Simplified residence time prediction models for constructed wetland water recycling systems
TL;DR: In this article, the authors developed a methodology for simplifying the prediction of residence time as a function of the flow rate and physical shape of these contaminant removal systems, and performed a series of two-dimensional simulation studies on surface flow through farmland-channel-wetland wetland of different shapes.
Abstract: The experimental farmland–channel–wetland systems (FCWS) in Guilin, China have been recently designed based on wetland water recycling systems in Midwest USA. The present article develops a methodology for simplifying the prediction of residence time as a function of the flow rate and physical shape of these contaminant removal systems. A series of two-dimensional simulation studies on surface flow through FCWS wetland of different shapes are performed. Parameters influencing hydraulic characteristics such as empirical values of inlet and outlet flow conditions, and wetland shapes are utilized as inputs to the study. Roughness coefficient was assumed to be constant across the different wetland designs discussed in this article. The mean velocity values within the wetland decreases with increase in ratio of variant inlet widths and wetland inflow rates. The results from the simulation are used as inputs for performing a multivariate multiparameter regression algorithm. This framework models the re...
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01 Jan 2015
TL;DR: The Green Campus Initiative (GCI) as mentioned in this paper is a residential school in the developing part of the world that transforms itself into a model, self sufficient sustainable campus through constant motivation sustained by the result of their positive actions towards the sustainable development of the campus.
Abstract: For several decades now, many institutions are doing their best to strive towards a sustainable future through education, research and out reach. According to UNESCO, the goal of education is to make people wiser, more knowledgeable, better informed, ethical, responsible, critical and capable of continuing to learn. Education is also the means to disseminate knowledge and develop skills, in order to not only bring about desired changes in behaviours, values, lifestyles but also to promote public support towards the continuing and fundamental changes that will be required if humanity is to alter its course towards sustainability. To meet ever growing global environmental challenges, every school, colleges and universities must prepare today’s students in all disciplines, and it cannot be implemented/achieved without students’ involvement. This article presents a case of a residential school in the developing part of the world that transforms itself into a model, self sufficient sustainable campus through constant motivation sustained by the result of their positive actions towards the sustainable development of the campus. While the green campus initiatives are more likely to focus solely on ecological issues (downplaying social and economic issues), this initiative revolves around the continually evolving and adaptive sustainability model that depends on the integrated knowledge from all the stakeholders in the school (lowest to the highest echelons) by bringing all of them to work as one single group with a vision on school sustainability. Emphasizing more on this, the Green Campus Initiative (GCI) is successfully evolved and implemented within 100 working days. This pilot scale Green Campus Initiative was evolved, based on the research done at Pondicherry University, and implemented as the student centered outreach programme, encompassing water-food-energy-ecosystems nexus, with an integrated systems approach. The various measures undertaken by the campus are discussed in brief and how they helped transform the campus into a Green Campus. The lessons learnt will be very useful for replication of similar experiments elsewhere in India or in any other developing country.
3 citations
TL;DR: In this article, the effects of substrate, configuration, hydraulic retention time (HRT) and temperature on nitrogen removal were evaluated in five pilot-scale horizontal subsurface-flow-constructed wetlands (CWs).
Abstract: The water quality of Yapu River flowing into Lake Taihu was monitored for one year and the effects of substrate, configuration, hydraulic retention time (HRT) and temperature on nitrogen removal were evaluated in five pilot-scale horizontal subsurface-flow-constructed wetlands (CWs). Additionally, the impact of adding external carbon on nitrogen removal was investigated. Yapu River was shown to be eutrophic, with a low C/N ratio (COD/TN ≤ 1.5) and the main pollutant was total nitrogen (TN ≥ 2 mg/L). CWs with substrates of combined gravel-zeolite and gravel-ceramsite showed higher ammonium nitrogen (-N) and chemical oxygen demand (COD) removal efficiencies than the CWs with gravel substrates. Trapezoidal CWs showed improved dissolved oxygen in the front when compared with the rectangular CWs, enabling complete nitrification. A longer HRT (four days) improved the removal efficiencies of organics, nitrogen, and phosphorus. CWs performed better during the warm period. Moreover, addition of 400 g catta...
3 citations
TL;DR: In this paper, a numerical visualization study of wetlands is performed using finite volume methods to evaluate the treatment efficiency of the wetlands in terms of the residence time distribution function, and the variation in the tracer concentration is studied as a function of recirculation volumes, flow rates, time and depth of the wetland for each of the different wetland shapes.
Abstract: A numerical visualization study of wetlands is detailed in this article using finite volume methods. The aim of this study is to model treatment efficiency of the wetlands in terms of the residence time distribution function. Shape and depth of wetlands are critically analysed to find the optimal flow requirement for effective treatment. Laminar three-dimensional flow dynamics is used to simulate the slow water flows that occur in treatment wetlands. Slow inlet flows are assumed. Dye is used as the tracer to characterize the hydrodynamics within the wetlands. Three different geometrical configurations, namely square, square with two islands, and triangle, respectively, are simulated. The variation in the tracer concentration is studied as a function of recirculation volumes, flow rates, time and depth of the wetland for each of the wetland shapes. The change in the variation of tracer concentration at inlet and exit helps to assess treatment effectiveness. In another case, glycerine is used to sim...
2 citations
Cites methods from "Simplified residence time predictio..."
...[10] performed simulations on various two-dimensional shapes of these FCWS wetlands and modelled an approach in which residence time can be written as a function of shape, mass inflow and inlet geometry [10,11]....
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TL;DR: The hydraulic performance of the basin was studied by combining the results of a stimulus–response tracer test with the monitoring of the tracer (fluoride) concentration throughout the basin at different times, and three of the most popular formulae developed for the calculation of the axial dispersion coefficient provided results spreading over three orders of magnitude, thus showing their limitations.
Abstract: The water treatment plant (WTP) of the city of Torino (NW Italy), which treats about 40 · 106 m3/year of raw water from Po river, has a 15-ha basin used as a lagooning pre-treatment facility. Since the efficiency of the lagooning process in the removal of pollutants from raw water depends on the internal hydrodynamics of the basin, the hydraulic performance of the basin was studied by combining the results of a stimulus–response tracer test with the monitoring of the tracer (fluoride) concentration throughout the basin at different times. The outcomes of the test demonstrated that the system was efficiently mixed and could be assimilated to a continuous stirred reactor presenting no flow anomalies, with an actual mean residence time (RT) of 12.7 days, compared with a nominal RT of 18 days. This assured that dissolved contaminants (such as fluoride) coming from the river were efficiently diluted before entering the WTP. The axial dispersion coefficient calculated from the RT distribution was approximately 47,300 m2/day. Three of the most popular formulae developed for the calculation of the axial dispersion coefficient provided results spreading over three orders of magnitude, thus showing their limitations. Finally, because of the width extent of the basin and the characteristics of its inflow, the 1-D advection–dispersion model failed in predicting the tracer concentration values in time at the outlet channel. On the contrary, the analytical solution of the 2-D advection–dispersion model proved to be suitable to fit the tracer concentration data over time at the outlet channel but it failed in describing the tracer distribution throughout the basin on the monitoring dates.
2 citations
Cites background or methods from "Simplified residence time predictio..."
...…simulated the flow patterns into a basin with computational fluid dynamics (CFD) software with the aim of obtaining the two parameters which describe the hydraulic characteristics of the basin, that is the actual RT and the dispersion number (Wei et al. 2013; Barrio et al. 2015; Singh et al. 2015)....
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...Several authors have simulated the flow patterns into a basin with computational fluid dynamics (CFD) software with the aim of obtaining the two parameters which describe the hydraulic characteristics of the basin, that is the actual RT and the dispersion number (Wei et al. 2013; Barrio et al. 2015; Singh et al. 2015)....
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01 Jan 2013
TL;DR: In this paper, the authors present a table of acknowledgements and acknowledgements for Vita and Table of Table of Contents for Table of Terms and References, including the table of references.
Abstract: .............................................................................................................................. ii Acknowledgements ............................................................................................................. v Vita ..................................................................................................................................... vi Table of
2 citations
Cites background or methods from "Simplified residence time predictio..."
...For example, Holland et al.(2004) found no effect when varying the flow rate whereas a simulation by Wei et al. (2013) reported an effect....
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...It is likely that distributed outlets will have an effect as several suggest (Persson et al., 1999; Su et al., 2009; Wei et al., 2013)....
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...Residence time was influenced more by the inlet dimensions than by the flow rate (Wei et al., 2013)....
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...Several studies consider more than one parameter, but only Min and Wise (2009) and Wei et al. (2013) attempt to determine the relative influence of a given parameter with respect to another....
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...Wei et al. (2013) use a computational fluid dynamics model to simulate the residence time function of an actual wetland and to evaluate proposed modifications to its shape....
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References
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TL;DR: In this paper, two new two-equation eddy-viscosity turbulence models are presented, which combine different elements of existing models that are considered superior to their alternatives.
Abstract: Two new two-equation eddy-viscosity turbulence models will be presented. They combine different elements of existing models that are considered superior to their alternatives. The first model, referred to as the baseline (BSL) model, utilizes the original k-ω model of Wilcox in the inner region of the boundary layer and switches to the standard k-e model in the outer region and in free shear flows. It has a performance similar to the Wilcox model, but avoids that model's strong freestream sensitivity
15,459 citations
"Simplified residence time predictio..." refers methods in this paper
...The k x model is used to simulate flow [24]....
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01 Jan 1959
TL;DR: This book discusses the development of Uniform Flow and its applications, as well as the theory and analysis of open channel flow, and the design of channels for Uniform Flow.
Abstract: Chapter 1: Basic PrinciplesChapter 2: Open-Channel Flow and its ClassificationsChapter 3: Open Channels and Their PropertiesChapter 4: Energy and Momentum PrinciplesChapter 5: Critical Flow: Its Computation and ApplicationsChapter 6: Uniform FlowChapter 7: Development of Uniform Flow and Its FormulasChapter 8: Computation of Uniform FlowChapter 9: Design of Channels for Uniform FlowChapter 10: Theoretical Concepts of Boundary LayerChapter 11: Surface RoughnessChapter 12: Velocity Distribution and Instability of Uniform FlowChapter 13: Gradually Varied FlowChapter 14: Theory and AnalysisChapter 15: Methods of ComputationChapter 16: Practical ProblemsChapter 17: Spatially Varied FlowChapter 18: Rapidly Varied FlowChapter 19: Flow Over SpillwaysChapter 20: Hydraulic Jump and its Use as Energy DissipatorChapter 21: Flow in Channels of Non-Linear AlignmentChapter 22: Flow Through Nonprismatic Channel SectionsChapter 23: Unsteady FlowChapter 24: Gradually Varied Unsteady FlowChapter 25: Rapidly Varied Unsteady Flow Flood RoutingAppendices
5,013 citations
Book•
12 Feb 2001TL;DR: In this article, the basic principles of specific energy, momentum, uniform flow, and uniform flow in alluvial channels are discussed, as well as simplified methods of flow routing.
Abstract: Chapter 1 Basic Principles Chapter 2 Specific Energy Chapter 3 Momentum Chapter 4 Uniform Flow Chapter 5 Gradually Varied Flow Chapter 6 Hydraulic Structures Chapter 7 Governing Equations of Unsteady Flow Chapter 8 Numerical Solution of the Unsteady Flow Equations Chapter 9 Simplified Methods of Flow Routing Chapter 10 Flow in Alluvial Channels
2,397 citations
"Simplified residence time predictio..." refers background in this paper
...the wetland wall by different plant species were studied by Chow [22]....
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...D ow nl oa de d by [ N an ya ng T ec hn ol og ic al U ni ve rs ity ] at 1 9: 00 0 2 Ju ly 2 01 3 the wetland wall by different plant species were studied by Chow [22]....
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TL;DR: A survey of the available literature on energy intensity for water use in the municipal and agricultural sectors and separating the process into several stages is presented in this article, where water supply, water treatment, residential end use, wastewater treatment, and agriculture end use are considered.
Abstract: Energy is consumed at every stage of the cycle of water supply, treatment, use and disposal. The intensity of energy consumption (kW h/m 3 ) depends upon the specific technologies applied at each stage of the water cycle. For some technologies, the intensity may be relatively low, whereas the intensity of other technologies is substantially greater. This report surveys the available literature on energy intensity for water use in the municipal and agricultural sectors and separates the process into several stages. Water supply, water treatment, residential end use, wastewater treatment, and agriculture end use are considered. Representative values of the energy consumed per unit water are given for a broad range of processes. Water extraction and pumping from ground and surface sources is considered. The energy intensity of treatment required for different types of water source is found to vary widely between the extremes of relatively fresh surface waters, which use energy mainly in pumping, and seawater, which requires desalination. Energy usage for different methods of irrigation including pressurized as well as surface irrigation is studied. The energy intensity of residential end use is very high relative to other parts of the water supply cycle. Processes such as heating water, washing clothes and dishes, and cooking are briefly studied within the water end-use stage. Hot water usage is responsible for making end use the most energy intensive stage of the water cycle. Hot water use in different buildings is briefly reviewed. Wastewater treated with various processes is considered, and the energy intensity is found to be highest when advanced wastewater treatment methods are applied. Energy consumption in the agricultural sector, which is principally related to irrigation pumping, is generally of lower energy intensity than for the municipal treatment or end use.
490 citations
TL;DR: In this paper, a new measure for hydraulic efficiency that combines existing measures of flow uniformity and effective volume is proposed to assess the effects of different pond and wetland shapes, locations of inlet and outlet, botanical layouts and basin morphology on the flow hydrodynamics.
384 citations