It is Allah’s will that all living beings on earth are dependent for their existence on water. Referring to this, Allah Almighty says, [We made from water every living thing] (Al-Anbiya ‘ 21:30). If water treatment restores the taste, color, and smell of unclean water to its original state, then it becomes pure and hence there is nothing wrong to use it for irrigation and other useful purposes.
Some scholars state that such treated water can be used for washing clothes, for making ablution and even for drinking purposes, if it is good for health and has been categorically proven that it doesn’t lead to health risks.
The Saudi House of Fatwa issued the following: Wastewater treatment was one of the issues studied by the Supreme Scholars Council in Saudi Arabia. The following resolution was issued as follows: According to the report set by the experts in this regard, a large amount of water would be deemed pure from any impurity if the impurity is removed, if more water is added to it, or if the impurity is eliminated by the passing of time, the sun, the wind, or any other cause that would remove it.
Impure water can be purified by using modern filtering techniques that are the best and most efficient methods for purifying water. Many additives are put in impure water to remove impurities, as attested to by water treatment experts.
therefore, the council believes that such water would be completely pure and it may be used for ritual purification and drinking as long as there are no negative consequences on people’s health. If it is recommended that water not be drunken, it would be due to reasons of public health and safety and not Islamic law.
The council recommends avoiding using treated water for drinking purposes to avoid health problems and also in consideration of the negative public sentiment about this water. However, using this water for the irrigation of crops or park areas is permissible.