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Water scarcity has generated the need to identify new sources. Due to its low organic contaminant load, greywater reuse has emerged as a potential alternative. Moreover, the search for decentralized treatment systems in urban areas has prompted research on using green roofs for greywater treatment. However, the performance of organic matter removal is limited by the type of substrate and height of the growing media. Bioelectrochemical systems (BESs) improve treatment performance by providing an additional electron acceptor (the electrode). In this study, nine reactors under three different conditions, i.e., open circuit (OC), microbial fuel cell (MFC), and microbial electrolysis cell (MEC), were built to evaluate the treatment of synthetic greywater in a substrate-growing medium composed of perlite and coconut fiber and operated in batch-cycle mode for 397 days. The results suggested that using BESs enables greywater treatment and the removal of pollutants to levels that allow their reuse for irrigation. Furthermore, electrical conductivity was reduced from 732.4 ± 41.2 µS/cm2 in OC to 637.32 ± 22.73 µS/cm2 and 543.15 ± 19.69 µS/cm2 in MEC and MFC, respectively. The soluble chemical oxygen demand in the latter treatments reached 76% removal, compared to levels above the OC, which only reached approximately 67%. Microbial community analysis revealed differences, mainly in the cathodes, showing a higher development of Flavobacterium, Azospirillum, and Zoogloea in MFCs, which could explain the higher levels of organic matter removal in the other conditions, suggesting that the BES could produce an enrichment of beneficial bacterial groups for treatment. Therefore, implementing BESs in green roofs enables sustainable long-term greywater treatment.

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Greywater reuse has emerged as a promising solution for addressing water shortages. However, greywater needs treatment before reuse to meet the required water quality standards. Conventional wastewater treatment technologies are unsuitable for recreating highly decentralized domestic greywater. This study evaluated bioelectrochemical reactors (BERs) with granular activated carbon (GAC) as a sustainable alternative for developing decentralized and low-cost biological treatment systems. BERs using GAC as the anode material and conventional GAC biofilters (BFs) for synthetic greywater treatment were operated in batch mode for 110 days in two stages: (i) with polarized anodes at -150 mV vs. Ag/AgCl and (ii) as a microbial fuel cell with an external resistance of 1 kΩ. Anode polarization produced an electrosorption effect, increasing the ion removal of the BERs. Power production during the operation and cyclic voltammetry tests of the extracted granules revealed electrochemically active biofilm development on the BERs. Although low power density (0.193 ± 0.052 µW m-3) was observed in BERs, they showed a similar performance in sCOD removal (BER = 91.6-89.6 %; BF = 96.2-93.2 %) and turbidity removal (BER = 81-82 %; BF = 30-62 %) to BFs that used 50 % aeration. Additionally, scanning electron microscopy of sampled granules showed higher biomass formation in BER granules than in BF granules, suggesting a higher contribution of sessile (vs. planktonic) cells to the treatment. Thus, the results highlight the synergistic removal effect of the GAC-based BER. The scalable design presented in this study represents a proof-of-concept for developing BERs to use in decentralized greywater treatment systems.

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Laundry greywater is considered as an alternative source of non-potable water, as it is discharged in approximately 70% of homes. Because this water contains compounds such as biodegradable and recalcitrant organic matter, surfactants, and microbiological compounds, it must be treated prior to reuse. Therefore, the objective of this study was to assess the behavior of organic matter and antibiotic-resistant bacteria (ARB) in greywater treated by a constructed wetland (CW). The results show that the organic matter removal efficiencies were 67.19%, 50.15%, and 63.57% for biological oxygen demand (BOD5), chemical oxygen demand (COD) and total organic carbon (TOC), respectively; these efficiencies were not significant (p > 0.05). In addition, the CW allows the distribution of TOC and ionic compounds in the fractions below 1000 Da to increase by 5.03% and 13.05%, respectively. Meanwhile, the treatment of microbiological compounds generated non-significant removals (p > 0.05), along with increases in bacteria resistant to the antibiotics ciprofloxacin (CIP) and ceftriaxone (CTX) of 36.34%, and 40.79%, respectively. In addition, a strong association between ARB to CIP, CTX, cationic and non-ionic surfactants was determined, indicating the role of surfactants in ARB selection. It is suggested that disinfection systems should be employed prior to the reuse of the treated water.

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Residents of informal settlements, the world over, suffer consequences due to the lack of drainage and greywater management, impacting human and environmental health. In Brazil, the presence of the Aedes aegypti mosquito in urban areas promotes infections of the Zika virus as well as companion viruses, such as dengue, chikungunya and yellow fever. By using observation and interviews with the community, this paper shows how a simple sustainable drainage system approach could prevent the accumulation of on-street standing water, and thus reduce opportunities for the mosquito to breed and reduce infection rates. During the interview phase, it became apparent that underlying misinformation and misunderstandings prevail related to existing environmental conditions in favelas and the role of the mosquito in infecting residents. This inhibits recommendations made by professionals to reduce breeding opportunities for the disease vector. Whilst unrest is an issue in favelas, it is not the only issue preventing the human right to reliable, safe sanitation, including drainage. In "pacified" favelas which may be considered safe(r), the infrastructure is still poor and is not connected to the city-wide sanitation/treatment networks.

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ABSTRACT The high consumption of water and the generation of greywater in laundromats underscore the need to investigate advanced treatment techniques to reuse this effluent. Based on the estimated growth figures of the laundromat sector in Brazil, this study looked into the efficiency of electrocoagulation to treat laundromat greywater. Electrodes were connected to an EC reactor on a monopolar parallel connection mode, with electric current of 6 A and current density of 400 A.m2. The highest efficiency to treat laundromat greywater was observed at a distance of 15 mm between electrodes, voltage of 17.14 V, and operation time of 30 min, when the removal values of apparent color, true color, turbidity, biochemical oxygen demand, chemical oxygen demand, and surfactants were 92, 97, 88, 91, 98, and 96%, respectively. Electrode consumption was measured at 1.82 g.h, while energy consumption was 20.54 kWh.m3 and the total cost was US$ 4.10 per cubic meter of treated effluent. However, despite the high efficiency of the treatment, reuse of treated laundromat effluent requires polishing in order to meet the standards defined by Brazilian regulations.

RESUMO O elevado consumo de água potável e a consequente geração de efluentes associados ao segmento de lavanderias domésticas justificam o estudo de tratamentos avançados que proporcionem o reuso dessas águas. Considerando-se uma perspectiva de crescimento desse setor em nível nacional, esta pesquisa avaliou a eletrocoagulação como tecnologia de tratamento de tais efluentes. Foram executados testes de bancada utilizando eletrodos em alumínio, arranjados como monopolar paralelo. A corrente elétrica e a densidade de corrente foram fixadas em 6A e 400A.m², respectivamente. Entre as variáveis avaliadas estão a distância entre eletrodos, o tempo de operação, o tipo de roupa, a utilização de alvejante e o suporte para eletrólise. O melhor tratamento foi obtido sem a utilização do suporte para eletrólise, para uma distância entre eletrodos de 15 mm, tensão elétrica aplicada no sistema de 17,14 V e tempo de operação igual a 30 min. Nessas condições, as eficiências do tratamento obtidas foram de 92% para cor aparente, 97% para cor verdadeira, 88% para turbidez, 91% para demanda bioquímica de oxigênio, 98% para demanda química de oxigênio e 96% para surfactantes. O sistema resultou no consumo de eletrodo de 1,83 g.h e no consumo de energia elétrica igual a 20,57 kWh.m³. O custo final do tratamento foi calculado em US$ 4,10.m³ de efluente tratado. Embora tenham sido obtidas elevadas remoções nas concentrações dos poluentes, para o reuso do efluente ainda é necessário um tratamento adicional.

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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.

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RESUMO Com a crescente demanda e escassez de água são necessários esforços para viabilizar fontes alternativas de abastecimento. Assim, este trabalho teve como objetivo otimizar o tratamento da água cinza, associando os coagulantes químicos sulfato de alumínio e cloreto férrico para possibilitar o reúso da água tratada. Para tanto, a pesquisa foi dividida em três etapas: caracterização da água cinza proveniente de lavatório e chuveiro de uma residência unifamiliar; avaliação do uso combinado de sulfato de alumínio e cloreto férrico, preparados em solução de 5%, para o tratamento da água cinza, otimizando as concentrações dos coagulantes químicos aplicando o Delineamento Composto Central Rotacional e avaliando os dados via Metodologia de Superfície de Resposta e Desejabilidade Global; e avaliação da eficiência do tratamento proposto, confrontando as dosagens ótimas determinadas com os testes em laboratório. Os resultados indicaram que a associação do sulfato de alumínio (concentração de 0,470 g.L-1) e do cloreto férrico (concentração de 0,115 g.L-1) potencializou o tratamento, atingindo uma remoção de turbidez da água cinza de até 94%. Além desses resultados, houve redução de coliformes termotolerantes e do cloro residual, possibilitando o reúso na descarga das bacias sanitárias e em processos de irrigação.

ABSTRACT With the growing demand and shortage of water, efforts are needed to enable alternative sources of supply. Thus, this work was focused on optimizing the treatment of greywater by associating the chemical coagulants aluminum sulfate and ferric chloride, to enable their reuse. Therefore, the research was divided into three stages: characterization greywater from basin and shower of a single-family residence; assessing the combined use of aluminum sulfate and ferric chloride, prepared in 5% solution for the treatment of greywater, optimizing the concentrations of chemical coagulants applying Central Composed of Rotational Design and evaluating the data via Methodology Surface Response and Global Desirability; and evaluating the effectiveness of the proposed treatment, comparing the optimum dosages determined with laboratory tests. The results indicated that the combination of aluminum sulfate (concentration 0.470 g.L-1) and ferric chloride (concentration 0.115 g.L-1) potentiated treatment, achieving a removal of greywater turbidity of up to 94%; also, thermotolerant coliforms and residual chlorine were reduced, making it possible to reuse them in the discharge of toilets and in irrigation.

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The objective of this study is to assess the environmental benefit of using rainwater, greywater, water-efficient appliances and their combinations in low-income houses. The study was conducted surveying twenty households located in southern Brazil, which resulted in water end-uses estimation. Then, embodied energy, potential for potable water savings and sewage reduction when using the different strategies were estimated. The environmental benefit analysis of these strategies was performed using an indicator that includes embodied energy, potable water savings, reduction of sewage and energy consumption in the water utility, and sewage production during the life cycle of the system. The results indicated that the strategy with the greatest environmental benefit is the use of water-efficient appliances, which resulted in substantial water savings and reduction of sewage, causing low environmental impact due to lower embodied energy over the life cycle.

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Water availability pressures, competing end-uses and sewers at capacity are all drivers for change in urban water management. Rainwater harvesting (RWH) and greywater reuse (GWR) systems constitute alternatives to reduce drinking water usage and in the case of RWH, reduce roof runoff entering sewers. Despite the increasing popularity of installations in commercial buildings, RWH and GWR technologies at a household scale have proved less popular, across a range of global contexts. For systems designed from the top-down, this is often due to the lack of a favourable cost-benefit (where subsidies are unavailable), though few studies have focused on performing full capital and operational financial assessments, particularly in high water consumption households. Using a bottom-up design approach, based on a questionnaire survey with 35 households in a residential complex in Bucaramanga, Colombia, this article considers the initial financial feasibility of three RWH and GWR system configurations proposed for high water using households (equivalent to >203 L per capita per day). A full capital and operational financial assessment was performed at a more detailed level for the most viable design using historic rainfall data. For the selected configuration ('Alt 2'), the estimated potable water saving was 44% (equivalent to 131 m3/year) with a rate of return on investment of 6.5% and an estimated payback period of 23 years. As an initial end-user-driven design exercise, these results are promising and constitute a starting point for facilitating such approaches to urban water management at the household scale.

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RESUMO A desinfecção adequada de águas cinzas é necessária para garantir a segurança de sua reutilização, principalmente em aplicações com potencial de exposição humana. Diversos processos oxidativos avançados têm sido empregados nos últimos anos para a degradação de contaminantes orgânicos, bem como para desinfecção de águas e efluentes. O objetivo deste trabalho foi testar TiO2 suportado em microtubos para desinfetar águas cinzas por meio da fotocatálise heterogênea, visando ao reúso hídrico em bacia sanitária. A água cinza utilizada nos experimentos foi coletada após passar por um sistema de tratamento composto de um tanque de evapotranspiração seguido de banhado construído de fluxo horizontal. Foram realizados testes em batelada utilizando-se um reator fotoquímico cilíndrico de 1,0 L (volume total do reator), preenchido com pequenos cilindros de vidro do tipo Pyrex com TiO2 suportado. Para os testes de desinfecção, foram utilizados os processos UV, H2O2, UV/TiO2, UV/H2O2 e UV/TiO2/H2O2. Foi possível obter uma camada homogênea de TiO2 depositada nos pequenos tubos de vidro Pyrex, com espessura média de 35,3 µm, capaz de promover um incremento na desinfecção de águas cinzas. Porém, mesmo com um maior poder de desinfecção do TiO2 - se comparado com a fotólise (UV) -, os processos em que se empregou o peróxido de hidrogênio foram bem mais eficientes, tanto na desinfecção (inativação total de coliformes totais, enterococos e Pseudomonas aeruginosa) quanto na remoção de matéria orgânica em termos de demanda química de oxigênio (em torno de 60%). As amostras mantidas em temperatura ambiente e envolvidas por plástico escuro não apresentaram recrescimento bacteriano com 24h de armazenamento após os experimentos, mostrando assim a viabilidade da água cinza tratada em reúso doméstico.

ABSTRACT Proper disinfection of greywater is needed to ensure the safety of its reuse, especially in applications with potential for human exposure. Various advanced oxidation processes have been used in recent years for the degradation of organic contaminants, as well as for disinfection of water and wastewater. The purpose of this study was to test TiO2 supported in microtubes to disinfect greywater by photocatalysis in order to reuse it in sanitary bowl. The greywater used in the experiments was collected after passing through a treatment system consisting of an evapotranspiration tank followed by constructed wetland with horizontal flow. Batch tests were conducted using a cylindrical photochemical reactor of 1.0 L (total volume of the reactor), filled with small glass Pyrex cylinders with supported TiO2. For disinfection tests, the processes UV, H2O2, UV/TiO2, UV/H2O2 and UV/TiO2/H2O2 were used. It was possible to obtain a homogeneous layer of TiO2 deposited in small Pyrex glass tubes with an average thickness of 35.3 µm; this layer was able to promote an increase in the greywater disinfection. However, even with a greater disinfection power of TiO2 compared with photolysis (UV), the processes with hydrogen peroxide was much more efficient in disinfection (total inactivation of total coliforms, enterococci and Pseudomonas aeruginosa) and in the removal of organic matter in terms of chemical oxygen demand (around 60%). Samples stored at a room temperature and wrapped in plastic dark showed no bacterial regrowth after 24 hours of storage after the experiments, thus showing the viability of treated greywater for domestic reuse.

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RESUMO O presente trabalho teve como objetivo aplicar a ferramenta de avaliação quantitativa de riscos microbiológicos (AQRM) para avaliação do reúso de águas cinza, a fim de definir uma faixa de valores máximos permitidos (VMP) para Escherichia coli por meio do conceito de riscos aceitáveis 10-3 e 10-6 por pessoa por ano (pppa), para as diversas finalidades de reúso. Para tal, foram avaliadas a exposição, a dose-resposta e a probabilidade de infecção para diferentes finalidades de reúso. O modelo de Beta-Poisson foi empregado para a avaliação da probabilidade de infecção. Os dados de entrada para AQRM foram avaliados mediante a compilação sistemática de dados da literatura. Os maiores riscos de infecção decorrem das culturas alimentares e da balneabilidade com águas cinza misturadas, resultando em VMP de 5,25 a 105 Número Mais Provável (NMP)/100 mL e de 3,95 a 39,5 NMP/100 mL respectivamente, para risco aceitável de 10-3 e 0,00 a 0,10 NMP/100 mL e 0,00 a 0,04 NMP/100 mL, simultaneamente, para risco de 10-6 pppa. Já o menor risco de infecção decorre do reúso de águas cinza de lavatório para lavagem de pisos, proporcionando VMP de 21,4 × 101 a 2,14 × 103 NMP/100 mL para risco aceitável de 10-3 e 0,71 a 14,3 NMP/100 mL, sucessivamente, para risco de 10-6 pppa. A AQRM com riscos aceitáveis de 10-3 pppa mostra-se uma potencial ferramenta para avaliação dos VMP em água cinza bruta, visando sua reutilização, e pode subsidiar decisões normativas nacionais.

ABSTRACT The current study had the objective to apply the tool of quantitative microbiological risk assessment (QMRA) to evaluate the reuse of greywater in order to define a range of maximum value allowed (MVA) to Escherichia coli by means of the concept of acceptable risk 10-3 and 10-6 per person per year (pppy), for the various purposes of reuse. For that, the following criteria were evaluated: the exposure, the dose-response and the probability of infection for different purposes of reuse. The Beta-Poisson model was used to assess the probability of infection. The input data for QMRA were evaluated from a systematic compilation of literature data. The greatest risks of infection resulted from food crops and balneability in mixed greywaters, resulting in MVA from 5.25 to 105 MPN/100 mL and from 3.95 to 39.5 MPN/100 mL respectively, to an acceptable risk of 10-3 and 0.00 to 0.10 NMP/100 mL and from 0.00 to 0.04 MPN/100 mL, simultaneously, to a risk of 10-6 pppy. Yet, the lowest risk of infection was due to the reuse of greywater from lavatories for washing floors, providing MVA from 21.4 × 101 to 2.14 × 103 MPN/100 mL to an acceptable risk of 10-3 and 0.71 to 14.3 MPN/100 mL, for a risk of 10-6 pppy. The QMRA with acceptable risk of 10-3 pppy has been a potential tool for the assessment of MVA in crude greywater aiming the reuse and the possibility of support in national policy decisions.