Water

1121 KiB

Open AccessArticle

Framework of National Non-Structural Measures for Flash Flood Disaster Prevention in China

by Dongya Sun, Dawei Zhang and Xiaotao Cheng

Water 2012, 4(1), 272-282; https://doi.org/10.3390/w4010272 - 19 Mar 2012

Cited by 42 | Viewed by 11436

In recent years, disasters caused by flash floods with many casualties have occurred frequently in China. In order to effectively prevent flash flood disasters, the State Council approved the National Flash Flood Control Planning (NFFCP) in 2006. In this planning, non-structural measures are [...] Read more.

In recent years, disasters caused by flash floods with many casualties have occurred frequently in China. In order to effectively prevent flash flood disasters, the State Council approved the National Flash Flood Control Planning (NFFCP) in 2006. In this planning, non-structural measures are recommended as the first step to be adopted in the prevention of flash floods, debris flow and landslide disasters caused by heavy rainfall. In order to effectively build up a comprehensive non-structural measure system for flash flood disaster prevention, the Ministry of Water Resources has asked the local authorities to conduct studies in 103 pilot counties aiming to explore practical schemes. Based on the experience from these pilot counties, the construction of non-structural measures on flash flood disaster prevention for 1836 counties was officially initiated in 2010. The contents of non-structural measures for flash flood disaster prevention at county level include eight aspects. This paper will systematically illustrate the main contents of this national project for the construction of non-structural measures for flash flood disaster prevention in China. This work could provide a reference for other countries and regions in terms of flash flood prevention. Full article

(This article belongs to the Special Issue Flood Risk Management)

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222 KiB

Open AccessArticle

Treatment of Olive Mill Wastewater with Constructed Wetlands

by Iosif E. Kapellakis, Nikolaos V. Paranychianakis, Konstantinos P. Tsagarakis and Andreas N. Angelakis

Water 2012, 4(1), 260-271; https://doi.org/10.3390/w4010260 - 12 Mar 2012

Cited by 42 | Viewed by 9338

Abstract

The objective of this study was to investigate the application of constructed wetlands as a mean to manage olive mill wastewater (OMW). Two free water surface (FWS) constructed wetlands, one without (CW1) and one with effluent recirculation (CW2), were operated for a two-year [...] Read more.

The objective of this study was to investigate the application of constructed wetlands as a mean to manage olive mill wastewater (OMW). Two free water surface (FWS) constructed wetlands, one without (CW1) and one with effluent recirculation (CW2), were operated for a two-year period with diluted OMW (1:10) and evaluated in terms of the removal of COD, TSS, TKN, NH₄⁺-N, NO₃⁻-N, TP and total phenols. The organic loading rate of CWs was adjusted to 925 kg BOD/ha·d. In CW1 the removal efficiency averaged 80%, 83%, 78%, 80%, and 74% for COD, TSS, TKN, TP, and total phenols, respectively, during the operation period. Effluent recirculation further improved the treatment efficiency which approached 90%, 98%, 87%, 85%, and 87% for COD, TSS, TKN, TP, and total phenols, respectively. Constructed wetlands also showed high removal efficiency for NH₄⁺-N. Nitrate concentration maintained low in both CWs basins, probably due to the prevalence of high denitrification rates that efficiently removed the NO₃^--N produced by NH₄⁺-N oxidation. Despite the increased removal percentages, pollutant concentration in effluent exceeded the allowable limits for discharge in water bodies, suggesting that additional practices, including enhanced pre-application treatment and/or higher dilution rates, are required to make this practice effective for OMW management. Full article

(This article belongs to the Special Issue Water Recycling and Reuse)

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3463 KiB

Open AccessArticle

A Perspective on Sea Level Rise and Coastal Storm Surge from Southern and Eastern Africa: A Case Study Near Durban, South Africa

by Andrew A. Mather and Derek D. Stretch

Water 2012, 4(1), 237-259; https://doi.org/10.3390/w4010237 - 5 Mar 2012

Cited by 50 | Viewed by 20774

Abstract

Recent coastal storms in southern Africa have highlighted the need for more proactive management of the coastline. Within the southern and eastern African region the availability of coastal information is poor. The greatest gap in information is the likely effects of a combination [...] Read more.

Recent coastal storms in southern Africa have highlighted the need for more proactive management of the coastline. Within the southern and eastern African region the availability of coastal information is poor. The greatest gap in information is the likely effects of a combination of severe sea storms and future sea level rise (SLR) on the shoreline. This lack of information creates a barrier to informed decision making. This research outlines a practical localized approach to this problem, which can be applied as a first order assessment within the region. In so doing it provides a cost effective and simple decision support tool for the built environment and disaster professionals in development and disaster assessments. In a South African context the newly promulgated Integrated Coastal Management Act requires that all proposed coastal developments take into consideration future SLR, however such information currently does not exist, despite it being vital for informed planning in the coastal zone. This practical approach has been applied to the coastline of Durban, South Africa as a case study. The outputs are presented in a Geographic Information System (GIS) based freeware viewer tool enabling ease of access to both professionals and laypersons. This demonstrates that a simple approach can provide valuable information about the current and future risk of flooding and coastal erosion under climate change to buildings, infrastructure as well as natural features along the coast. Full article

(This article belongs to the Special Issue Flood Risk Management)

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604 KiB

Open AccessArticle

Economic Assessment of an Integrated Membrane System for Secondary Effluent Polishing for Unrestricted Reuse

by Amos Bick, Leonid Gillerman, Yossi Manor and Gideon Oron

Water 2012, 4(1), 219-236; https://doi.org/10.3390/w4010219 - 5 Mar 2012

Cited by 34 | Viewed by 12112

Abstract

Extra treatment stages are required to polish the secondary effluent for unrestricted reuse, primarily for agricultural irrigation. Improved technology for the removal of particles, turbidity, bacteria and cysts, without the use of disinfectants is based on MicroFiltration (MF) and UltraFiltration (UF) membrane technology [...] Read more.

Extra treatment stages are required to polish the secondary effluent for unrestricted reuse, primarily for agricultural irrigation. Improved technology for the removal of particles, turbidity, bacteria and cysts, without the use of disinfectants is based on MicroFiltration (MF) and UltraFiltration (UF) membrane technology and in series with Reverse Osmosis (RO) for dissolved solids removal. Field experiments were conducted using a mobile UF and RO membrane pilot unit at a capacity of around 1.0 m³/hr. A management model was defined and tested towards optimal polishing of secondary effluent. The two major purposes of the management model are: (i) to delineate a methodology for economic assessment of optimal membrane technology implementation for secondary effluent upgrading for unrestricted use, and; (ii) to provide guidelines for optimal RO membrane selection in regards to the pretreatment stage. The defined linear model takes into account the costs of the feed secondary effluent, the UF pretreatment and the RO process. Technological constraints refer primarily to the longevity of the membrane and their performance. Final treatment cost (the objective function) includes investment, operation and maintenance expenses, UF pretreatment, RO treatment, post treatment and incentive for low salinity permeate use. The cost range of water for irrigation according to the model is between 15 and 42 US cents per m³. Full article

(This article belongs to the Special Issue Water Recycling and Reuse)

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319 KiB

Open AccessArticle

Physical Vulnerability Assessment Based on Fluid and Classical Mechanics to Support Cost-Benefit Analysis of Flood Risk Mitigation Strategies

by Bruno Mazzorana, Laura Levaggi, Omar Formaggioni and Claudio Volcan

Water 2012, 4(1), 196-218; https://doi.org/10.3390/w4010196 - 28 Feb 2012

Cited by 6 | Viewed by 7949

Abstract

The impacts of flood events that occurred in autumn 2011 in the Italian regions of Liguria and Tuscany revived the engagement of the public decision-maker to enhance the synergy of flood control and land use planning. In this context, the design of efficient [...] Read more.

The impacts of flood events that occurred in autumn 2011 in the Italian regions of Liguria and Tuscany revived the engagement of the public decision-maker to enhance the synergy of flood control and land use planning. In this context, the design of efficient flood risk mitigation strategies and their subsequent implementation critically relies on a careful vulnerability analysis of the fixed and mobile elements exposed to flood hazard. In this paper we develop computation schemes enabling dynamic vulnerability and risk analyses for a broad typological variety of elements at risk. To show their applicability, a series of prime examples are discussed in detail, e.g. a bridge deck impacted by the flood and a car, first displaced and subsequently exposed to collision with fixed objects. We hold the view that it is essential that the derivation of the computational schemes to assess the vulnerability of endangered objects should be based on classical and fluid mechanics. In such a way, we aim to complement from a methodological perspective the existing, mainly empirical, vulnerability and risk assessment approaches and to support the design of effective flood risk mitigation strategies by defusing the main criticalities within the systems prone to flood risk. Full article

(This article belongs to the Special Issue Flood Risk Management)

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476 KiB

Open AccessArticle

Mean Sea Level Variability and Influence of the North Atlantic Oscillation on Long-Term Trends in the German Bight

by Sönke Dangendorf, Thomas Wahl, Hartmut Hein, Jürgen Jensen, Stephan Mai and Christoph Mudersbach

Water 2012, 4(1), 170-195; https://doi.org/10.3390/w4010170 - 24 Feb 2012

Cited by 52 | Viewed by 11523

Abstract

Changes in the seasonal cycle of mean sea level (MSL) may affect the heights of storm surges and thereby flood risk in coastal areas. This study investigates the intra- and inter-annual variability of monthly MSL and its link to the North Atlantic Oscillation [...] Read more.

Changes in the seasonal cycle of mean sea level (MSL) may affect the heights of storm surges and thereby flood risk in coastal areas. This study investigates the intra- and inter-annual variability of monthly MSL and its link to the North Atlantic Oscillation using records from 13 tide gauges located in the German Bight. The amplitudes of the seasonal MSL cycle are not regionally uniform and vary between 20 and 29 cm. Generally, the amplitudes are smaller at the southwestern stations, increasing as one travels to the northeastern part. The amplitudes, as well as the phase of the seasonal cycle, are characterized by a large inter-annual and inter-decadal variability, but no long-term trend could be detected. Nevertheless, in the last two decades annual maximum peaks more frequently occurred in January and February, whereas beforehand an accumulation was detected for the November and December period. These changes in phase in the various sea level time series are consistent with a shift in the annual cycle, which is, however, not significant. The changes are associated with strongly increasing trends in monthly MSL of the winter season (J–M), which are considerably higher compared to the remaining seasons. For the same season, the MSL and North Atlantic Oscillation (NAO) indices show strong similarities, resulting in statistically significant correlations (r ~ 0.7). Hence, these changes are linked with changing pressure conditions over the North Atlantic, which lead to a strong phase of positive values in the NAO index between the 1960’s and 1990’s. Full article

(This article belongs to the Special Issue Flood Risk Management)

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1111 KiB

Open AccessArticle

Flood Management in California

by Jay R. Lund

Water 2012, 4(1), 157-169; https://doi.org/10.3390/w4010157 - 14 Feb 2012

Cited by 21 | Viewed by 12527

Abstract

California’s development and success have been shaped by its ability to manage floods. This management has varied over the history of California’s economic and political development and continues in various forms today. California will always have flood problems. A range of options are [...] Read more.

California’s development and success have been shaped by its ability to manage floods. This management has varied over the history of California’s economic and political development and continues in various forms today. California will always have flood problems. A range of options are available to aid in flood management problems and have been used over time. These options can be contrasted with flood management elsewhere and the types of options used to manage other types of hazards in California, such as earthquakes, wildfires, and droughts. In the future, flood management in California will require greater reliance on local funding and leadership, reflecting diminished federal and state funding, with more effective state and federal guidance. Effective flood management will also tend to integrate flood management with actions to achieve environmental and other water supply objectives, both to gain revenues from a broader range of beneficiaries as well as to make more efficient use of land and water in a state where both are often scarce. Full article

(This article belongs to the Special Issue Flood Risk Management)

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577 KiB

Open AccessArticle

Towards a Risk Governance Culture in Flood Policy—Findings from the Implementation of the “Floods Directive” in Germany

by Marc Daniel Heintz, Maria Hagemeier-Klose and Klaus Wagner

Water 2012, 4(1), 135-156; https://doi.org/10.3390/w4010135 - 2 Feb 2012

Cited by 57 | Viewed by 12326

Abstract

The European Directive on the Assessment and Management of Flood Risks is likely to cause changes to flood policy in Germany and other member states. With its risk governance approach, it introduces a holistic and catchment-oriented flood risk management and tries to overcome [...] Read more.

The European Directive on the Assessment and Management of Flood Risks is likely to cause changes to flood policy in Germany and other member states. With its risk governance approach, it introduces a holistic and catchment-oriented flood risk management and tries to overcome shortcomings of the past, such as the event-driven construction of mainly structural measures. However, there is leeway for interpretation in implementing the directive. The present paper gives an overview on the implementation of the floods directive in Germany and is divided into two qualitative empirical case studies. Case Study I investigates the level of acceptance of the floods directive among decision-makers in the German part of the Rhine river basin. Findings show that the federal states respond differently to the impulse given by the floods directive. Whereas some decision-makers opt for a pro-forma implementation, others take it as a starting point to systematically improve their flood policy. Case Study II presents recommendations for a successful implementation of flood risk management plans that have been developed within a project for the water authority in Bavaria and might be interesting for other federal/member states. For a participation of the interested parties on the level of shared decision-making, the planning process has to work on sub-management-plan level (15–20 communities). The water resources authority has to adopt a multi-faceted role (expert, responsible or interested party depending on the discussed topics). Full article

(This article belongs to the Special Issue Flood Risk Management)

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195 KiB

Open AccessArticle

Improving Water Supply Systems for Domestic Uses in Urban Togo: The Case of a Suburb in Lomé

by Laurent Ahiablame, Bernard Engel and Taisha Venort

Water 2012, 4(1), 123-134; https://doi.org/10.3390/w4010123 - 1 Feb 2012

Cited by 14 | Viewed by 9822

Abstract

The rapid urbanization facing developing countries is increasing pressure on public institutions to provide adequate supplies of clean water to populations. In most developing countries, the general public is not involved in strategies and policies regarding enhancement, conservation, and management of water supply [...] Read more.

The rapid urbanization facing developing countries is increasing pressure on public institutions to provide adequate supplies of clean water to populations. In most developing countries, the general public is not involved in strategies and policies regarding enhancement, conservation, and management of water supply systems. To assist governments and decision makers in providing potable water to meet the increasing demand due to the rapid urbanization, this study sought to characterize existing water supply systems and obtain public opinion for identifying a community water supply system model for households in a residential neighborhood in Lomé, Togo. Existing water supply systems in the study area consist of bucket-drawn water wells, mini water tower systems, rainwater harvesting, and public piped water. Daily domestic water consumption in the study area compared well with findings on water uses per capita from Sub-Saharan Africa, but was well below daily water usage in developed nations. Based on the surveys, participants thought highly of a large scale community water tower and expressed interest in maintaining it. Even though people rely on water sources deemed convenient for drinking, they also reported limited confidence in the quality of these sources. Full article

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2079 KiB

Open AccessArticle

Relevance and Benefits of Urban Water Reuse in Tourist Areas

by Valentina Lazarova, Vincent Sturny and Gaston Tong Sang

Water 2012, 4(1), 107-122; https://doi.org/10.3390/w4010107 - 31 Jan 2012

Cited by 11 | Viewed by 10692

Abstract

Urban water reuse is one of the most rapidly growing water reuse applications worldwide and one of the major elements of the sustainable management of urban water cycle. Because of the high probability of direct contact between consumers and recycled water, many technical [...] Read more.

Urban water reuse is one of the most rapidly growing water reuse applications worldwide and one of the major elements of the sustainable management of urban water cycle. Because of the high probability of direct contact between consumers and recycled water, many technical and regulatory challenges have to be overcome in order to minimize health risks at affordable cost. This paper illustrates the keys to success of one of the first urban water reuse projects in the island Bora Bora, French Polynesia. Special emphasis is given on the reliability of operation of the membrane tertiary treatment, economic viability in terms of pricing of recycled water and operating costs, as well as on the benefits of water reuse for the sustainable development of tourist areas. Full article

(This article belongs to the Special Issue Water Recycling and Reuse)

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3642 KiB

Open AccessArticle

Inundation Mapping Initiatives of the Iowa Flood Center: Statewide Coverage and Detailed Urban Flooding Analysis

by Daniel Gilles, Nathan Young, Harvest Schroeder, Jesse Piotrowski and Yi-Jia Chang

Water 2012, 4(1), 85-106; https://doi.org/10.3390/w4010085 - 16 Jan 2012

Cited by 65 | Viewed by 20508

Abstract

The State of Iowa, located in the Midwestern United States, has experienced an increased frequency of large floods in recent decades. After extreme flooding in the summer of 2008, the Iowa Flood Center (IFC) was established for advanced research and education specifically related [...] Read more.

The State of Iowa, located in the Midwestern United States, has experienced an increased frequency of large floods in recent decades. After extreme flooding in the summer of 2008, the Iowa Flood Center (IFC) was established for advanced research and education specifically related to floods. IFC seeks to improve Iowa’s flood hazard awareness through the development of easily accessible, high-quality mapping products. Mapping initiatives consist of two model development approaches: (1) statewide floodplain delineation using one-dimensional (1D) models, and (2) urban flood mapping using detailed one-dimensional/two-dimensional (2D) coupled models. The statewide floodplain project will benefit Iowans through the creation of a comprehensive set of floodplain maps developed under a single consistent methodology. These will be important tools in evaluating flood risk, regulating floodplains, and participating in the National Flood Insurance Program. Detailed urban flood analyses are used to develop inundation map libraries. These map libraries are meant to supplement National Weather Service river stage flood forecasts by providing a visual representation of potential flood extent according to predicted river stage at stream gage locations. Full article

(This article belongs to the Special Issue Flood Risk Management)

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1068 KiB

Open AccessArticle

Climate Change Impacts on Water Availability and Use in the Limpopo River Basin

by Tingju Zhu and Claudia Ringler

Water 2012, 4(1), 63-84; https://doi.org/10.3390/w4010063 - 16 Jan 2012

Cited by 43 | Viewed by 14899

Abstract

This paper analyzes the effects of climate change on water availability and use in the Limpopo River Basin of Southern Africa, using a linked modeling system consisting of a semi-distributed global hydrological model and the Water Simulation Module (WSM) of the International Model [...] Read more.

This paper analyzes the effects of climate change on water availability and use in the Limpopo River Basin of Southern Africa, using a linked modeling system consisting of a semi-distributed global hydrological model and the Water Simulation Module (WSM) of the International Model for Policy Analysis of Agricultural Commodities and Trade (IMPACT). Although the WSM simulates all major water use sectors, the focus of this study is to evaluate the implications of climate change on irrigation water supply in the catchments of the Limpopo River Basin within the four riparian countries: Botswana, Mozambique, South Africa, and Zimbabwe. The analysis found that water resources of the Limpopo River Basin are already stressed under today’s climate conditions. Projected water infrastructure and management interventions are expected to improve the situation by 2050 if current climate conditions continue into the future. However, under the climate change scenarios studied here, water supply availability is expected to worsen considerably by 2050. Assessing hydrological impacts of climate change is crucial given that expansion of irrigated areas has been postulated as a key adaptation strategy for Sub-Saharan Africa. Such expansion will need to take into account future changes in water availability in African river basins. Full article

(This article belongs to the Special Issue Managing Water Resources and Development in a Changing Climate)

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727 KiB

Open AccessArticle

Integrating the Carbon and Water Footprints’ Costs in the Water Framework Directive 2000/60/EC Full Water Cost Recovery Concept: Basic Principles Towards Their Reliable Calculation and Socially Just Allocation

by Vasilis Kanakoudis, Stavroula Tsitsifli and Anastasia Papadopoulou

Water 2012, 4(1), 45-62; https://doi.org/10.3390/w4010045 - 16 Jan 2012

Cited by 33 | Viewed by 11207

Abstract

This paper presents the basic principles for the integration of the water and carbon footprints cost into the resource and environmental costs respectively, taking the suggestions set by the Water Framework Directive (WFD) 2000/60/EC one step forward. WFD states that full water cost [...] Read more.

This paper presents the basic principles for the integration of the water and carbon footprints cost into the resource and environmental costs respectively, taking the suggestions set by the Water Framework Directive (WFD) 2000/60/EC one step forward. WFD states that full water cost recovery (FWCR) should be based on the estimation of the three sub-costs related: direct; environmental; and resource cost. It also strongly suggests the EU Member States develop and apply effective water pricing policies to achieve FWCR. These policies must be socially just to avoid any social injustice phenomena. This is a very delicate task to handle, especially within the fragile economic conditions that the EU is facing today. Water losses play a crucial role for the FWC estimation. Water losses should not be neglected since they are one of the major “water uses” in any water supply network. A methodology is suggested to reduce water losses and the related Non Revenue Water (NRW) index. An Expert Decision Support System is proposed to assess the FWC incorporating the Water and Carbon Footprint costs. Full article

(This article belongs to the Special Issue Managing Water Resources and Development in a Changing Climate)

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735 KiB

Open AccessArticle

Climate Change Impacts on Water Supply and Demand in Rheraya Watershed (Morocco), with Potential Adaptation Strategies

by Saloua Rochdane, Barbara Reichert, Mohammed Messouli, Abdelaziz Babqiqi and Mohammed Yacoubi Khebiza

Water 2012, 4(1), 28-44; https://doi.org/10.3390/w4010028 - 9 Jan 2012

Cited by 58 | Viewed by 14764

Abstract

Rheraya watershed already suffers from the impacts of climate variability and will be further affected by climate change. Severe water shortages and extremely fragile ecological conditions necessitate careful attention to water resources management. The aim of this study is to analyze Rheraya’s future [...] Read more.

Rheraya watershed already suffers from the impacts of climate variability and will be further affected by climate change. Severe water shortages and extremely fragile ecological conditions necessitate careful attention to water resources management. The aim of this study is to analyze Rheraya’s future water situation under different scenarios of socio-economic development and climate change until 2100. The Water Evaluation and Planning System model (WEAP) has been applied to estimate the current water demands and the increased water demands resulting from climate change. WEAP was calibrated using meteorological and demand observations, then, updated with present-day and future climatic conditions using the Statistical Down-scaling Model with two projections (A2, B2) of the Intergovernmental Panel on Climate Change. Those projections show an increase in temperature of about 2–3 °C and a reduction in precipitation of 40–60% with respect to baseline. The results show that the pressure on Rheraya’s water resources will increase, leading to greater competition for surface water, and that domestic, tourist, livestock and agricultural demands will not be met by the year 2100. The Results also demonstrate that the assessments of adaptation strategies proposed by decision makers are effective but not sustainable for the watershed. Full article

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2104 KiB

Open AccessArticle

Neglected Canals: Deterioration of Indigenous Irrigation System by Urbanization in the West Peri-Urban Area of Bangkok Metropolitan Region

by Vudipong Davivongs, Makoto Yokohari and Yuji Hara

Water 2012, 4(1), 12-27; https://doi.org/10.3390/w4010012 - 9 Jan 2012

Cited by 28 | Viewed by 12593

Abstract

This paper discusses the deterioration of indigenous irrigation system traditionally developed in the past to serve the peri-urban agricultural lands that have been affected by rapid urbanization in the Bangkok Metropolitan Region. The study is based on data collection from mapping, field survey [...] Read more.

This paper discusses the deterioration of indigenous irrigation system traditionally developed in the past to serve the peri-urban agricultural lands that have been affected by rapid urbanization in the Bangkok Metropolitan Region. The study is based on data collection from mapping, field survey and interview analyses and identifies current canal deteriorating conditions in four categories: filled, covered, narrowed and shallow, and normal. The findings reveal that different types of canal deteriorations are associated with their private ownership. A typology of land configurations of urban and non-urban land uses along private canals is pointed out in order to understand their relation with canal deterioration types. Caused by urbanization, the degradation of the existing canal networks has provoked conflicts between local farmers and new proprietors, especially real estate developers. Such canal deterioration essentially reduces their ability to convey a water supply to feed agricultural lands, consequently leading to the discontinuation of land use for agriculture and its eventual transformation into urban developments. Full article

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427 KiB

Open AccessArticle

Optimizing the Air Dissolution Parameters in an Unpacked Dissolved Air Flotation System

by Adam Dassey and Chandra Theegala

Water 2012, 4(1), 1-11; https://doi.org/10.3390/w4010001 - 27 Dec 2011

Cited by 22 | Viewed by 13781

Abstract

Due to the various parameters that influence air solubility and microbubble production in dissolved air flotation (DAF), a multitude of values that cover a large range for these parameters are suggested for field systems. An unpacked saturator and an air quantification unit were [...] Read more.

Due to the various parameters that influence air solubility and microbubble production in dissolved air flotation (DAF), a multitude of values that cover a large range for these parameters are suggested for field systems. An unpacked saturator and an air quantification unit were designed to specify the effects of power, pressure, temperature, hydraulic retention time, and air flow on the DAF performance. It was determined that a pressure of 621 kPa, hydraulic retention time of 18.2 min, and air flow of 8.5 L/h would be the best controlled parameters for maximum efficiency in this unit. A temperature of 7 °C showed the greatest microbubble production, but temperature control would not be expected in actual application. The maximum microbubble flow from the designed system produced 30 mL of air (±1.5) per L of water under these conditions with immediate startup. The maximum theoretical dissolved air volume of 107 mL (±6) was achieved at a retention time of 2 h and a pressure of 621 kPa. To isolate and have better control over the various DAF operational parameters, the DAF unit was operated without the unsaturated flow stream. This mode of operation led to the formation of large bubbles at peak bubble production rates. In a real-world application, the large bubble formation will be avoided by mixing with raw unsaturated stream and by altering the location of dissolved air output flow. Full article

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Water, Volume 4, Issue 1 (March 2012) – 16 articles , Pages 1-282

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