Search

This paper explores the current context for decentralised approaches in the provision of urban water services. It examines the recent history of decentralised systems' implementation in Australia and identifies its drivers. The drivers included addressing capacity constraints of centralised systems, mitigating the environmental impact of urban development, and increasing the resilience of urban water systems to episodic droughts and the projected impacts of climate change. The concepts of integrated urban water management and water sensitive urban design were prevalent in many of the innovative approaches used for the provision of decentralised urban water services. However, there remains a degree of confusion among water professionals in the terminology adopted for on-site and decentralised systems. Based on a literature review, consultation with water industry professionals and examination of decentralised urban developments in Australia, this paper has developed a generalised definition of decentralised systems for adoption across the water sector. The definition encompasses the various development scales in which decentralised systems are implemented, and reflects the new functions and characteristics inherent to those systems.

Water sensitive urban developments are designed with integrated urban water management concepts and water sensitive urban design measures. The initiatives that may be included are the substitution of imported drinking water with alternative sources using a fit-for-purpose approach and structural and non-structural measures for the source control of stormwater. A water sensitive approach to urban development can help in achieving sustainability objectives by minimising disturbance to ecological and hydrological processes, and also relieve stress on conventional water systems. Water sensitive urban developments remain novel in comparison with conventional approaches, so the understanding and knowledge of the systems in regards to their planning; design; implementation; operation and maintenance; health impacts and environmental impacts is still developing and thus the mainstream uptake of these approaches faces many challenges. A study has been conducted to understand these challenges through a detailed literature review, investigating a large number of local greenfield and infill developments, and conducting extensive consultation with water professionals. This research has identified the social, economic, political, institutional and technological challenges faced in implementing water sensitive urban design in greenfield and infill developments. The research found in particular that there is the need for long-term monitoring studies of water sensitive urban developments. This monitoring is important to validate the performance of novel approaches implemented and improve associated guidelines, standards, and regulatory and governance frameworks, which can lead to mainstream acceptance of water sensitive urban development approaches. The dissemination of this research will help generate awareness among water professionals, water utilities, developers, planners and regulators of the research challenges to be addressed in order to achieve more mainstream acceptance of water sensitive approaches to urban development. This study is based on existing water sensitive urban developments in Australia, however, the methodology adopted in investigating impediments to the uptake of these developments can be applied globally. It is hoped that insights from this study will benefit water professionals in other countries where there is also a move towards water sensitive urban development.

Cities worldwide are challenged by a number of urban water issues associated with climate change, population growth and the associated water scarcity, wastewater flows and stormwater run-off. To address these problems decentralised solutions are increasingly being considered by water authorities, and integrated urban water management (IUWM) has emerged as a potential solution to most of these urban water challenges, and as the key to providing solutions incorporating decentralised concepts at a city wide scale. To incorporate decentralised options, there is a need to understand their performance and their impact on a city's total water cycle under alternative water and land management options. This includes changes to flow, nutrient and sediment regimes, energy use, greenhouse gas emissions, and the impacts on rivers, aquifers and estuaries. Application of the IUWM approach to large cities demands revisiting the fundamental role of water system design in sustainable city development. This paper uses the extended urban metabolism model (EUMM) to expand a logical definition for the aims of IUWM, and discusses the role of decentralised systems in IUWM and how IUWM principles can be incorporated into urban water planning.

This study describes the use of rainwater and greywater (originated from bathroom only) for provision of non-contact indoor and outdoor use in high-rise buildings. A brownfield development site in Box Hill suburb of Melbourne was selected as case study site for this investigation. The performance of alternative servicing options was compared with conventional water supply, stormwater and wastewater servicing. A water balance model UVQ (Urban Volume and Quality) was applied to determine storage capacities and to evaluate the percentage reduction in water supplying, stormwater run-off and wastewater disposal, as well as volumes of rainwater use and greywater reuse. In this study, the impact of variation in collection area (600 m(2) and 900 m(2)) and appliance discharge volumes was examined. A number of demand management options were also investigated. The results of this study indicate greywater reuse is more suited than rainwater use for this development because of the steady, constant supply of greywater compared to the highly fluctuating, storm-event supply of rainwater and the high population density creating comparatively large volumes of greywater.

The expected increase in urbanization and population in coming years is going to increase the impervious land area, leading to substantial increases in stormwater runoff and hydrological challenges, and presents significant challenges for urban potable water supply. These are worldwide challenges that can potentially be ameliorated by harvesting stormwater for potable use or for other uses that can reduce the pressure on potable water supply. This study sought to assist the local water authority in planning for future potable water supply through a review of the scientific literature to determine the likely chemical and microbial characteristics of stormwater, the treatment train (TT) requirements, and the likely costs of treatment to achieve potable standards for the high-growth metropolitan region of Melbourne, Australia. Literature stormwater quality statistical data and treatment process performance data were used to model the expected product water microbial and chemical quality after treatment using a number of advanced TT options. The results of the modelling were compared with literature microbial log reduction targets (LRTs) for the potable use of stormwater and with the Australian Drinking Water Guidelines (ADWG). It was found that a reverse osmosis (RO)-based TT with microfiltration pre-treatment and post-RO advanced oxidation and chlorination in storage reservoirs is a conservative stormwater potable use treatment option. A less conservative and less expensive ozone-and-biologically active filtration (O3/BAF)-based TT option is also proposed if RO concentrate disposal is deemed to be too challenging. These results could be useful in climate change adaptation involving the evaluation of options for the mitigation of future population-growth- and climate-change-driven water supply challenges, as well as urbanization-driven stormwater hydrology and receiving water pollution challenges. [ABSTRACT FROM AUTHOR]

Diversified water supply schemes can reduce both peak demand and overall demand in the urban water supply network. Consequently, they provide benefits to both the water utility and their customers including deferring network augmentations and reducing household water bills, respectively. However, the installation of different water saving scenarios also incurs additional costs which present a financial burden to the householder. This paper investigates the financial viability of installing alternative water supplies and water efficient appliances in a large scale area, taking into account both their benefits and incurred costs. Water demand profiles were developed for the baseline and various water saving scenarios for new dwellings in Queensland, Australia. Hydraulic model runs were conducted to determine system augmentation and pump power requirements for various water saving scenarios across different planning horizons in a water supply study area. The results of the modeling showed deferred augmentations and reduced pumping requirements for the water savings scenarios, compared to the baseline scenario; contributing to monetary savings to the utility. Cost benefits to the householders are from reduced mains water and energy consumption, with incurred costs from installing the water saving systems. A total net cost balance appraisal demonstrated monetary savings for the water efficient and rainwater tank scenarios while the greywater scenario produced negative net costs. The results are discussed along with incentives and potential savings to promote sustainable alternative water use in an urban area. [ABSTRACT FROM AUTHOR]

Commercial buildings are central to cities and contribute significantly to the urban demand for natural resources, including freshwater. Green building benchmarking tools include more efficient water use as key indicator of sustainability. This paper explores options for substituting mains drinking water with an alternative, non-potable water source on a fit for purpose basis. The research findings are based on a monitoring study of a commercial building in Brisbane, Australia that is harvesting rainwater for meeting non-potable water demand. The results demonstrated that the system is only achieving moderate reliability in meeting demand due to operational problems. The case study analysis has highlighted the need to include validation and monitoring to ensure the system is operating as per design intent. The paper also investigates the potential of other local, non-potable water sources for high-rise commercial buildings, in particular air conditioning condensate and groundwater inflow to a basement wet well. The paper concludes by comparing the advantages and disadvantages of different local water sources which highlights the need to undertake a site specific investigation to identify a suitable alternative water source, which considers O&M complexity and the capacity of facilities management. [ABSTRACT FROM AUTHOR]

In a study to identify strategies to deal with rapid urbanization and threatening climate change, in Can Tho City, Vietnam, a survey of 1200 households was undertaken to investigate water access and sanitation services. The survey targeted three different groups based on their access to water services: (a) those with piped water supply, (b) without piped water, and (c) a mix of (a) and (b). Socio-economic factors and level of urbanization significantly influenced the different water sources accessed by households and their type of sanitation. Results indicated that householders often employed multiple water sources in an attempt to match source with intended use. The use of multiple water sources, levels of sanitation and the quality of water were found to be good indicators of reported rates of illness. Results also showed that the provision of piped water does not always provide the desired health outcomes, as the definition of adequate water supply does not include water quality objectives. Therefore, more detailed assessments may be required to understand how people use and access water and sanitation, and the impacts on public health. [ABSTRACT FROM PUBLISHER]

Abstract: Communal rainwater tank systems provide an alternative urban water supply solution for reducing dependence on centralised water supply networks. Rainwater from household roofs is transported through a gravity collection system and stored in a centralised communal tank before being treated and supplied back to homes through a reticulated pumping system. Literature on the design, life cycle costing and economies of scale of communal rainwater tank systems is currently limited. This study intends to develop a methodology for the system design, assess the economies of scale of communal systems and identify the main cost contributors for the total capital and life cycle costs. A methodology developed for this analysis is presented for the benefit of water professionals across the globe to support similar studies in their local regions. Housing layouts were developed, designed and costed for a flat topography and a centralised storage and treatment scenario, ranging from 4 to 576 homes. An economic assessment was then carried out using the net present value method (NPV). The results show that costs of storage and treatment units are more influential for a group of households at lower scale, whilst the diseconomy of scale of pipes is a major cost factor for higher scale of household groups. An optimal scale was observed between 192 and 288 households and sensitivity analysis on the discount rate showed no changes within this range. A basic analysis showed that topography of the land does influence overall NPV. However, the influence factor depends on the nature of the slope, with costs varying for differing scenarios and further work required to have a thorough understanding of its influence in final NPV. [Copyright &y& Elsevier]

Cities in developed countries have increasingly adopted rainwater tanks as an alternative water source over the last 15 years. The rapid uptake of rainwater tanks has been driven by the need to reduce demand for centralised water services that are under pressure to adapt to population growth and climate change impacts. Rainwater tanks are part of integrated urban water management approach that considers the whole water cycle to provide water services on a fit for purpose basis that minimises the impact on the local environment and receiving waters. Rainwater tanks are typically applied at the household scale for non-potable water source uses such as toilet flushing and garden irrigation. However, this paper reports on a communal approach to rainwater harvesting, where the water is treated for potable use. A communal approach to rainwater harvesting can offer benefits, such as: economies of scale for capital costs, reduced land footprint, centralised disinfection and flexibility in matching supply and demand for different households. The analysis showed that the communal approach could provide a reliable potable water source to a small urban development. However, there was an energy penalty associated with this water source compared to centralised systems that could be addressed through more appropriate pump sizing. The outputs from this monitoring and modelling study demonstrated rainwater harvesting can be expanded beyond the current mainstream practices of household systems for non-potable use in certain development contexts. The analysis contained in this paper can be used for the improved planning and design of communal approaches to rainwater harvesting. [ABSTRACT FROM AUTHOR]

• Building typology affected the performance of alternative water supply systems. • Alternative water supply scenarios were analyzed against sustainability criteria. • Alternative supply options in the local context were evaluated. • Net zero water use was not fully achieved through alternative supply systems. • High potable demand was a deterrent against achieving net zero water use target. The water crisis in urban areas has manifested concerns for sustainable water supply practices in buildings. Although efforts have been taken to reduce freshwater consumption through demand management techniques and alternative supply strategies to some extent, when it comes to a more sophisticated concept like net zero water (NZW) use, practically implemented cases are rare. Due to building characteristics, geographical location, and uncertainties in the decision-making process, the feasibility of the NZW target needs to be explored. This research used a framework with a case study in Melbourne, Australia, to evaluate alternative water supply scenarios that may have the potential to approach this target in mixed-use buildings. Alongside their technical performance in reducing mains water consumption, wastewater discharge, and stormwater runoff, alternative systems were analyzed against environmental, economic and social aspects of sustainability. For each sustainability criterion, an indicator was selected. Through the proposed scenarios, the goal of NZW use was not fully achieved. However, the three performance indicators exhibited considerable reductions in net water flows. Supposing that the three sustainability aspects are equally valued, a hybrid utilization of rainwater and treated greywater may be the preferred option for mixed-use buildings in a temperate climate. [ABSTRACT FROM AUTHOR]

Summary: Planning of regional and urban water resources, and in particular with Integrated Urban Water Management approaches, often considers inter-relationships between human uses of water, the health of the natural environment as well as the cost of various management strategies. Decision makers hence typically need to consider a combination of social, environmental and economic goals. The types of strategies employed can include water efficiency measures, water sensitive urban design, stormwater management, or catchment management. Therefore, decision makers need to choose between different scenarios and to evaluate them against a number of criteria. This type of problem has a discipline devoted to it, i.e. Multi-Criteria Decision Analysis, which has often been applied in water management contexts. This paper describes the application of Subjective Logic in a basic Bayesian Network to a Multi-Criteria Decision Analysis problem. By doing this, it outlines a novel methodology that explicitly incorporates uncertainty and information reliability. The application of the methodology to a known case study context allows for exploration. By making uncertainty and reliability of assessments explicit, it allows for assessing risks of various options, and this may help in alleviating cognitive biases and move towards a well formulated risk management policy. [ABSTRACT FROM AUTHOR]

This study describes the use of rainwater and greywater (originated from bathroom only) for provision of non-contact indoor and outdoor use in high-rise buildings. A brownfield development site in Box Hill suburb of Melbourne was selected as case study site for this investigation. The performance of alternative servicing options was compared with conventional water supply, stormwater and wastewater servicing. A water balance model UVQ (Urban Volume and Quality) was applied to determine storage capacities and to evaluate the percentage reduction in water supplying, stormwater run-off and wastewater disposal, as well as volumes of rainwater use and greywater reuse. In this study, the impact of variation in collection area (600m2 and 900m2) and appliance discharge volumes was examined. A number of demand management options were also investigated. The results of this study indicate greywater reuse is more suited than rainwater use for this development because of the steady, constant supply of greywater compared to the highly fluctuating, storm-event supply of rainwater and the high population density creating comparatively large volumes of greywater. [ABSTRACT FROM AUTHOR]

Flow pattern mapping of a water distribution network is important for operators and managers for its efficient operation, maintenance and management. Such a pattern can be developed for a water supply system from flow paths, which can be generated by travelling in the opposite direction of flow in the pipes from a demand (withdrawal) node to a supply (input) node in a pipe network. Similarly, the information about pipes forming primary loops is an essential part of the data for the analysis of a water distribution system. The loop data do not constitute information independent of the link-node information and theoretically it is possible to generate loop data from this information. Presented herein is an algorithm for flow paths generation and its application in flow pattern mapping and loop data formulation including identification of the water supply boundaries of each input point in a multi-input source water distribution system. [ABSTRACT FROM AUTHOR]

Gravity or pumping water transmission lines are planned for a predetermined time horizon generally called design period. For a static population the lines can be designed, either for a design period equal to the life of the pipes sharing the maximum cost of the system or for the perpetual existence of the supply system. For a growing population or water demand, it is always economical to design the mains in staging periods and then strengthen the system after the end of every staging period. In the absence of a rational criterion, the design period of water supply mains is generally based on the designer's intuition, disregarding the useful life of the component sharing maximum cost, pattern of population growth or increase in water demand and discount rate. Provided herein are numerical criteria for the design period of water transmission mains. [ABSTRACT FROM AUTHOR]

The present study examines the optimal water supply portfolio under the impact of climate change constructed by the authors previously. It incorporates feasibility planning for water supply projects, assesses a feasible water supply portfolio for central Taiwan, and uses the shadow price method to assess the rationality of the compensation policy for transferring agricultural water to ensure water supply security for the industrial sector. The study finds that Changhua and Yunlin have the highest per-unit costs of raw water, and the Nantou region has the highest carbon emission coefficient (carbon footprint) per unit of water produced. The cumulative value (2021–2031) of the water resources policy to reallocate agricultural water to achieve water supply security is about TWD 15.904–31.13 billion. The shadow price of industrial water is about TWD 40.18/cubic meter. Therefore, a compensation price for agricultural water transfer of less than TWD 40.18/cubic meter represents a rational policy. [ABSTRACT FROM AUTHOR]

Rainwater tanks are increasingly being implemented as part of the integrated urban water management paradigm where all sources of water, including potable, stormwater and recycled, are considered eligible to contribute to the urban water supply. Over the last decade or so, there has been a rapid uptake of rainwater tank systems in urban areas, especially in Australian cities, encouraged through financial incentives, but more importantly, from change in residential building codes effectively mandating the installation of rainwater tanks. Homes with rainwater tanks in Australian cities have increased from 15% to 28% over six years to 2013. These building codes specify certain rainwater tank specifications to achieve a stated rainwater use, and hence potable water savings. These specifications include minimum rainwater tank size, minimum connected roof area, plumbing for internal supply for toilets and washing machines, and external supply for garden watering. These expected potable water savings from households are often factored into regional strategic water planning objectives. Hence if rainwater tanks do not deliver the expected saving due to sub-standard installation and/or poor maintenance, it will have an adverse impact on the regional water plan in the longer term. In this paper, a methodology to assess the effectiveness of a government rainwater tank policy in achieving predicted potable water savings is described and illustrated with a case study from South East Queensland, Australia. It is anticipated that water professionals across the globe should be able to use the same methodology to assess the effectiveness of similar rainwater policies, or indeed any other distributed water saving policy, in their local planning communities. [ABSTRACT FROM AUTHOR]

• A methodology of ranking water sourcing from rivers, bores, irrigation excess and potable options is presented. • The ranking is utilised to inform about the most viable water sourcing option for aquaculture. • Life cycle costing and CO 2 -equivalent emission analyses are incorporated in the ranking. In this case study, we investigated the options for freshwater sources for a medium-sized aquaculture business in North West (NW) Tasmania. We considered four different options for water sourcing including from local rivers, groundwater, drinking water from local water supply utility as well as from nearby irrigation schemes. Our investigation employed the life cycle costing (LCC) approach for assessing the different options. Based on the locations of the future aquaculture plant, water demand, water availability from various sources, local topography, net present worth of total capital cost, operational and annual maintenance cost of required infrastructures, we found that both the river and groundwater options performed equally well. However, given the uncertainties in the long term environmental and hydrogeological impacts on the aquifer water quantity and quality resulting from continuous extraction of groundwater, water supply from the rivers in NW Tasmania offered the most preferred option for aquaculture business in NW Tasmania. Our proposed methodology for the assessment of alternative water sourcing options demonstrated ranking of the options based on net present values (NPV) of capital, operational and maintenance costs as well as on the amount of greenhouse gas emissions (CO 2 equivalent) generated from options considered. This ranking approach can be employed to other industries where large amount of water is required for process operations. [ABSTRACT FROM AUTHOR]

There are pressures on existing centralized water infrastructures in urban centers which justify the search for alternatives. An increasingly important alternative is to shift from centralized to hybrid systems, often in response to climate variability and demographic changes. In a hybrid system, water is supplied and discharged through a mix of centralized and decentralized systems. There is usually no single objective that justifies the choice of hybrid water systems, but they typically are justified based on the consideration of a number of different criteria in order to evaluate the overall quality of service provision. The most important criteria include meeting water demand, as well as reducing demand for fresh water and instead using local alternative water supplies. Integration of multiple objectives to evaluate the hybrid water supply systems can be accomplished by multi-criteria decision aid techniques. This paper evaluates a number of hybrid water supply scenarios using a case study based on the Northern Growth Area of Melbourne, Australia. It uses the Preference Ranking Organization METHod for Enrichment Evaluations (PROMETHEE) and Geometrical Analysis for Interactive Decision Aid (GAIA), one of the multi-criteria decision-making methods through D-Sight software, to rank the hybrid water supply scenarios, and this ranking is validated by means of sensitivity analysis. The centralized system combined with stormwater harvesting and the centralized system combined with treated wastewater and rainwater tanks yielded the first and second most preferred scenarios, while the centralized water supply system combined with treated wastewater yielded the worst hybrid water supply option. [ABSTRACT FROM AUTHOR]

Water efficiency measures and alternative supply sources alleviate peak water demand on urban water supply networks. Consequently, they also provide benefits to water service providers, in terms of augmentation deferrals and reduced sized infrastructure. However, while these benefits are acknowledged in the literature, they have not been thoroughly investigated and quantified. This paper empirically demonstrates how the installation of different potable water saving measures would affect the design of urban water supply networks. Peak day water demand profiles were developed for the baseline scenario, which represented the typical building code mandated for new dwellings constructed in Queensland, Australia, and for households fitted with water saving measures. The core novel feature of this study relates to the use of an innovative bottom-up approach to the development of demand profiles based on smart meters enabling comprehensive water end use datasets (i.e. demand in shower, tap, etc.) to be obtained. Hydraulic model runs were conducted for various water savings scenarios across different planning horizons to determine the scheduling of augmentations in a water supply study area. The results of the model runs showed deferred and eliminated augmentations, as well as reductions in infrastructure sizing for the water savings scenarios compared to the baseline scenario. Financial analysis (i.e. NPV) on trunk main augmentation requirements over 50 year asset life cycles indicated that savings of between $1,574,289 (11.4%) and $7,030,796 (51%) could be achieved by incorporating water efficiency and potable source substitution measures in new infill developments in the study region. [ABSTRACT FROM AUTHOR]

Summary: Provision of urban water supplies to rapidly growing cities of South East Asia is difficult because of increasing demand for limited water supplies, periodic droughts, and depletion and contamination of surface and groundwater. In such adverse environments, effective policy and planning processes are required to secure adequate water supplies. Developing a Water Needs Index reveals key elements of the complex urban water supply by means of a participatory approach for rapid and interdisciplinary assessment. The index uses deliberative interactions with stakeholders to create opportunities for mutual understanding, confirmation of constructs and capacity building of all involved. In Can Tho City, located at the heart of the Mekong delta in Vietnam, a Water Needs Index has been developed with local stakeholders. The functional attributes of the Water Needs Index at this urban scale have been critically appraised. Systemic water issues, supply problems, health issues and inadequate, poorly functioning infrastructure requiring attention from local authorities have been identified. Entrenched social and economic inequities in access to water and sanitation, as well as polluting environmental management practices has caused widespread problems for urban populations. The framework provides a common language based on systems thinking, increased cross-sectoral communication, as well as increased recognition of problem issues; this ought to lead to improved urban water management. Importantly, the case study shows that the approach can help to overcome biases of local planners based on their limited experience (information black spots), to allow them to address problems experienced in all areas of the city. [Copyright &y& Elsevier]