Potential for potable water savings by using rainwater and greywater in a multi-storey residential building in southern Brazil

Studies on the use of rainwater and greywater to promote potable water savings have been performed in different countries. The main objective of this article is to evaluate the potential for potable water savings by using rainwater and greywater in a multi-storey residential building composed of three blocks, located in Florianópolis, southern Brazil. Water end-uses were estimated by applying questionnaires and measuring water flow rates. An economic analysis was performed to evaluate the cost effectiveness of using rainwater and greywater either separately or together. Results show that the average potential for potable water savings range from 39.2% to 42.7% amongst the three blocks, considering that water for toilet flushing, clothes washing and cleaning does not need to be potable. By using rainwater, the potable water savings would actually range from 14.7% to 17.7%. When greywater is considered alone, potable water savings are higher, i.e., ranging from 28.7% to 34.8%. As for the use of rainwater and greywater combined, the potable water savings range from 36.7% to 42.0%. The main conclusion that can be made from the research is that the three systems that were investigated are cost effective as the payback periods were lower than 8 years, but the greywater system was the most cost effective one, followed closely by the rainwater one.     

Conceptual framework for decentralized green water‐infrastructure systems

We present a model for a decentralized green water‐infrastructure system (DGWIS) based on a new conceptual framework that optimises the use of captured rainwater, recycled wastewater and renewable energy resources. DGWIS is designed for building‐scale localised water supply systems that utilise rainwater and greywater and incorporate advanced small‐scale water treatment systems and renewable local energy sources such as solar and wind. Several constraints are considered: (i) available renewable energy; (ii) greywater production rate; (iii) potential captured rainwater; (iv) water demand; (v) water storage volumes required to accommodate greywater, harvested rainwater and separate water/energy supplies from the city and (vi) water treatment capacities. The proposed DGWIS optimisation framework demonstrates proof‐of‐concept and provides a solid foundation for an innovative paradigm shift towards water and energy sustainability.     

Seasonal patterns and socio-economic predictors of household rainwater and greywater use

Seasonal water insecurity is a growing concern in many countries. For some households, rainwater and greywater are important alternative water sources. This study examines household patterns and socio-economic predictors of using rainwater and greywater in urban Philippines, in rainy versus dry seasons. Results from a household survey (N = 396) and in-depth interviews (N = 18) suggest that rainwater and greywater use are widespread, particularly among households with more members, less financial resources, and less access to the public utility, in seasonal ways. Future research into the adoption and diffusion of these practices may inform policies that promote equitable water access year-round.     

Potential for potable water savings by combining the use of rainwater and greywater in houses in southern Brazil

Research on rainwater and greywater have been performed all over the world as a way of promoting potable water savings. The main objective of this article is to evaluate the potential for potable water savings by using rainwater and greywater in two houses in southern Brazil. An economic analysis is performed to evaluate the benefits of using rainwater and greywater either separately or together. Results indicate that the potential for potable water savings in both houses range from 33.8% (house B) to 36.6% (house A), considering that water for toilet flushing and washing machine does not need to be potable. By using rainwater, the potable water savings in house A would be 35.5% and in house B, 33.6%. When greywater is considered alone, potable water savings are lower, i.e., 30.4% in house A and 25.6% in house B. As for the use of rainwater and greywater combined, the potable water savings are 36.4% in house A and 33.8% in house B. The three systems that were investigated seem not to be cost effective as the payback periods were very high (above 17 years), but the greywater system was the most attractive one. The main conclusion that can be made from the research is that there needs to be government incentives in order to promote the use of rainwater or greywater in houses in southern Brazil.     

Rainwater harvesting for human consumption and livelihood improvement in rural Nepal: benefits and risks

Use of rooftop rainwater as a source of drinking water in developing countries is increasing. However, scepticism about the potential of this source and the associated health risks is still prevalent among water planners. A free listing and a household survey among 120 households was conducted in the hills of Nepal to examine the performance of rainwater harvesting systems. Users perceive few health risks and in contrast, reported a wide range of benefits, including health benefits associated with the consumption of rainwater. Water quality testing results generally demonstrate good water quality but confirm that appropriate operation and maintenance practices are critical to ensure the collection of good quality water. Deficiencies in technical design and construction, lack of awareness, no market for spare parts and the inability of vulnerable households to maintain the system pose a risk to the collection and storage of safe water and to the long‐lasting performance of the systems.     

Planning an urban wastewater system with centralised greywater reuse: a case in Beijing

This paper presents a proposed centralised greywater reuse (CGR) system for Daxing New City, Beijing. This system would use separate greywater and blackwater discharge pipes in residences and public buildings. Greywater would be treated in a centralised plant and reused for public purposes. Water supply–demand balance analysis showed that this system would conserve 28.5% of freshwater resources. A centralised wastewater reuse system that would conserve the same water resources and serve the same consumers was developed for comparison. The greywater reuse system would cost 1.2% more than the reference system, but would decrease the pollution load by 10% and improve the water-quality compliance of the Xinfeng River (total phosphorous: 24–42%, total nitrogen: 0–7%). The proposed CGR system exhibited acceptable water conservation, environmental impact, and construction and operation costs, and would thus be suitable in urbanising areas that face water shortages and aqueous environmental deterioration.     

Dilemma of roof rainwater quality: applications of physical and organic treatment methods in a water scarce region of Mekelle,Ethiopia

The public health field has built a body of literature showing health benefits from improvements in water quality. However, the connection between roof harvested rainwater and health is not well documented especially in developing countries. Understanding the application of locally available treatment methods provides insight into this problem. This paper reports on experimental investigations where rainwater collected from a typical domestic roof in Mekelle, Ethiopia was treated using Moringa stenopetala seed, sand filter and boiling. The quality of the raw and treated roof harvested rainwater were compared against the Ethiopian and World Health Organization drinking water standards to investigate its suitability as a supplement for potable water supply. The pollutants analysed were total coliforms and turbidity. A significant improvement of turbidity and total coliforms was observed. This implies that application of plant coagulant followed by filtration can sufficiently treat rainwater and can be used as a low-cost treatment option in water scarce areas.     

Economical viability analysis of an innovative gravity-driven rainwater harvesting system for a commercial office building

Gravity-driven rainwater harvesting (RWH) system showcases a promising alternative solution to reduce energy consumption in rainwater recycling. However, the economic efficiency is one of the most concerns with regard to the adoption of this green infrastructure. In this study, a commercial official building has a rooftop area of 1600 m² and with 560 inhabitants was assumed to apply two configurations of RWH system (i.e., gravity system and pressure system), and comparative study was conducted to evaluate the economic performance of two RWH systems. The potential water saving quantity of the RWH system was simulated based on a daily water balance model and their expected economic efficiency were discussed in terms of benefit cost ratio and net present value. Results shown that only when the building height is higher than 102 m or the property rent is less than 0.4 CNY (China Yuan) per square metre per day, can make the gravity system economically attractive. This study provides an innovative approach to utilize roof rainwater in a more low-energy mode; it is of great significance to promote building energy-saving and carbon reduction.     

Assessing integrated water management options for urban developments – Canberra case study

Urban water services in the Australian Capital Territory (ACT) are currently provided through conventional centralised systems, involving large-scale water distribution, wastewater collection, water and wastewater treatment. A study was conducted to assist Environment ACT in setting broad policies for future water services in Canberra. The current paper presents the outcomes of a study examining the effects of various water servicing options on water resources and the environment, for two townships in Canberra, one existing and one greenfield site. Three modelling tools were used to predict the effects of various alternative water servicing scenarios, including demand management options, rainwater tanks, greywater use, on-site detention tanks, gross pollutant traps, swales and ponds. The results show that potable water reductions are best achieved by demand management tools or a combination of greywater and rainwater use for existing suburbs, while third pipe systems are preferred for greenfield sites. For this specific climatic region and end use demands, modelling predicted increased water savings from raintanks compared to greywater systems alone, with raintanks providing the additional benefit of reduced peak stormwater flows at the allotment scale. Rainwater and stormwater reuse from stormwater ponds within the catchments was found to provide the highest reduction in nutrient discharge from the case study areas. Environment ACT amended planning controls to facilitate installation of raintanks and greywater systems, and commenced a Government funded rebate scheme for raintanks as a result of this study.     

The effect of roofing material on the quality of harvested rainwater

Due to decreases in the availability and quality of traditional water resources, harvested rainwater is increasingly used for potable and non-potable purposes. In this study, we examined the effect of conventional roofing materials (i.e., asphalt fiberglass shingle, Galvalume^® metal, and concrete tile) and alternative roofing materials (i.e., cool and green) on the quality of harvested rainwater. Results from pilot-scale and full-scale roofs demonstrated that rainwater harvested from any of these roofing materials would require treatment if the consumer wanted to meet United States Environmental Protection Agency primary and secondary drinking water standards or non-potable water reuse guidelines; at a minimum, first-flush diversion, filtration, and disinfection are recommended. Metal roofs are commonly recommended for rainwater harvesting applications, and this study showed that rainwater harvested from metal roofs tends to have lower concentrations of fecal indicator bacteria as compared to other roofing materials. However, concrete tile and cool roofs produced harvested rainwater quality similar to that from the metal roofs, indicating that these roofing materials also are suitable for rainwater harvesting applications. Although the shingle and green roofs produced water quality comparable in many respects to that from the other roofing materials, their dissolved organic carbon concentrations were very high (approximately one order of magnitude higher than what is typical for a finished drinking water in the United States), which might lead to high concentrations of disinfection byproducts after chlorination. Furthermore the concentrations of some metals (e.g., arsenic) in rainwater harvested from the green roof suggest that the quality of commercial growing media should be carefully examined if the harvested rainwater is being considered for domestic use. Hence, roofing material is an important consideration when designing a rainwater catchment.     

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.     

MODELLING THE IMPACTS OF DOMESTIC WATER CONSERVATION ON THE SUSTAIN ABILITY OF THE URBAN SEWERAGE SYSTEM

A computer model was developed to evaluate the impact of various technologies for water conservation in domestic households, in terms of the Impact on the operation of downstream infrastructure. These technologies, which include (a) low-flush toilets, (b) greywater re-use, and (c) re-use of rainwater from roof runoff for toilet flushing, were compared using indicators of sustainability to measure water consumption, sewerage-system operational performance and process treatment efficiency. The results demonstrated that rainwater re-use is potentially the most sustainable strategy in terms of the benefits associated with water conservation and reduction in sewage discharges from combined-sewer overflows (CSOs). The benefits were observed without the problems associated with increased sedimentation in sewers during dry weather, associated with other water-conservation strategies such as reduced-flush toilets, greywater re-use and the resultant increase in pollutants from CSOs during wet weather.     

Scenario analysis of rainwater harvesting and use on a large scale – assessment of runoff,storage and economic performance for the case study Amsterdam Airport Schiphol

Research on rainwater harvesting mainly focuses on a building scale. Scant information is available about its performance on a large scale. This study aims to determine the potential for, and economic viability of meeting non-potable water demand by rainwater harvesting for a large scale case (21.5 km²): Amsterdam Airport Schiphol. A dynamic model was developed to analyse scenarios of varying rainfall, catchment surfaces and storage capacity. Four potential system configurations of catchments and non-potable uses were analysed for their economic performance with different water prices and storage options. This study found that, given sufficient storage and catchment size, all non-potable water demand of Schiphol can be supplied, reducing drinking water demand by up to 58%. Diminishing returns for adding storage and catchment to the system make full supply inefficient. Current water charges make most large scale system configurations not viable due to high investment costs for supply networks and storage infrastructure.     

Roof-harvested rainwater for potable purposes: Application of solar collector disinfection (SOCO-DIS)

The efficiency of solar disinfection (SODIS), recommended by the World Health Organization, has been determined for rainwater disinfection, and potential benefits and limitations discussed. The limitations of SODIS have now been overcome by the use of solar collector disinfection (SOCO-DIS), for potential use of rainwater as a small-scale potable water supply, especially in developing countries. Rainwater samples collected from the underground storage tanks of a rooftop rainwater harvesting (RWH) system were exposed to different conditions of sunlight radiation in 2-L polyethylene terephthalate bottles in a solar collector with rectangular base and reflective open wings. Total and fecal coliforms were used, together with Escherichia coli and heterotrophic plate counts, as basic microbial and indicator organisms of water quality for disinfection efficiency evaluation. In the SOCO-DIS system, disinfection improved by 20–30% compared with the SODIS system, and rainwater was fully disinfected even under moderate weather conditions, due to the effects of concentrated sunlight radiation and the synergistic effects of thermal and optical inactivation. The SOCO-DIS system was optimized based on the collector configuration and the reflective base: an inclined position led to an increased disinfection efficiency of 10–15%. Microbial inactivation increased by 10–20% simply by reducing the initial pH value of the rainwater to 5. High turbidities also affected the SOCO-DIS system; the disinfection efficiency decreased by 10–15%, which indicated that rainwater needed to be filtered before treatment. The problem of microbial regrowth was significantly reduced in the SOCO-DIS system compared with the SODIS system because of residual sunlight effects. Only total coliform regrowth was detected at higher turbidities. The SOCO-DIS system was ineffective only under poor weather conditions, when longer exposure times or other practical means of reducing the pH were required for the treatment of stored rainwater for potable purposes.     

结合节能楼工程试谈福建推广雨水回收利用的设想探究

目前雨水回用技术在全国乃至世界范围内的应用十分广泛,对于城市节水有重大意义。本文对雨水回用技术在城区建筑物中的推广进行探究;分析了福建雨水回用技术在具体工程中应用;综合雨水回用工程的技术性和经济性分析福建省雨水回用技术推广发展前景。     

A dimensionless approach for the urban-scale evaluation of domestic rainwater harvesting systems for toilet flushing and garden irrigation

A dimensionless methodology to evaluate the water saving obtainable from large-scale implementation of domestic rain water harvesting (RWH) systems in urban areas is presented. The methodology combines the use of regressive relationships for water saving evaluation based on the results of the dimensionless rainwater tank water balance and of catchment-wide information obtained from geospatial databases. The adopted RWH scheme included internal use of rainwater for toilet flushing and external use for garden irrigation. An application to a portion of the city of Rome, Italy showed the methodology to allow systematic and accurate evaluation of RWH system performance at the selected urban scale. Results pointed out high water saving potential for toilet flushing ranging between 38–65% for tank sizes within 1–50 m³. Furthermore, more than one third of the systems provided water saving benefit for irrigation larger than 20% by using a 50 m³ tank.     

实践中不断完善的美国水环境管理政策

三十多年来,美国的水环境管理政策在实践中不断完善,使曾经受到严重污染的水环境逐步得到了修复,走出了一条世界闻名的“先污染后治理”的水管理道路。笔者详细介绍了美国的水资源管理机构设置以及水源和饮用水管理、污水管理、湿地和海洋水域系统管理、科学技术发展管理、资金管理的体制和运作方式,以期为国内的水资源管理提供借鉴。     

Health-based targets for greywater reuse in residential schools in Madhya Pradesh,India

In line with developments in the water reuse sector, this paper applied quantitative microbial risk assessment (QMRA) techniques to seven greywater reuse systems used for recycling shower water for toilet flushing. The objective of the study was to establish a scientific basis for health-based greywater targets for India. It involved qualitative risk assessments and quantitative microbiological analysis using Enterococci, thermotolerant coliforms (TTC) and coliphage indicator organisms. Four conclusions are drawn from this study. Firstly, the systems indicated a low risk and high quality, and secondly that low levels of risk were present in systems, resulting in the recommendation of guideline of 5000 cfu/100 mL rather than 10 000 cfu/100 mL for greywater utilised for direct toilet flushing. Thirdly, disability adjusted life years (DALYs) are a useful indicator of risk for evaluating the performance of a greywater reuse system in addition to chemical/microbiological indicators DALYs, and finally that TTC are a useful surrogate microbial indicator for analysis of greywater in developing countries with limited analytical facilities.     

Guidelines for Greywater Re-Use: Health Issues

This paper discusses the potential threat to health associated with the microbial contamination of grey-water. Although it has been shown that greywater may contain large numbers of potentially pathogenic microorganisms, the incidence of disease is dependent upon more than just the concentration of organisms. Other factors include the degree of exposure and the health and age of affected individuals. Proposed guidelines for the re-use of greywater focus upon faecal coliform contamination and suggest limits based upon the end use of recycled water.
The paper (a) proposes modifications to the guidelines to better represent the delicate balance between protection of public health and the levels of risk posed by greywater re-use within the context of everyday human activity, and (b) attempts to identify areas where there is either an expectation for responsibility or a personal acceptance of responsibility with regard to public or personal health.     

Greywater reuse systems for toilet flushing in multi-storey buildings – over ten years experience in Berlin

Water reuse in Germany has gained in significance in the last 10 years. Several greywater systems, built according to guidelines introduced in 1995, operate today with no public health risk. Two greywater treatment systems are described in this paper: a rotary biological contactor (RBC) built in 1989 for 70 persons, and a fluidized-bed reactor for a one-family household built in 1995 as the biological stage for the treatment of household greywater for use in toilet flushing. Both systems were optimized in the following years with consideration of a minimal energy and maintenance demand. As numerous investigations have shown, biological treatment of the greywater is indispensable in order to guarantee a risk-free service water for reuse applications other than potable water.