The Experts below are selected from a list of 50853 Experts worldwide ranked by ideXlab platform
Zhiguo Yuan - One of the best experts on this subject based on the ideXlab platform.
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the rapid chemically induced corrosion of concrete Sewers at high h2s concentration
Water Research, 2019Co-Authors: Xuan Li, Guangming Jiang, Zhiguo Yuan, Liza Omoore, Yarong Song, Philp L Bond, Simeon Wilkie, Lucija HanzicAbstract:Abstract Concrete corrosion in Sewers is primarily caused by H2S in sewer atmosphere. H2S concentration can vary from several ppm to hundreds of ppm in real Sewers. Our understanding of sewer corrosion has increased dramatically in recent years, however, there is limited knowledge of the concrete corrosion at high H2S levels. This study examined the corrosion development in Sewers with high H2S concentrations. Fresh concrete coupons, manufactured according to sewer pipe standards, were exposed to corrosive conditions in a pilot-scale gravity sewer system with gaseous H2S at 1100 ± 100 ppm. The corrosion process was continuously monitored by measuring the surface pH, corrosion product composition, corrosion loss and the microbial community. The surface pH of concrete was reduced from 10.5 ± 0.3 to 3.1 ± 0.5 within 20 days and this coincided with a rapid corrosion rate of 3.5 ± 0.3 mm year −1. Microbial community analysis based on 16S rRNA gene sequencing indicated the absence of sulfide-oxidizing microorganisms in the corrosion layer. The chemical analysis of corrosion products supported the reaction of cement with sulfuric acid formed by the chemical oxidation of H2S. The rapid corrosion of concrete in the gravity pipe was confirmed to be caused by the chemical oxidation of hydrogen sulfide at high concentrations. This is in contrast to the conventional knowledge that is focused on microbially induced corrosion. This first-ever systematic investigation shows that chemically induced oxidation of H2S leads to the rapid corrosion of new concrete Sewers within a few weeks. These findings contribute novel understanding of in-sewer corrosion processes and hold profound implications for sewer operation and corrosion management.
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corrosion of reinforcing steel in concrete Sewers
Science of The Total Environment, 2019Co-Authors: Philip L Bond, Zhiguo Yuan, Xuan Li, Yarong Song, E M Wightman, Yimei Tian, Kevin S Jack, Huiyun Zhong, Guangming JiangAbstract:Hydrogen sulfide is a controlling factor for concrete corrosion in Sewers, although its impact on sewer rebar corrosion has not been investigated to date. This study determined the corrosion mechanism of rebar in Sewers by elucidating the roles of chloride ions, apart from the effects of hydrogen sulfide and biogenic sulfuric acid. The nature and distribution of rusts at the steel/concrete interface were delineated using the advanced mineral analytical techniques, including mineral liberation analysis and micro X-ray diffraction which is the first-ever use in such studies. The corrosion products were found to be mainly iron oxides or oxy-hydroxides. HS and biogenic sulfuric acid did not directly participate in the product formation of steel partly covered by concrete or directly exposed to sewer atmosphere. Instead, chloride ions played an important role in initiating steel corrosion in Sewers, supported by a thin chloride-enriched layer at the steel/rust interface. Away from the chloride-enriched layer, iron oxides accumulated on both sides of the mill-scale to form a corrosion layer and corrosion-filled paste respectively. The corrosion layer around rebar circumference was non-uniform and the rust thickness with respect to polar coordinates followed a Gaussian model. These findings support predictions of sewer service lifetime and developments of corrosion prevention strategies.
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stability of illicit drugs as biomarkers in Sewers from lab to reality
Environmental Science & Technology, 2017Co-Authors: Jiaying Li, Zhiguo Yuan, Phong K Thai, Jochen F Mueller, Guangming JiangAbstract:Systematic sampling and analysis of wastewater samples are increasingly adopted for estimating drug consumption in communities. An understanding of the in-sewer transportation and transformation of illicit drug biomarkers is critical for reducing the uncertainty of this evidence-based estimation method. In this study, biomarkers stability was investigated in lab-scale sewer reactors with typical sewer conditions. Kinetic models using the Bayesian statistics method were developed to simulate biomarkers transformation in reactors. Furthermore, a field-scale study was conducted in a real pressure sewer pipe with the systematical spiking and sampling of biomarkers and flow tracers. In-sewer degradation was observed for some spiked biomarkers over typical hydraulic retention time (i.e., a few hours). Results indicated that sewer biofilms prominently influenced biomarker stability with the retention time in wastewater. The fits between the measured and the simulated biomarkers transformation demonstrated that the lab-based model could be extended to estimate the changes of biomarkers in real Sewers. Results also suggested that the variabilities of biotransformation and analytical accuracy are the two major contributors to the overall estimation uncertainty. Built upon many previous lab-scale studies, this study is one critical step forward in realizing wastewater-based epidemiology by extending biomarker stability investigations from laboratory reactors to real Sewers.
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nitrite production from urine for sulfide control in Sewers
Water Research, 2017Co-Authors: Zhiguo Yuan, Min Zheng, Yizhen Zhang, Qian Dong, Xia HuangAbstract:Most commonly used methods for sewer sulfide control involves dosing chemical agents to wastewater, which incurs high operational costs. Here, we propose and demonstrate a cost-effective and environmentally attractive approach to sewer sulfide control through urine separation and its subsequent conversion to nitrite prior to intermittent dosage to Sewers. Urine collected from a male toilet urinal was fed to laboratory-scale sequencing batch reactors. The reactors stably converted roughly 50% of the nitrogen in urine to nitrite, with high abundance (at 17.46%) of known ammonia-oxidizing bacteria (AOB) of the genus Nitrosomonas, and absence (below detection level) of typical nitrite-oxidizing bacteria of the genus Nitrospira, according to 454 pyrosequencing analysis. The stable nitrite production was achieved at both relatively high (1.0–2.0 mg/L) and low (0.2–0.3 mg/L) dissolved oxygen concentrations. Dosing tests in laboratory-scale sewer systems confirmed the sulfide control effectiveness of free nitrous acid generated from urine. Life cycle assessment indicated that, compared with commodity chemicals, nitrite/free nitrous acid (FNA) production from urine for sulfide control in Sewers would lower the operational costs by approximately 2/3 and greenhouse gas (GHG) emissions by 1/3 in 20 years.
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Predicting concrete corrosion of Sewers using artificial neural network
Water Research, 2016Co-Authors: Guangming Jiang, Philip L Bond, Jurg Keller, Zhiguo YuanAbstract:Corrosion is often a major failure mechanism for concrete Sewers and under such circumstances the sewer service life is largely determined by the progression of microbially induced concrete corrosion. The modelling of sewer processes has become possible due to the improved understanding of in-sewer transformation. Recent systematic studies about the correlation between the corrosion processes and sewer environment factors should be utilized to improve the prediction capability of service life by sewer models. This paper presents an artificial neural network (ANN)-based approach for modelling the concrete corrosion processes in Sewers. The approach included predicting the time for the corrosion to initiate and then predicting the corrosion rate after the initiation period. The ANN model was trained and validated with long-term (4.5 years) corrosion data obtained in laboratory corrosion chambers, and further verified with field measurements in real Sewers across Australia. The trained model estimated the corrosion initiation time and corrosion rates very close to those measured in Australian Sewers. The ANN model performed better than a multiple regression model also developed on the same dataset. Additionally, the ANN model can serve as a prediction framework for sewer service life, which can be progressively improved and expanded by including corrosion rates measured in different sewer conditions. Furthermore, the proposed methodology holds promise to facilitate the construction of analytical models associated with corrosion processes of concrete Sewers.
Guangming Jiang - One of the best experts on this subject based on the ideXlab platform.
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the rapid chemically induced corrosion of concrete Sewers at high h2s concentration
Water Research, 2019Co-Authors: Xuan Li, Guangming Jiang, Zhiguo Yuan, Liza Omoore, Yarong Song, Philp L Bond, Simeon Wilkie, Lucija HanzicAbstract:Abstract Concrete corrosion in Sewers is primarily caused by H2S in sewer atmosphere. H2S concentration can vary from several ppm to hundreds of ppm in real Sewers. Our understanding of sewer corrosion has increased dramatically in recent years, however, there is limited knowledge of the concrete corrosion at high H2S levels. This study examined the corrosion development in Sewers with high H2S concentrations. Fresh concrete coupons, manufactured according to sewer pipe standards, were exposed to corrosive conditions in a pilot-scale gravity sewer system with gaseous H2S at 1100 ± 100 ppm. The corrosion process was continuously monitored by measuring the surface pH, corrosion product composition, corrosion loss and the microbial community. The surface pH of concrete was reduced from 10.5 ± 0.3 to 3.1 ± 0.5 within 20 days and this coincided with a rapid corrosion rate of 3.5 ± 0.3 mm year −1. Microbial community analysis based on 16S rRNA gene sequencing indicated the absence of sulfide-oxidizing microorganisms in the corrosion layer. The chemical analysis of corrosion products supported the reaction of cement with sulfuric acid formed by the chemical oxidation of H2S. The rapid corrosion of concrete in the gravity pipe was confirmed to be caused by the chemical oxidation of hydrogen sulfide at high concentrations. This is in contrast to the conventional knowledge that is focused on microbially induced corrosion. This first-ever systematic investigation shows that chemically induced oxidation of H2S leads to the rapid corrosion of new concrete Sewers within a few weeks. These findings contribute novel understanding of in-sewer corrosion processes and hold profound implications for sewer operation and corrosion management.
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corrosion of reinforcing steel in concrete Sewers
Science of The Total Environment, 2019Co-Authors: Philip L Bond, Zhiguo Yuan, Xuan Li, Yarong Song, E M Wightman, Yimei Tian, Kevin S Jack, Huiyun Zhong, Guangming JiangAbstract:Hydrogen sulfide is a controlling factor for concrete corrosion in Sewers, although its impact on sewer rebar corrosion has not been investigated to date. This study determined the corrosion mechanism of rebar in Sewers by elucidating the roles of chloride ions, apart from the effects of hydrogen sulfide and biogenic sulfuric acid. The nature and distribution of rusts at the steel/concrete interface were delineated using the advanced mineral analytical techniques, including mineral liberation analysis and micro X-ray diffraction which is the first-ever use in such studies. The corrosion products were found to be mainly iron oxides or oxy-hydroxides. HS and biogenic sulfuric acid did not directly participate in the product formation of steel partly covered by concrete or directly exposed to sewer atmosphere. Instead, chloride ions played an important role in initiating steel corrosion in Sewers, supported by a thin chloride-enriched layer at the steel/rust interface. Away from the chloride-enriched layer, iron oxides accumulated on both sides of the mill-scale to form a corrosion layer and corrosion-filled paste respectively. The corrosion layer around rebar circumference was non-uniform and the rust thickness with respect to polar coordinates followed a Gaussian model. These findings support predictions of sewer service lifetime and developments of corrosion prevention strategies.
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stability of illicit drugs as biomarkers in Sewers from lab to reality
Environmental Science & Technology, 2017Co-Authors: Jiaying Li, Zhiguo Yuan, Phong K Thai, Jochen F Mueller, Guangming JiangAbstract:Systematic sampling and analysis of wastewater samples are increasingly adopted for estimating drug consumption in communities. An understanding of the in-sewer transportation and transformation of illicit drug biomarkers is critical for reducing the uncertainty of this evidence-based estimation method. In this study, biomarkers stability was investigated in lab-scale sewer reactors with typical sewer conditions. Kinetic models using the Bayesian statistics method were developed to simulate biomarkers transformation in reactors. Furthermore, a field-scale study was conducted in a real pressure sewer pipe with the systematical spiking and sampling of biomarkers and flow tracers. In-sewer degradation was observed for some spiked biomarkers over typical hydraulic retention time (i.e., a few hours). Results indicated that sewer biofilms prominently influenced biomarker stability with the retention time in wastewater. The fits between the measured and the simulated biomarkers transformation demonstrated that the lab-based model could be extended to estimate the changes of biomarkers in real Sewers. Results also suggested that the variabilities of biotransformation and analytical accuracy are the two major contributors to the overall estimation uncertainty. Built upon many previous lab-scale studies, this study is one critical step forward in realizing wastewater-based epidemiology by extending biomarker stability investigations from laboratory reactors to real Sewers.
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prediction of concrete corrosion in Sewers with hybrid gaussian processes regression model
RSC Advances, 2017Co-Authors: Yarong Song, Jurg Keller, Philip L Bond, Guangming JiangAbstract:Concrete corrosion is a major concern for sewer authorities due to the significantly shortened service life, which is governed by the corrosion rate and the corrosion initiation time. This paper proposes a hybrid Gaussian Processes Regression (GPR) model to approach the evolution of the corrosion rate and corrosion initiation time, thereby supporting the calculation of service life of Sewers. A major challenge in practice is the limited availability of reliable corrosion data obtained in well-defined sewer environments. To enhance the predictability of the hybrid GPR model, an interpolation technique was implemented to extend the limited dataset. The trained model was able to estimate the corrosion initiation time and corrosion rates very close to those measured in Australian Sewers.
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wastewater enhanced microbial corrosion of concrete Sewers
Environmental Science & Technology, 2016Co-Authors: Guangming Jiang, Jurg Keller, Mi Zhou, Tsz Ho Chiu, Philip L BondAbstract:Microbial corrosion of concrete in Sewers is known to be caused by hydrogen sulfide, although the role of wastewater in regulating the corrosion processes is poorly understood. Flooding and splashing of wastewater in Sewers periodically inoculates the concrete surface in sewer pipes. No study has systematically investigated the impacts of wastewater inoculation on the corrosion of concrete in Sewers. This study investigated the development of the microbial community, sulfide uptake activity, and the change of the concrete properties for coupons subjected to periodic wastewater inoculation. The concrete coupons were exposed to different levels of hydrogen sulfide under well-controlled conditions in laboratory-scale corrosion chambers simulating real Sewers. It was evident that the periodic inoculation induced higher corrosion losses of the concrete in comparison to noninoculated coupons. Instantaneous measurements such as surface pH did not reflect the cumulative corrosion losses caused by long-term microb...
Keshab Sharma - One of the best experts on this subject based on the ideXlab platform.
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methane emission from Sewers
Science of The Total Environment, 2015Co-Authors: Bingjie Ni, Keshab Sharma, Zhiguo YuanAbstract:Abstract Recent studies have shown that sewer systems produce and emit a significant amount of methane. Methanogens produce methane under anaerobic conditions in sewer biofilms and sediments, and the stratification of methanogens and sulfate-reducing bacteria may explain the simultaneous production of methane and sulfide in Sewers. No significant methane sinks or methanotrophic activities have been identified in Sewers to date. Therefore, most of the methane would be emitted at the interface between sewage and atmosphere in gravity Sewers, pumping stations, and inlets of wastewater treatment plants, although oxidation of methane in the aeration basin of a wastewater treatment plant has been reported recently. Online measurements have also revealed highly dynamic temporal and spatial variations in methane production caused by factors such as hydraulic retention time, area-to-volume ratio, temperature, and concentration of organic matter in sewage. Both mechanistic and empirical models have been proposed to predict methane production in Sewers. Due to the sensitivity of methanogens to environmental conditions, most of the chemicals effective in controlling sulfide in Sewers also suppress or diminish methane production. In this paper, we review the recent studies on methane emission from Sewers, including the production mechanisms, quantification, modeling, and mitigation.
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degradation of methanethiol in anaerobic Sewers and its correlation with methanogenic activities
Water Research, 2015Co-Authors: Shihu Hu, Keshab Sharma, Bingjie Ni, Zhiguo YuanAbstract:Abstract Methanethiol (MT) is considered one of the predominant odorants in sewer systems. Therefore, understanding MT transformation in Sewers is essential to sewer odor assessment and abatement. In this study, we investigated the degradation of MT in laboratory anaerobic Sewers. Experiments were carried out in seven anaerobic sewer reactors with biofilms at different stages of development. MT degradation was found to be strongly dependent on the methanogenic activity of sewer biofilms. The MT degradation rate accelerated with the increase of methanogenic activity of sewer biofilms, resulting in MT accumulation (i.e. net production) in sewer reactors with relatively low methanogenic activities, and MT removal in reactors with higher methanogenic activities. A Monod-type kinetic expression was developed to describe MT degradation kinetics in anaerobic Sewers, in which the maximum degradation rate was modeled as a function of the maximum methane production rate through a power function. It was also found that MT concentration had a linear relationship with acetate concentration, which may be used for preliminary assessment of MT presence in anaerobic Sewers.
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Corrosion and odor management in sewer systems
2015Co-Authors: Guangming Jiang, Jing Sun, Keshab Sharma, Zhiguo YuanAbstract:Sewers emit hydrogen sulfide and various volatile organic sulfur and carbon compounds, which require control and mitigation. In the last 5-10 years, extensive research was conducted to optimize existing sulfide abatement technologies based on newly developed in-depth understanding of the in-sewer processes. Recent advances have also led to low-cost novel solutions targeting sewer biofilms. Online control has been demonstrated to greatly reduce the chemical usage. Dynamic models for both the water, air and solid (concrete) phases have been developed and used for the planning and maintenance of sewer systems. Existing technologies primarily focused on 'hotspots' in Sewers. Future research should aim to achieve network-wide corrosion and emission control and management of Sewers as an integrated component of an urban water system.
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Sulfide and methane production in sewer sediments
Water Research, 2014Co-Authors: Bingjie Ni, Keshab Sharma, Ramon Ganigué, Ursula Werner, Zhiguo YuanAbstract:Recent studies have demonstrated significant sulfide and methane production by sewer biofilms, particularly in rising mains. Sewer sediments in gravity Sewers are also biologically active; however, their contribution to biological transformations in Sewers is poorly understood at present. In this study, sediments collected from a gravity sewer were cultivated in a laboratory reactor fed with real wastewater for more than one year to obtain intact sediments. Batch test results show significant sulfide production with an average rate of 9.20 +/- 0.39 g S/m(2).d from the sediments, which is significantly higher than the areal rate of sewer biofilms. In contrast, the average methane production rate is 1.56 +/- 0.14 g CH4/m(2).d at 20 degrees C, which is comparable to the areal rate of sewer biofilms. These results clearly show that the contributions of sewer sediments to sulfide and methane production cannot be ignored when evaluating sewer emissions. Microsensor and pore water measurements of sulfide, sulfate and methane in the sediments, microbial profiling along the depth of the sediments and mathematical modelling reveal that sulfide production takes place near the sediment surface due to the limited penetration of sulfate. In comparison, methane production occurs in a much deeper zone below the surface likely due to the better penetration of soluble organic carbon. Modelling results illustrate the dependency of sulfide and methane productions on the bulk sulfate and soluble organic carbon concentrations can be well described with half-order kinetics. (C) 2014 Elsevier Ltd. All rights reserved.
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effects of nitrate dosing on methanogenic activity in a sulfide producing sewer biofilm reactor
Water Research, 2013Co-Authors: Guangming Jiang, Keshab Sharma, Zhiguo YuanAbstract:Nitrate dosing is widely used by water industry to control hydrogen sulfide production in Sewers. This study assessed the impact of nitrate addition on methane generation by sewer biofilms using a lab-scale rising main sewer reactor. It was found that methanogenesis could coexist with denitrification and sulfate reduction in Sewers dosed with nitrate. However, methane production was substantially reduced by nitrate addition. Methanogenic rates remained below 10% of its baseline level, with 30 mg-N/L of nitrate dosing for each pump event. By calculating the substrate penetration depth in biofilms, it is suggested that methanogenesis may persist in deeper biofilms due to the limited penetration of nitrate and sulfate, and better penetration of soluble organic substrates. The control of methane and sulfide production was found to be determined by the nitrate penetration depth in biofilms and nitrate presence time in Sewers, respectively. The presence of nitrous oxide after nitrate addition was transient, with a negligible discharge of nitrous oxide from the sewer reactor due to its further reduction by denitrifiers after nitrate depletion.
Jurg Keller - One of the best experts on this subject based on the ideXlab platform.
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prediction of concrete corrosion in Sewers with hybrid gaussian processes regression model
RSC Advances, 2017Co-Authors: Yarong Song, Jurg Keller, Philip L Bond, Guangming JiangAbstract:Concrete corrosion is a major concern for sewer authorities due to the significantly shortened service life, which is governed by the corrosion rate and the corrosion initiation time. This paper proposes a hybrid Gaussian Processes Regression (GPR) model to approach the evolution of the corrosion rate and corrosion initiation time, thereby supporting the calculation of service life of Sewers. A major challenge in practice is the limited availability of reliable corrosion data obtained in well-defined sewer environments. To enhance the predictability of the hybrid GPR model, an interpolation technique was implemented to extend the limited dataset. The trained model was able to estimate the corrosion initiation time and corrosion rates very close to those measured in Australian Sewers.
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wastewater enhanced microbial corrosion of concrete Sewers
Environmental Science & Technology, 2016Co-Authors: Guangming Jiang, Jurg Keller, Mi Zhou, Tsz Ho Chiu, Philip L BondAbstract:Microbial corrosion of concrete in Sewers is known to be caused by hydrogen sulfide, although the role of wastewater in regulating the corrosion processes is poorly understood. Flooding and splashing of wastewater in Sewers periodically inoculates the concrete surface in sewer pipes. No study has systematically investigated the impacts of wastewater inoculation on the corrosion of concrete in Sewers. This study investigated the development of the microbial community, sulfide uptake activity, and the change of the concrete properties for coupons subjected to periodic wastewater inoculation. The concrete coupons were exposed to different levels of hydrogen sulfide under well-controlled conditions in laboratory-scale corrosion chambers simulating real Sewers. It was evident that the periodic inoculation induced higher corrosion losses of the concrete in comparison to noninoculated coupons. Instantaneous measurements such as surface pH did not reflect the cumulative corrosion losses caused by long-term microb...
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Predicting concrete corrosion of Sewers using artificial neural network
Water Research, 2016Co-Authors: Guangming Jiang, Philip L Bond, Jurg Keller, Zhiguo YuanAbstract:Corrosion is often a major failure mechanism for concrete Sewers and under such circumstances the sewer service life is largely determined by the progression of microbially induced concrete corrosion. The modelling of sewer processes has become possible due to the improved understanding of in-sewer transformation. Recent systematic studies about the correlation between the corrosion processes and sewer environment factors should be utilized to improve the prediction capability of service life by sewer models. This paper presents an artificial neural network (ANN)-based approach for modelling the concrete corrosion processes in Sewers. The approach included predicting the time for the corrosion to initiate and then predicting the corrosion rate after the initiation period. The ANN model was trained and validated with long-term (4.5 years) corrosion data obtained in laboratory corrosion chambers, and further verified with field measurements in real Sewers across Australia. The trained model estimated the corrosion initiation time and corrosion rates very close to those measured in Australian Sewers. The ANN model performed better than a multiple regression model also developed on the same dataset. Additionally, the ANN model can serve as a prediction framework for sewer service life, which can be progressively improved and expanded by including corrosion rates measured in different sewer conditions. Furthermore, the proposed methodology holds promise to facilitate the construction of analytical models associated with corrosion processes of concrete Sewers.
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score ct a new method for testing effectiveness of sulfide control chemicals used in sewer systems
Water Science and Technology, 2011Co-Authors: Jurg Keller, Keshab Sharma, Oriol Gutierrez, Gatut Sudarjanto, Zhiguo YuanAbstract:A new method for testing the effectiveness of chemical products for sulfide control in Sewers is reported. The method, called SCORe-CT (Sewer Corrosion and Odour Research – Chemical Testing), consists of two specially designed laboratory-scale systems that mimic sulfide production in real rising main Sewers, and a multi-phase and multi-facet testing protocol. The monitoring tools/methods include both routine chemical analysis of various sulfurous and carbonaceous compounds in liquid and their on-line monitoring using advanced sensors. Molecular methods and microelectrodes can also be employed to examine the microbial structure and activity of sewer biofilms. The SCORe-CT method is not proposed to replace field trials but to screen chemicals prior to their often costly trials/applications in field conditions. For effective chemicals the method helps to reveal the mechanisms involved, and assists with the design of optimal dosage strategies, which would significantly reduce application costs. In this paper, the method is explained in detail and demonstrated with several case studies.
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optimization of intermittent simultaneous dosage of nitrite and hydrochloric acid to control sulfide and methane productions in Sewers
Water Research, 2011Co-Authors: Guangming Jiang, Jurg Keller, Keshab Sharma, Oriol Gutierrez, Zhiguo YuanAbstract:Free nitrous acid (FNA) was previously demonstrated to be biocidal to anaerobic sewer biofilms. The intermittent dosing of FNA as a measure for controlling sulfide and methane productions in Sewers is investigated. The impact of three key operational parameters namely the dosing concentration, dosing duration and dosing interval on the suppression and subsequent recovery of sulfide and methane production was examined experimentally using lab-scale sewer reactors. FNA as low as 0.26 mg-N/L was able to suppress sulfide production after an exposure of 12 h. In comparison, 0.09 mg-N/L of FNA with 6-h exposure was adequate to restrain methanogenesis effectively. The recovery of sulfide production was well described by an exponential recovery equation. Model-based analysis revealed that 12-h dosage at an FNA concentration of 0.26 mg-N/L every 5 days can reduce the average sulfide production by >80%. Economic analysis showed that intermittent FNA dosage is potentially a cost-effective strategy for sulfide and methane control in Sewers.
Albert Guisasola - One of the best experts on this subject based on the ideXlab platform.
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sulfur transformation in rising main Sewers receiving nitrate dosage
Water Research, 2009Co-Authors: Guangming Jiang, Jurg Keller, Keshab Sharma, Albert Guisasola, Zhiguo YuanAbstract:The anoxic and anaerobic sulfur transformation pathways in a laboratory-scale sewer receiving nitrate were investigated. Four reactors in series were employed to imitate a rising main sewer. The nitrate-dosing strategy was effective in controlling sulfide, as confirmed by the long-term sulfide measurements. Anoxic sulfide oxidation occurred in two sequential steps, namely the oxidation of sulfide to elemental sulfur (S(0)) and the oxidation of S(0) to sulfate (SO(4)(2-)). The second oxidation step, which primarily occurred when the first step was completed, had a rate that is approximately 15% of the first step. When nitrate was depleted, sulfate and elemental sulfur were reduced simultaneously to sulfide. Sulfate reduction had a substantially higher rate (5 times) than S(0) reduction. The relatively slower S(0) oxidation and reduction rates implied that S(0) was an important intermediate during anoxic and anaerobic sulfur transformation. Electron microscopic studies indicated the presence of elemental sulfur, which was at a significant level of 9.9 and 16.7 mg-S/g-biomass in nitrate-free and nitrate-exposed sewer biofilms, respectively. A conceptual sulfur transformation model was established to characterize predominant sulfur transformations in rising main Sewers receiving nitrate dosage. The findings are pertinent for optimizing nitrate dosing to control sulfide in rising main Sewers.
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development of a model for assessing methane formation in rising main Sewers
Water Research, 2009Co-Authors: Jurg Keller, Keshab Sharma, Albert Guisasola, Zhiguo YuanAbstract:Significant methane formation in Sewers has been reported recently, which may contribute significantly to the overall greenhouse gas emission from wastewater systems. The understanding of the biological conversions occurring in Sewers, particularly the competition between methanogenic and sulfate-reducing populations for electron donors, is an essential step for minimising methane emissions from Sewers. This work proposes an extension to the current state-of-the-art models characterising biological and physicochemical processes in Sewers. This extended model includes the competitive interactions of sulfate-reducing bacteria and methanogenic archaea in Sewers for various substrates available. The most relevant parameters of the model were calibrated with lab-scale experimental data. The calibrated model described field data reasonably well. The model was then used to investigate the effect of several key sewer design and operational parameters on methane formation. The simulation results showed that methane production was highly correlated with the hydraulic residence time (HRT) and pipe area to volume (A/V) ratio showing higher methane concentrations at a long HRT or a larger A/V ratio.
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Methane formation in sewer systems
Water Research, 2008Co-Authors: Albert Guisasola, Jurg Keller, David De Haas, Zhiguo YuanAbstract:Methane formation and emission in sewer systems has not received as much attention as hydrogen sulphide formation. Through field measurements from two rising mains, with an average sewage temperature of 28.4 and 26.6 °C, respectively, at the time of sampling, this study shows that a significant amount of methane can be produced in sewer systems, and that this production is positively correlated with the hydraulic retention time of wastewater in these systems. The experimental results from a laboratory-scale sewer system fed with real sewage with a temperature of approximately 21 °C confirmed these field observations and further revealed that methanogenesis and sulphate reduction occur simultaneously in Sewers, with methane production contributing considerably more to the loss of soluble COD in Sewers than sulphate reduction. The production of methane in Sewers at levels revealed by this study is a serious environmental concern as it potentially results in greenhouse emissions that is comparable to that caused by the energy consumption for the treatment of the same wastewater. Further, methane production in Sewers influences sulphide production and its management due to the competition between methanogens and sulphate-reducing bacteria for potentially the same electron donors. The potential interactions between sulphate-reducing and methanogenic bacteria in sewer networks are discussed.
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Methane formation in sewer systems.
Water research, 2007Co-Authors: Albert Guisasola, Jurg Keller, David De Haas, Zhiguo YuanAbstract:Methane formation and emission in sewer systems has not received as much attention as hydrogen sulphide formation. Through field measurements from two rising mains, with an average sewage temperature of 28.4 and 26.6 degrees C, respectively, at the time of sampling, this study shows that a significant amount of methane can be produced in sewer systems, and that this production is positively correlated with the hydraulic retention time of wastewater in these systems. The experimental results from a laboratory-scale sewer system fed with real sewage with a temperature of approximately 21 degrees C confirmed these field observations and further revealed that methanogenesis and sulphate reduction occur simultaneously in Sewers, with methane production contributing considerably more to the loss of soluble COD in Sewers than sulphate reduction. The production of methane in Sewers at levels revealed by this study is a serious environmental concern as it potentially results in greenhouse emissions that is comparable to that caused by the energy consumption for the treatment of the same wastewater. Further, methane production in Sewers influences sulphide production and its management due to the competition between methanogens and sulphate-reducing bacteria for potentially the same electron donors. The potential interactions between sulphate-reducing and methanogenic bacteria in sewer networks are discussed.
