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1.
Iron release from corroded iron pipes in drinking water distribution systems: effect of dissolved oxygen 总被引:14,自引:0,他引:14
Sarin P Snoeyink VL Bebee J Jim KK Beckett MA Kriven WM Clement JA 《Water research》2004,38(5):1259-1269
Iron release from corroded iron pipes is the principal cause of "colored water" problems in drinking water distribution systems. The corrosion scales present in corroded iron pipes restrict the flow of water, and can also deteriorate the water quality. This research was focused on understanding the effect of dissolved oxygen (DO), a key water quality parameter, on iron release from the old corroded iron pipes. Corrosion scales from 70-year-old galvanized iron pipe were characterized as porous deposits of Fe(III) phases (goethite (alpha-FeOOH), magnetite (Fe(3)O(4)), and maghemite (alpha-Fe(2)O(3))) with a shell-like, dense layer near the top of the scales. High concentrations of readily soluble Fe(II) content was present inside the scales. Iron release from these corroded pipes was investigated for both flow and stagnant water conditions. Our studies confirmed that iron was released to bulk water primarily in the ferrous form. When DO was present in water, higher amounts of iron release was observed during stagnation in comparison to flowing water conditions. Additionally, it was found that increasing the DO concentration in water during stagnation reduced the amount of iron release. Our studies substantiate that increasing the concentration of oxidants in water and maintaining flowing conditions can reduce the amount of iron release from corroded iron pipes. Based on our studies, it is proposed that iron is released from corroded iron pipes by dissolution of corrosion scales, and that the microstructure and composition of corrosion scales are important parameters that can influence the amount of iron released from such systems. 相似文献
2.
Profiling iron corrosion coating on iron grains in a zerovalent iron system under the influence of dissolved oxygen 总被引:1,自引:0,他引:1
Rapid oxidation of Fe(0) by O(2) occurred when Fe(0) grains were bathed in 0.54 mM FeCl(2) solution saturated with dissolved oxygen (DO), forming a substantial corrosion coating on Fe(0) grains. A sonication method was developed to strip the corrosion coating off the iron grains layer by layer. The transformation of the constituents and the morphology of the corrosion coating along its depth and over reaction time were investigated with composition analysis, X-ray diffraction and scanning electron microscopy. Results indicate that the sonication method could consistently recover >90% iron oxides produced by the Fe(0)-DO redox reaction. Magnetite (Fe(3)O(4)) and lepidocrocite (gamma-FeOOH) were identified as the corrosion products. Initially, lepidocrocite was the preferential product in the presence of DO. As the oxide coating thickened, the inner layer transformed to magnetite, which retained as the only stable corrosion product once DO was depleted. The study confirms the phase transformations between gamma-FeOOH and Fe(3)O(4) within a stratified corrosion coating. The sonication technique exemplifies a new approach for investigating more complicated processes in Fe(0)/oxides/contaminants systems. 相似文献
3.
Effects of disinfectant and biofilm on the corrosion of cast iron pipes in a reclaimed water distribution system 总被引:2,自引:0,他引:2
The effects of disinfection and biofilm on the corrosion of cast iron pipe in a model reclaimed water distribution system were studied using annular reactors (ARs). The corrosion scales formed under different conditions were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM), while the bacterial characteristics of biofilm on the surface were determined using several molecular methods. The corrosion scales from the ARs with chlorine included predominantly α-FeOOH and Fe2O3, while CaPO3(OH)·2H2O and α-FeOOH were the predominant phases after chloramines replaced chlorine. Studies of the consumption of chlorine and iron release indicated that the formation of dense oxide layers and biofilm inhibited iron corrosion, causing stable lower chlorine decay. It was verified that iron-oxidizing bacteria (IOB) such as Sediminibacterium sp., and iron-reducing bacteria (IRB) such as Shewanella sp., synergistically interacted with the corrosion product to prevent further corrosion. For the ARs without disinfection, α-FeOOH was the predominant phase at the primary stage, while CaCO3 and α-FeOOH were predominant with increasing time. The mixed corrosion-inducing bacteria, including the IRB Shewanella sp., the IOB Sediminibacterium sp., and the sulfur-oxidizing bacteria (SOB) Limnobacter thioxidans strain, promoted iron corrosion by synergistic interactions in the primary period, while anaerobic IRB became the predominant corrosion bacteria, preventing further corrosion via the formation of protective layers. 相似文献
4.
Permeable reactive barriers are successfully applied for the removal of various contaminants. The concomitant reduction of hydrogen ions and the subsequent formation of hydrogen gas by anaerobic corrosion lead to decreased pore volume filled with water and thus residence times, so called gas clogging. Long term column experiments were conducted to elucidate the impact of ubiquitous water constituents on the formation of hydrogen gas and potential passivation due to corrosion products. The collected gas volumes revealed a relation to the hydronium concentration (pH) but were only slightly increased in the presence of chloride and sulfate and not significantly influenced in the presence of phosphate, silicate, humic acid and ammonium compared to deionized water. Significant gas volumes within the reactive filling were verified by gravimetry. The presence of nitrate completely eliminated hydrogen formation by competition for electrons. Solid phase analyses revealed that neither chloride nor sulfate was incorporated in corrosion products in concentrations above 0.1 weight percent, and they did not alter the formation of mainly magnetite in comparison to deionized water. 相似文献
5.
Reduction of nitrobenzene and formation of corrosion coatings in zerovalent iron systems 总被引:1,自引:0,他引:1
Batch tests were conducted to investigate reduction of nitrobenzene in a zerovalent iron system (Fe0) under various conditions. The results indicated that a limited amount of nitrobenzene (ArNO2) could be reduced to aniline by Fe0, but formation of a lepidocrocite (gamma-FeOOH) coating could significantly slow down the reaction. However, augmenting Fe0 with substoichiometric FeCl2 could dramatically accelerate the reaction. Surface-adsorbed Fe(II), not pH nor Cl-, was found to be responsible for rejuvenating the system. O2 and nitrobenzene could be concomitantly reduced by Fe0 in the presence of Fe2+. In the Fe0 system, both nitrobenzene and O2 favored formation of lepidocrocite; in the presence of aq. Fe(II), a stratified corrosion coating could develop, with magnetite (Fe3O4) as the inner layer and lepidocrocite as the outer layer. Fe2+ was not the main reductant for the reactions, but might accelerate the autoreduction of lepidocrocite to magnetite by the underlying Fe0. Our understanding on the role of Fe(II) in conjunction with a stratified, evolving corrosion coating may be useful for establishing an iron aquatic corrosion model. 相似文献
6.
Speciation and distribution of vanadium in drinking water iron pipe corrosion by-products 总被引:1,自引:0,他引:1
Vanadium (V) when ingested from drinking water in high concentrations (> 15 μg L− 1) is a potential health risk and is on track to becoming a regulated contaminant. High concentrations of V have been documented in lead corrosion by-products as Pb5(V5+O4)3Cl (vanadinite) which, in natural deposits is associated with iron oxides/oxyhydroxides, phases common in iron pipe corrosion by-products. The extent of potential reservoirs of V in iron corrosion by-products, its speciation, and mechanism of inclusion however are unknown. The aim of this study is to assess these parameters in iron corrosion by-products, implementing synchrotron-based μ-XRF mapping and μ-XANES along with traditional physiochemical characterization. The morphologies, mineralogies, and chemistry of the samples studied are superficially similar to typical iron corrosion by-products. However, we found V present as discrete grains of Pb5(V5+O4)3Cl likely embedded in the surface regions of the iron corrosion by-products. Concentrations of V observed in bulk XRF analysis ranged from 35 to 899 mg kg− 1. We calculate that even in pipes with iron corrosion by-products with low V concentration, 100 mg kg− 1, as little as 0.0027% of a 0.1-cm thick X 100-cm long section of that corrosion by-product needs to be disturbed to increase V concentrations in the drinking water at the tap to levels well above the 15 μg L− 1 notification level set by the State of California and could adversely impact human health. In addition, it is likely that large reservoirs of V are associated with iron corrosion by-products in unlined cast iron mains and service branches in numerous drinking water distribution systems. 相似文献
7.
为研究硫酸盐腐蚀下结构耐久性及其修复,本文主要针对钢筋混凝土结构,分析硫酸盐腐蚀的机理,论述了受蚀前提高钢筋混凝土结构耐久性的措施,探讨了修复和加固受蚀后钢筋混凝土结构的方法,并以一化工厂为例,在其受蚀后,采用添加一定比例外加剂的普通硅酸盐水泥进行修复,结果表明新老混凝土结合良好,工作状态正常。通过分析其腐蚀机理得到的修补措施行之有效。 相似文献
8.
Silica fume is used as an admixture to concrete to improve the engineering properties. Additions of silica fume improve the bond between concrete and steel reinforcing bars. The authors describe a laboratory study which explores the ultimate pullout load of steel reinforcing bars from concrete enhanced with silica fume. Les fumees de silice utilisees comme adjuvant ameliorent les proprietes techniques du beton et notamment l'adherence entre le beton et les fers d'armature. Les auteurs decrivent une etude de laboratoire qui porte sur la resistance a l'arrachement des fers d'armature dans du beton traite aux fumees de silice. 相似文献
9.
Implications of nutrient release from iron metal for microbial regrowth in water distribution systems 总被引:2,自引:0,他引:2
Control of microbial regrowth in iron pipes is a major challenge for water utilities. This work examines the inter-relationship between iron corrosion and bacterial regrowth, with a special focus on the potential of iron pipe to serve as a source of phosphorus. Under some circumstances, corroding iron and steel may serve as a source for all macronutrients necessary for bacterial regrowth including fixed carbon, fixed nitrogen and phosphorus. Conceptual models and experimental data illustrate that levels of phosphorus released from corroding iron are significant relative to that necessary to sustain high levels of biofilm bacteria. Consequently, it may not be possible to control regrowth on iron surfaces by limiting phosphorus in the bulk water. 相似文献
10.
The corrosion scales on iron pipes could have great impact on the water quality in drinking water distribution systems (DWDS). Unstable and less protective corrosion scale is one of the main factors causing “discolored water” issues when quality of water entering into distribution system changed significantly. The morphological and physicochemical characteristics of corrosion scales formed under different source water histories in duration of about two decades were systematically investigated in this work. Thick corrosion scales or densely distributed corrosion tubercles were mostly found in pipes transporting surface water, but thin corrosion scales and hollow tubercles were mostly discovered in pipes transporting groundwater. Magnetite and goethite were main constituents of iron corrosion products, but the mass ratio of magnetite/goethite (M/G) was significantly different depending on the corrosion scale structure and water source conditions. Thick corrosion scales and hard shell of tubercles had much higher M/G ratio (>1.0), while the thin corrosion scales had no magnetite detected or with much lower M/G ratio. The M/G ratio could be used to identify the characteristics and evaluate the performances of corrosion scales formed under different water conditions. Compared with the pipes transporting ground water, the pipes transporting surface water were more seriously corroded and could be in a relatively more active corrosion status all the time, which was implicated by relatively higher siderite, green rust and total iron contents in their corrosion scales. Higher content of unstable ferric components such as γ-FeOOH, β-FeOOH and amorphous iron oxide existed in corrosion scales of pipes receiving groundwater which was less corroded. Corrosion scales on groundwater pipes with low magnetite content had higher surface area and thus possibly higher sorption capacity. The primary trace inorganic elements in corrosion products were Br and heavy metals. Corrosion products obtained from pipes transporting groundwater had higher levels of Br, Ti, Ba, Cu, Sr, V, Cr, La, Pb and As. 相似文献
11.
This study explored the feasibility of utilizing industrial waste iron oxide tailings for phosphate removal in laboratory experiments. The experimental work emphasized on the evaluation of phosphate adsorption and desorption characteristics of the tailing material. The adsorption isotherm, kinetics, pH effect and desorption were examined in batch experiments. Five isotherm models were used for data fitting. The three-parameter equations (Redlich-Peterson and Langmuir-Freundlich) showed more applicability than the two-parameter equations (Freundlich, Langmuir and Temkin). A modified equation for calculation of the separation factor using the Langmuir-Freundlich equation constants was developed. The initial phosphate adsorption on the tailings was rapid. The adsorption kinetics can be best described by either the simple Elovich or power function equation. The phosphate adsorption on the tailings tended to decrease with an increase of pH. A phosphate desorbability of approximately 13-14% was observed, and this low desorbability likely resulted from a strong bonding between the adsorbed PO(4)(3-)and iron oxides in the tailings. Column flow-through tests using both synthetic phosphate solution and liquid hog manure confirmed the phosphate removal ability of the tailings. Due to their low cost and high capability, this type of iron oxide tailings has the potential to be utilized for cost-effective removal of phosphate from wastewater. 相似文献
12.
Batch tests were conducted in zero-valent iron (ZVI or Fe0) systems to investigate oxygen consumption and the effect of dissolved oxygen (DO) on formation of iron corrosion products, nitrate reduction, the reactivity of Fe0, the role Fe2+ (aq) played, and the fate of Fe2+. The study indicates that without augmenting Fe2+ (aq), neither nitrate nor DO could be removed efficiently by Fe0. In the presence of Fe2+ (aq), nitrate and DO could be reduced concomitantly with limited interference with each other. Unlike nitrate reduction, DO removal by Fe0 did not consume Fe2+ (aq). A two-layer structure, with an inner layer of magnetite and an outer layer of lepidocrocite, may be formed in the presence of DO. When DO depleted, the outer lepidocrocite layer was transformed to magnetite. The inner layer of magnetite, even in a substantial thickness, might not impede the Fe0 reactivity as much as the thin interfacial layer between the oxide coating and liquid. Surface-bound Fe2+ may greatly enhance the electron transfer from the Fe0 core to the solid-liquid interface, and thus improve the performance of the Fe0 process. 相似文献
13.
T.A. Netto 《Journal of Constructional Steel Research》2005,61(8):1185-1204
The loss of metal in a pipeline due to corrosion usually results in localized pits with various depths and irregular shapes on its external and internal surfaces. The effect of external corrosion defects was studied via a series of small-scale experiments and through a nonlinear numerical model based on the finite element method. After calibration was conducted, based on the experimental results, the model was used to determine the burst pressure as a function of material and geometric parameters of different pipes and defects. This paper briefly summarizes these results, which are subsequently used to develop a simple procedure for estimating the burst pressure of corroded pipes. 相似文献
14.
Coprecipitation of arsenate with iron(III) in aqueous sulfate media: effect of time, lime as base and co-ions on arsenic retention 总被引:2,自引:0,他引:2
The removal and immobilization of arsenic from industrial mineral-processing effluents typically involves lime neutralization and coprecipitation of arsenate with ferric iron. Despite the wide practice and environmental importance of this technique, no laboratory study has focused on the roles of lime as base and third ions like Ca2+, Ni2+ and SO(2)4(-) on the kinetics of arsenic retention by the coprecipitates. In this work, coprecipitation was performed at 22 degrees C by fast (10 min) neutralization of industrially relevant concentrated arsenate-iron(III) (Fe/As=2, 4) acidic sulfate solutions to different pHs (4, 6, 8) in batch reactors, and the concentration of arsenic was monitored up to 1 year. The tests showed that maximum removal of arsenic was achieved upon neutralization to the target pH. Arsenic was found to be released back into solution from the precipitates upon continuing mild agitation at constant pH. Near-equilibrium was attained at different times depending on the applied pH: 10 days at pH 4, 6 months at pH 6 and 9 months at pH 8. An aging treatment at pH 4 significantly enhanced arsenic retention (arsenic release was reduced by at least 50%) after the system was finally stabilized at pH 8. The retention of arsenic at pH 8 was multifold improved (by a factor x 25) when lime was used instead of NaOH. Similarly, the retention of arsenic was enhanced by the presence of calcium and nickel ions in the starting solution. Finally, evidence of Ca(II)-Fe(III)-As(V) association was found, but not sulfate incorporation at pH 8. 相似文献
15.
Results of numerical investigations on the effects of material degradation due to corrosion on the dynamic characteristics of ground-based, anchored, steel liquid storage tanks are presented. Internal corrosion is considered as a time-dependent constant thinning of the wall, at locations in contact with residual water, water condensate, atmospheric oxygen and acid gases. Dynamic analyses are performed on numerical tank-liquid models, having different aspect ratios and wall thicknesses at different stages of wall thinning at the specified locations. The aim of the analyses is to determine the corrosion effects on the natural periods and mode shapes of vibration. Steady-state, harmonic base excitation analyses are also carried out to determine the corrosion effects on the hydrodynamic pressures produced in the liquid. It is found that progressive corrosion has significant effects on the tank fundamental period and its associated mode shape of vibration as well as the magnitude and location of the maximum hydrodynamic pressure and that as design provisions should cover the service life of the tank, the errors associated with the current code provisions for design of such tanks cannot be ignored. 相似文献
16.
Abdullah A. Almusallam 《Construction and Building Materials》2001,15(8):361-368
This paper reports results of a study conducted to assess the effect of degree of corrosion of reinforcing steel bars on their mechanical properties. Reinforcing steel bars, 6 and 12 mm in diameter, that were corroded in reinforced concrete specimens were removed and tested in tension. Results indicated that the level of reinforcement corrosion does not influence the tensile strength of steel bars, calculated on the actual area of cross-section. However, when the nominal diameter is utilized in the calculation, the tensile strength is less than the ASTM A 615 requirement of 600 MPa when the degree of corrosion was 11 and 24% for 6- and 12-mm diameter steel bars, respectively. Furthermore, reinforcing steel bars with more than 12% corrosion indicates a brittle failure. 相似文献
17.
Characterization of elemental and structural composition of corrosion scales and deposits formed in drinking water distribution systems 总被引:4,自引:0,他引:4
Ching-Yu Peng Gregory V. Korshin Andrew S. Hill Steve H. Reiber 《Water research》2010,44(15):4570-5563
Corrosion scales and deposits formed within drinking water distribution systems (DWDSs) have the potential to retain inorganic contaminants. The objective of this study was to characterize the elemental and structural composition of extracted pipe solids and hydraulically-mobile deposits originating from representative DWDSs. Goethite (α-FeOOH), magnetite (Fe3O4) and siderite (FeCO3) were the primary crystalline phases identified in most of the selected samples. Among the major constituent elements of the deposits, iron was most prevalent followed, in the order of decreasing prevalence, by sulfur, organic carbon, calcium, inorganic carbon, phosphorus, manganese, magnesium, aluminum and zinc. The cumulative occurrence profiles of iron, sulfur, calcium and phosphorus for pipe specimens and flushed solids were similar. Comparison of relative occurrences of these elements indicates that hydraulic disturbances may have relatively less impact on the release of manganese, aluminum and zinc, but more impact on the release of organic carbon, inorganic carbon, and magnesium. 相似文献
18.
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. 相似文献
19.
Process streams with high concentrations of metals and sulfate are characteristic for the mining and metallurgical industries. This study aims to selectively recover nickel from a nickel-iron-containing solution at pH 5.0 using a single stage bioreactor that simultaneously combines low pH sulfate reduction and metal-sulfide formation. The results show that nickel was selectively precipitated in the bioreactor at pH 5.0 and the precipitates consisted of ≥83% of the nickel content. The nickel-iron precipitates were partly crystalline and had a metal/sulfur ratio of 1, suggesting these precipitates were NiS and FeS. Experiments focusing on nickel recovery at pH 5.0 and 5.5 reached a recovery of >99.9%, resulting in a nickel effluent concentration <0.05 μM. The mixed microbial population included known sulfate reducers and acetogens. This study shows that selective metal precipitation in a single stage sulfate reducing bioreactor operated at low pH has the potential to produce metal-sulfides that can be used by the metallurgical industry as a resource for metal production. 相似文献
20.
Influence of dry and wet curing conditions on compressive strength of silica fume concrete 总被引:2,自引:0,他引:2
C.D. Ati F.
zcan A. Kl O. Karahan C. Bilim M.H. Severcan 《Building and Environment》2005,40(12):1678-1683
This paper reports a part of an ongoing laboratory investigation in which the compressive strength of silica fume concrete is studied under dry and wet curing conditions. In the study, a total of 48 concretes, including control Portland cement concrete and silica fume concrete, were produced with four different water–cement ratios (0.3, 0.4, 0.5, 0.6), three different cement dosages (350, 400, 450 kg/m3) and three partial silica fume replacement ratios (10%, 15%, 20%). A hyperplastisizer was used in concrete at various quantities to provide and keep a constant workability. Three cubic samples produced from fresh concrete were demoulded after a day; then, they were cured at 20±2 °C with 65% relative humidity (RH), and three other cubic samples were cured at 20±2 °C with 100% RH until the samples were used for compressive strength measurement at 28 days. The comparison was made on the basis of compressive strength between silica fume concrete and control Portland cement concrete. Silica fume concretes were also compared among themselves. The comparisons showed that compressive strength of silica fume concrete cured at 65% RH was influenced more than that of Portland cement concrete. It was found that the compressive strength of silica fume concrete cured at 65% RH was, at average, 13% lower than that of silica fume concrete cured at 100% RH. The increase in the water–cementitious material ratios makes the concrete more sensitive to dry curing conditions. The influence of dry curing conditions on silica fume concrete was marked as the replacement ratio of silica fume increased. 相似文献