Understanding the preferences for different types of urban greywater uses and the impact of qualitative attributes

Dynamic simulation for reclaimed water reuse under multi-intervention policies in China

Unconventional water constitutes the fundamental approach to addressing global water scarcity and achieving the sustainable circulation of water resources. Due to the significant environmental advantages and economical production costs, reclaimed water has emerged as a preeminent unconventional source. However, the use in China confronts the predicament of oversupply relative to demand, requiring policy measures to overcome this challenge. Limited research exists on the combined impact of subsidies and water quality information disclosure supervision on reclaimed water utilization, potentially underestimating the practical incentivizing role of water quality information disclosure. Therefore, based on the framework of 'external environment-perceived value-utilization intention,' a multi-agent-based simulation model driven by evolutionary game theory is constructed, from micro to macro perspective, to investigate the composite effects of subsidies and water quality information disclosure supervision on public intentions for reclaimed water utilization and the evolutionary track of public decision-making. The results showed that (1) The influence of subsidies on the public's inclination toward reclaimed water has regional heterogeneity. In regions with average economic development, the subsidy policy shows an inverted U-shaped correlation with the public's intention to reclaimed water, indicating the presence of an optimal value for maximizing the promotional effect of subsidies. Conversely, the effect is less discernible in regions with higher economic development. (2) In regions with average economic development, supervision of information disclosure behavior can avert the diminishing incentivizing effects under radical subsidies, but the assistance of various supervision intensities is different. (3) In regions with higher economic development, the incentive effect of subsidies can be positively modulated by the supervision policy. Interactions between subsidy and supervision policies evoke diverse chain reactions under varying intensities in these regions, and the combination of moderate subsidies and high supervision emerges as the most optimal strategy to advance reclaimed water development.

Acceptance of on-site wastewater treatment and reuse in Bengaluru, India: The role of perceived costs, risks, and benefits

In dealing with water pollution and freshwater scarcity, on-site treatment and reuse of domestic wastewater has shown to be a promising solution. To increase on-site wastewater treatment and reuse, some cities, among them Bengaluru in India, have mandated the installation and use of the necessary technology in certain building types. However, even with a mandate, a successful and sustainable implementation of the technology, including reliable operation, monitoring, and maintenance, depends on the acceptance (i.e. positive valuation) of the technology and its use by the (prospective) users. Literature on technology acceptance indicates perceived costs, risks, and benefits of the respective technology as key predictors of acceptance. Therefore, the present online study assessed this relationship for on-site systems in Bengaluru. The relation was analysed separately for mandated users of on-site systems (N = 103) and current non-users (i.e. potential prospective users, should the mandate be expanded; N = 232), as the perceptions might differ between the two groups, due to the personal experience with the technology among users. The results show that for mandated users and non-users, acceptance of on-site systems is explained by perceived benefits only, namely a positive image of users, environmental benefits, and, only for non-users, also financial benefits for the city. The findings suggest that interventions aimed at promoting on-site systems should include emphasis on the benefits of on-site systems. Whenever possible, interventions should be tailored to the target group's individual cost, risk, and benefit perception.

Economics of household preferences for water-saving technologies in urban South Africa

Drought severity is expected to increase in South Africa in the coming years, given the deteriorating effects of climate change on rainfall patterns, global temperature, and evaporation. A common mitigation strategy adopted by households is to promote water demand management initiatives to reduce water consumption volume and complement existing water supply management approaches implemented by suppliers. This study contributes to the discussion on adaptation strategies by investigating household preference heterogeneity for water-saving technologies through empirical evidence from urban Cape Town, South Africa. Using a choice modelling framework, we collected primary survey data from 512 urban households in five of the city's major suburbs and investigated heterogeneity among the households based on their preferences for characteristics embedded in four water-saving technologies. Four preference classes were identified by accounting for taste heterogeneity. Overall, respondents had the highest marginal willingness to pay (MWTP) for the greywater technology alternative at 17,025 ZAR (US$ 1142) while rainwater technology has the least willingness to pay value at 5206 ZAR (US$ 349). In addition, the results show that respondents in classes 1 and 2 have a high interest in technologies that save a large quantity of water, whereas members of classes 3 and 4 rely on inexpensive conservation and behavioral habits as climate adaptation measures. This study has important policy implications for many water-stressed and arid cities within and outside South Africa since like Cape Town, many large cities require long-lasting measures that help reduce the pressure on their strained water systems.

Optimal Water Resources Allocation in the Yinma River Basin in Jilin Province, China, Using Fuzzy Programming

Being one of the most important sources of water in the Jilin Province in China, the Yinma River Basin (YRB) is facing problems of water scarcity in low economic areas and low utilization in richer areas mainly caused by the irrational allocation of water, excessive pursuit of economic benefits, and neglect of environmental problems. Restricting watershed development involves potential decision-making risks. Some scholars have used the interval two-stage stochastic planning method to adjust water resource allocation in the Drinking Horse River Basin, but the method uses historical statistics for projection and does not take into account the ambiguity and uncertainty in real planning situations. Therefore, this study addresses the problems prevalent in the allocation of water resources in the YRB through optimization using stochastic programming methods, interval and two-stage, and introduces the fuzzy mathematical programming method, with the aim of coordinating the water balance of various water-consuming sectors in the YRB, so as to reconfigure the water allocation. The goal is to solve the existing problems of irrational water allocation, reduce system risks posed by excessive economic development, mitigate water shortages in the water-consuming sectors, and alleviate potential decision-making risks and vague uncertainties associated with the allocation of water resources. Additionally, optimization of the pollution-holding capacity improvement project was carried out. The interval fuzzy two-stage model simulation developed in this study shows that the distribution of water across the different administrative regions can be reduced by up to 30% compared with the original model, effectively reducing the problem of water wastage. Post-optimization, the impact of water shortage in the water resources allocation scheme is alleviated to a significant degree, and there is no water shortage in some areas. At the same time, the eco-environmental sector has gradually taken the leading role in the distribution of water reuse among the different water-consuming sectors. The pollution-holding capacity has been enhanced, and the discharge and river entry chemical oxygen demand (COD) and ammonia nitrogen, two typical pollutants, have been reduced. The membership interval in the interval fuzzy two-stage model reflects the relationship between the possible level of the target value and the risk level. This study provides a guideline for decision makers for balancing the relationship between benefits and risks and proposes a planning scheme that is more conducive to the development of the river basin.

The third route: A techno-economic evaluation of extreme water and wastewater decentralization

Water systems need to become more locally robust and sustainable in view of increased population demands and supply uncertainties. Decentralized treatment is often assumed to have the potential to improve the technical, environmental, and economic performance of current technologies. The techno-economic feasibility of implementing independent building-scale decentralized systems combining rainwater harvesting, potable water production, and wastewater treatment and recycling was assessed for six main types of buildings ranging from single-family dwellings to high-rise buildings. Five different treatment layouts were evaluated under five different climatic conditions for each type of building. The layouts considered varying levels of source separation (i.e., black, grey, yellow, brown, and combined wastewater) using the corresponding toilet types (vacuum, urine-diverting, and conventional) and the appropriate pipes and pumping requirements. Our results indicate that the proposed layouts could satisfy 100% of the water demand for the three smallest buildings in all but the aridest climate conditions. For the three larger buildings, rainwater would offset annual water needs by approximately 74 to 100%. A comprehensive economic analysis considering CapEx and OpEx indicated that the cost of installing on-site water harvesting and recycling systems would increase the overall construction cost of multi-family buildings by around 6% and single-family dwellings by about 12%, with relatively low space requirements. For buildings or combined water systems with more than 300 people, the estimated total price of on-site water provision (including harvesting, treatment, recycling, and monitoring) ranged from $1.5/m³ to $2.7/m,³ which is considerably less than the typical tariffs collected by utilities in the United States and Western Europe. Where buildings can avoid the need to connect to centralized supplies for potable water and sewage disposal, water costs could be even lower. Urine-diversion has the potential to yield the least expensive solution but is the least well developed and had higher uncertainty in the cost analysis. More mature layouts (e.g., membrane bioreactors) exhibited less cost uncertainty and were economically competitive. Our analysis indicates that existing technologies can be used to create economically viable systems that greatly reduce demands on centralized utilities and, under some conditions, eliminate the need for centralized water supply or sewage collection.

Reclamation of Treated Wastewater for Irrigation in Chile: Perspectives of the Current State and Challenges

Reclamation of treated wastewater is considered a viable option for reducing the agricultural and national water deficit, especially in Mediterranean-type and arid climatic conditions. Given that Chile is a country around 40% of whose territory is classified as semi-arid and desert and 20% as Mediterranean, with serious water scarcity problems, and which uses a great deal of the resource in agricultural irrigation, the present paper offers perspectives on the current state of treated wastewater reuse and considers challenges to improving the development of water reclamation for irrigation in Chile as a case study. The methods followed included a systematic literature review to answer two important questions: (a) What is the state of reclamation of treated wastewater for irrigation in Chile? and (b) What criteria/parameters determine the feasibility of reclaiming treated wastewater for irrigation in Chile? The results showed that Chile has been affected by climate change in a short time: a megadrought has occurred over the last ten years, increasing the necessity for the country to secure alternative water sources for irrigation. The country has advanced greatly in wastewater treatment coverage, achieving almost 100% in urban areas, with technologies that can produce quality water as a new water source for irrigation. However, the lack of regulations and limited frameworks could explain the low direct reuse at present—below 1% of total flow. Regarding challenges, the necessity of updates to Chile’s institutional and legal frameworks, besides the inclusion of rural communities and the study of emerging contaminants, will be discussed. By these means, it will be possible to more efficiently utilize recycled wastewater as a new source for irrigation in this country.

Life cycle assessment of greywater treatment systems for water-reuse management in rural areas

Water scarcity is a major concern worldwide. Population growth, as well as the intensive use of water resources for industrial and agricultural activities, among others, have caused water stress in various regions of the world. Rural areas are usually more affected due to water scarcity and a lack of sanitary infrastructure. The current practices associated with urban water management have been considered inefficient to respond to these problems. In recent years, the reuse of greywater has emerged as a promising and sustainable alternative. Several pilot greywater treatment systems have been implemented in rural areas of different countries, however, studies about the environmental impacts of these decentralized systems under different scenarios are lacking. In this work, the life cycle assessment of greywater treatment systems considering several scenarios was studied. Our results showed that the decrease in environmental impacts due to the saving of drinking water is more evident when the water supply is carried out through cistern trucks. This occurs because the environmental impact of land transport of water is extremely high and represents over 89% of the global warming indicator [kg CO₂ eq] and 96% ozone depletion [kg CFC-11 eq] contributions of the system. Greywater treatment systems with backwashing and solar panels as a source of energy have lower environmental impacts, reducing CO₂ and CFC emissions by 50% for the maintenance phase and by 85% (CO₂) and 47% (CFC) for the operation phase. Furthermore, the acquisition of solar panels was economically feasible, with a payback of 19.7 years. This analysis showed the environmental feasibility of small-scale greywater treatment systems in rural areas affected by water scarcity. Furthermore, the proposed approach has contributed to understand the impact of greywater treatment systems in rural areas, which could become a support tool to integrate greywater reuse practices in different communities.

An Assessment of Treated Greywater Reuse in Irrigation on Growth and Protein Content of Prosopis and Albizia

This study investigated the influence of treated greywater on growth and protein content of multipurpose (forage and ornamental) transplants, Prosopis juliflora L., Prosopis tamarugo L., and Albizia lebbeck L. Transplants of tested species were irrigated with treated greywater, diluted greywater (grey + distilled water, 1:1/by volume), and distilled water (control) for seven months. Water quality analysis showed that the concentrations of nutrients and heavy metals found in the greywater were within the acceptable range compared with Jordan Institution for Standard and Metrology (JISM) and the World Health Organization (WHO) thresholds for safe use of greywater. Escherichia coli found in the greywater were lower compared to JISM and WHO guidelines for the safe use of greywater. Irrigation with treated greywater increased shoot fresh weight by 24–39% and dry weight by 34–40% compared to diluted greywater and control. No significant difference in crude protein was noticed between water treatments. Prosopis species (P. juliflora Albizia lebbeck L. and P. tamarugo Albizia lebbeck L.) had higher shoot fresh (35%) and dry weight the same species had lower crude protein (44%) when compared to Albizia lebbeck Albizia lebbeck L. The reuse of treated greywater for landscaping or forage production alleviates the demand for water resources and reduces the pressure on wastewater treatment plants. However, considering the controversial findings of previous studies on greywater quality (especially, long-term reuse), the reuse of treated greywater needs to be considered with caution and periodic quality analyses and economic assessments are required.

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.