Environmental performance of building integrated grey water reuse systems based on Life-Cycle Assessment: A systematic and bibliographic analysis

Treated greywater as a novel water resource: The perspective of greywater treatment for reuse from a bibliometric analysis

The current global water crisis has prompted research into technologies that can reuse different water resources to mitigate water scarcity. The use of treated greywater can be proposed to provide additional water resources. By reusing this water in different applications, this water crisis can be mitigated at the local scale. This study presents a bibliometric analysis to assess the state of the art of greywater treatment and its reuse technologies. This analysis is based on the scientific literature published until 2023 in Scopus regarding greywater treatment and 1,024 documents were found. The results showed a clear exponential increase in the accumulated number of publications in this topic, which was spurred during the mid-1990s. The most prolific country was the United States, while China, the other typical scientific superpower in most fields, occupied the sixth position in the ranking. Environmental Sciences was the knowledge subject with more documents, followed by Engineering and Chemical Engineering. The bibliometric study was complemented using SciMAT to create bibliometric networks that represent the dynamic evolution of the themes. The most important themes were identified, among which three key points stand out: greywater characterization, technologies for greywater treatment, and water management, including the reuse of treated greywater.

Decision support tools for water reuse: a systematic review

This article provides a comprehensive review of decision support tools for water reuse (DST4WR), focusing on microbiological risk assessment (MRA), life cycle analysis (LCA), life cycle cost (LCC), and multi-criteria decision analysis (MCDA). A systematic review of 35 articles published between 2020 and 2024, plus one from 2019, was conducted. The studies were categorised based on the DST4WR applied, with each tool discussed individually. MRA tools assess public health risks in different case studies. LCA identifies key environmental indicators, and its integration with LCC facilitates comprehensive cost analysis. MCDA, applied in various case studies, uses criteria like environmental, social, economic, technical, public health, and functional aspects. Integrating DST4WR tools identifies synergies and trade-offs between criteria, aiding informed decision-making. Combining MRA, LCA/LCC, and MCDA is especially beneficial, as each tool provides a distinct perspective. Using these tools together offers a holistic view of water reuse management, ensuring that all relevant factors are balanced. This approach enhances decision-making and builds stakeholder confidence and acceptance by transparently addressing public health, environmental, economic, and social concerns.

Treatment of greywater and presence of microplastics in on-site systems

Eight on-site greywater treatment facilities of four different types (A, B, C and D) were investigated. Three were commercially available package plants (A-C) and one was a conventional sand filter (D). The treatment unit of Type A consisted of a geotextile-fitted trickling filter and a sand filter bottom layer, the Type B consisted of packs of fibrous mineral wool filter materials, and the Type C consisted of a fine-meshed plastic filter. The treatment systems were assessed in terms of their removal efficiency for organic matter (e.g. BOD, COD, TOC), nutrients (nitrogen and phosphorus), surfactants, indicator bacteria (E. coli and enterococci) as well as microplastics. Systems A and D effectively reduced organic matter by >96% BOD, >94% COD and >90% TOC. Their effluent BOD was <29 mg/l. The BOD reduction in the treatment facilities of types B and C was in the range of 70-95%. Removal of anionic surfactants was >90% with effluent concentration <1 mg/l in all facilities. In general, the treatment systems were ineffective in removing E. coli and enterococci; the most efficient was the sand filter (type D), achieving 1.4-3.8 log10 for E. coli and 2.3-3.3 log10 for enterococci. Due to the high E. coli in the effluents, all the on-site systems were classified as Poor (score: 0-44) according to the water quality index (WQI) assessment. In two of the studied facilities, nine microplastic polymers were targeted (i.e. PVC, PS, PET, PE, PC, NG, PMMA, PP and PA6) and analyzed using the thermal extraction desorption gas chromatography-mass spectrometry (TED-GCMS) technique. PVC, PS, PET and PA6 were commonly detected in the influent and effluent. The effluent quality from type A and D systems was found to comply with the European Commission's guideline for the reuse of reclaimed water except for the indicator bacteria concentration.

The COP27 screened through the lens of global water security

Water security is an expression of resilience. In the recent past, scientists and public organizations have built considerable work around this concept launched in 2013 by the United Nations as "the capacity of a population to safeguard sustainable access to adequate quantities of acceptable quality water for sustaining livelihoods, human well-being, and socio-economic development, for ensuring protection against water-borne pollution and water-related disasters, and for preserving ecosystems in a climate of peace and political stability". In the 27th Conference of the Parties (COP27), held in Sharm El-Sheikh (Egypt) in last November, water security was considered a priority in the climate agenda, especially in the adaption and loss and damage axes. This discussion paper represents the authors' opinion about how the conference coped with water security and what challenges remain to attend. As discussion paper, it had the purpose to stimulate further discussion in a broader scientific forum.

Unequal exposure to heatwaves in Los Angeles: Impact of uneven green spaces

Cities worldwide are experiencing record-breaking summer temperatures. Urban environments exacerbate extreme heat, resulting in not only the urban heat island but also intracity variations in heat exposure. Understanding these disparities is crucial to support equitable climate mitigation and adaptation efforts. We found persistent negative correlations between daytime land surface temperature (LST) and median household income across the Los Angeles metropolitan area based on Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station observations from 2018 to 2021. Lower evapotranspiration resulting from the unequal distribution of vegetation cover is a major factor leading to higher LST in low-income neighborhoods. Disparities worsen with higher regional mean surface temperature, with a $10,000 decrease in income leading to ~0.2°C LST increase at 20°C and up to ~0.7°C at 45°C. With more frequent and intense heat waves projected in the future, equitable mitigation measures, such as increasing surface albedo and tree cover in low-income neighborhoods, are necessary to address these disparities.

Meeting the Water and Sanitation Challenges of Underbounded Communities in the U.S

Water and sanitation (wastewater) infrastructure in the United States is aging and deteriorating, with massive underinvestment over the past several decades. For many years, lack of attention to water and sanitation infrastructure has combined with racial segregation and discrimination to produce uneven access to water and wastewater services resulting in growing threats to human and environmental health. In many metropolitan areas in the U.S., those that often suffer disproportionately are residents of low-income, minority communities located in urban disadvantaged unincorporated areas on the margins of major cities. Through the process of underbounding (the selective expansion of city boundaries to exclude certain neighborhoods often based on racial demographics or economics), residents of these communities are disallowed municipal citizenship and live without piped water, sewage lines, and adequate drainage or flood control. This Perspective identifies the range of water and sanitation challenges faced by residents in these communities. We argue that future investment in water and sanitation should prioritize these communities and that interventions need to be culturally context sensitive. As such, approaches to address these problems must not only be technical but also social and give attention to the unique geographic and political setting of local infrastructures.

Modelling Treated Laundry Greywater Reuse for Irrigation Using an Affordable Treatment Method and Seed Germination Test

A potential solution in areas facing water shortages is greywater (GW) reuse. GW is produced in bathrooms, laundry rooms, and kitchens of households. With proper treatment, it can be an alternative source for the agriculture sector, which consumes approximately 70% of the world’s water. This paper represents the characterization of synthetic laundry GW fraction (LGW), its treatment and modelling of treated LGW reuse for irrigation using a seed germination test. LGW’s constant quality (pH = 8.0 ± 0.3, turbidity = 174 ± 73 NTU, BOD5 = 300 ± 60 mgL−1, TOC = 162 ± 40 mgL−1) is suitable for testing the treatment method’s efficiency. Coagulation–flocculation, applying iron(III) chloride and sand filtration as a simple treatment combination, generates good-quality irrigation water (pH = 7.27 ± 0.23, turbidity = 0.6 ± 0.4 NTU, BOD5 = 17 ± 8 mgL−1, TOC = 16 ± 6 mgL−1). Seed germination tests with different waters, and elemental analysis of water, roots, and stems of the plants were done to verify the plants’ quality. The sodium adsorption ratio (SAR) for the raw LGW (SAR = 4.06) was above the threshold (<3) for safe irrigation, thus it is not recommended for this purpose. Based on the elemental analysis results and SAR value of treated LGW (SAR = 2.84), it can potentially be used for irrigation purposes.

Reshaping sustainable development trajectory due to COVID-19 pandemic

Humanity could face the COVID-19 epidemic to crystallize a sustainable future for the water, hygiene, and food sectors. The epidemic has affected the sustainability of water, food, and health institutions in Egypt. Water consumption levels have increased in the agricultural sector to ensure food security. Regular handwashing is one of the most important measures to prevent the epidemic, and this has an impact on water consumption. The purpose of the research is to reshape sustainable development trajectory due to COVID-19 pandemic in Egypt through three interdependent phases: the first is devoted to forecast how the pandemic could be spreading in Egypt, the second is assigned to foresee implications and consequences of the pandemic on water, food, and human activities, and the third is dedicated to exploring how Egypt could utilize non-conventional water resources as a precious resource to fight the pandemic and explore sustainable recovery strategies. The results could be summarized as the diffusion of COVID-19 pandemic may be considered a group of evolutionary processes. The vision of growth to a limit may be applied; the number of cases of COVID-19 grows rapidly, but the growth will be reduced due to negative feedback signals from the environment. The paper concludes that the COVID-19 epidemic could be addressed by enhancing the water sector to better cope with future shocks. Water, food, health, and work opportunities could be provided and managed sustainably. The need to provide water to wash the hands of all citizens has been emphasized to fight the coronavirus. Non-conventional water resources could be an engine to ambitious plans to drive economic growth through megaprojects. Egypt would enable transforming this crisis into an opportunity to accelerate the pace of action towards achieving Sustainable Development Goals.

Analysis of potential of Napier grass, Vetiver and Equisetum plants for the treatment of domestic greywater using box-type constructed wetlands

The management of wastewater generated as a byproduct of various human activities from agricultural, industrial, and domestic sectors is a matter of global concern today. Greywater is a class of wastewater generated from the domestic sector. Greywater management can be done effectively by treating greywater at the source itself. In this context, constructed wetlands (CWs) come handy with low-tech, environmental, and economic-friendly options. In the present study, box-type horizontal subsurface flow constructed wetlands were designed and the efficiency of Napier grass (Pennisetum purpureum), Vetiver (Vetiveria zizanioides), and Equisetum (Equisetum hyemale) were assessed in treating domestic greywater. There was a drastic significant increase in DO with 47.0% in Vetiver, 92.5% in Napier grass, and 97.2% in Equisetum. The average percent pollutant removal of some major parameters was 92.4% for turbidity, 92.7% for acidity, 81.3% for BOD, 91.0% for COD with Napier grass. In the case of Vetiver, the removal percent was 82.5% turbidity, 87.9% acidity, 81.8% BOD, and 92.9% COD. For Equisetum, the average pollutant removal efficiency varied with 94.6% turbidity, 91.4% acidity, 80.0% BOD, and 88.1%COD. The study thus proves the efficiency of all the three plants to be used in box-type constructed wetlands.

Optimal Implementation of Wastewater Reuse in Existing Sewerage Systems to Improve Resilience and Sustainability in Water Supply Systems

A transition from conventional centralized to hybrid decentralized systems has been increasingly advised recently due to their capability to enhance the resilience and sustainability of urban water supply systems. Reusing treated wastewater for non-potable purposes is a promising opportunity toward the aforementioned resolutions. In this study, we present two optimization models for integrating reusing systems into existing sewerage systems to bridge the supply–demand gap in an existing water supply system. In Model-1, the supply–demand gap is bridged by introducing on-site graywater treatment and reuse, and in Model-2, the gap is bridged by decentralized wastewater treatment and reuse. The applicability of the proposed models is evaluated using two test cases: one a proof-of-concept hypothetical network and the other a near realistic network based on the sewerage network in Chennai, India. The results show that the proposed models outperform the existing approaches by achieving more than a 20% reduction in the cost of procuring water and more than a 36% reduction in the demand for freshwater through the implementation of local on-site graywater reuse for both test cases. These numbers are about 12% and 34% respectively for the implementation of decentralized wastewater treatment and reuse.

A State of the Art of the Overall Energy Efficiency of Wood Buildings-An Overview and Future Possibilities

The main goal of this study was to review current studies on the state of the art of wood constructions with a particular focus on energy efficiency, which could serve as a valuable source of information for both industry and scholars. This review begins with an overview of the role of materials in wood buildings to improve energy performance, covering structural and insulation materials that have already been successfully used in the market for general applications over the years. Subsequently, studies of different wood building systems (i.e., wood-frame, post-and-beam, mass timber and hybrid constructions) and energy efficiency are discussed. This is followed by a brief introduction to strategies to increase the energy efficiency of constructions. Finally, remarks and future research opportunities for wood buildings are highlighted. Some general recommendations for developing more energy-efficient wood buildings are identified in the literature and discussed. There is a lack of emerging construction concepts for wood-frame and post-and-beam buildings and a lack of design codes and specifications for mass timber and hybrid buildings. From the perspective of the potential environmental benefits of these systems as a whole, and their effects on energy efficiency and embodied energy in constructions, there are barriers that need to be considered in the future.

Bioelectrochemical Greywater Treatment for Non-Potable Reuse and Energy Recovery

Greywater normally represents the largest fraction of wastewater generated in buildings and may be suitable for non-potable reuse after on-site treatment. Conventional technologies for greywater treatment include sequencing batch reactors, membrane filtration, and membrane biological reactors. Even though these can be very effective, they are highly energy consuming and may negatively impact the energy balance of the building where they are installed. Microbial fuel cells (MFCs) have emerged as a sustainable technology for contaminant removal and energy production from a variety of substrates. In this study, the application of MFCs for greywater treatment is reported, with a particular focus on the analysis of energy losses, in view of non-potable reuse. MFCs were fed with different types of greywater, characterized by either high or low conductivity, because greywater’s conductivity may greatly differ based on its origin; in either case, organic matter (chemical oxygen demand; COD) removal was higher than 85% and not influenced by the influent conductivity, coupled with a maximum power production of 0.46 mW L−1 and 0.38 mW L−1. Electrolyte overpotentials were dramatically higher in the case of low conductivity greywater (20% vs. 10%, compared to high conductivity influent); these overpotentials are related to the conductivity of the influent, showing that low conductivity hindered energy generation, but not COD removal. Polarization and power curves showed higher internal resistance in the case of low conductivity, confirming the overpotentials’ analysis. Results showed the feasibility of the use of MFCs in greywater treatment, with potential to reduce the energy demand connected to its reuse compared to conventional technologies; coupling with a disinfection stage would be necessary to fully comply with most non-potable reuse regulations.

Pollution control in urban China: A multi-level analysis on household and industrial pollution

This paper studies the effectiveness of pollution control in urban China by constructing a two sub-system analysis: household pollution control subsystem and industrial pollution control subsystem. We integrate slack-based model with undesirable outputs to estimate the pollution control efficiency in two subsystems for Chinese provinces from 2011 to 2015. The results show strong evidence on provincial and regional heterogeneity in pollution control efficiency for both systems. At provincial level, Beijing, Shanghai, Jiangsu, Guangdong, Hainan, and Qinghai have achieved full efficiency in both household and industrial pollution control compared with other provinces. At regional level, the Eastern Coastal region is the most effective area in environmental protection among eight economic regions in China. We then measure the economic importance of controlling various pollutants by dual price approach. Policy suggestions for each region are given to improve the effectiveness of pollution control in urban China.

Environmental impact of water-use in buildings: Latest developments from a life-cycle assessment perspective

Globally, buildings are recognized as one of the highest users of freshwater resources. Consuming enormous amounts of constructional and operational water deplete water resources and ultimately generates a high environmental impact. This is mainly due to the energy required for the water cycle of built environments, which involves raw water treatment and distribution, use within buildings, and wastewater treatment. Moreover, the impact of water use varies significantly among countries/regions, due to different water use cycles. For example, many countries use conventional water treatments, while others rely on advanced desalination. Unlike building energy use, the impact of water use in buildings has not been captured fully in research. Given the significant impact of water use in buildings and global environmental degradation, we aimed to review studies concentrating on constructional and operational water use and associated environmental impacts, as well as studies that employed life cycle assessment (LCA) on this topic. The review indicated that a limited number of studies have focused on this serious issue in recent years, and their aims differed greatly. Therefore, there is a notable research gap in comprehensive environmental impact assessment including the total human water use cycle. Complete environmental assessment through LCA enables building professionals to understand the wide-ranging impact of water use in a building's life cycle from the environmental perspective in a given region. Additionally, this approach can benefit policymakers setting guidelines for new sustainable water strategies aimed at reducing environmental impacts.