Dual Water Supply System Research Articles

Beneficial Evaluation of Residential Dual Water Supply System

The scientific development and utilization of regional unconventional water resources and the implementation of high-quality water supply at the county level is beneficial both in the water resources allocation and the water shortage alleviation. It is also important in improving the human society as well as protecting the ecological environment, which shows significant economic, social and environmental benefits. The beneficial evaluation analysis of the development and utilization of regional unconventional water resources and the potential of dual water supply are conducted in this study. The reasonable beneficial evaluation of the utilization of unconventional water resources and regional dual water supply system are of great significance to the regional effective water sources allocation and water supply method.

Study on sustainable defluoridization approaches for rural drinking water treatment in northern China

Groundwater for potable uses containing high fluoride is a worldwide threat to human health. Electrocoagulation is a sustainable approach for decentralized treatment. This study aims to analyse the economic and environmental impacts of electrocoagulation applied at different scale in rural area of northern China by life cycle cost (LCC) and life cycle assessment (LCA) methods. Decentralized treatment for defluoridization in rural Fangshan District, Beijing, where the groundwater quality is typical in northern China, is surveyed as a case study. Three scenarios were evaluated. In scenario 1 (S1) all domestic water is electrocoagulated at community scale without dual water supply system. In scenario 2 (S2) only water for potable uses is electrocoagulated at community scale and raw water and treated water are distributed via dual water pipeline systems. In scenario 3 (S3) water for potable uses is electrocoagulated at household scale. Life cycle assessment is performed with openLCA software and Ecoinvent database. S1 has the highest impacts for eutrophication and global warming. S2 has the lowest impact for toxicity but highest impact for ozone layer depletion. S3 has the lowest impact for global warming and acidification but highest impact for human toxicity. S2 is the costliest while S3 is the most economical. In this case, life cycle cost and global warming impact are the most restricted factors so electrocoagulation at household scale is recommended.

Smart Rainwater Harvesting for Sustainable Potable Water Supply in Arid and Semi-Arid Areas

This paper presents a smart rainwater harvesting (RWH) system to address water scarcity in Palestine. This system aims to improve the water harvesting capacity by using a shared harvesting system at the neighborhood level and digital technology. The presentation of this system is organized as follows: (i) identification of the challenges of the rainwater harvesting at the neighborhood level, (ii) design of the smart RWH system architecture that addresses the challenges identified in the first phase, (iii) realization of a simulation-based reliability analysis for the smart system performance. This methodology was applied to a residential neighborhood in the city of Jenin, Palestine. The main challenges of smart water harvesting included optimizing the shared tank capacity, and the smart control of the water quality and leakage. The smart RWH system architecture design is proposed to imply the crowdsourcing-based and automated-based smart chlorination unit to control and monitor fecal coliform and residual chlorine: screens, filters, and the first flush diverter address RWH turbidity. Water level sensors/meters, water flow sensors/meters, and water leak sensors help detect a water leak and water allocation. The potential time-based reliability (Re) and volumetric reliability (Rv) for the smart RWH system can reach 38% and 41%, respectively. The implication of the smart RWH system with a dual water supply results in full reliability indices (100%). As a result, a zero potable water shortage could be reached for the dual water supply system, compared to 36% for the municipal water supply and 59% for the smart RWH system. Results show that the smart RWH system is efficient in addressing potable water security, especially when combined with a dual water supply system.

The influence of water price and the number of residents on the economic efficiency of water recovery from grey water

This article presents the results of an analysis of the economic viability of using an installation for the treatment of grey water. Economic indicators in the form of simple payback time (SPBT) and net present value (NPV) were used in the analysis. The use of a dual water supply system should theoretically enable the reduction of the costs of both water supply and sewage disposal, ensuring investment profitability. The article presents the impact of the number of residents as well as the impact of water and sewage on the profitability of using example water-recovery systems. It was found that both factors have a huge impact on the result of the economic analysis. For a small number of residents and at a low price of water supply and sewage disposal, it is not profitable to invest in a water-recovery system. This is due to the high price of purification devices.

Water savings and reduction of costs through the use of a dual water supply system in a sports facility

In sustainable urban management, rainwater, greywater, and groundwater are increasingly being considered as alternative water sources where quality drinking water is not required for the water supply. Current technological solutions allow for the use of dual water supply systems in both private and public buildings. The latter, due to the potential to better manage an alternative water source in a sustainable manner, are recommended for larger scale use. In this article, the function of a dual water supply system operating in a sports facility, including the collection and use of rainwater for non-potable purposes, was evaluated on the basis of technical, quantitative and financial data. The analyses were performed to determine the facility’s water savings efficiency and cost reduction during period of 3 years. The results of the research prove that it is possible to manage rainwater for the benefit of the environment and achieve financial gain as a result of savings on charges for water from the municipal water supply and sewage disposal. While the findings of this study should encourage the use of rainwater in sports facilities, they also point to the need for properly designed of water storage tanks to maximise system efficiency.

Development of dual water supply using rooftop rainwater harvesting and groundwater systems

The aim of this study was to gain a better understanding on dual water supply system consisting of rainwater and groundwater. The pilot study of the designed system was carried out at the Universiti Tun Hussein Onn Malaysia, Batu Pahat, Johor. The first part of the analysis was carried out to assess the rainwater harvesting system efficiency. The monthly results on total quantities of the collected rainfall in storage tank was 48.97 m3 while the actual rainfall calculated was 56.04 m3 with 75% of collection efficiency. The rainfall-storage rating curve was then plotted using 150 rain events data versus the volume of harvested rainwater collected during the study period. The second part of the analysis was to determine the total average pumping rate by conducting a step drawdown test, which gave Q = 39.5 m3 / h. For the daily discharge rate, the well was capable to supply water approximately 1.69 m3. In the current study, the daily water demand calculated was 0.59 m3, which gave the total volume per month approximately from 16.5 to 18.3 m3. Based on the performance of the system, most of the days rainwater could not meet the water demand, thus have to be supported by the groundwater.

Engineering and Costs of Dual Water Supply Systems

Fresh water is becoming an ever more valuable and scarce resourcenowadays, and any method or approach that can contribute to the saving of fresh water resources is therefore beneficial. Dual water supply systems are water supply distribution systems employing two sources, consisting of one fresh water system for potable use, and another system of either seawater, untreated raw fresh water, or treated / reclaimed wastewater for toilet flushing purposes. The purpose of this book is to discuss the engineering and cost aspects of dual water supply systems drawing on the author's experience obtained in Hong Kong, where dual water supply systems have been used for fifty years. The book is suitable for use as a text book or reference book at undergraduate and postgraduate levels. University undergraduate students and postgraduate students in water science, civil engineering, environmental engineering and environmental science or management will be the principal audiences. Practicing engineers, managers and other practitioners in these fields will also find this an invaluable reference source. This title belongs to Water Research Foundation Report Series ISBN: 9781843391326 (Print) ISBN: 9781780402062 (eBook)

Design of dual water supply system using rainwater and groundwater at arsenic contaminated area in Vietnam

Fresh water, a renewable but limited resource, is scarce in many areas of the developing world. This paper proposes a dual water supply consisting of both rainwater and groundwater to provide sustainable water for an arsenic contaminated area. In this paper, a novel model has been developed based on rainfall variance. A rainwater harvesting (RWH) system can obtain optimal performance by changing the demand for water use according to rainfall. This model was then used to design a RWH system for Cukhe village. Using rainwater for potable purposes on dry days and for all purposes on rainy days is recommended. The cost of RWH systems is also analyzed. In order to achieve 100% reliability for a four-member household, a RWH system should have a roof area of 100 m2. Additionally, a tank size of 2 m3 is recommended for overall cost efficiency. From the yearly water supply chart, it is recommended that rainwater be supplied for potable purposes only in January–April and October–December, while it should be supplied for all purposes in May–September.

Urban Water Management: Best Practice Cases

Current water resources management practices in most developing countries result in unnecessarily high economic and environmental costs. The magnitude and consequences of such costs have spurred the emergence of a global consensus on principles for improving water resource management. India will face an acute scarcity of water by 2025, more than most nations in the developing world. There is compelling evidence that improved water resources policies can have major impacts. In a number of cases in developed and developing countries pricing and tariff combined with regulations have produced savings of 20% to 30% and more. Improving water management will require that developing countries address the major constraints that currently undermine the allocation and efficient use of their water resources. Experiences in both developing and developed countries, as presented in this article, showed that improved policies for conservation and reallocation can have major benefits. The concerned authorities should look for various alternatives such as rainwater harvesting, recycling of wastewater, reducing un-accounted water and other options. Rainwater harvesting should be made compulsory; wastewater reuse has to be made with dual water supply system for new layouts. As the suburbs in the city are increasing day by day, rainwater harvesting would be able to serve the city for much longer time.

Integration of seawater and grey water reuse to maximize alternative water resource for coastal areas: the case of the Hong Kong International Airport

Development, population growth and climate change have pressurized water stress in the world. Being an urbanized coastal city, Hong Kong has adopted a dual water supply system since the 1950s for seawater toilet flushing for 80% of its 7 million inhabitants. Despite its success in saving 750,000 m(3)/day of freshwater, the saline sewage (consisting of about 20-30% of seawater) appears to have sacrificed the urban water cycle in terms of wastewater reuse and recycling. Can seawater toilet flushing be applied without affecting the urban water cycle with respect to sustainable water resource management? To address this issue, we examined the entire urban water cycle and developed an innovative water resource management system by integrating freshwater, seawater and reclaimed grey water into a sustainable, low-freshwater demand, low-energy consumption, and low-cost triple water supply (TWS) system. The applicability of this novel system has been demonstrated at the Hong Kong International Airport which reduced 52% of its freshwater demand.

Establishing components of community satisfaction with recycled water use through a structural equation model

The use of recycled water is being promoted through policy in many parts of the world with the aim of achieving sustainable water management. However there are some major barriers to the success of recycled water use policies and their instruments, in particular for potable reuse schemes. One of these barriers can be a lack of community support. Despite the critical nature of community attitudes to recycled water to the success of projects, they are often little understood. Further information is required to ensure the successful implementation of recycled water policy and to ensure sustainable management of water resources is achieved. The aim of this paper is to establish the key components of community satisfaction with recycled water. This was investigated through a case study of the Mawson Lakes population in South Australia, where recycled water is used for non-potable purposes through a dual water supply system (the ‘recycled water system’). This paper reports results from a survey of 162 Mawson Lakes residents. A structural equation model (SEM) was developed and tested to explain and predict components of community satisfaction with recycled water use (for non-potable use) through the dual water supply system. Results indicate the components of satisfaction with recycled water use were an individual's positive perception of: the Water Authority's communication, trust in the Water Authority, fairness in the recycled water system's implementation, quality of the recycled water, financial value of the recycled water system, and risk associated with recycled water use (negative relationship). The results of this study have positive implications for the future management and implementation of recycled water projects in particular through dual water supply systems. The results indicate to water authorities and water policy developers guiding principles for community consultation with regards to the management of recycled water projects.

An inexact-stochastic dual water supply programming model

This paper introduces an inexact-stochastic dual water supply programming (ISDWSP) model based on analysis of the inexact characteristics in demand and supply subsystems of dual water supply system and their dynamic interactions. The model is based on an inexact chance-constrained programming (ICCP) method allowing both distribution information in B (right parameter in the model constrain) and uncertainties in A (left parameter in the model constrain) and C (parameter in the model function) with objective of maximizing economic return, and constrained to available water resource, economical, environmental and social constrains. The decision-making variables of ISDWSP model are water demanded amount by different sectors and waterworks building scale. In the solution process, the ISDWSP is transformed into two deterministic sub-models, which correspond to the upper and lower bounds of the objective function, and the reasonable interval solution set in the given decision space can be obtained by solving the two sub-models. Thus, decision alternatives can be obtained by adjusting decision variable values within their solution intervals and will be useful for decision makers to choose the projected applicable conditions considering tradeoffs between eco-environmental and economic objectives. The model is also applied in a new developing zone of North China with the results of the case study providing reasonable solutions for dynamic planning of different source water (DSW) allocation in a regional system. Finally, waterworks building plan is generated based on the projected applicable conditions.

Health risk assessment of non-potable domestic water supplies in the Netherlands

Dual water supply systems were installed in several newly built housing estates in the Netherlands in the late1990s. These residential homes were provided with both drinking water and separately with so-called household water for toilet flushing, laundry and the garden tap. Household water was produced by limited treatment from a variety of sources and had a lower quality than drinking water. No legislation for (the quality of) this type of water was present at the time and the Dutch government appointed six of these estates as pilot projects. Four pilot projects were intensively monitored for toxicological and microbiological safety as well as microbiological stability during a period of almost 16 months. Specific incidents such as cross connections between drinking water and household water and observations of viruses and pathogenic protozoa in treated water demonstrated that some of these systems were microbiologically unsafe. Furthermore certain household waters had a relatively high biofilm formation potential leading to growth of Legionella sp. and Aeromonas and complaints from customers about the smell and colour of the household water. In nearly all cases concentrations of heavy metals and organic pollutants were below drinking water standards, hence the toxicological risk caused by chemical substances was not significant. Based on the results of this study the Dutch government decided to discourage the production and distribution of household water on a large scale. At present all projects owned by water companies in the Netherlands have been terminated by replacing household water with drinking water.

Demand management aspects of urban water policy in the industrial sector: the case of the city of Thessaloniki, Greece

The present paper presents the main results of a research project. It deals with consumers' perception of water issues in the industrial sector, and examines and analyses water use patterns, water conservation methods and water pricing issues. Issues presented are the contribution of water to production processes, water consumption levels, water conservation options, the possibility of construction of a dual water supply system, the evaluation of different pricing policies, the willingness to pay (WTP) and the potential impact of a price increase. The study has shown that there is limited use of recycling methods, few pollution control practices and small effect of industrial water price on water consumption levels. As far as industrial consumers are concerned, they present inaccurate perception of water consumption levels and low willingness to pay for the improvement of water services.

Comparison of engineering costs of raw freshwater, reclaimed water and seawater for toilet flushing in Hong Kong

AbstractHong Kong is one of the very few coastal cities in the world that use ‘dual water supply systems’. Dual water supply involves two distribution systems: a freshwater system for potable use and a seawater system for toilet flushing. This study looks into the feasibility, from an engineering cost point of view, of extending seawater supply into districts where potable water is still being used for toilet flushing, including South District of Hong Kong Island, Sai Kung, Northern New Territories and Northwest New Territories. Besides seawater, raw (untreated) freshwater and reclaimed water (treated effluent from local sewage treatment works) are also considered to be used for toilet flushing for these districts. Six cases are developed for comparison by using the lowest net present value of cost criterion. The result shows that using seawater for toilet flushing in these districts has the best engineering economy.

Analysis of a rainwater collection system for domestic water supply in Ringdansen, Norrköping, Sweden

The possibilities for implementing a rainwater collection system in Ringdansen, a residential area in Norrköping, Sweden, have been explored by analysing four scenarios for using rainwater in a dual water supply system to supplement drinking water. A computer model has been generated to quantify the water saving potential of the rainwater collection scheme. The performance of the rainwater system is described by its water saving efficiency (WSE). Standard and low water consumption appliances have been taken into account in evaluating WSE and water conservation. According to the analysis, suggested rainwater tank sizes are presented.

Is direct nanofiltration with air fluxh an alternative for household water production for Amsterdam?

Amsterdam is building a new housing estate IJburg. It will house 45,000 residents. A dual water supply system, supplying drinking water and household water to the customers, appears to be an attractive alternative. Household water will be used for toilet flushing and for washing clothes. This concept has environmental advantages, while it is economically feasible. Household water will be produced from local surface water by a local production plant and must be sustainable. A treatment scheme, comprising coagulation-flotation-filtration and nanofiltration, complies with all the requirements. Direct nanofiltration with air flush may be an attractive alternative, provided that it results in a stable and robust operation. Direct nanofiltration with air flush will be compared with the originally system of coagulation/flotation followed by rapid filtration and spiral-wound nanofiltration. In a pilot plant research at Amsterdam Water Supply air flush nanofiltration was investigated in a 20 runs trial using IJ-Lake water with only a micro screen before the capillary nanofiltration. Quality and operational aspects of this system were investigated. From a membrane autopsy a lot of clay and organic fouling was found.

Economic, water quantity and quality impacts from the use of a rainwater tank in the inner city

A dual water supply system (rainwater and mains water) has been installed at an old house in Maryville a inner city suburb of Newcastle in New South Wales, Australia. A design was developed for the installation of a rainwater tank to supply rainwater for toilet, hot water and outdoor uses. The rainwater supply is supplemented with mains water via a trickle top-up system when water levels are low in the tank. An air gap is used for backflow prevention in accordance with Australian standards. The design, construction and performance of the dual water supply system at the Maryville house are examined in this paper. Monitoring of water quality from the rainwater tank and from an instantaneous hot water service at the Maryville house has revealed that the rainwater was acceptable for hot water, toilet and outdoor uses. Rainwater used in the hot water service was compliant with Australian drinking water standards. The cost of rainwater has been found to be $0.30 per kL which is less than the price of mains water in the Lower Hunter region and the commonly assumed cost of $1.00 to $14.00 per kL.

Rouse Hill – Australia's first full scale domestic non-potable reuse application

There has been increasing interest in reuse of effluent from sewage treatment plants in Australia in recent years, not only for agricultural or land irrigation purposes but also for the provision of dual water supplies to residential areas for the non-potable purposes of toilet flushing, car washing, garden watering and park or other open space irrigation. The Rouse Hill development in the north west of Sydney is Australia's first full scale application of domestic non-potable reuse, with the sewage treatment plant and the dual water distribution system being commissioned in late 1994. This paper describes the Rouse Hill project as a whole including the reasoning behind the installation of the dual water supply system, the design of the sewage treatment plant, the effluent qualities achieved, the design of the dual water distribution system and the requirements of the regulatory authority, the NSW Environmental Protection Authority.

Rouse Hill - Australiaʼn9s first full scale domestic non-potable reuse application

There has been increasing interest in reuse of effluent from sewage treatment plants in Australia in recent years, not only for agricultural or land irrigation purposes but also for the provision of dual water supplies to residential areas for the non-potable purposes of toilet flushing, car washing, garden watering and park or other open space irrigation. The Rouse Hill development in the north west of Sydney is Australiaʼns first full scale application of domestic non-potable reuse, with the sewage treatment plant and the dual water distribution system being commissioned in late 1994. This paper describes the Rouse Hill project as a whole including the reasoning behind the installation of the dual water supply system, the design of the sewage treatment plant, the effluent qualities achieved, the design of the dual water distribution system and the requirements of the regularory authority, the NSW Environmental Protection Authority.