Ruling on impure water if processed by a refining substance

Q: What is the ruling on using sewage water to perform Wudu' (ablution) or Ghusl (ritual bath) after it has been treated?

A: All Praise is due to Allah Alone and peace and blessings be upon His Messenger, his family, and companions. To commence: The Council of Senior Scholars has studied this matter before in the Kingdom of Saudi Arabia and issued a decision regarding it to the following content: The council has read the study that was made on this matter by the Permanent Committee for Scholarly Research and Ifta'. The council has also read the letter of his Excellency, the Minister of Agriculture and Water No. 1 / 1299 on 30/05/1398 A. H. After studying and discussing the matter, the following was decreed:According to what has been mentioned by scholars. Large amounts of water which has been changed by Najasah (impurity), becomes Tahir (pure) if this change happens either on its own, by adding Tahir water to it, by the passage of time, by the effects of the sun or wind, etc. As a ruling is terminated (Part No. 5; Page No. 80) when its `Illah (effective cause) is no longer existent.The Council is of the view that such impure water can be considered Tahir after refining it fully in a way through which it regains its first original nature with no change in its taste, color, or smell. This is because impure water can be purified by various means. Usage of modern technical ways of purification is guaranteed in this regard as many tangible mediums are utilized to insure that water is free from all impurities. Specialized experts whom no one can doubt their work and experience are witnesses to this.Such water, after being purified, can be used to remove major and minor ritual impurity. It can also be drunk but if doing so will harm a person's health, it should be abandoned to avoid harm, not because the water is impure.If possible, it is preferred not to drink from such water to protect health, avoid harm, and to be far above doing something that people naturally detest and regard filthy.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.