Decentralized Water Reuse Research Articles

Financial analysis of decentralized water reuse systems in mission critical facilities at U.S. Army installations

Decentralized water reuse is a financially viable fit-for-purpose approach for water sustainment in mission critical facilities.

Enhancing Water Safety in Decentralized Water Reuse Systems With Low-Cost Prussian Blue Amperometric Sensors for Free Chlorine Monitoring

Enhancing Water Safety in Decentralized Water Reuse Systems With Low-Cost Prussian Blue Amperometric Sensors for Free Chlorine Monitoring

Economic analysis of hybrid rainwater-greywater systems between demand and supply sides based on cooperative theory

Hybrid rainwater-greywater systems (HRGs) are efficient decentralized water reuse systems with a profound potential for conserving water in buildings. However, the economic unfeasibility of HRGs has hindered their implementation. Methods to improve the economic benefits of HRGs have rarely been explored. This study proposes a comprehensive economic analysis based on the cooperative theory to explore the economic potential of HRGs. An HRG on campus in Japan was selected as a case study to evaluate its water-saving performance. The economic feasibility of the HRG was then analyzed based on the life cycle cost model. Finally, considering that the implementation of the HRG weakened the profit of the main water plants, the cooperative feasibility and driving factors between the HRG and main water plants were explored in terms of mutual benefits based on the cooperative theory. The results highlight that the construction costs significantly reduce the economic benefits of HRGs. HRGs have more substantial economic benefits in cooperation than in non-cooperation. In addition, the subsidy of the government for HRGs makes it easier to drive the success of the cooperation. This study not only provides a new idea for improving the economic feasibility of HRGs but also provides policy orientations to the government to promote decentralized water reuse systems.

An assessment of technological development and applications of decentralized water reuse: A critical review and conceptual framework

AbstractRapid development, urbanization, and population growth have contributed to water stress in many parts of the world. As freshwater sources are finite, it is essential to source for alternatives to ensure water security. Reclamation of non‐conventional water sources (i.e., rainwater and greywater) can be a viable alternative to alleviate water stress. In this work, various laboratory, pre‐commercialization scale, and commercialized products for rainwater harvesting and greywater treatment and reuse were reviewed. As a result, a conceptual framework is proposed to provide an overview on the applicability of technologies under various settings, which were mapped against the intended use of treated water and the potential for water supply expansion. This conceptual framework could aid decision makers in deciding on a suitable decentralized solution for water reclamation depending on limiting criteria. Decentralized systems of rainwater harvesting and greywater treatment for reuse are going to be crucial in reducing the dependence on the centralized water supply.This article is categorized under: Engineering Water > Planning Water Water and Life > Conservation, Management, and Awareness Science of Water > Water Quality

Public perceptions and perspectives on alternative sources of water for reuse generated at the household level

AbstractStudying perceptions about reuse of alternative water sources informs about conditions necessary for transition to large-scale decentralized water reuse. We administered a perceptions survey to the public based on results of initial open interviews of water management experts in Israel. Experts indicated their views on impediments to widespread household water reuse which became the basis for developing the questionnaire. The latter aimed to understand views among the general public of: (a) willingness to adopt reuse practices from three sources: greywater, air conditioner condensate and roof-harvested rainwater; and (b) preferences for targeted use of these three types of reused water. The survey elicited 372 responses. A maximum-likelihood regression analysis was conducted using independent variables (i.e., demographic characteristics, individual positions regarding the state of the country's water resources and plans for the provision of domestic water (i.e., desalination), knowledge of the reuse practices and views about risks from various uses of the reused water, including off-premise uses). Willingness to implement reuse practices served as the dependent variable. We found that respondents indicating that they heard of the reuse of the particular types of reuse practices (variable: ‘Knowledge’) was the most significant of the independent variables for all three alternative water sources. Also, using an analytic hierarchy process, we determined that health risks were much more important when compared to convenience of use and costs under hypothetical scenarios of both moderate and significant savings in monthly water expenditures.

Nature-based solutions coupled with advanced technologies: An opportunity for decentralized water reuse in cities

Decentralized water reuse in cities is a prominent alternative to mainstream top-down models for urban water treatment, which are based on centralized, linear dynamics of resource management. In this sense, Nature-based Solutions (“green” technologies) coupled with advanced technologies (“grey” technologies) constitute a promising approach for fomenting onsite water treatment and reuse in cities, while also providing multiple co-benefits. This article puts forward a conceptual advancement by providing a better understanding of coupled “green-grey”/“grey-green” technologies (CGGT). To do this, we critically discuss the main reasons for pairing these technologies instead of using them separately, as well as their treatment performance and constraints regarding data reporting issues. Moreover, the article discloses the most common treatment configurations, water quality parameters being evaluated, potential reuse schemes, costs, and energy requirements. A systematic selection and analysis of scientific articles was carried out to this end. Of 395 pre-selected articles, only 17 addressed coupled (green-grey/grey-green) technologies in the treatment of urban wastewaters for further reuse or safe discharge onsite. Despite the relatively low number of articles, 80% were published in the past five years, showing the increased interest in this novel topic. The selected articles were analysed and here we present the resulting comprehensive Excel database (343 datasets) containing detailed information about the design, operation, and performance of such systems. Green-grey technologies were found to be predominant, the configuration constructed wetlands followed by advanced oxidation process and electrochemical process being the most studied. Grey technologies are normally applied at a second stage to remove pathogens in compliance with reuse standards (normally when green technologies alone cannot deliver the standards). Meanwhile, green technologies are commonly used at a second stage to break down slowly biodegradable substances that have not been completely removed by grey technologies (normally as a polishing step following grey technology). The design parameters for combining these technologies have not yet been fully optimized, since they were mainly designed as sole technologies and forcibly put together as a coupled treatment. Hence, further studies should focus on variables and parameters influencing the functioning of coupled technologies as a whole. Finally, due to the novelty and relevance of the topic, transparency and consistency in data reporting is essential to support the optimization and competitiveness of coupled green-grey/grey-green technologies against existing decentralized/centralized approaches.

Dimensionless parameter method for evaluating decentralized water reuse systems in buildings

• Propose a regionalization method to design RWHs, GWRs, and HRGs. • Obtain the design curves under the stable and seasonal water demand scenarios. • The best scenarios and configurations of RWHs, GWRs, and HRGs are discussed. • GWRs are not recommended to implement in the seasonal water demand buildings. The performance of the decentralized water reuse systems that are widely implemented for the conservation of building water is affected by various characteristics, such as the location and type of building. Generalized methods to evaluate and compare different system configurations under various scenarios are currently lacking. Previously devised methods have focused on specific parameters describing buildings and are therefore not suitable for regionalized application. This study proposes a dimensionless parameter method for the evaluation of three decentralized systems in buildings with stable and seasonal daily non-potable water demands: rainwater harvesting systems (RWHs), graywater recycling systems (GWRs), and hybrid rainwater-graywater systems (HRGs). Japan was selected as a case study to illustrate the feasibility of this method. The results indicate that the favorable precipitation patterns in Japan support the use of RWHs rather than GWRs for conserving water, especially in buildings with seasonal daily non-potable water demands. Upgrading the existing systems to HRGs when RWHs and GWRs cannot meet the demand can increase the maximum water-saving efficiency by 40%. Thus, the method can effectively determine the optimum scenarios and configurations of RWHs, GWRs, and HRGs and provide policy guidance for the regional implementation of decentralized water reuse systems.

Capturing and analysing heterogeneity in residential greywater reuse preferences using a latent class model

To legally permit greywater reuse as a management strategy, it is necessary to establish allowed uses, as well as guarantee legitimacy, safety and maintain public trust. Cities with previous experience in greywater reuse have reconfigured their regulations according to their own evidence with decentralized water reuse systems. This has allowed them to encourage or restrict certain indoor uses of treated greywater. However, cities starting to use these residential schemes lack the experience to reconfigure their water and sanitation regulation, and thus need “blindly” decide on the type of greywater uses to allow in order to achieve a balance between users’ acceptability and avoiding public health problems.In this research, we analyse hypothetical situations of greywater reuse based on real evidence related to decentralized water systems. The main objective of this study is to evaluate the heterogeneity of individuals' preferences regarding residential greywater reuse for six intended indoor uses, using stated choice experiments and a latent class model. Hence, we obtain preliminary evidence about the direction that the regulation or pilot tests should take. We use the context of Santiago (Chile) as a reference, where although allowed, greywater reuse is not taking place widely. Our results show that survey respondents can be classified into four classes (enthusiasts, greywater sceptics, appearance conscious and water expenditure conscious), according to the preferences for the different types of indoor greywater reuse and the appearance of the treated greywater. From a policy perspective, our results show differences across classes as a function of socioeconomic characteristics and previous greywater reuse knowledge, as well as wider household characteristics, including the presence of sensitive individuals (under 15 and over 74 years old), number of residents, number of sanitary devices, and location and type of garden.

Decentralized Water Reuse: Implementing and Regulating Onsite Nonpotable Water Systems

Decentralized Water Reuse: Implementing and Regulating Onsite Nonpotable Water Systems

Droplet digital PCR quantification of norovirus and adenovirus in decentralized wastewater and graywater collections: Implications for onsite reuse

Risk-based treatment of onsite wastewaters for decentralized reuse requires information on the occurrence and density of pathogens in source waters, which differ from municipal wastewater due to scaling and dilution effects in addition to variable source contributions. In this first quantitative report of viral enteric pathogens in onsite-collected graywater and wastewater, untreated graywater (n = 50 samples) and combined wastewater (i.e., including blackwater; n = 28) from three decentralized collection systems were analyzed for two norovirus genogroups (GI/GII) and human adenoviruses using droplet digital polymerase chain reaction (ddPCR). Compared to traditional quantitative PCR (qPCR), which had insufficient sensitivity to quantify viruses in graywater, ddPCR allowed quantification of norovirus GII and adenovirus in 4% and 14% of graywater samples, respectively (none quantifiable for norovirus GI). Norovirus GII was routinely quantifiable in combined wastewater by either PCR method (96% of samples), with well-correlated results between the analyses (R2 = 0.96) indicating a density range of 5.2–7.9 log10 genome copies/L. These concentrations are greater than typically reported in centralized municipal wastewater, yet agree well with an epidemiology-based model previously used to develop pathogen log-reduction targets (LRTs) for decentralized non-potable water systems. Results emphasize the unique quality of onsite wastewaters, supporting the previous LRTs and further quantitative microbial risk assessment (QMRA) of decentralized water reuse.

Performance assessment of water reuse strategies using integrated framework of urban water metabolism and water-energy-pollution nexus

This paper evaluates the metabolism-based performance of a number of centralised and decentralised water reuse strategies and their impact on integrated urban water systems (UWS) based on the nexus of water-energy-pollution. The performance assessment is based on a comprehensive and quantitative framework of urban water metabolism developed for integrated UWS over a long-term planning horizon. UWS performance is quantified based on the tracking down of mass balance flows/fluxes of water, energy, materials, costs, pollutants, and other environmental impacts using the WaterMet2 tool. The assessment framework is defined as a set of key performance indicators (KPIs) within the context of the water-energy-pollution nexus. The strategies comprise six decentralised water reuse configurations (greywater or domestic wastewater) and three centralised ones, all within three proportions of adoption by domestic users (i.e. 20, 50, and 100%). This methodology was demonstrated in the real-world case study of San Francisco del Rincon and Purisima del Rincon cities in Mexico. The results indicate that decentralised water reuse strategies using domestic wastewater can provide the best performance in the UWS with respect to water conservation, green house gas (GHG) emissions, and eutrophication indicators, while energy saving is almost negligible. On the other hand, centralised strategies can achieve the best performance for energy saving among the water reuse strategies. The results also show metabolism performance assessment in a complex system such as integrated UWS can reveal the magnitude of the interactions between the nexus elements (i.e. water, energy, and pollution). In addition, it can also reveal any unexpected influences of these elements that might exist between the UWS components and overall system.

Decentralized water reuse planning: Evaluation of life cycle costs and benefits

The objective of this paper is to comparatively evaluate the life cycle costs and expected monetary benefits of decentralized greywater reuse systems. Specifically, added life cycle costs and estimated life cycle monetary benefits of satellite and onsite greywater reuse systems are evaluated in comparison with the prevailing centralized systems. Centralized systems refer to the traditional form of water delivery where one centralized treatment plant treats and distributes potable water to a large service area through a water distribution network while a sewer network collects used water for treatment at a centralized wastewater treatment plant before the wastewater effluent is disposed into the environment. Satellite greywater reuse systems collect raw greywater at neighborhood or district level for treatment and re-distribution for non-potable uses within the same neighborhood or district. Onsite greywater reuse systems collect raw greywater for treatment on the premises of where it is produced after which it is re-distributed for permitted non-potable use on the same premises. Infrastructure needs and associated life cycle cost information for both types of greywater reuse systems are appropriately modeled or synthesized from literature. The skeletal layout of a real-world water distribution network is adapted for performing the cost-benefit analysis in this study. Finally, sensitivity of the cost-benefit tradeoff associated with satellite and onsite greywater reuse adoption scenarios is evaluated for various uncertainties associated with technological evolution, policy incentives, and planning schemes. Given that several states in the U.S. are expected to face water shortages in the near future, this paper will provide guidance to water utilities and policy makers in planning of future water supply alternatives.

Decentralised water reuse in Sydney, Australia: drivers for implementation and energy consumption

Water recycling and reuse is becoming increasingly common throughout the world. The objective of this study was to compare five decentralised water recycling and reuse systems in Sydney, Australia, in terms of the drivers for their implementation and their ongoing energy consumption, allowing comparison to conventional water sources. The security of supply was found to be the main driver for four out of the five schemes. For the fifth scheme, the driver was to obtain a high environmental rating for the building it is located in. The analysis shows that water reuse can provide water at the same or less energy consumption compared to water supplied through the mains network. However, where the water recycling ethos of ‘fit for purpose’ is not considered, this can often lead to a significant overall increase in power consumption. This study highlights the need for regulatory bodies to consider a wider range of impacts when preparing guidelines and incentive schemes for water reuse. When the focus is too narrow, there is a risk that unintentional negative impacts such as increased power consumption and potential carbon dioxide emissions are the outcomes.

Sewer-mining: A water reuse option supporting circular economy, public service provision and entrepreneurship

Water scarcity, either due to increased urbanisation or climatic variability, has motivated societies to reduce pressure on water resources mainly by reducing water demand. However, this practice alone is not sufficient to guarantee the quality of life that high quality water services underpin, especially within a context of increased urbanisation. As such, the idea of water reuse has been gaining momentum for some time and has recently found a more general context within the idea of the Circular Economy. This paper is set within the context of an ongoing discussion between centralized and decentralized water reuse techniques and the investigation of trade-offs between efficiency and economic viability of reuse at different scales. Specifically, we argue for an intermediate scale of a water reuse option termed ‘sewer-mining’, which could be considered a reuse scheme at the neighbourhood scale. We suggest that sewer mining (a) provides a feasible alternative reuse option when the geography of the wastewater treatment plant is problematic, (b) relies on mature treatment technologies and (c) presents an opportunity for Small Medium Enterprises (SME) to be involved in the water market, securing environmental, social and economic benefits. To support this argument, we report on a pilot sewer-mining application in Athens, Greece. The pilot, integrates two subsystems: a packaged treatment unit and an information and communications technology (ICT) infrastructure. The paper reports on the pilot's overall performance and critically evaluates the potential of the sewer-mining idea to become a significant piece of the circular economy puzzle for water.

Application of the CANARY event detection software for real-time performance monitoring of decentralized water reuse systems.

Real-time monitoring of water reuse systems ensures the production of high quality water to protect human health at the point-of-use. In this study, several online real-time sensors were utilized to monitor effluent from a wastewater fed laboratory-scale membrane bioreactor (MBR) under natural and simulated failure conditions. These simulated failures included adding reactor mixed liquor to emulate a membrane breach, and spiking MS2 bacteriophage into the reactor to create a high viral load, which might be observed during an outbreak. The CANARY event detection software was used to analyze sensor data and report changes in water quality that might be indicative of poor system behavior. During simulated failure conditions, CANARY reported 20 alarms, accurately detecting each failure. During natural operating conditions, 219 alarms were produced and 189 were attributed to known events (e.g., system and sensor maintenance). The remaining alarms (23) during natural operating conditions were considered to have an unknown cause. However, 13 of those had signal deviations similar to known events, but could not be definitively linked to a source. The results of this study suggest that real-time monitoring in conjunction with CANARY analysis may be useful as an early warning system for monitoring the effluent of water reuse systems, and may help to quickly identify treatment malfunctions or other abnormal conditions.

Simulation of enteric pathogen concentrations in locally-collected greywater and wastewater for microbial risk assessments

As decentralized water reuse continues to gain popularity, risk-based treatment guidance is increasingly sought for the protection of public health. However, efforts to evaluate pathogen risks and log-reduction requirements have been hindered by an incomplete understanding of pathogen occurrence and densities in locally-collected wastewaters (i.e., from decentralized collection systems). Of particular interest is the potentially high enteric pathogen concentration in small systems with an active infected excreter, but generally lower frequency of pathogen occurrences in smaller systems compared to those with several hundred contributors. Such variability, coupled with low concentrations in many source streams (e.g., sink, shower/bath, and laundry waters), has limited direct measurement of pathogens. This study presents an approach to modeling pathogen concentrations in variously sized greywater and combined wastewater collection systems based on epidemiological pathogen incidence rates, user population size, and fecal loadings to various residential wastewater sources. Pathogen infections were modeled within various population sizes (5-, 100-, and 1,000-person) for seven reference pathogens (viruses: adenoviruses, Norovirus, and Rotavirus; bacteria: Campylobacter and Salmonella spp.; and protozoa: Cryptosporidium and Giardia spp.) on each day of 10,000 possible years, accounting for intermittent infection and overlap of infection periods within the population. Fecal contamination of fresh greywaters from bathroom sinks, showers/baths, and laundry, as well as combined greywater and local combined wastewater (i.e., including toilets), was modeled based on reported fecal indicators in the various sources. Simulated daily infections and models of fecal contamination were coupled with pathogen shedding characteristics to generate distributions of pathogen densities in the various waters. The predicted frequency of pathogen occurrences in local wastewaters was generally low due to low infection incidence within small cohort groups, but increased with collection scale (population size) and infection incidence rate (e.g., Norovirus). When pathogens did occur, a decrease in concentrations from 5- to 100- and from 100- to 1,000-person systems was observed; nonetheless, overall mean concentrations (i.e., including non-occurrences) remained the same due to the increased number of occurrences. This highlights value of the model for characterizing scaling effects over averaging methods, which overestimate the frequency of pathogen occurrence in small systems while underestimating concentration peaks that likely drive risk periods. Results of this work will inform development of risk-based pathogen reduction requirements for decentralized water reuse.

Energy consumptions and associated greenhouse gas emissions in operation phases of urban water reuse systems in Korea

Water reuse systems have been widely implemented across the globe as a solution to water shortage and freshwater contamination. Ongoing controversies regarding supposedly high energy cost and the lack of sufficient data to support benefits of water reuse are delaying further expansion of implementation of water reuse systems in South Korea. In order to clarify the ambiguity regarding the energy demand and provide an unbiased comparison between the water reuse alternatives and the conventional water supply system, energy consumptions and greenhouse gas emissions in operation phases of different water reuse facilities and the conventional water supply system were examined. The average total energy consumption and the greenhouse gas emission of the conventional process were calculated to be 0.511 kWh/m3 and 0.43 kgCO2e/m3, respectively. Centralized wastewater reuse systems had prohibitively high energy consumptions (1.224–1.914 kWh/m3) and greenhouse gas emissions (0.72–0.83 kgCO2e/m3). The decentralized wastewater reuse systems, greywater reuse and rainwater harvesting systems, all used for non-potable purposes, had comparable or higher energy demands than the conventional process (0.246–0.970 kWh/m3 after adjustment), although estimated greenhouse gas emissions from these processes were lower than the conventional process (0–0.33 kgCO2e/m3 after adjustment). Considering the hidden environmental benefit (0.357 kWh/m3) from reduction of contaminant release, the energy demand of greywater reuse drops far below that of the conventional system, suggesting that decentralized water reuse is the key to an energy-efficient water management with minimal impact on climate change.

Application of disease burden to quantitative assessment of health hazards for a decentralized water reuse system

The aim of this article is to introduce the methodology of disease burden (DB) to quantify the health impact of microbial regrowth during wastewater reuse, using the case study of a decentralized water reuse system in Xi'an Si-yuan University, located in Xi'an, China. Based on field investigation findings, Escherichia coli (E. coli), Salmonella and rotavirus were selected as typical regrowth pathogens causing potential health hazards during the reuse of reclaimed water. Subsequently, major exposure routes including sprinkler irrigation, landscape fountains and toilet flushing were identified. Mathematical models were established to build the relationship between exposure dose and disease burden by calculating the disability adjusted life year (DALY). Results of disease burden for this case study show that DALYs attributed to E. coli were significantly greater than those caused by other pathogens, and DALYs associated with sprinkler irrigation were higher than those originating from other routes. A correlation between exposure dose and disease was obtained by introducing a modified calculation of morbidity, which can extend the assessment endpoint of health risk to disease burden from the conventional infection rate.

Life-Cycle Energy Use and Greenhouse Gas Emissions of a Building-Scale Wastewater Treatment and Nonpotable Reuse System

Treatment and water reuse in decentralized systems is envisioned to play a greater role in our future urban water infrastructure due to growing populations and uncertainty in quality and quantity of traditional water resources. In this study, we utilized life-cycle assessment (LCA) to analyze the energy consumption and greenhouse gas (GHG) emissions of an operating Living Machine (LM) wetland treatment system that recycles wastewater in an office building. The study also assessed the performance of the local utility's centralized wastewater treatment plant, which was found to be significantly more efficient than the LM (79% less energy, 98% less GHG emissions per volume treated). To create a functionally equivalent comparison, the study developed a hypothetical scenario in which the same LM design flow is recycled via centralized infrastructure. This comparison revealed that the current LM has energy consumption advantages (8% less), and a theoretically improved LM design could have GHG advantages (24% less) over the centralized reuse system. The methodology in this study can be applied to other case studies and scenarios to identify conditions under which decentralized water reuse can lower GHG emissions and energy use compared to centralized water reuse when selecting alternative approaches to meet growing water demands.

Modelling metabolism based performance of an urban water system using WaterMet2

This paper presents a new quantitative model called ‘WaterMet2’ for the metabolism based assessment of the integrated urban water system (UWS) performance. WaterMet2 quantifies a number of UWS flows/fluxes (e.g. water and energy) which can be used to derive sustainability-based performance metrics. The generic WaterMet2 model overcomes the drawbacks of the existing UWS models and strives to bridge the gaps related to the nexus of water, energy and other environmental impacts in an integrated UWS. The main features of WaterMet2 are: (1) conceptual simulation model of UWS comprised of water supply, stormwater and wastewater subsystems with possible centralised and decentralised water reuse; (2) UWS represented by an arbitrary number of key UWS components for each type in four spatial scales (System, Subcatchment, Local and Indoor areas) in a distributed modelling type approach; (3) quantifying the metabolism-based performance of UWS including the caused and avoided environmental impact categories (GHG emissions, acidification and eutrophication potentials) and resource recovery in UWS. WaterMet2 is tested, validated and demonstrated by evaluating the long-term performance of the UWS of a northern European city for three states including business as usual and two intervention strategies: addition of new water resources and large scale localised water recycling. The results obtained demonstrate the effectiveness of WaterMet2 in evaluating the sustainability related UWS performance, the suitability of using WaterMet2 at the strategic level UWS planning and the importance of using an integrated assessment approach covering the full urban water cycle.