Non-potable Water Demand Research Articles

Metagenomic Characterization of Antibiotic Resistance Genes in Full-Scale Reclaimed Water Distribution Systems and Corresponding Potable Systems.

Water reclamation provides a valuable resource for meeting nonpotable water demands. However, little is known about the potential for wastewater reuse to disseminate antibiotic resistance genes (ARGs). Here, samples were collected seasonally in 2014-2015 from four U.S. utilities' reclaimed and potable water distribution systems before treatment, after treatment, and at five points of use (POU). Shotgun metagenomic sequencing was used to profile the resistome (i.e., full contingent of ARGs) of a subset ( n = 38) of samples. Four ARGs ( qnrA, blaTEM, vanA, sul1) were quantified by quantitative polymerase chain reaction. Bacterial community composition (via 16S rRNA gene amplicon sequencing), horizontal gene transfer (via quantification of intI1 integrase and plasmid genes), and selection pressure (via detection of metals and antibiotics) were investigated as potential factors governing the presence of ARGs. Certain ARGs were elevated in all ( sul1; p ≤ 0.0011) or some ( blaTEM, qnrA; p ≤ 0.0145) reclaimed POU samples compared to corresponding potable samples. Bacterial community composition was weakly correlated with ARGs (Adonis, R2 = 0.1424-0.1734) and associations were noted between 193 ARGs and plasmid-associated genes. This study establishes that reclaimed water could convey greater abundances of certain ARGs than potable waters and provides observations regarding factors that likely control ARG occurrence in reclaimed water systems.

Analysis of Rooftop Rainwater Harvesting in Kabul New City: A Case Study for Family Houses and Educational Facilities

The Afghan government has planned the project of Kabul New City (KNC) to cope with the rapid growth of Kabul, an existing capital city. Due to climatic and topographical reasons, it is supposed that KNC suffers from a water scarcity problem. This study investigates the feasibility of a rooftop rainwater harvesting system in KNC to relieve the water scarcity problem. An applicability of the rooftop rainwater harvesting system was discussed for several types of residential houses and schools, using 11 years rainfall data. This study also examined the cost-effectiveness of the system by considering the service life of the system. Furthermore, an optimal size of the rainwater storage tank was discussed based on the balance among harvested rainwater volume, non-potable water demand, and cost-effectiveness.

Quantification of mains water savings from decentralised rainwater, greywater, and hybrid rainwater-greywater systems in tropical climatic conditions

Decentralised rainwater harvesting, greywater recycling, and hybrid rainwater-greywater systems mitigate water scarcity in urban areas. However, data on the mains water savings potential of these systems is not well documented in Malaysia, and real site characteristics are often neglected. The main objectives of this study were to (i) quantify mains water savings potential of six rainwater harvesting systems, two greywater recycling systems, and a hybrid rainwater-greywater system in Malaysia using real site characteristics as inputs to an in-house spreadsheet RainTANK water balance model; (ii) evaluate and recommend optimal connected roof area and rainwater tank volume combinations to maximise yields in rainwater systems; (iii) determine differences in mains water savings potential between domestic and commercial rainwater and greywater systems; and (iv) evaluate the possibility of upgrading an existing rainwater system to a hybrid rainwater-greywater system. Results showed that domestic rainwater systems supplied more than 90% of non-potable water demand for toilet flushing, laundry, and irrigation (i.e. with an overall reliability ranging between 35.5% and 52.5% for the modelled sites), whereas commercial rainwater system supplied less than 43% of non-potable water demand for toilet flushing and irrigation (i.e. with an overall reliability ranging between 11.2% and 22.1% for the modelled sites). Greywater recycling provided overall reliabilities of 21.1% and 41.0% for commercial and domestic systems, respectively, for toilet flushing and irrigation. Domestic rainwater systems had optimal roof areas and tank volumes, whereas commercial rainwater systems can improve rainwater yields by 41–67% by increasing either connected roof area or total rainwater tank volume. Upgrading to a hybrid system increases mains water savings for both domestic and commercial buildings, and maximum overall reliabilities of 32.3%, 57.1%, and 25.1% at Sites 1, 2, and SP, respectively, can be gained from reusing rainwater followed by greywater. A domestic hybrid system should primarily reuse rainwater and supply remaining demand with greywater, whereas a commercial hybrid system should reuse greywater and top-up with rainwater.

Life cycle assessment of small-scale greywater reclamation systems combined with conventional centralized water systems for the City of Atlanta, Georgia

This study examines a hybrid system (HS) that combines a greywater reclamation system with the centralized water system. Greywater is collected from laundry, showers, faucets and dishwashing and is reclaimed for non-potable on-site purposes (i.e., irrigation and toilet flushing) by using submerged membrane bioreactors (MBRs). This technology can reduce the burden of the conventional system (CS), defined as the water supply and wastewater treatment systems within the City of Atlanta. We conducted a life cycle assessment (LCA) comparison of the HS and CS using TRACI v2.1, which simulates ten impacts related to the ecosystem, human health and natural resources. We simulated the technology feasibility for nine residential zones, including five single-family house zones (SFZs) and four multi-family apartment building zones (MFZs) that vary by land use and population density (0.4–62.2 persons per 1000 m2). The greywater reclamation system reduces non-potable water demand in SFZs (by 17–49%) and MFZs (by 6–32%) while simultaneously reducing electricity consumption by 17–49% and 32–41% for SFZs and MFZs, respectively. Moreover, the LCA score of the CS is 20–41% lower than that of the HS. However, the sensitivity analysis indicates that energy sources in electricity generation play a critical role in reducing and stabilizing life cycle impacts. The results indicate that the LCA scores stabilize at higher population densities. Therefore, once the greywater reclamation capacity is exhausted, municipalities can further decrease the life cycle impacts related to water infrastructure through improvements in the electricity generation infrastructure.

Assessing efficiency and economic viability of rainwater harvesting systems for meeting non-potable water demands in four climatic zones of China

Rainwater harvesting is now increasingly used to manage urban flood and alleviate water scarcity crisis. In this study, a computational tool based on water balance equation is developed to assess stormwater capture and water saving efficiency and economic viability of rainwater harvesting systems (RHS) in eight cities across four climatic zones of China. It requires daily rainfall, contributing area, runoff losses, first flush volume, storage capacity, daily water demand and economic parameters as inputs. Three non-potable water demand scenarios (i.e., toilet flushing, lawn irrigation, and combination of them) are considered. The water demand for lawn irrigation is estimated using the Cropwat 8.0 and Climwat 2.0. Results indicate that higher water saving efficiency and water supply time reliability can be achieved for RHS with larger storage capacities, for lower water demand scenarios and located in more humid regions, while higher stormwater capture efficiency is associated with larger storage capacity, higher water demand scenarios and less rainfall. For instance, a 40m3 RHS in Shanghai (humid climate) for lawn irrigation can capture 17% of stormwater, while its water saving efficiency and time reliability can reach 96% and 98%, respectively. The water saving efficiency and time reliability of a 20m3 RHS in Xining (semi-arid climate) for toilet flushing are 19% and 16%, respectively, but it can capture 63% of stormwater. With the current values of economic parameters, economic viability of RHS can be achieved in humid and semi-humid regions for reasonably designed RHS; however, it is not financially viable to install RHS in arid regions as the benefit-cost ratio is much smaller than 1.0.

Reservoir volume optimization and performance evaluation of rooftop catchment systems in arid regions: A case study of Birjand, Iran

This study evaluated the performance of rooftop catchment systems in securing non-potable water supply in Birjand, located in an arid area in southeastern Iran. The rooftop catchment systems at seven study sites of different residential buildings were simulated for dry, normal, and wet water years, using 31-year rainfall records. The trial and error approach and mass diagram method were employed to optimize the volume of reservoirs in five different operation scenarios. Results showed that, during the dry water year from 2000 to 2001, for reservoirs with volumes of 200–20000 L, the proportion of days that could be secured for non-portable water supply was on average computed to be 16.4%–32.6% across all study sites. During the normal water year from 2009 to 2010 and the wet water year from 1995 to 1996, for reservoirs with volumes of 200–20000 L, the proportions were 20.8%–69.6% and 26.8%–80.3%, respectively. Therefore, a rooftop catchment system showed a high potential to meet a significant portion of non-potable water demand in the Birjand climatic region. Reservoir volume optimization using the mass diagram method produced results consistent with those obtained with the trial and error approach, except at sites #1, #2, and #5. At these sites, the trial and error approach performed better than the mass diagram method due to relatively high water consumption. It is concluded that the rooftop catchment system is applicable under the same climatic conditions as the study area, and it can be used as a drought mitigation strategy as well.

Performance of rainwater harvesting systems under scenarios of non-potable water demand and roof area typologies using a stochastic approach

Urban water systems throughout the world are under recurring and increasing water scarcity, given demand growth, aging infrastructure, variability and uncertainty imposed by climate change. Rainwater harvesting systems (RWHS) represent a promising alternative to increase flexibility and robustness of water supply systems. Given the importance of the tank size in establishing a reliable RWHS, we propose an implicit stochastic approach to assess performance and aid designers. The main objective of this study is to simulate common non-potable water demand and roof area typologies and verify how the demand and roof area affect the efficiency of the RWHS. To highlight the usefulness of the model to aid in the definition of tank sizes, we have also performed an economic assessment. Results are specific to the study region’s climate and might vary under different climate. However, we have chosen a rather unfavourable climate, with poor rainfall distribution along the year. Under such conditions, results are likely closer to lower bound benefits. This indicates potential water savings benefits of a RWHS even for unfavourable scenarios. The RWHS indicated to be more efficient at meeting demands with smaller Demand-Roof Area ratios. Furthermore, it was possible to determine the efficiency of the RWHS under various scenarios, identifying the minimum and maximum likely benefits. Several scenarios were compared directly allowing for the establishment of a general maximum tank size per unit roof area in a given region of interest, beyond which no significant benefits are likely. The economic assessment indicates positive net present values for investing in RWHS, especially for large rooftop areas and small Demand-Roof Area ratios. Under such conditions, investing in a RWHS has very low risk and will most likely have short payback times.

Assessment of the potential for potable water savings by using rainwater in houses in southern Brazil

The state of Santa Catarina, southern Brazil, has been suffering from water scarcity mainly over summer due to high potable water consumption and outdated water supply system. On the coast, several cities have their population doubled due to tourism during summer. In this context, this paper aims to evaluate the potential for potable water savings by using rainwater in the residential sector of 60 cities located in Santa Catarina state. Computer simulations using the Netuno computer programme were performed considering long-term daily rainfall time series for each city and typical characteristics of houses such as roof area, number of people per house, potable water demand and non-potable water demand (rainwater demand). In total, 2,700 simulations were performed. From the computer simulations, an ideal rainwater tank capacity and the corresponding potential for potable water savings for each case were obtained. Results showed average potable water savings ranging from 75 to 461 litres/day per house and rainwater tank capacities ranging from 1,000 to 16,000 litres. Despite the production of average outcomes using long-term daily rainfall data in cities with a high inter-annual variation of rainfall, results showed that the use of rainwater in houses may bring considerable potable water savings in Santa Catarina state and so could contribute to mitigating the potable water shortages.

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.

A decision support system for the technical sustainability assessment of water distribution systems

The purpose of this study is to develop a decision support system (DSS) for the technical sustainability assessment of water distribution systems (WDSs). The technical sustainability is assessed based on the sustainability index methodology using reliability, resiliency, and vulnerability as performance criteria. These performance criteria are visualized by the DSS combining several visualization techniques to improve the raw data readability and the effectiveness of the decision-making process. The technical sustainability of the existing WDS is assessed using the sustainability index methodology and two alternative scenarios are proposed to improve the sustainability. The “new pump” scenario is based on adding network components. The second scenario is based on using reclaimed water for non-potable water demand and fire flow. The results show that the DSS is effective to illustrate time-dependent variables in the WDS and that the sustainability index methodology is a credible approach to compare scenarios and to identify problematic locations.

Avaliação do potencial de redução do consumo de água potável por meio da implantação de sistemas de aproveitamento de água de chuva em edificações unifamiliares

In a scenario of relative water scarcity, it is advisable to implement public policies aiming at maintaining adequate potable water supply. A relevant alternative regarding water supply policies is the use of rainwater harvesting systems in residential buildings in order to meet the households non-potable water demands. This paper suggests a methodology to evaluate the potential for drinking water savings in urban area using rainwater for non-potable purposes in single-family dwellings. Hydraulic and financial assessments were performed, taking as case study Belo Horizonte, 2.4 million-inhabitant city that is the capital of the state of Minas Gerais. Results suggest that, in a scenario of widespread use of domestic rainwater harvesting systems, one can get the equivalent of two months of drinking water supply as drinking water annual savings. On the other hand, for the adopted scenario, results suggest economic feasibility of the systems, although with a high payback and internal rate of return very close to the attractive interest rates. These results suggest that the dissemination of these systems may require funding models and other economic tools to promote them for large scale use

Quantitative assessment of residential water end uses and greywater generation in the City of Al Ain

Diversification of water sources and water demand reduction are two vital tools in maintaining the security of urban water supplies in the United Arab Emirates (UAE). Reuse of greywater for non-potable end uses can be an effective alternative, but this resource has not yet received much attention in the UAE. Since the generation of greywater significantly differs from country to country – depending on age, gender, habits, lifestyle, living standards and the degree of water abundance – an attempt was made to estimate internal water consumption and greywater generation in the city of Al Ain, UAE. The frequency and water requirement for personal water uses (e.g. showers, ablutions, teeth brushing, hand washing, face washing and toilet flushing) and family water uses (e.g. laundry, dish washing and house cleaning) were estimated from about 100 villa-type detached homes randomly distributed across the city. A frequency analysis was carried out using normal, lognormal, gamma and logistic distribution. The estimated average generation rate of greywater was found to be 192 litres per capita per day, which is about 69% of the average internal water consumption. The generated greywater originates from showers (49%), ablutions (18%), laundry (10%) and washbasins (23%). Based on average quantities, it was shown that the generated greywater is sufficient to fulfil the non-potable water demand in houses, but further, more rigorous, investigation is required.

Evaluation of alternative water sources for commercial buildings: A case study in Brisbane, Australia

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.

Water Supply and Stormwater Management Benefits of Residential Rainwater Harvesting in U.S. Cities

AbstractThis article presents an analysis of the projected performance of urban residential rainwater harvesting systems in the United States (U.S.). The objectives are to quantify for 23 cities in seven climatic regions (1) water supply provided from rainwater harvested at a residential parcel and (2) stormwater runoff reduction from a residential drainage catchment. Water‐saving efficiency is determined using a water‐balance approach applied at a daily time step for a range of rainwater cistern sizes. The results show that performance is a function of cistern size and climatic pattern. A single rain barrel (190 l [50 gal]) installed at a residential parcel is able to provide approximately 50% water‐saving efficiency for the nonpotable indoor water demand scenario in cities of the East Coast, Southeast, Midwest, and Pacific Northwest, but <30% water‐saving efficiency in cities of the Mountain West, Southwest, and most of California. Stormwater management benefits are quantified using the U.S. Environmental Protection Agency Storm Water Management Model. The results indicate that rainwater harvesting can reduce stormwater runoff volume up to 20% in semiarid regions, and less in regions receiving greater rainfall amounts for a long‐term simulation. Overall, the results suggest that U.S. cities and individual residents can benefit from implementing rainwater harvesting as a stormwater control measure and as an alternative source of water.

Assessment of residential rainwater harvesting efficiency for meeting non-potable water demands in three climate conditions

Global demand for clean water supplies is on the rise due to population growth. This is also true in most cities of Iran. Non-conventional water resources must be developed to partially offset the increasing demand. In this study, the applicability and performance of rainwater harvesting (RWH) systems to supply daily non-potable water were assessed. Storage of rain falling on the roofs of residential buildings and directed into installed tanks was simulated in three cities of varying climatic conditions, namely Tabriz (Mediterranean climate), Rasht (humid climate), and Kerman (arid climate). Daily rainfall statistics for a period of 53 years as well as the information on the contributing roof area, available tank volumes and non-potable water demand were collected in each city. Typical residential buildings with roof areas of 60, 120, 180 and 240m2 with an average of four residents in each house were considered for the study. According to the results in humid climate, it is possible to supply at least 75% of non-potable water demand by storing rainwater from larger roof areas for a maximum duration of 70% of the times. For roofs with small surface area, the supply meets 75% of non-potable water demand for a maximum duration of 45% of the times. Moreover, for Mediterranean climate, it is possible to supply at least 75% of non-potable water demand in buildings with larger roof areas for a maximum duration of 40% of the times. It is also found that in arid climate, similar duration is only 23% of the times.

Urban stormwater harvesting – sensitivity of a storage behaviour model

The harvesting of urban stormwater to supply non-potable water demands is emerging as a viable option, amongst others, as a means to augment increasingly stressed urban water supply systems. This paper investigates the sensitivity of an urban stormwater harvesting system's capacity-yield-reliability relationship to variations in the behaviour modelling method used, focusing on the storage and demand components of a single reservoir system. The aim is to enhance our understanding of the appropriate computational method for assessing such volumetric reliability/storage capacity relationships. Four reference scenarios were developed, based on two different climates and two different water demand patterns. A sensitivity analysis was conducted, which considered the following computational, storage and demand parameters: yield-spillage order, modelling time-step, length of rainfall record, initial storage volume, open/closed storage surface, dead storage volume, diurnal and weekly pattern of water demand, and inter-annual variability of seasonal water demand. It was found that several parameters had an insignificant impact on the estimation of volumetric reliability for the scenarios tested, whilst the three most significant parameters were: length of rainfall record, inter-annual variability of seasonal demand, and storage surface type. Recommendations about the minimum length of rainfall record used and the inclusion of both the inter-annual variability of seasonal demand and net evaporative losses in the case of an open store are made.

Wastewater with advanced treatment: an option for meeting Kuwait's non-potable water demands

During the past few years, Kuwait has been encouraging the development of alternative water resources. This stems from the fact that the available natural water resources are scarce, and water demands are growing due to increasing population growth. A potential alternative water resource which may replace existing water resources in non-potable utilization is renovated wastewater. Currently, huge amount of municipal wastewater is conventionally treated in Kuwait sewage treatment plants and major portion of this treated effluent is discharged to the Gulf. Advanced treatment of treated wastewater would yield a better quality effluent which can be used as an alternative water resource and therefore reduce the demand in fresh and brackish water supplies. This paper intends to explore the potentials of using advanced treated wastewater in meeting the growing water demands in the State of Kuwait.

On-site water recycling systems in Japan

Non-potable urban water reuse is Japan's main water reuse practice, which includes water for environmental uses, in-stream flow augmentation, toilet flushing, and industrial reuse. On-site water recycling systems reclaim wastewater on site as well as harvest rainwater in one or more large buildings and distributing the reclaimed water within the buildings for non-potable reuse. Based on our survey conducted in 1999 on current status of on-site water recycling systems in 23 wards of the Tokyo Metropolitan Government District, the following findings are reported in this paper: (1) on the average, 61% of non-potable water demand is met by reclaimed water, and the deficit is made up by tap water from city water supply, (2) biological treatment or ultrafiltration processes can provide reliable treatment and suitable water quality. Some technical problems such as odor from on-site treatment facilities have occurred in a few buildings, (3) there has been no serious accident involving human health by accidentally ingesting reclaimed water, and (4) there is a scale merit in the construction cost of on-site water recycling systems. An on-site wastewater recycling system larger than 100 m3/d is more economically justifiable when compared to a conventional domestic water supply system. An on-site water recycling system can provide an effective, safe, and economical urban water resource for non-potable water reuse applications.