Effects of NOM properties on copper release from model solid phases

This study examined impacts of concentrations and properties of natural organic matter (NOM) on copper release from characteristic copper solid model phases such as tenorite CuO and malachite Cu₂(OH)₂CO₃. Unaltered Aldrich humic acid (AHA) and standard Suwannee River fulvic acid (SRFA) strongly increased copper release from the model phases but NOM alteration by chlorination or ozonation gradually suppressed or, at higher oxidant doses, eliminated these effects. The nature of NOM changes induced by chlorination and ozonation was examined using differential absorbance spectroscopy (DAS) and high-performance size-exclusion chromatography (HPSEC). The data of these methods show that NOM molecules with higher apparent molecular weight (AMW), higher aromaticities and contributions of protonation-active phenolic and carboxylic groups play a key role in adsorption and colloidal dispersion of the model solids. The data also show that metal release from model phases was well correlated with a number of spectroscopic parameters characterizing NOM properties, notably SUVA₂₅₄, spectral slopes of NOM absorbance, and differential absorbance at wavelength of 280 nm and 350 nm that is indicative of the contributions of carboxylic and phenolic functional groups. Changes of ζ-potential of the model solid phases were the strongest predictor of the enhancement of copper release especially in the system controlled by malachite. While effects of NOM on the ζ-potential of tenorite and malachite were prominent for unaltered NOM, its oxidation by chlorine and ozone was accompanied by a gradual decrease and ultimately disappearance of its surface activity.     

Influence of natural organic matter on the morphology of corroding lead surfaces and behavior of lead-containing particles

Influence of natural organic matter (NOM) on the morphology of lead surfaces exposed to drinking water and on the properties of lead-containing colloidal particles was explored based on the data of scanning electron microscopy, sequential filtrations, measurements of particle size distributions and electrophoretic potential. It was demonstrated that NOM prevented the formation of cerussite and hindered the growth of hydrocerussite crystals. Measurements of zeta-potential showed that the surface activity was highest for unaltered NOM, while ozonation and chlorination decreased it. The concentrations of soluble lead and tin increased several fold in the presence of NOM, while large colloidal particles of lead and solder corrosion products tended to break down to form smaller fragments. It is suggested that these phenomena are important for understanding of lead release mechanisms in drinking water.     

Secondary effects of anion exchange on chloride, sulfate, and lead release: systems approach to corrosion control

Water treatment processes can cause secondary changes in water chemistry that alter finished water quality including chloride, sulfate, natural organic matter (NOM), and metal release. Hence, the goal of this research was to provide an improved understanding of the chloride-to-sulfate mass ratio (CSMR) with regards to chloride and sulfate variations at full-scale water treatment plants and corrosion potential under simulated premise plumbing conditions. Laboratory corrosion studies were conducted using Pb-Sn solder/Cu tubing galvanic cells exposed to model waters with low (approx. 5 mg/L Cl⁻ and 10 mg/L SO₄^2-) and high (approx. 50 mg/L Cl⁻ and 100 mg/L SO₄^2-) concentrations of chloride and sulfate at a constant CSMR of ∼0.5. The role of NOM during corrosion was also evaluated by changing the type of organic material. In addition, full-scale sampling was conducted to quantify the raw water variability of chloride, sulfate, and NOM concentrations and the changes to these parameters from magnetic ion exchange treatment. Test conditions with higher concentrations of chloride and sulfate released significantly more lead than the lower chloride and sulfate test waters. In addition, the source of NOM was a key factor in the amount of lead released with the model organic compounds yielding significantly less lead release than aquatic NOM.     

Impacts of blending ground, surface, and saline waters on lead release in drinking water distribution systems

The impacts of distribution water quality changes caused by blending different source waters on lead release from corrosion loops containing small lead coupons were investigated in a pilot distribution study. The 1-year pilot study demonstrated that lead release to drinking water increased as chlorides increased and sulfates decreased. Silica and calcium inhibited lead release to a lesser degree than sulfates. An additional 3-month field study isolated and verified the effects of chlorides and sulfates on lead release. Lead release decreased with increasing pH and increasing alkalinity during the 1-year pilot study; however, the effects of pH and alkalinity on lead release, were not clearly elucidated due to confounding effects. A statistical model was developed using nonlinear regression, which showed that lead release increased with increasing chlorides, alkalinity and temperature, and decreased with increasing pH and sulfates. The model indicated that primary treatment processes such as enhanced coagulation and RO (reverse osmosis membrane) were related to lead release by water quality. Chlorides are high in RO-finished water and increase lead release, while sulfates are high following enhanced coagulation and decrease lead release.     

The valuation of water quality: Effects of mixing different drinking water qualities

As water supplies increasingly turn to use desalination technologies it becomes relevant to consider the options for remineralization and blending with mineral rich water resources. We present a method for analyzing economic consequences due to changes in drinking water mineral content. Included impacts are cardiovascular diseases, dental caries, atopic eczema, lifetime of dish and clothes washing machines, heat exchangers, distribution systems, bottled water consumption and soap usage. The method includes an uncertainty assessment that ranks the impacts having the highest influence on the result and associated uncertainty. Effects are calculated for a scenario where 50% of Copenhagen's water supply is substituted by desalinated water. Without remineralization the total impact is expected to be negative (€−0.44 ± 0.2/m³) and individual impacts expected in the range of €0.01-0.51/m³ delivered water. Health impacts have the highest contribution to impact size and uncertainty. With remineralization it is possible to reduce several negative impacts and the total impact is expected to be positive (€0.14 ± 0.08/m³).     

Effects of flow and water chemistry on lead release rates from pipe scales

Lead release from pipe scales was investigated under different water compositions, stagnation times, and flow regimes. Pipe scales containing PbO₂ and hydrocerussite (Pb₃(OH)₂(CO₃)₂) were developed on lead pipes by conditioning the pipes with water containing free chlorine for eight months. Water chemistry and the composition of the pipe scales are two key factors affecting lead release from pipe scales. The water rarely reached equilibrium with pipe scales within one day, which makes solid-water contact time and corrosion product dissolution rates the controlling factors of lead concentrations for the conditions tested. Among five water compositions studied, a solution with orthophosphate had the lowest dissolved lead release rate and highest particulate lead release rate. Free chlorine also decreased the dissolved lead release rate at stagnant conditions. Water flow increased rates of release of both dissolved and particulate lead by accelerating the mass transfer of lead out of the porous pipe scales and by physically destabilizing pipe scales. Dissolved lead comprised the majority of the lead released at both stagnant and laminar flow conditions.     

Effects of magnetic ion exchange pretreatment on low pressure membrane filtration of natural surface water

Magnetic ion exchange (MIEX) pretreatment has been increasingly employed by water treatment plants for removal of dissolved organic carbon (DOC). In this study, the effects of MIEX pretreatment on low pressure membrane filtration of natural surface water were investigated under different feedwater qualities, membrane properties, and MIEX dosing conditions. Regardless of feedwater DOC, moderate decrease in the total and hydraulically irreversible fouling was observed for a polyvinylidene fluoride (PVDF) microfiltration membrane and a polyethersulfone ultrafiltration (UF) membrane after MIEX pretreatment, which was coincident with moderate removals of high molecular weight DOC in the feedwaters. Comparatively, the fouling of a PVDF UF membrane did not decrease after MIEX pretreatment, revealing the impact of membrane properties on membrane fouling in the presence of MIEX pretreatment. Reuse of virgin or regenerated MIEX resulted in similar membrane fouling as observed with single use of the virgin MIEX. The level of DOC removal by MIEX was similar to the removal of MS2 bacteriophage spiked in the feedwater, suggesting a potential similarity in the removal of organic and microbial particles. In conclusion, MIEX pretreatment was effective for DOC removal, but less effective in controlling short-term membrane fouling or removing viruses.     

A historical review and bibliometric analysis of research on lead in drinking water field from 1991 to 2007

A bibliometric analysis based on Science Citation Index (SCI) published by Institute of Scientific Information (ISI) was carried out to identify the global research related to lead in drinking water field from 1991 to 2007 and to improve the understanding of research trends in the same period. The results from this analysis indicate that there have been an increasing number of annual publications mainly during two periods: from 1992 to 1997 and from 2004 to 2007. United States produced 37% of all pertinent articles followed by India with 8.0% and Canada with 4.8%. Science of the Total Environment published the most articles followed by Journal American Water Works Association and Toxicology. Summary of the most frequently used keywords are also provided. “Cadmium” was the most popular author keyword in the 17 years. Furthermore based on bibliometric results four research aspects were summarized in this paper and the historical research review was also presented.     

Removal of zinc, copper and lead by natural zeolite-a comparison of adsorption isotherms

An uptake of zinc (Zn), copper (Cu), and lead (Pb) from aqueous solutions by ion exchange on natural zeolitic tuff has been studied. The Croatian zeolite clinoptilolite from the Donje Jesenje deposit has been used as a natural ion exchanger. The efficiency of removal is higher for Pb and Cu than for Zn ions. Measured concentrations of Si in the liquid phase identify the detachment of the aluminosilicate structure during ion exchange in the presence of H(+) and OH(-) ions. The adsorption isotherm equations; Langmuir-Freundlich, Redlich-Petersen, Toth, Dubinin-Radushkevich, modified Dubinin-Radushkevich, and Lineweawer-Burk were derived from the basic empirical equations, and used for calculation of ion exchange parameters. The best fitting of experimental results to the proposed isotherms was observed in models that assume that ionic species bind first at energetically most favorable sites, with multi-layer adsorption taking place subsequently.     

Effect of flow rate and lead/copper pipe sequence on lead release from service lines

A pilot experiment examined lead leaching from four representative configurations of service lines including: (1) 100% lead (Pb), (2) 100% copper (Cu), (3) 50% Pb upstream of 50% Cu, and (4) 50% Pb-downstream of 50% Cu using a range of flow rates. The cumulative mass of lead release indicated that a typical partial replacement configuration (50% lead downstream of copper) did not provide a net reduction in lead when compared to 100% lead pipe (85 mg for 50% Pb-downstream versus 83 mg for 100%-Pb) due to galvanic and deposition corrosion. The partially replaced service line configuration also had a much greater likelihood of producing water with "spikes" of lead particulates at higher flow rates, while tending to produce lower levels of lead at very low flow rates. After the first 214 days the galvanic current between copper and lead was only reduced by 34%, proving that galvanic impacts can be highly persistent even in water with optimized corrosion control by dosing of zinc orthophosphate. Finally, this experiment raises concern about the low flow rates used during some prior home sampling events, which may underestimate exposure to lead during normal water use, especially when galvanic Pb:Cu connections are present.     

Impact of water treatment on the contribution of faucets to dissolved and particulate lead release at the tap

A field study was performed in a building complex to investigate the extent and sources of lead (Pb) release in tap water and brass material was found to be the main contributor in the very first draw (250 mL). Based on these results, a pilot installation was built to study Pb leaching from old and new faucets in the presence and absence of a connection to Cu piping. Four water quality conditions were tested: i) no treatment; ii) addition of 0.8 mg P/L of orthophosphate; iii) pH adjustment to 8.4; and iv) adjustment to a higher chloride to sulfate mass ratio (CSMR; ratio from 0.3 to 2.9). Pb concentrations in samples taken from the faucets without treatment ranged from 1 to 52 μg/L, with a mean of 11 μg/L. The addition of orthophosphate @ 0.8 mg P/L (OrthoP) was the most effective treatment for all types of faucets tested. On average, OrthoP reduced mean Pb leaching by 41%, and was especially effective for new double faucets (70%). In the presence of orthophosphates, the relative proportion of particulate Pb (Pbpart) (>0.45 μm) increased from 31% to 54%. However, OrthoP was not efficient to reduce Zn release. The higher CSMR condition was associated with greater dezincification of yellow brass but not of red brass. Corrosion control treatment influenced Pb concentration equilibrium, directly impacting maximal exposure. Significantly higher Pb release (3 fold) was observed for 1 of the 8 faucets connected to Cu exposed to high CSMR water, suggesting the presence of galvanic corrosion.     

Removal of natural organic matter and THM formation potential by ultra- and nanofiltration of surface water

Natural organic matter (NOM) and trihalomethane formation potential (THMFP) removal were evaluated by ultrafiltration (UF) and nanofiltration (NF). Ten different raw water sources in Alicante province (SE Spain) were analysed. Five types of membranes of different materials were tested with a dead-end-type stirred UF cell. Additional measurements, such as dissolved organic carbon, ultraviolet absorbance (254nm), THMFP, ion concentration, pH, conductivity, etc. were made on raw water, permeates and concentrates. The SUVA value was used to determine the hydrophobicity of the water analysed. The elimination of NOM and THMFP is correlated with the molecular weight (MW) of NOM determined by size exclusion chromatography (SEC). The flux decline trends were correlated with cation concentration. NOM removal by UF is low, which correlates with the average MW determined by SEC with an average value of 922g/mol (between 833 and 1031g/mol). However, the NOM removal obtained with the NF90 and NF270 NF membranes for all water sources is almost complete (90%). THMFP removal is related to hydrophobicity and permeability of membrane. The NFT50 membrane removes almost 100% of the THMFP of more hydrophobic waters.     

Impact of polymer flocculants on coagulation-microfiltration of surface water

Organic polymers are widely used as flocculants in pretreatment for microfiltration. However, their impact on microfiltration system performance was not well understood. In this study, the effects of three types of polymer flocculants on microfiltration permeate water quality and membrane fouling were evaluated using a hollow fiber membrane under two different operation modes, coagulation/flocculation-sedimentation-microfiltration (CFSM) and coagulation/flocculation-microfiltration (CFM). Interestingly, the effect of polymers on membrane fouling did not appear to reflect their impact on dissolved organic matter content or floc particle properties in the membrane feed water. The addition of polymer flocculants resulted in floc particles of larger size and smaller fractal dimension and slightly enhanced the removal of dissolved organic matter, both of which were expected to reduce membrane fouling. However, it significantly aggravated membrane fouling in all cases except when the positively charged poly(diallyldimethylammonium) chloride was used in the CFSM process. In particular, all polymers greatly increased hydraulically irreversible fouling in the CFM mode. The increased fouling in the CFSM mode is attributed to the residual polymer, while that in the CFM mode is attributed to the enhanced irreversible floc particle attachment on the membrane surface. Considering the potential severe membrane fouling and the small improvement in treated water quality when polymers are used, the application of polymers in microfiltration pretreatment needs to be carefully evaluated.     

Effects of organic matters coming from Chinese tea on soluble copper release from copper teapot

The morphology and elemental composition of the corrosion products of copper teapot's inner-surface were characterized by the scanning electron microscopy and energy dispersive X-ray surface analysis (SEM/EDS), X-ray powder diffraction (XRD) and X-ray photon spectroscopy (XPS) analysis. It was revealed that Cu, Fe, Ca, P, Si and Al were the main elements of corrosion by-products, and the alpha-SiO(2), Cu(2)O and CaCO(3) as the main mineral components on the inner-surface of copper teapot. The effects of organic matters coming from Chinese tea on soluble copper release from copper teapots in tap water were also investigated. The results showed that the doses of organic matter (as TOC), temperate and stagnation time have significant effects on the concentration of soluble copper released from copper teapots in tap water.     

Computational modelling to investigate the sampling of lead in drinking water

The monitoring of lead in drinking water is beset by difficulties relating to the inherent temporal variation of lead emissions at individual premises. Such difficulties are compounded by spatial variation when considering an entire water supply area (e.g., City or Town), which is necessary to determine compliance with regulatory standards and to judge the efficacy of corrective measures. A computational modelling system, that uses a Monte Carlo probabilistic framework for simulating lead emissions within a water supply area, has been successfully validated in a range of UK case studies and enabled corrective treatment measures to be optimised for a range of water types. This modelling system includes the simulation of a range of sampling methods, and has made it possible to undertake an exhaustive comparison between daily average lead emissions (DAC - which are equivalent to weekly average lead concentrations as a consequence of the modelling system used), random daytime sampling (RDT), 30 min stagnation sampling (30MS) and 6 h stagnation sampling (6HS). It is concluded that: (a) the stringency of UK and US compliance assessment methods for lead in drinking water is fairly similar for waters of reduced plumbosolvency, despite different sampling approaches; (b) RDT sampling is equivalent to random DAC for waters of moderate plumbosolvency; (c) RDT sampling is more stringent than random DAC for waters of low plumbosolvency; (d) all random sampling methods suffer from poor reproducibility, albeit less so for low plumbosolvency water; and (e) fixed point stagnation sampling may not be representative.     

海水淡化水与地表水掺混后的水质稳定性研究

以掺混水的朗格利尔指数作为评价标准,对掺混后的水的化学稳定性进行评价。结果表明,单纯依靠掺混无法满足水质稳定性;用Ca（OH）2对掺混水进行调值,可以增加pH值但不显著影响其他指标,且能部分满足水质的稳定性。在此基础上计算出水源水与海水淡化水在不同季节以不同比例进行掺混并调节pH后的水质稳定性,由于地表水水质随季节发生变化,同样的掺混比例获得的掺混水在某些季节是稳定的,在另一些季节可能存在风险。因此,单纯的掺混不是安全使用海水淡化水的可靠方案。     

Performance predictions of mature experimental constructed wetlands which treat urban water receiving high loads of lead and copper

The treatment efficiencies of vertical-flow wetland filters containing macrophytes and granular media of different adsorption capacities were investigated. Different concentrations of lead and copper sulphate were added to urban stream inflow water in order to simulate pre-treated (pH adjustment assumed) mine wastewater. After 1 year of operation, the metal mass load rate was increased by a factor of approximately 4.6. No breakthrough of metals was recorded. The use of macrophytes and adsorption media did not enhance heavy metal reduction significantly after 13 months of operation. A correlation analysis indicated strong positive correlations between conductivity on one side and other variables including temperature, total solids, dissolved oxygen and the redox potential on the other side. Some expensive or time-consuming variables (e.g., biochemical oxygen demand) can be predicted with less expensive ones (e.g., dissolved oxygen and temperature). The associated absolute mean errors were <10%.     

Microbiology, chemistry and biofilm development in a pilot drinking water distribution system with copper and plastic pipes

We studied the changes in water quality and formation of biofilms occurring in a pilot-scale water distribution system with two generally used pipe materials: copper and plastic (polyethylene, PE). The formation of biofilms with time was analysed as the number of total bacteria, heterotrophic plate counts and the concentration of ATP in biofilms. At the end of the experiment (after 308 days), microbial community structure, viable biomass and gram-negative bacterial biomass were analysed via lipid biomarkers (phospholipid fatty acids and lipopolysaccharide 3-hydroxy fatty acids), and the numbers of virus-like particles and total bacteria were enumerated by SYBR Green I staining. The formation of biofilm was slower in copper pipes than in the PE pipes, but after 200 days there was no difference in microbial numbers between the pipe materials. Copper ion led to lower microbial numbers in water during the first 200 days, but thereafter there were no differences between the two pipe materials. The number of virus-like particles was lower in biofilms and in outlet water from the copper pipes than PE pipes. Pipe material influenced also the microbial and gram-negative bacterial community structure in biofilms and water.     

Effects of chloride,sulfate and natural organic matter (NOM) on the accumulation and release of trace-level inorganic contaminants from corroding iron

This study examined effects of varying levels of anions (chloride and sulfate) and natural organic matter (NOM) on iron release from and accumulation of inorganic contaminants in corrosion scales formed on iron coupons exposed to drinking water. Changes of concentrations of sulfate and chloride were observed to affect iron release and, in lesser extent, the retention of representative inorganic contaminants (vanadium, chromium, nickel, copper, zinc, arsenic, cadmium, lead and uranium); but, effects of NOM were more pronounced. DOC concentration of 1 mg/L caused iron release to increase, with average soluble and total iron concentrations being four and two times, respectively, higher than those in the absence of NOM. In the presence of NOM, the retention of inorganic contaminants by corrosion scales was reduced. This was especially prominent for lead, vanadium, chromium and copper whose retention by the scales decreased from >80% in the absence of NOM to <30% in its presence. Some of the contaminants, notably copper, chromium, zinc and nickel retained on the surface of iron coupons in the presence of DOC largely retained their mobility and were released readily when ambient water chemistry changed. Vanadium, arsenic, cadmium, lead and uranium retained by the scales were largely unsusceptible to changes of NOM and chloride levels. Modeling indicated that the observed effects were associated with the formation of metal–NOM complexes and effects of NOM on the sorption of the inorganic contaminants on solid phases that are typical for iron corrosion in drinking water.