The increase in water demand in recent years led to the expansion of research and public policies on the reuse of water, especially greywater (GW). Given the diversity of research in the area, this paper proposes an analysis of the evolution of the area through an objectivity metric. Metadata of 1,524 publications indexed in the Scopus database between 1974 and 2021 were analyzed using the VOSviewer tool, and showed exponential growth in publications from 2013. Six different spelling variations were found for GW in the database. Despite the highly geographical scattering of academic production, developed countries, who began researching greywater earlier, had more connections and published more papers; except for Israel, which had the highest average of citations per article. While developed countries lead the research area, developing countries are emerging in GW reuse research. These aspects reveal both the dispersion of the research structure development and a trend of intellectual production in GW from developed to developing countries. Also, we noted that countries suffering from water scarcity stood out with the highest activity in paper publishing. Thus, we expect that future research on GW reuse will take place in developing countries that face water scarcity.

Water quality has been a global concern, as evidenced by UN Sustainable Development Goals. The current paper has focused on the Piabanha River rehabilitation as a case study which can be generalized to other similar watersheds. A monitoring program during a hydrological year was carried out, and different databases were used to calibrate and validate the QUAL-UFMG water quality model. Sanitation is the major problem in the watershed, notably in its headwater catchments, which concentrate the most urbanized regions where water quality is worse in the dry season due to low river flows. Thus, simulations of the river water quality have been performed through computational modeling suggesting organic load reductions in some sub-basins. In conclusion, some strategies to improve water quality have been discussed: (i) The water quality rehabilitation must consider progressive goals of pollution reduction starting with an initial implementation in a reduced area. The monitoring should be based on a few parameters relevant and simple to monitor. (ii) Pollution reduction ought to be carried out strategically with deadlines and intermediate goals that must be agreed upon between the stakeholders in the watershed. (iii) Watershed committees should supervise projects to improve water quality in partnership with the State Prosecutor’s Office.

Water scarcity is one of the global challenges that threatens economic development and imposes constraints on societal growth. In the semi-arid expanse of West Texas, small communities are struggling with both growing populations and decreasing water resources in the regional aquifer. This study compares two nature-based methods that could solve this problem. The first approach uses ponds and wetlands to make natural processes work together to treat the wastewater that the community receives. We applied a novel Pond-in-Pond system, which offers advantages compared to conventional pond system configurations. This system unlocks strategic hydrodynamic advantages by introducing a deeper anaerobic pit surrounded by berms, which then outflows into a larger pond. The second approach consists of an alternative strategy which integrates waste stabilization ponds, a storage basin, and the reuse of wastewater for crop irrigation—a feat that not only treats water but also enriches soil fertility. Both approaches were analyzed in terms of economic potential and pollution control. The land application had a better return on investment and emphasized the importance of innovative solutions for sustainable water management in arid regions, offering economic and community benefits. The application conveys a clear message: where water is scarce, innovation can grow; where problems are big, solutions are available; and where nature’s processes are understood, they can be used.

Due to the rising costs of transportation and the more advanced treatment needed to meet the water demands of the urban population, the costs of potable water tend to increase as cities expand. For some water uses, potable water is not required, such as concrete mixing industries. Previous studies have proven the viability of using reused water in concrete production. In Caju, Rio de Janeiro, four large concrete mixing plants (CMPs) are located close to the Alegria Wastewater Treatment Plant. This study focused on assessing the technical and financial feasibility of reusing these effluents as an alternative source of water for the four CMPs. The alternatives were potable and reused water via two supply methods, water tank trucks and pipelines. All costs were analyzed and projected into the future with the market cost of capital. After comparing the costs, the use of reclaimed water proved to be highly feasible, especially when a using pipeline to supply the CMPs. The present costs for the reclaimed water supply were calculated to be USD 0.99 per m³ for the pipeline alternative and the other alternatives varied in being 5 to 7 times more costly. This water reuse project using pipelines to transport reclaimed water to concrete mixing plants provides a feasible, sustainable alternative water supply in water stressed regions such as Rio de Janeiro.

O presente artigo visa contribuir para a implementação do reúso de águas servidas e consequentemente para uma gestão mais sustentável dos recursos hídricos em áreas urbanas. Para isso são levantados apresentados dados de pesquisas acadêmicas e aplicações práticas voltadas para o reaproveitamento de resíduos e efluentes em usos não potáveis, no caso na produção de concreto. São ainda compilados e comparados dados de parâmetros de qualidade requeridos por marcos normativos nacionais e internacionais, bem como as características recomendadas para o reúso de águas servidas como agua de amassamento, utilizando como estudo de caso os efluentes da estação de tratamento de esgotos Alegria e as demandas de quatro centrais dosadoras de concreto - CDCs situadas no seu entorno. Pôde-se constatar a conformidade dos efluentes tratados em relação dos parâmetros de qualidade avaliados bem como a disponibilidade de águas de reúso para atendimento com folgas das demandas das CDCs abrangidas.

Diante do cenário de estresse hídrico já enfrentado em diferentes regiões do Brasil, a prática do reúso de água pode ser uma importante alternativa para aliviar as pressões nos mananciais, garantir água em quantidade e em qualidade para os diversos usos, reduzir conflitos pelo uso da água e contribuir para o desenvolvimento socioeconômico regional. Para que a prática seja institucionalizada e sistematizada no país, é necessário que a cultura da conservação, do uso racional e do reúso de água seja implantada em todos os níveis da sociedade, desde usuários e produtores de água, até técnicos, tomadores de decisão egestores de recursos hídricos e saneamento, além daqueles que tomam ações conjuntas em setores como o agrícola, o industrial, o recreacional, o de energia e outros. Estudos de avaliação estratégica do potencial regional devem ser elaborados com critérios bem definidos de forma a estabelecer um planejamento adequado, com maior possibilidade de sucesso na implantação e operação de futuros empreendimentos.Neste contexto, foi elaborado um conjunto de quatro Notas Técnicas (NT), tendo como principal objetivo a proposição de uma metodologia estruturada de avaliação do potencial regional de reúso de água no Brasil. O presente documento constitui a NT01 que tem como objetivo contextualizar a temática, além de apresentar a estruturação das demais NT e os aspectos mais relevantes para o entendimento geral da prática de reúso de água. A NT02 fornece elementos essenciais para o desenvolvimento de projetos no setor saneamento. A NT03 apresenta o caminho técnico para estudos de avaliação de potencial, considerando aspectos de demanda e oferta de água de reúso. A NT04 questiona os desafios relacionados com o futuro do reúso de água e, em especial, a sua relevância para o Brasil.