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Water, Volume 7, Issue 3 (March 2015) , Pages 836-1323

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Open AccessArticle
Effect of Disc Filtration with and without Addition of Flocculent on Nano- and Micro-Particles and Their Associated Polycyclic Aromatic Hydrocarbons in Stormwater
Water 2015, 7(3), 1306-1323; https://doi.org/10.3390/w7031306 - 20 Mar 2015
Cited by 6 | Viewed by 2914
Abstract
Many municipalities in Denmark and around Europe currently work towards separating stormwater and sewage. In existing urban areas this may imply disconnecting stormwater from the old combined sewer systems suffering from hydraulic overloading and discharging directly to nearby surface waters. Stormwater runoff may, [...] Read more.
Many municipalities in Denmark and around Europe currently work towards separating stormwater and sewage. In existing urban areas this may imply disconnecting stormwater from the old combined sewer systems suffering from hydraulic overloading and discharging directly to nearby surface waters. Stormwater runoff may, however, be heavily polluted and Best Available Technologies (BAT) are therefore needed to treat the stormwater before discharge. The aim here was to determine the sizes of particles found in stormwater from roads and to evaluate the use of a cationic organic flocculant to increase the size of the particles and thereby increase the removal efficiency of a 10 µm woven polyester disc filter. The samples were collected in connection with a project testing a pilot scale disc filter for treating stormwater runoff. The micro-sized particles were found to be mainly below 10 µm (6.9–19 µm) and nano-sized particles were also observed (ca. 76–228 nm). The flocculent increased the observed particle micrometer sizes by 46% and the removal of particle-associate Polycyclic Aromatic Hydrocarbons (PAHs) was confirmed. The majority of the particles were, however, still below 10 µm after addition of flocculant, which shows that application of flocculants with the woven disc filter technology for stormwater treatment needs further refinement. Full article
(This article belongs to the Special Issue Water Quality Control and Management)
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Open AccessArticle
Behavior of a Fully-Looped Drainage Network and the Corresponding Dendritic Networks
Water 2015, 7(3), 1291-1305; https://doi.org/10.3390/w7031291 - 20 Mar 2015
Cited by 3 | Viewed by 2143
Abstract
Hydraulic and hydrologic analysis in urban catchments is typically accompanied by a number of uncertainties, such as a lack of required information for modeling purposes or complex loops inside a drainage network. In this article, Gibbs’ stochastic network model is utilized in order [...] Read more.
Hydraulic and hydrologic analysis in urban catchments is typically accompanied by a number of uncertainties, such as a lack of required information for modeling purposes or complex loops inside a drainage network. In this article, Gibbs’ stochastic network model is utilized in order to achieve a dendritic network that corresponds to a fully looped network in terms of the peak of the runoff hydrograph at the outlet. A synthetic catchment with a drainage network composed of 8 × 8 grids is introduced to investigate the behavior of a fully looped network for a given rainfall event using the Storm Water Management Model. Dendritic networks are generated from the Gibbsian model for a given value of the parameter, β. The results showed that the shape of the hydrograph and the peak flow of a fully looped network are heavily dependent on the catchment slope. Moreover, the results showed that it is possible to find the corresponding dendritic networks generated by the Gibbsian model that match the fully looped network depending on the catchment slope in terms of peak flows. The results of this study imply the potential improvement of drainage network analysis providing a relationship between the catchment slope of a fully looped network and the corresponding dendritic network generated by the Gibbsian model. Full article
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Open AccessArticle
Impact of Population Growth and Climate Change on the Freshwater Resources of Lamu Island, Kenya
Water 2015, 7(3), 1264-1290; https://doi.org/10.3390/w7031264 - 18 Mar 2015
Cited by 6 | Viewed by 4751
Abstract
Demand for freshwater is rising with factors, such as population growth, land use change and climate variations, rendering water availability in the future uncertain. Groundwater resources are being increasingly exploited to meet this growing demand. The aim of this study is to identify [...] Read more.
Demand for freshwater is rising with factors, such as population growth, land use change and climate variations, rendering water availability in the future uncertain. Groundwater resources are being increasingly exploited to meet this growing demand. The aim of this study is to identify the influence of population growth induced by land use change and climate change on the future state of freshwater resources of Lamu Island in Kenya where a major port facility is under construction. The results of this study show that the “no industrial development” population scenario (assuming the port was not constructed) would be expected to reach ~50,000 people by 2050, while the projected population upon completion is expected to reach 1.25 million in the same year when the Lamu Port-South Sudan-Ethiopia Transport Corridor Program (LAPSSET) port reaches its full cargo-handling capacity. The groundwater abstraction in 2009 was 0.06 m3 daily per capita, while the demand is expected to raise to 0.1 m3 by 2050 according to the “LAPSSET development” projection. The modelling results show that the Shela aquifer in Lamu, which is the main source of water on the island, will not experience stress by 2065 for the “no industrial development” population scenario, whereas for the “LAPSSET development projection” population scenario, it will occur sooner (between 2020 and 2028). The modelling results show that the Representative Concentration Pathways (RCP) climate change scenarios will have a smaller impact on the effective water volume reserves than Special Report on Emissions Scenarios (SRES) for the “no industrial development”, while the impact is expected to be similar for the “LAPSSET development”, suggesting that population growth exacerbated by land use change will be a more significant driving force than climate change in affecting freshwater availability. Full article
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Open AccessArticle
Robust Parameter Estimation Framework of a Rainfall-Runoff Model Using Pareto Optimum and Minimax Regret Approach
Water 2015, 7(3), 1246-1263; https://doi.org/10.3390/w7031246 - 18 Mar 2015
Cited by 6 | Viewed by 2175
Abstract
This study developed a robust parameter set (ROPS) selection framework for a rainfall-runoff model that considers multi-events using the Pareto optimum and minimax regret approach (MRA). The calibrated parameter sets based on the Nash-Sutcliffe coefficient (NSE) for two events were derived using a [...] Read more.
This study developed a robust parameter set (ROPS) selection framework for a rainfall-runoff model that considers multi-events using the Pareto optimum and minimax regret approach (MRA). The calibrated parameter sets based on the Nash-Sutcliffe coefficient (NSE) for two events were derived using a genetic algorithm. We generated 41 combinations for weighting values between two events for the multi-event objective function and derived 41 Pareto optimum points that were considered as the ROPS candidates. Then, two different approaches for parameter selection were proposed to determine the ROPS among the candidates: one uses NSE only and the other uses four performance measures (NSE, peak flow error, root mean square error and percentage of bias). In the NSE-only method, five events, including two events from the calibration set and three events from the evaluation set, were used, and the ROPS was selected based on the regrets of both the calibration and the evaluation sets. In the multiple (i.e., four) performance measure method, only three events from the evaluation set were used and the ROPS was determined based on the regrets of twelve different cases, including three events with four measures. As a result, while single- and multi-event optimizations produced satisfying results for the calibration events, the optimized parameters from the single-event calibration do not perform well for another event, even one with the same criteria, such as NSE. The results of this study suggest that the optimized parameter set from the well-weighted objective function can successfully simulate not only hydrographs in general but also others, such as peak flow. In addition, the ROPS can be selected by considering the multiple performance measures of multiple validation events, as well as the NSE only of multiple calibration and validation events. Note that the study provides a framework that could be performed reasonably well with a limited number of events. While the computational resources might not be a limiting factor these days, it is still valuable to have such a tool for several reasons: one could utilize it for an operational decision making support tool, as the full searches for an optimal set of parameters might not be performed in the operational facility. It could also be used in a situation where one has a limited number of good-quality observational data for some reason. Full article
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Open AccessArticle
Comparison of the Spatio-Temporal Variability of Annual Minimum Daily Extreme Flow Characteristics as a Function of Land Use and Dam Management Mode in Quebec, Canada
Water 2015, 7(3), 1232-1245; https://doi.org/10.3390/w7031232 - 18 Mar 2015
Cited by 3 | Viewed by 2053
Abstract
This study presents a comparison of the spatio-temporal variability of characteristics (magnitude, duration and timing) of annual minimum daily extreme flows (AMEF) as a function of land use and the mode of management of dams. Streamflow measured at stations not affected by dams [...] Read more.
This study presents a comparison of the spatio-temporal variability of characteristics (magnitude, duration and timing) of annual minimum daily extreme flows (AMEF) as a function of land use and the mode of management of dams. Streamflow measured at stations not affected by dams at Joliette, along the L’Assomption River (agricultural watershed, 1340 km2), and at Saint-Michel-des-Saints, on the Matawin River (forested watershed, 1390 km2) on one hand, and downstream from the Rawdon dam (regulated natural-type management mode), on the Ouareau River (1260 km2), which is the main tributary of the L’Assomption River, and from the Matawin dam (inverted-type management mode), on the Matawin River (4070 km2), on the other hand, were compared over the period from 1930 to 2010. As far as the spatial variability of natural rivers is concerned, the magnitude and duration of AMEF are higher in the forested watershed than in the agricultural watershed. In regulated rivers, AMEF magnitude is higher downstream from the dam characterized by a natural-type management mode than downstream from the dam characterized by inversion-type management. However, downstream from the latter, AMEF occur much more frequently and very early in the year. As for temporal variability, the Lombard method did not reveal any influence of land use differences on the stationarity of series of AMEF characteristics. In contrast, differences in dam management mode result in occurrences of AMEF downstream from the inversion-type dam progressively earlier in the year. The duration and timing of AMEF are not correlated with the same climate variables, be it in natural rivers or downstream from dams. Full article
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Open AccessArticle
Home Water Treatment Habits and Effectiveness in a Rural Arizona Community
Water 2015, 7(3), 1217-1231; https://doi.org/10.3390/w7031217 - 18 Mar 2015
Cited by 13 | Viewed by 2798
Abstract
Drinking water quality in the United States (US) is among the safest in the world. However, many residents, often in rural areas, rely on unregulated private wells or small municipal utilities for water needs. These utilities may violate the Safe Drinking Water Act [...] Read more.
Drinking water quality in the United States (US) is among the safest in the world. However, many residents, often in rural areas, rely on unregulated private wells or small municipal utilities for water needs. These utilities may violate the Safe Drinking Water Act contaminant guidelines, often because they lack the required financial resources. Residents may use alternative water sources or install a home water treatment system. Despite increased home water treatment adoption, few studies have examined their use and effectiveness in the US. Our study addresses this knowledge gap by examining home water treatment in a rural Arizona community. Water samples were analyzed for metal(loid)s, and home treatment and demographic data were recorded in 31 homes. Approximately 42% of homes treated their water. Independent of source water quality, residents with higher income (Odds Ratio [OR] = 1.25; 95% Confidence Interval [CI] (1.00–1.64)) and education levels (OR = 1.49; 95%CI (1.12–2.12)) were more likely to treat their water. Some contaminant concentrations were effectively reduced with treatment, while some were not. We conclude that increased educational outreach on contaminant testing and treatment, especially to rural areas with endemic water contamination, would result in a greater public health impact. Full article
(This article belongs to the Special Issue Water Treatment and Human Health)
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Open AccessArticle
Evaluation of an Ultrafiltration-Based Procedure for Simultaneous Recovery of Diverse Microbes in Source Waters
Water 2015, 7(3), 1202-1216; https://doi.org/10.3390/w7031202 - 18 Mar 2015
Cited by 13 | Viewed by 2284
Abstract
In this study, hollow-fiber ultrafiltration (UF) was assessed for recovery of Escherichia coli, Clostridium perfringens spores, Cryptosporidium parvum oocysts, echovirus 1, and bacteriophages MS2 and ΦX174 from ground and surface waters. Microbes were seeded into twenty-two 50-L water samples that were collected [...] Read more.
In this study, hollow-fiber ultrafiltration (UF) was assessed for recovery of Escherichia coli, Clostridium perfringens spores, Cryptosporidium parvum oocysts, echovirus 1, and bacteriophages MS2 and ΦX174 from ground and surface waters. Microbes were seeded into twenty-two 50-L water samples that were collected from the Southeastern United States and concentrated to ~500 mL by UF. Secondary concentration was performed for C. parvum by centrifugation followed by immunomagnetic separation. Secondary concentration for viruses was performed using centrifugal ultrafilters or polyethylene glycol precipitation. Nine water quality parameters were measured in each water sample to determine whether water quality data correlated with UF and secondary concentration recovery efficiencies. Average UF recovery efficiencies were 66%–95% for the six enteric microbes. Average recovery efficiencies for the secondary concentration methods were 35%–95% for C. parvum and the viruses. Overall, measured water quality parameters were not significantly associated with UF recovery efficiencies. However, recovery of ΦX174 was negatively correlated with turbidity. The recovery data demonstrate that UF can be an effective method for concentrating diverse microbes from ground and surface waters. This study highlights the utility of tangential-flow hollow fiber ultrafiltration for recovery of bacteria, viruses, and parasites from large volume environmental water samples. Full article
(This article belongs to the Special Issue Water Quality Control and Management)
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Open AccessArticle
On the Modeling of Bank Storage in a Groundwater Model: The April, 1983, Flood Event in the Neuwieder Becken (Middle Rhine)
Water 2015, 7(3), 1173-1201; https://doi.org/10.3390/w7031173 - 17 Mar 2015
Cited by 2 | Viewed by 2046
Abstract
For predictive numerical simulations of subsurface floods (groundwater head rise due to high water in a contiguous river), it is important to know how to represent the bank storage process in a numerical groundwater model. Whilst leakage approaches are frequently used for modeling [...] Read more.
For predictive numerical simulations of subsurface floods (groundwater head rise due to high water in a contiguous river), it is important to know how to represent the bank storage process in a numerical groundwater model. Whilst leakage approaches are frequently used for modeling bank storage, another option is the application of a head boundary condition. In order to get a better understanding of the bank storage process, we analyze the bank storage event in the Neuwieder Becken (Middle Rhine) in April 1983, which has been reported by Ubell (1987). We found the leakage function to be nonlinear and hysteretic. The evaluation of different model variants for Ubell’s bank storage event shows that both a head boundary condition and a leakage boundary condition are appropriate modeling approaches. For practical reasons, the leakage boundary condition is preferred. A linear leakage function represents the bank storage process for the analyzed event sufficiently. A hysteretic course of the leakage function can be achieved in a three-dimensional groundwater model by layering the hydraulic soil properties in the vicinity of the bank. Full article
(This article belongs to the Special Issue Surface Water Groundwater Interactions: From Theory to Practice)
Open AccessArticle
Full-Scale Implementation of a Vertical Membrane Bioreactor for Simultaneous Removal of Organic Matter and Nutrients from Municipal Wastewater
Water 2015, 7(3), 1164-1172; https://doi.org/10.3390/w7031164 - 17 Mar 2015
Cited by 5 | Viewed by 2612
Abstract
In nutrient-sensitive estuaries, wastewater treatment plants (WWTPs) are required to implement more advanced treatment methods in order to meet increasingly stringent effluent guidelines for organic matter and nutrients. To comply with current and anticipated water quality regulations and to reduce the volume of [...] Read more.
In nutrient-sensitive estuaries, wastewater treatment plants (WWTPs) are required to implement more advanced treatment methods in order to meet increasingly stringent effluent guidelines for organic matter and nutrients. To comply with current and anticipated water quality regulations and to reduce the volume of produced sludge, we have successfully developed a vertical membrane bioreactor (VMBR) that is composed of anoxic (lower layer) and oxic (upper layer) zones in one reactor. Since 2009, the VMBR has been commercialized (Q = 1100–16,000 m3/d) under the trade-name of DMBRTM for recycling of municipal wastewater in South Korea. In this study, we explore the performance and stability of the full-scale systems. As a result, it was found that the DMBRTM systems showed excellent removal efficiencies of organic substances, suspended solids (SS) and Escherichia coli (E. coli). Moreover, average removal efficiencies of total nitrogen (TN) and total phosphorus (TP) by the DMBRTM systems were found to be 79% and 90% at 18 °C, 8.3 h HRT and 41 d SRT. Moreover, transmembrane pressure (TMP) was maintained below 40 kPa at a flux of 18 L/m2/h (LMH) more than 300 days. Average specific energy consumption of the full-scale DMBRTM systems was found to be 0.94 kWh/m3. Full article
(This article belongs to the Special Issue Wastewater Treatment and Reuse)
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Open AccessArticle
The Effect of the Hydraulic Retention Time on the Performance of an Ecological Wastewater Treatment System: An Anaerobic Filter with a Constructed Wetland
Water 2015, 7(3), 1149-1163; https://doi.org/10.3390/w7031149 - 17 Mar 2015
Cited by 15 | Viewed by 3012
Abstract
This work assesses the performance of a municipal pilot wastewater treatment system employing an up-flow anaerobic filter (UAF) followed by a horizontal subsurface constructed wetland (HSSCW). This pilot scale demonstration project was implemented in a zone with subtropical climate in order to protect [...] Read more.
This work assesses the performance of a municipal pilot wastewater treatment system employing an up-flow anaerobic filter (UAF) followed by a horizontal subsurface constructed wetland (HSSCW). This pilot scale demonstration project was implemented in a zone with subtropical climate in order to protect Lake Chapala from wastewater loads that are discharged by small communities in the Lake’s vicinity. The filters were filled with tezontle as the media for biofilm support and the HSSCW was planted with two ornamental plants species, Canna hybrids and Strelitzia reginae. The experiment evaluated three hydraulic retention times (HRT) of 18, 28 and 38 h in the UAF, which corresponds to two, three and four days in HSSCW over 66 weeks. The mean efficiencies found for the complete system were 80% and 90% of BOD, 80% and 86% of COD, 30% and 33% of Ntot and between 24% and 44% of Ptot. It was possible to remove almost 80% of organic matter in 18 h in the UAF while the HSSCW reached 30% of removal for Ntot in a HRT of three days. As expected, the UAF was responsible for removing most of the organic matter and the HSSCW removed most of the nitrogen. Full article
(This article belongs to the Special Issue Water Quality Control and Management)
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Open AccessArticle
Leak Signature Space: An Original Representation for Robust Leak Location in Water Distribution Networks
Water 2015, 7(3), 1129-1148; https://doi.org/10.3390/w7031129 - 13 Mar 2015
Cited by 11 | Viewed by 2085
Abstract
In this paper, an original model-based scheme for leak location using pressure sensors in water distribution networks is introduced. The proposed approach is based on a new representation called the Leak Signature Space (LSS) that associates a specific signature to each leak location [...] Read more.
In this paper, an original model-based scheme for leak location using pressure sensors in water distribution networks is introduced. The proposed approach is based on a new representation called the Leak Signature Space (LSS) that associates a specific signature to each leak location being minimally affected by leak magnitude. The LSS considers a linear model approximation of the relation between pressure residuals and leaks that is projected onto a selected hyperplane. This new approach allows to infer the location of a given leak by comparing the position of its signature with other leak signatures. Moreover, two ways of improving the method’s robustness are proposed. First, by associating a domain of influence to each signature and second, through a time horizon analysis. The efficiency of the method is highlighted by means of a real network using several scenarios involving different number of sensors and considering the presence of noise in the measurements. Full article
Open AccessArticle
Assessment of Long-Term Evolution of Groundwater Hydrochemical Characteristics Using Multiple Approaches: A Case Study in Cangzhou, Northern China
Water 2015, 7(3), 1109-1128; https://doi.org/10.3390/w7031109 - 13 Mar 2015
Cited by 7 | Viewed by 3042
Abstract
Water shortage is severe in the North China Plain (NCP). In addition to a deficiency of water resources, deterioration of groundwater quality should be of great concern. In this study, hydrogeological analysis was conducted in combination with principal component analysis, correlation analysis and [...] Read more.
Water shortage is severe in the North China Plain (NCP). In addition to a deficiency of water resources, deterioration of groundwater quality should be of great concern. In this study, hydrogeological analysis was conducted in combination with principal component analysis, correlation analysis and the co-kriging method to identify factors controlling the content of major ions and total dissolved solids (TDS) in areal shallow and deep groundwater and to assess groundwater evolution in Cangzhou, China. The results suggested that groundwater quality degradation occurred and developed in the study area, as indicated by increasing concentrations of major ions, TDS and hardness in both shallow and deep groundwater. In shallow groundwater, whose hydrochemical water types changed from HCO3–Ca.Na.Mg and HCO3.Cl–Na in the west (Zone II) to Cl.SO4–Na and Cl–Na in the east (Zone III). Areas with TDS concentrations between 1500 and 2000 mg/L occupied 79.76% of the total in the 1980s, while areas with a TDS concentration ranging from 2500 to 3000 mg/L comprised 59.11% of the total in the 2010s. In deep groundwater, the area with TDS over 1000 mg/L expanded from 5366.39 km2 in the 1960s to 7183.52 km2 in the 2010s. Natural processes (water-rock interactions) and anthropogenic activities (groundwater exploitation) were the dominant factors controlling the major ions’ content in local groundwater. Dissolution of dolomite, calcite, feldspar and gypsum were the primary sources of major ions in groundwater, and the ion exchange reaction had a strong effect on the cation content, especially for deep groundwater. Full article
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Open AccessReview
Assessment of Agricultural Best Management Practices Using Models: Current Issues and Future Perspectives
Water 2015, 7(3), 1088-1108; https://doi.org/10.3390/w7031088 - 12 Mar 2015
Cited by 18 | Viewed by 2732
Abstract
Best management practices (BMPs) are the most effective and practicable means to control nonpoint source (NPS) pollution at desired levels. Models are valuable tools to assess their effectiveness. Watershed managers need to choose appropriate and effective modelling methods for a given set of [...] Read more.
Best management practices (BMPs) are the most effective and practicable means to control nonpoint source (NPS) pollution at desired levels. Models are valuable tools to assess their effectiveness. Watershed managers need to choose appropriate and effective modelling methods for a given set of conditions. This paper considered state-of-the-art modelling strategies for the assessment of agricultural BMPs. Typical watershed models and specific models were analyzed in detail. Further improvements, including simplified tools, model integration, and incorporation of climate change and uncertainty analysis were also explored. This paper indicated that modelling methods are strictly scale dependent, both spatially and temporally. Despite current achievements, there is still room for future research, such as broadening the range of the pollutants considered, introducing more local BMPs, improving the representation of the functionality of BMPs, and gathering monitoring date for validation of modelled results. There is also a trend towards agricultural decision support systems (DSSs) for assessing agricultural BMPs, in which models of different scales are seamlessly integrated to bridge the scale and data gaps. This review will assist readers in model selection and development, especially those readers concerned about NPS pollution and water quality control. Full article
(This article belongs to the Special Issue Water Quality Control and Management)
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Open AccessArticle
Accuracy of Hourly Water Temperatures in Rivers Calculated from Air Temperatures
Water 2015, 7(3), 1068-1087; https://doi.org/10.3390/w7031068 - 12 Mar 2015
Cited by 5 | Viewed by 2515
Abstract
Water temperature is a critical variable for water quality control and management. The primary objective of this paper was to develop and compare simple methods to estimate hourly water temperatures in rivers. The wave function (WF) model, originally used to calculate hourly air [...] Read more.
Water temperature is a critical variable for water quality control and management. The primary objective of this paper was to develop and compare simple methods to estimate hourly water temperatures in rivers. The wave function (WF) model, originally used to calculate hourly air temperature, was modified and applied to eight Alabama rivers. The results show significant improvement by using the modified WF model instead of direct linear and non-linear (polynomial and logistic) regression models with time lags (4–5 h). The average Nash–Sutcliffe coefficient (NS) used to evaluate model accuracy for the eight rivers improved from 0.71 for the linear model to 0.89 for the modified WF model with NS for most rivers exceeding 0.90. A lumped modified WF model was also developed by combining water temperature data for all eight rivers and can be applied for rivers in Alabama when no observed water temperatures are available to develop a site-specific WF model. The procedure to develop a modified WF model can be applied to other regions. Full article
(This article belongs to the Special Issue Water Quality Control and Management)
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Open AccessArticle
Urban Sediment Transport through an Established Vegetated Swale: Long Term Treatment Efficiencies and Deposition
Water 2015, 7(3), 1046-1067; https://doi.org/10.3390/w7031046 - 12 Mar 2015
Cited by 10 | Viewed by 3436
Abstract
Vegetated swales are an accepted and commonly implemented sustainable urban drainage system in the built urban environment. Laboratory and field research has defined the effectiveness of a vegetated swale in sediment detention during a single rainfall-runoff event. Event mean concentrations of suspended and [...] Read more.
Vegetated swales are an accepted and commonly implemented sustainable urban drainage system in the built urban environment. Laboratory and field research has defined the effectiveness of a vegetated swale in sediment detention during a single rainfall-runoff event. Event mean concentrations of suspended and bed load sediment have been calculated using current best analytical practice, providing single runoff event specific sediment conveyance volumes through the swale. However, mass and volume of sediment build up within a swale over time is not yet well defined. This paper presents an effective field sediment tracing methodology and analysis that determines the quantity of sediment deposited within a swale during initial and successive runoff events. The use of the first order decay rate constant, k, as an effective pollutant treatment parameter is considered in detail. Through monitoring tagged sediment deposition within the swale, the quantity of sediment that is re-suspended, conveyed, re-deposited or transported out of the swale as a result of multiple runoff events is illustrated. Sediment is found to continue moving through the vegetated swale after initial deposition, with ongoing discharge resulting from resuspension and conveyance during subsequent runoff events. The majority of sediment initially deposited within a swale is not detained long term or throughout its design life of the swale. Full article
(This article belongs to the Special Issue Sustainable Drainage Systems) Printed Edition available
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Open AccessArticle
Stable Isotopic Analysis on Water Utilization of Two Xerophytic Shrubs in a Revegetated Desert Area: Tengger Desert, China
Water 2015, 7(3), 1030-1045; https://doi.org/10.3390/w7031030 - 12 Mar 2015
Cited by 10 | Viewed by 2278
Abstract
Stable isotope studies on stable isotope ratios of hydrogen and oxygen in water within plants provide new information on water sources and water use patterns under natural conditions. In this study, the sources of water uptake for two typical xerophytic shrubs, Caragana korshinskii [...] Read more.
Stable isotope studies on stable isotope ratios of hydrogen and oxygen in water within plants provide new information on water sources and water use patterns under natural conditions. In this study, the sources of water uptake for two typical xerophytic shrubs, Caragana korshinskii and Artemisia ordosica, were determined at four different-aged revegetated sites (1956, 1964, 1981, and 1987) in the Tengger Desert, a revegetated desert area in China. Samples from precipitation, soil water at different soil layers, and xylem water from each species were collected in 2013. The proportion of plant water sources derived from different potential sources was determined using oxygen (δ18O) and hydrogen (δD) stable isotope analysis combined with a multiple-source linear mixing model. Results showed that the local meteoric water line (LMWL) at Shapotou was as follows: δD = 7.39δ18O + 3.91 (R2 = 0.93; n = 26). The vertical distribution of soil water content in older vegetation areas (1956a and 1964a) was much lower than that in relatively younger vegetation areas (1981a and 1987a). Mean soil water δD and δ18O values varied with depth, and the variation decreased as the age of the revegetated site increased. In general, C. korshinskii and A. ordosica mainly tapped water from the upper soil layer (10–100 cm) during the wet seasons. With increasing sand stabilization age, the proportion of water sources from shallow soil water decreased, whereas deep soil moisture utilization increased. During the dry season, C. korshinskii and A. ordosica showed evident hierarchical utilization of soil water in different soil layers. Small rainfall events did not significantly affect the water source of C. korshinskii and A. ordosica. However, large rainfall events not only complemented the deep soil moisture, but also recharged the shallow soil water after a few days, and the proportion of soil water source from deep soil layer increased from 2% ± 0.7% to 10% ± 1.4% for both plants. Full article
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Open AccessArticle
Potential Benefits from Sharing Rainwater Storages Depending on Characteristics in Demand
Water 2015, 7(3), 1013-1029; https://doi.org/10.3390/w7031013 - 11 Mar 2015
Cited by 5 | Viewed by 2075
Abstract
A rainwater harvesting system (RWHS) is an alternative water resource that collects and stores rainwater from rooftops. It helps smooth out variations in water supply and sustainable water resources management. In this study, we investigated the potential benefits from sharing RWHS with nearby [...] Read more.
A rainwater harvesting system (RWHS) is an alternative water resource that collects and stores rainwater from rooftops. It helps smooth out variations in water supply and sustainable water resources management. In this study, we investigated the potential benefits from sharing RWHS with nearby neighbors in a community. We introduced different mean, variance, and correlation in water demand for each water user. A simple case of a community composed of four prospective users is introduced to investigate the benefit from sharing RWHSs. Using the historical rainfall records from four catchments in South Korea, a storage-reliability-yield analysis is applied to obtain the required storage and corresponding reliability for a given yield ratio. The results indicate that the required total storage is reduced when RWHSs are shared among users and the rate of reduction is proportional to the degree of sharing. The required total storage was reduced down to 61% compared to the original storage when RWHSs are shared for a target reliability of 80%. The benefit from sharing also depends on the demands, which are different among users. Test cases with different means and variances as well as correlation disclose the conditions when the benefit from sharing RWHSs is maximized. The result showed that difference in mean and variance additionally reduces the required storage up to 3% and correlation in demand also as much affects the required storage. Full article
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Open AccessReview
A Mapping of Tools for Informing Water Sensitive Urban Design Planning Decisions—Questions, Aspects and Context Sensitivity
Water 2015, 7(3), 993-1012; https://doi.org/10.3390/w7030993 - 11 Mar 2015
Cited by 17 | Viewed by 3321
Abstract
Water Sensitive Urban Design (WSUD) poses new challenges for decision makers compared with traditional stormwater management, e.g., because WSUD offers a larger selection of measures and because many measures are multifunctional. These challenges have motivated the development of many decision support tools. This [...] Read more.
Water Sensitive Urban Design (WSUD) poses new challenges for decision makers compared with traditional stormwater management, e.g., because WSUD offers a larger selection of measures and because many measures are multifunctional. These challenges have motivated the development of many decision support tools. This review shows that the tools differ in terms of the types of questions they can assist in answering. We identified three main groups: “How Much”-tools, “Where”-tools and “Which”-tools. The “How Much”-tools can further be grouped into tools quantifying hydraulic impacts, hydrologic impacts, water quality impacts, non-flow-related impacts and economic impacts. Additionally, the tools differ in terms of how many aspects of water they address, from those focused only on bio-physical aspects to those attempting to find the best WSUD based on multiple criteria. Finally, we suggest that variability among the tools can partly be explained by variability in local context including conditions such as type of existing stormwater systems, groundwater conditions and legislative frameworks. Full article
(This article belongs to the Special Issue Sustainable Drainage Systems) Printed Edition available
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Open AccessReview
Water Scarcity and Future Challenges for Food Production
Water 2015, 7(3), 975-992; https://doi.org/10.3390/w7030975 - 10 Mar 2015
Cited by 72 | Viewed by 10984
Abstract
Present water shortage is one of the primary world issues, and according to climate change projections, it will be more critical in the future. Since water availability and accessibility are the most significant constraining factors for crop production, addressing this issue is indispensable [...] Read more.
Present water shortage is one of the primary world issues, and according to climate change projections, it will be more critical in the future. Since water availability and accessibility are the most significant constraining factors for crop production, addressing this issue is indispensable for areas affected by water scarcity. Current and future issues related to “water scarcity” are reviewed in this paper so as to highlight the necessity of a more sustainable approach to water resource management. As a consequence of increasing water scarcity and drought, resulting from climate change, considerable water use for irrigation is expected to occur in the context of tough competition between agribusiness and other sectors of the economy. In addition, the estimated increment of the global population growth rate points out the inevitable increase of food demand in the future, with an immediate impact on farming water use. Since a noteworthy relationship exists between the water possessions of a country and the capacity for food production, assessing the irrigation needs is indispensable for water resource planning in order to meet food needs and avoid excessive water consumption. Full article
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Open AccessArticle
Probabilistic-Multiobjective Comparison of User-Defined Operating Rules. Case Study: Hydropower Dam in Spain
Water 2015, 7(3), 956-974; https://doi.org/10.3390/w7030956 - 10 Mar 2015
Cited by 6 | Viewed by 2169
Abstract
A useful tool is proposed in this paper to assist dam managers in comparing and selecting suitable operating rules. This procedure is based on well-known multiobjective and probabilistic methodologies, which were jointly applied here to assess and compare flood control strategies in hydropower [...] Read more.
A useful tool is proposed in this paper to assist dam managers in comparing and selecting suitable operating rules. This procedure is based on well-known multiobjective and probabilistic methodologies, which were jointly applied here to assess and compare flood control strategies in hydropower reservoirs. The procedure consisted of evaluating the operating rules’ performance using a simulation fed by a representative and sufficiently large flood event series. These flood events were obtained from a synthetic rainfall series stochastically generated by using the RainSimV3 model coupled with a deterministic hydrological model. The performance of the assessed strategies was characterized using probabilistic variables. Finally, evaluation and comparison were conducted by analyzing objective functions which synthesize different aspects of the rules’ performance. These objectives were probabilistically defined in terms of risk and expected values. To assess the applicability and flexibility of the tool, it was implemented in a hydropower dam located in Galicia (Northern Spain). This procedure allowed alternative operating rule to be derived which provided a reasonable trade-off between dam safety, flood control, operability and energy production. Full article
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Open AccessArticle
Estimation of CN Parameter for Small Agricultural Watersheds Using Asymptotic Functions
Water 2015, 7(3), 939-955; https://doi.org/10.3390/w7030939 - 10 Mar 2015
Cited by 18 | Viewed by 2084
Abstract
This paper investigates a possibility of using asymptotic functions to determine the value of curve number (CN) parameter as a function of rainfall in small agricultural watersheds. It also compares the actually calculated CN with its values provided in the Soil Conservation Service [...] Read more.
This paper investigates a possibility of using asymptotic functions to determine the value of curve number (CN) parameter as a function of rainfall in small agricultural watersheds. It also compares the actually calculated CN with its values provided in the Soil Conservation Service (SCS) National Engineering Handbook Section 4: Hydrology (NEH-4) and Technical Release 20 (TR-20). The analysis showed that empirical CN values presented in the National Engineering Handbook tables differed from the actually observed values. Calculations revealed a strong correlation between the observed CN and precipitation (P). In three of the analyzed watersheds, a typical pattern of the observed CN stabilization during abundant precipitation was perceived. It was found that Model 2, based on a kinetics equation, most effectively described the P-CN relationship. In most cases, the observed CN in the investigated watersheds was similar to the empirical CN, corresponding to average moisture conditions set out by NEH-4. Model 2 also provided the greatest stability of CN at 90% sampled event rainfall. Full article
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Open AccessArticle
Carbon Footprint Analyses of Mainstream Wastewater Treatment Technologies under Different Sludge Treatment Scenarios in China
Water 2015, 7(3), 918-938; https://doi.org/10.3390/w7030918 - 05 Mar 2015
Cited by 22 | Viewed by 3551
Abstract
With rapid urbanization and infrastructure investment, wastewater treatment plants (WWTPs) in Chinese cities are putting increased pressure on energy consumption and exacerbating greenhouse gas (GHG) emissions. A carbon footprint is provided as a tool to quantify the life cycle GHG emissions and identify [...] Read more.
With rapid urbanization and infrastructure investment, wastewater treatment plants (WWTPs) in Chinese cities are putting increased pressure on energy consumption and exacerbating greenhouse gas (GHG) emissions. A carbon footprint is provided as a tool to quantify the life cycle GHG emissions and identify opportunities to reduce climate change impacts. This study examined three mainstream wastewater treatment technologies: Anaerobic–Anoxic–Oxic (A–A–O), Sequencing Batch Reactor (SBR) and Oxygen Ditch, considering four different sludge treatment alternatives for small-to-medium-sized WWTPs. Following the life cycle approach, process design data and emission factors were used by the model to calculate the carbon footprint. Results found that direct emissions of CO2 and N2O, and indirect emissions of electricity use, are significant contributors to the carbon footprint. Although sludge anaerobic digestion and biogas recovery could significantly contribute to emission reduction, it was less beneficial for Oxygen Ditch than the other two treatment technologies due to its low sludge production. The influence of choosing “high risk” or “low risk” N2O emission factors on the carbon footprint was also investigated in this study. Oxygen Ditch was assessed as “low risk” of N2O emissions while SBR was “high risk”. The carbon footprint of A–A–O with sludge anaerobic digestion and energy recovery was more resilient to changes of N2O emission factors and control of N2O emissions, though process design parameters (i.e., effluent total nitrogen (TN) concentration, mixed-liquor recycle (MLR) rates and solids retention time (SRT)) and operation conditions (i.e., nitrite concentration) are critical for reducing carbon footprint of SBR. Analyses of carbon footprints suggested that aerobic treatment of sludge not only favors the generation of large amounts of CO2, but also the emissions of N2O, so the rationale of reducing aerobic treatment and maximizing anaerobic treatment applies to both wastewater and sludge treatment for reducing the carbon footprint, i.e., the annamox process for wastewater nutrient removal and the anaerobic digestion for sludge treatment. Full article
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Open AccessArticle
Exploring the Modifiable Areal Unit Problem in Spatial Water Assessments: A Case of Water Shortage in Monsoon Asia
Water 2015, 7(3), 898-917; https://doi.org/10.3390/w7030898 - 03 Mar 2015
Cited by 12 | Viewed by 4167
Abstract
Water shortage (availability per capita) is a key indicator of vulnerability to water scarcity. Spatial datasets enable the assessment of water shortage on multiple scales. The use of river basins and subbasins as analysis and management units is currently commonplace. An important but [...] Read more.
Water shortage (availability per capita) is a key indicator of vulnerability to water scarcity. Spatial datasets enable the assessment of water shortage on multiple scales. The use of river basins and subbasins as analysis and management units is currently commonplace. An important but less acknowledged fact is that spatial assessments are strongly influenced by the choice of the unit of analysis due to the Modifiable Areal Unit Problem (MAUP). Climate conditions, agricultural activities, and access to groundwater also influence water availability and demand. In this study, a total of 21 different criteria were used to define areal units of analysis, i.e., zonings, for which water shortage was calculated. Focusing on Monsoon Asia, where water scarcity is a pressing problem, we found that zoning had a considerable impact, resulting in up to three-fold differences in the population under high water shortage (<1000 m3/cap/year), ranging from 782 million to 2.11 billion. In most zonings, however, the Indus and Yellow River Basins and northwest parts of India and China are under high water shortage. The study indicates that a multizonal and multiscale analysis is needed to minimize skewed or even misleading information that might be produced when using only one zoning. Full article
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Open AccessConcept Paper
Testing Metallic Iron Filtration Systems for Decentralized Water Treatment at Pilot Scale
Water 2015, 7(3), 868-897; https://doi.org/10.3390/w7030868 - 02 Mar 2015
Cited by 24 | Viewed by 4837
Abstract
There are many factors to consider for the design of appropriate water treatment systems including: cost, the concentration and type of biological and/or chemical contamination, concentration limits at which contaminant(s) are required to be removed, required flow rate, level of local expertise for [...] Read more.
There are many factors to consider for the design of appropriate water treatment systems including: cost, the concentration and type of biological and/or chemical contamination, concentration limits at which contaminant(s) are required to be removed, required flow rate, level of local expertise for on-going maintenance, and social acceptance. An ideal technology should be effective at producing clean, potable water; however it must also be low-cost, low-energy (ideally energy-free) and require low-maintenance. The use of packed beds containing metallic iron (Fe0 filters) has the potential to become a cheap widespread technology for both safe drinking water provision and wastewater treatment. Fe0 filters have been intensively investigated over the past two decades, however, sound design criteria are still lacking. This article presents an overview of the design of Fe0 filters for decentralized water treatment particularly in the developing world. A design for safe drinking water to a community of 100 people is also discussed as starting module. It is suggested that Fe0 filters have the potential for significant worldwide applicability, but particularly in the developing world. The appropriate design of Fe0 filters, however, is site-specific and dependent upon the availability of local expertise/materials. Full article
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Open AccessArticle
Influence of Temperature on the Performance of a Full-Scale Activated Sludge Process Operated at Varying Solids Retention Times Whilst Treating Municipal Sewage
Water 2015, 7(3), 855-867; https://doi.org/10.3390/w7030855 - 02 Mar 2015
Cited by 7 | Viewed by 2427
Abstract
In this study, the solid retention time (SRT) was varied with the ambient temperature for a full-scale municipal activated sludge plant with capacity of 200,000 PE (Population Equivalent) located in a humid sub-tropical environment. The effects of ambient temperature on treatment performance were [...] Read more.
In this study, the solid retention time (SRT) was varied with the ambient temperature for a full-scale municipal activated sludge plant with capacity of 200,000 PE (Population Equivalent) located in a humid sub-tropical environment. The effects of ambient temperature on treatment performance were investigated. Off-line samples were collected and analyzed from the treatment plant. The actual temperature variation during the study period was divided into three overlapping ranges and the SRT was adjusted accordingly with temperature in order to achieve the desired effluent quality. The plant’s observed effluent quality and thereby its overall removal efficiency was evaluated in terms of measuring standard biochemical parameters. The results indicate that significant improvement in effluent quality can be obtained by applying the variable SRT (5–7 days) dependent on temperature variation. Full article
(This article belongs to the Special Issue Water Quality Control and Management)
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Open AccessArticle
Soil and Waste Matrix Affects Spatial Heterogeneity of Bacteria Filtration during Unsaturated Flow
Water 2015, 7(3), 836-854; https://doi.org/10.3390/w7030836 - 27 Feb 2015
Cited by 1 | Viewed by 2474
Abstract
Discontinuous flows resulting from discrete natural rain events induce temporal and spatial variability in the transport of bacteria from organic waste through soils in which the degree of saturation varies. Transport and continuity of associated pathways are dependent on structure and stability of [...] Read more.
Discontinuous flows resulting from discrete natural rain events induce temporal and spatial variability in the transport of bacteria from organic waste through soils in which the degree of saturation varies. Transport and continuity of associated pathways are dependent on structure and stability of the soil under conditions of variable moisture and ionic strength of the soil solution. Lysimeters containing undisturbed monoliths of clay, clay loam or sandy loam soils were used to investigate transport and pathway continuity for bacteria and hydrophobic fluorescent microspheres. Biosolids, to which the microspheres were added, were surface applied and followed by serial irrigation events. Microspheres, Escherichia coli, Enterococcus spp., Salmonella spp. and Clostridium perfringens were enumerated in drainage collected from 64 distinct collection areas through funnels installed in a grid pattern at the lower boundary of the monoliths. Bacteria-dependent filtration coefficients along pathways of increasing water flux were independent of flow volume, suggesting: (1) tracer or colloid dependent retention; and (2) transport depended on the total volume of contiguous pores accessible for bacteria transport. Management decisions, in this case resulting from the form of organic waste, induced changes in tortuosity and continuity of pores and modified the effective capacity of soil to retain bacteria. Surface application of liquid municipal biosolids had a negative impact on transport pathway continuity, relative to the solid municipal biosolids, enhancing retention under less favourable electrostatic conditions consistent with an initial increase in straining within inactive pores and subsequent by limited re-suspension from reactivated pores. Full article
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