominantly affected by the growth rate, follicle or apocrine gland activity, and external factors such as cosmetic use and exposure to environmental xenobiotics. The data from this study may have important implications for forensic science, toxicology and systemic intoxication, or other studies involving hair as a research matrix.

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.

Characteristics of vanadium release from layered steel pipe scales to bulk, steady, and occluded water in drinking water distribution systems

The release of vanadium (V) from drinking water distribution systems (DWDS) can endanger water quality and human health. Therefore, in this study, the physicochemical characteristics of old steel pipe scales were analyzed, and dynamic pipeline devices were constructed. Subsequently, static release experiments were conducted to find an optimum scale-water ratio and investigate the release behaviors of V in lumpy pipe scales. Besides, the release behaviors of V from layered pipe scales to bulk, steady, and occluded water under the combined effect of multiple water quality conditions were studied for the first time. Computational fluid dynamics (CFD) was adopted to explain the release behaviors of V in the dynamic pipeline. Results revealed that the adsorption performance of the layered scales decreased in the order of surface layer > porous core layer > hard shell-like layer. The release behaviors of V in the lumpy pipe scales were mainly divided into rapid desorption and colloidal agglomeration stages. The Double constant and Weber-Morris models can suitably describe release stage I (R² > 0.919) and release stage II (R² > 0.948), respectively. Notably, the release of V was aggravated by low pH, high temperature, and high SO₄^2- concentration, and the release amount of V in the pipeline was more significant than the layered pipe scales. Steady water in the gaps of scales contained more V than bulk water, and the malignant occluded water encased in scales contained relatively low V concentrations. In short, the main mechanism of V release was competitive adsorption in the early stage, and pH was the main influencing factor in the later stage. The above results are of great significance for revealing the release behaviors of V and reducing its release in DWDS.

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.

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.

A workflow for spatio-seasonal hydro-chemical analysis using multivariate statistical techniques

Multivariate statistical techniques are powerful in data interpretation and pattern recognition, which play a vital role in pollutant source identification for water environment management. Despite of their wide application in hydro-chemical analysis, absence of a comprehensive workflow hinders the practices and further studies. The present study constructed a workflow on the application of multivariate statistical techniques in spatio-seasonal hydro-chemical analysis, which provided a basic guidance for practices and a systematic support to future exploration. Selection of the methods and work paths for spatio-seasonal analysis largely depends on the structure of data set and the requirements of specific tasks. Trial and adjustment could be repeatedly performed to optimize the analysis strategy and identify more underlying patterns. Given a multiscale dataset concerning complex spatio-seasonal variations, temporal or spatial grouping using appropriate methods to reasonably divide the complicated data set contributes to data interpretation and pattern recognition. The upper Yangtze River basin (UYRB, China) was employed for case analysis to demonstrate how the workflow guides an efficient and effective data exploration. Efforts could be made in future works to continually improve the workflow to involve more complicated analysis and techniques and the integrated application in various fields.

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.

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

The presence of galvanized pipe in drinking water distribution systems is known to be associated with heavy metal release, especially after the aging of zinc coating. This study examined release of lead and other heavy metals (e.g., cadmium, chromium) from galvanized steel coupons with a low-lead zinc coating. Metal release data were obtained in 12-week long jar tests which were conducted at varying temperatures and alkalinities. The morphology of the exposed surfaces was dominated by spherical and acicular formations. Exposures at 36 °C were associated with increased corrosion rates, accelerated depletion of zinc coating and faster development of corrosion scales, compared with 4 and 20 °C. The protective action of zinc coating was enhanced at increasing alkalinities. Metal release data showed a significant enrichment of Pb and Cd levels in the particulates released from the low-Pb galvanized steel.