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.     

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.     

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.     

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.     

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.     

Decentralized water management: rainwater harvesting and greywater reuse in an urban area of Beijing,China

Large-scale centralised wastewater treatment system has often prevailed in industrial countries, and has been regarded as a successful approach during the last century. However, transfer of this highly water-consuming system and so-called ‘end-of-pipe’ technology to developing countries, especially in fast-growing cities with scarce water resources, has been extremely limited. Decentralized water treatment is not a new technology and has been successfully implemented in many rural areas worldwide. However, there are few applications in urban areas. This study at Tianxiu Garden in Beijing, China, investigated the potential and feasibility of water management based on a decentralized approach, but modified for application of greywater recycling and rainwater harvesting in a densely populated semi-urban area. A high degree of drinking water substitution (more than 25%) could not be attained by rainwater harvesting. Recycling of treated greywater for toilet flushing was shown to be an efficient method for minimisation of drinking water consumption, and a more suitable technique than rainwater harvesting for saving water in Beijing, China.     

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.     

Biodegradation of domestic wastewater under the simulated conditions of Thailand

Serious concerns have been raised about the sustainability of conventional mechanized linear wastewater treatment systems in the developing world. Bangkok in Thailand is no exception to these concerns, and merits closer examination. This paper is aimed at unveiling the fundamental facts and characteristics relating to the organic degradation potentials of domestic wastewater in Bangkok. It is supported by evidence from simple laboratory experiments in which existing local conditions were simulated. The results showed that greywater‐like qualities of domestic wastewater do predominate in Bangkok, most probably as a result of three main factors: (1) continued use of leaching septic tanks, (2) the tradition of using water after defecation, instead of toilet paper, and (3) high organic degradation potentials under tropical monsoon conditions. Considering the small organic content, coupled with high organic degradation rates of the freshly collected greywater‐based sewage in Bangkok, low‐cost and decentralized natural treatment systems could be far more suitable for environmental sustainability in such tropical monsoon areas than the implementation of large‐scale sewage works.     

Presence and fate of priority substances in domestic greywater treatment and reuse systems

A wide range of household sources may potentially contribute to contaminant loads in domestic greywater. The ability of greywater treatment systems to act as emission control barriers for household micropollutants, thereby providing environmental benefits in addition to potable water savings, have not been fully explored. This paper investigates the sources, presence and potential fate of a selection of xenobiotic micropollutants in on-site greywater treatment systems. All of the investigated compounds are listed under the European Water Framework Directive as either “Priority Substances” (PS) or “Priority Hazardous Substances” (PHS). Significant knowledge gaps are identified. A wide range of potential treatment trains are available for greywater treatment and reuse but treatment efficiency data for priority substances and other micropollutants is very limited. Geochemical modelling indicates that PS/PHS removal during treatment is likely to be predominantly due to sludge/solid phase adsorption, with only minor contributions to the water phase. Many PS/PHS are resistant to biodegradation and as the majority of automated greywater treatment plants periodically discharge sludge to the municipal sewerage system, greywater treatment is unlikely to act as a comprehensive PS/PHS emission barrier. Hence, it is important to ensure that other source control options (e.g. eco-labeling, substance substitution, and regulatory controls) for household items continue to be pursued, in order that PS/PHS emissions from these sources are effectively reduced and/or phased out as required under the demands of the European Water Framework Directive.     

The implications of household greywater treatment and reuse for municipal wastewater flows and micropollutant loads

An increasing worldwide interest in water recycling technologies such as greywater treatment and reuse suggests that additional research to elucidate the fate of xenobiotics during such practices would be beneficial. In this paper, scenario analyses supported by empirical data are used for highlighting the potential fate of a selection of xenobiotic micropollutants in decentralised greywater treatment systems, and for investigation of the possible implications of greywater recycling for the wider urban water cycle. Potential potable water savings of up to 43% are predicted for greywater recycling based on Danish water use statistics and priority substance monitoring at a greywater treatment plant in Denmark. Adsorption represents an important mechanism for the removal of cadmium, nickel, lead and nonylphenol from influent greywater and therefore the disposal route adopted for the generated sludge can exert a major impact on the overall efficiency and environmental sustainability of greywater treatment.     

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.     

A statistical approach to the optimisation of membrane operation

A bench‐scale analysis has been conducted on the ultrafiltration of synthetic and real domestic wastewaters post‐biotreatment by a biological aerated filter. This paper presents a rigorous analytical technique to identify the process parameters that have a significant influence on a membrane system performance. By applying statistical techniques, the influence of each parameter and the level of uncertainty were quantified within a highly complex, interrelated and variable process. The results showed that the fouling propensity for real greywater was significantly variable, both during the trial and from one trial to the next. The variability was primarily due to the inherent variability of greywater quality and the extent of settling within the storage facility. However, the fouling propensity for real greywater was generally lower than for settled sewage. The results of the analysis were extended to produce a predictive model that can be used as a guide in the design of membrane systems and their operation. The methodology is readily transferable and adaptable to other membrane systems.     

Nutrient addition to enhance biological treatment of greywater.

This study compares the chemical oxygen demand (COD) removal and respiration rates of a microbial population treating real and synthetic greywaters dosed with nutrient supplements. The nutrient composition of the real and synthetic greywaters was analysed and the dosing regime for nitrogen, phosphorus and a range of trace metals planned accordingly. The doses consisted of eight single additives (macronutrients and trace metals) to the control greywater and six trace metal additions to C: N : P balanced greywater. The COD removal for the control real and synthetic greywater in lab-scale activated sludge systems (0.038 and 0.286 kg COD kg MLSS(-1) d(-1), respectively) confirmed nutrient limitation and the poor degree of greywater treatment. Nutrient dosing increased the COD removal rate and oxygen uptake rate in many cases. The greatest stimulation of microbial activity was observed with zinc additions to C: N: P balanced real greywater (1.291 kg COD kg MLSS(-1) d(-1) over 30 times the control). Inhibitory effects to various extents were rare and limited mainly to the additions of metals to synthetic greywater. The dominance of chemicals effects was observed on addition of some micronutrients; notably iron and aluminium, metals on which many coagulants for use in biotreatment of other wastewaters are based. The data indicate that the impact of understanding microbial processes and the nutrients required for wastewater treatment can only serve to optimise process efficiency for the proposed treatment of greywater.     

Benchmarking energy consumption and CO2 emissions from rainwater‐harvesting systems: an improved method by proxy

Life cycle analyses (LCAs) show the main operational energy contribution for rainwater‐harvesting (RWH) systems come from ultraviolet (UV) disinfection and pumping rainwater from tank to building. Simple methods of estimating pump energy consumption do not differentiate between pump start‐up and pump‐operating energy or include pump efficiency parameters. This paper outlines an improved method incorporating these parameters that indirectly estimates pump energy consumption and carbon dioxide (CO₂) emissions using system performance data. The improved method is applied to data from an office‐based RWH system. Comparison of the simple and improved methods identified the former underestimates pump energy consumption and carbon emissions by 60%. Results of the improved method corresponded well to directly measured energy consumption and energy consumption represented 0.07% of an office building's total energy consumption. Consequently, the overall energy consumption associated with RWH systems is a very minor fraction of total building energy consumption.     

绿色住宅建设中的可再生能源技术

近年绿色建筑和可再生能源技术越来越得到社会和业界的认同,文章从近年来在智能小区建设中常用的太阳能发电、风力发电、太阳导光管照明、太阳能灯具、LED节能灯、太阳能热水、中水回收和雨水收集利用、地源和水源热泵等方面入手,阐述采用可再生能源技术的应用前景及其重要作用.     

Performance of UV disinfection and the microbial quality of greywater effluent along a reuse system for toilet flushing

This paper examines the microbial quality of treated RBC (Rotating Biological Contactor) and MBR (Membrane Bioreactor) light greywater along a continuous pilot-scale reuse system for toilet flushing, quantifies the efficiency of UV disinfection unit, and evaluates the regrowth potential of selected microorganisms along the system. The UV disinfection unit was found to be very efficient in reducing faecal coliforms and Staphylococcus aureus. On the other hand, its efficiency of inactivation of HPC (Heterotrophic Plate Count) and Pseudomonas aeruginosa was lower. Some regrowth occurred in the reuse system as a result of HPC regrowth which included opportunistic pathogens such as P. aeruginosa. Although the membrane (UF) of the MBR system removed all bacteria from the greywater, bacteria were observed in the reuse system due to “hopping phenomenon.” The microbial quality of the disinfected greywater was found to be equal or even better than the microbial quality of “clean” water in toilet bowls flushed with potable water (and used for excretion). Thus, the added health risk associated with reusing the UV-disinfected greywater for toilet flushing (regarding P. aeruginosa and S. aureus), was found to be insignificant. The UV disinfection unit totally removed (100%) the viral indicator (F-RNA phage, host: E. coli F_amp⁺) injected to the treatment systems simulating transient viral contamination. To conclude, this work contributes to better design of UV disinfection reactors and provides an insight into the long-term behavior of selected microorganisms along on-site greywater reuse systems for toilet flushing.     

Assessment of greywater reuse as a potential mitigation measure for water shortages and sanitation problems in senior high schools

The study assessed water shortages and its effects on sanitation in Senior High Schools using structured questionnaires involving water availability, water use pattern and perception of greywater reuse. Additionally, an observation of the sanitation situation was done to validate the responses. The study found that water availability was an issue as this caused students to use more than an hour round trip to access water resulting in poor sanitation and hygiene practices. Meanwhile, an average greywater generation rate of 14.5 L per person per day, is always disposed of despite its potential reuse. Greywater reuse was accepted by respondents as 59% proposed reusing it if available for non‐potable applications (94%) such as toilet cleaning and flushing. This is because, there is a significant association between cleanliness of the toilet facilities and usage (P < 0.05). Respondents who declined greywater reuse cited health risks (58%), uncomfortable feeling (37%) and cultural issue (5%).     

城镇排水系统设计与运行中的若干问题探讨

按照传统规范设计的排水系统,在实际运行中存在很多问题,不便于维护管理。为此对雨水系统设计运行中的以下内容提出了改进措施:雨水口和淹没出水口的设置,在适当位置铺设雨水系统的连通管,积水严重段临时增设直通污水检查井的雨水口,合理铺设住宅区雨水系统、加快雨洪资源利用的推广应用等。另外,还对污水系统中的以下内容提出了改进措施:设计运行改进检查井构造,在适当位置铺设污水管系统之间的连通管,铺设污水厂进水总管复线,闸槽井做法,旧泵站集水池有效容积和最低水位线的确定,污水厂的规模和效率,排水体制的确定等,可供相关人员参考。     

An optimal solution of thermal energy usage in the integrated system of stormwater collection and domestic-water heating

A solution is proposed to make use of the rainwater thermal energy in highly urbanised areas. It is demonstrated that the stormwater heat represents an additional on-site renewable energy available for hot water production. The proposed solution increases multi-functionality in the urban infrastructure that is essentially used to mitigate impacts from extreme climate events. The integrated system model applications correspond to local area conditions in the north-eastern Baltic region. This study considers the optimal collection of stormwater through maximizing the water absorbed heat usage in relation to hot water consumption in different building types (residential, public and commercial). Two key parameters, ‘stormwater volume in storage tank’ and ‘rainwater catchment area’, are determined. A genetic algorithm finds a number of storage tank fillings corresponding to rainfall statistics and the hot water consumption of buildings. System cumulative expenses are related to the stormwater storage and the rainwater harvesting expenses.     

Whole life cost performance of domestic rainwater harvesting systems in the United Kingdom

Rainwater harvesting (RWH) can be used to reduce the demand for potable mains water. At the single‐building scale, previous research has focused on water‐saving potential, while financial assessment has either been omitted or considered in an ad hoc manner. This paper reports on the application of a more rigorous financial analysis of domestic RWH systems than had been conducted previously. Whole life costing was selected as the most appropriate financial assessment technique. A total of 3840 domestic system configurations were assessed at a daily time step, taking into account various stakeholder perspectives and future cost scenarios. In each case, it was found that harvesting rainwater was significantly less cost effective than relying solely on mains‐only water. The domestic RWH systems generally resulted in financial losses approximately equal to their capital costs. Without significant financial support, domestic RWH is unlikely to be cost effective for all reasonably foreseeable scenarios.