## 2 Integrated and Decentralised Urban Water Management: A Resilient Approach
### Quality and Treatment of Water for Non-Potable Reuse  
Water reuse has evolved globally, covering a variety of uses, from agricultural, industrial, urban, and even potable. Treated wastewater is seen as an alternative source of water for various purposes. However, it is essential to ensure that potential adverse effects on health and the environment are minimised, which requires a strict definition of quality standards [1]. According to Decree-Law no. 119, 2019, which establishes the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Device or Use** & **Unit Consumption** & \begin{tabular}{c} **Estimated Monthly or** \\ **Annual Consumption** \\ \end{tabular} \\ \hline Flushing toilets (category ”A”) (1) in residences & 24 L/(person.day) & 720 L/(person.month) \\  & & 8800 L/(person.year) \\ \hline Flushing toilets (category ”A”) (1) in-service buildings (offices and others) & 12 L/(person.day) & 360 L/(person.month) \\  & & 4400 L/(person.year) \\ \hline Laundry (category ”A” machine) (2) & 10 L/(person.day) & 300 L/(person.month) \\  & & 3600 L/(person.year) \\ \hline General Cleaning (3) & \begin{tabular}{c} Floor washing \\ Car washing \\ (self-service) \\ \end{tabular} & \begin{tabular}{c} 5 L/m\({}^{2}\) \\ 50 L/car \\ \end{tabular} & \begin{tabular}{c} 100 L/(person.month) \\ 1000 L/(person.year) \\ \end{tabular} \\ \hline Watering green areas (figures for \\ \begin{tabular}{c} average years) (4) \\ \end{tabular} & \begin{tabular}{c} Total values: April \\ to September \\ \end{tabular} & \begin{tabular}{c} Lawns (5) \\ Gardens (6) \\ \end{tabular} & - & 450 to 800 L/m\({}^{2}\) \\ \cline{2-4}  & Maximum values & \
\begin{tabular}{c} Lawns (5) \\ (per day): Summer \\ \end{tabular} &
\begin{tabular}{c} 5 to 7 L/m\({}^{2}\) \\ \end{tabular} & - \\ \hline \hline \end{tabular}  
* (1) Flushing toilet 6 L with dual flush. (2) Machine consuming 9 to 12 L per kg. (3) This is a rough estimate for homes, as the overall figure can vary significantly. (4) In mainland Portugal, the irrigation of green areas in rainwater harvesting systems is considered to be limited in time, as the highest irrigation demand occurs during prolonged dry periods. Therefore, the totals should not exceed half-yearly average estimates. In addition, there is a current trend towards gardens that do not require irrigation. In the Autonomous Regions, irrigation needs may be lower or non-existent. (5) Depending on the type of lawn, the type of soil, and the area of the country. (6) Depending on the type of crops, the type of soil, and the area of the country (considering a mix of lawns and shrub areas).  
\end{table} 
Table 4: Unit and annual consumption by device or use [52]. legal regime for the production and use of regenerated water from treated wastewater in an urban context, its reuse includes recreational applications, landscaping, street washing, firefighting, cooling, flushing toilets, and washing cars. On the other hand, ANQIP ETA 0905, 2023 defines technical criteria for building systems that use greywater, allowing it to be used for watering gardens, flushing toilets, washing clothes, and washing cars after appropriate treatment. The quality of the water and the treatment required are determined by the end use, the likelihood of human contact, and the level of risk involved. Risk management should include treatment of reclaimed water, maintenance of systems, sampling for monitoring, control of system condition, and identification of pipes supplying water for reuse [46]. Greywater treatment systems vary in complexity and size, depending on the characteristics of the water collected and the quality requirements for the intended application.