In Egypt, treated sewage water is used to spread greenery in the desert.

There is a 200 hectare (2㎢) forest called 'Serapium Forest' near Ismailia , an Egyptian city along the Suez Canal. The most distinctive feature of Therapium Forest is the use of treated sewage from the town of Ismailia, which has been followed by tree planting projects by 21 countries, including Egypt.

How Egypt is growing forests in middle of the desert
https://www.al-monitor.com/pulse/originals/2020/10/egypt-africa-desert-forests-plant-trees-wastewater.html

SERAPIUM FOREST PLANTATION, ISMAILIA, EGYPT: SPATIAL ANALYSIS REPORT OF THE PLANTATION AREA FOR THE FOREST MANAGEMENT PLAN 2013-2022
(PDF file) http://www.fao.org/forestry/35800-094f4eedb0c86a4a33be1a3d906d80d3f.pdf

The location of Therapium Forest is here. Southwest of the town of Ismailia.


Documentary footage is also available.

و ثائقى غابة سرابيوم فى الاسماعيلية التى تم زرعتها بستخدام مياه الصرف الصحى --YouTube


There is also a video of the German public broadcaster DW reporting on Therapium Forest.

Egypt: The Amazing Forest in the Desert | Global 3000 --YouTube


The project was started in 1998 by the Egyptian Ministry of Agriculture. The energy of the sun shining on the desert is as strong as about 2200 kWh per square meter, which is twice the energy of the sun in Germany, and it does not become 'living soil' as long as it is exposed to direct sunlight.

The Serapium Forest has the purpose of protecting the soil enriched by the trees that form the forest. It also aims to be a permanent source of income for Egypt as a material for the export industry and the local timber industry by planting mahogany and camphor trees.

Water is needed to grow forests, but Serapium Forest uses treated sewage from the nearby town of Ismailia. According to project manager Ragaei Saafan, trees grow four times faster in therapium forests than in sunny European forests, where trees take 60 years to mature in Europe in just 15 years. He says he grows up at a pace of doing things.

With the success of the plan, a tree-planting project called the 'Great Green Wall' by 21 countries across Africa from Senegal in the west to Djibouti in the east started in 2019. The progress of the project is about 15% as of 2020. It is expected to be completed by the end of 2030, and will cost 8 billion dollars (about 850 billion yen) to create a forest with a total area of 100 million hectares.

Great Green Wall — The Great Green Wall
https://www.greatgreenwall.org/about-great-green-wall

The trailer video for the 'Great Green Wall' project looks like this.

THE GREAT GREEN WALL TRAILER --YouTube