The frequency of floods caused by extreme precipitation has increased in Lisbon, especially in riverside areas, due to urban expansion and climate change. The Lisbon Drainage Master Plan (LDMP) aims to protect the city from heavy rainfall by constructing 6 km of tunnels, which will act as rainwater collectors, and by using interbasin water transfers to mitigate the environmental, economic, and social impacts of floods. The project is expected to be completed by 2030.

The LDMP also includes anti-pollution basins designed to capture the first, most polluted rainwater, which contains debris from the streets. This water is then transported to the city's three Water Factories for treatment. One of the basins will have a compartment to ensure a minimum flow of water to a mini-hydro plant, producing energy for the Alcântara Water Factory. Additionally, the LDMP plans to reinforce and rehabilitate the existing sanitation network.

Lisbon's three Water Factories—Alcântara, Beirolas, and Chelas—treat wastewater and rainwater using various physical, chemical, and biological processes to separate solids and remove organic matter, phosphates, nitrates, and pathogens. Some of the recycled water is treated with ultraviolet radiation and used for urban irrigation, street cleaning, firefighting, and industrial purposes, through a 55 km distribution network. The rest is safely returned to the Tagus River.

The potential for reusing this treated water is vast. When subjected to ozonation and reverse osmosis, it can even be used for human consumption, as demonstrated by the production of Vira brand beer in Lisbon. 
 

LDMP
https://www.youtube.com/watch?v=pjFezZEMYIc
https://www.youtube.com/watch?app=desktop&v=yWG4t8m2tHU
https://www.youtube.com/watch?v=NbeNHvPi78c
https://lisboaparapessoas.pt/wp-content/uploads/2022/05/pgdl_brochura.pdf
https://planodrenagem.lisboa.pt/sobre-o-plano

Water Factories
https://www.aguasdotejoatlantico.adp.pt/content/tratamento-de-aguas-residuais
https://www.aguasdotejoatlantico.adp.pt/content/fabrica-de-agua
https://aguasdotejoatlantico.adp.pt/content/vira-turn-beer-produced-recycled-water
https://www.youtube.com/watch?v=rQWqdBu7Y6w
https://www.observatorios-lisboa.pt/agua.html
 

• SDG 6 - Clean water and sanitation
  Water Factories transform wastewater and rainwater into recycled water and drinking water, reducing pollution and improving sanitation.
• SDG 11 – Making cities and communities more inclusive, safe, resilient and sustainable
  Lisbon Drainage Master Plan (LDMP) reduces the risk of disasters due to extreme precipitation and the Water Factories reduce the negative environmental impact.
• SDG 13 – Adopt urgent measures to combat climate change and its impacts 
  Water reuse is crucial facing climate change and extreme factors, such as long term drought and floods.

1. Why is the Lisbon Drainage Master Plan needed?
2. What is the aim of the Water Factories?
3. What is recycled water used for?

In the first stage of treatment at the water factories, larger waste that could damage equipment is removed, followed by a similar process for smaller debris. Fats are then skimmed off the surface by a scraping system, while sand settles at the bottom and is pumped out. The water undergoes an initial decanting process to eliminate remaining residues.

Next, the water is biologically treated through aeration, promoting the growth of microorganisms that degrade the main pollutants. The resulting biological floc is sent to a second decantation process, where it settles at the bottom, leaving the treated and clarified water on the surface.

Finally, the water is filtered and disinfected using ultraviolet radiation or chlorine, which eliminates all pathogenic elements. This treated water can then be used for various purposes, including irrigation, washing, industrial applications, or safe discharge back into the water ecosystem.

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