Your brother is very inventive, I have a survival book kept in my emergency bag that is full of techniques like this just in case our infrastructure is destroyed by natural disaster that takes our electrical grid down. I expected the filter to be dirty but seeing what we might be drinking kinda grossed me out....
I read that most of our minerals used to come from water and clean dirt which isn't bad but now our sediment is full of farm runoff. Big factory farms use huge amounts of chemicals which are silent killers because they take a long time to build up in the bodies systems and eventually cause dysfunction and disease. Antibiotics cause disease resistant bacteria. That is what I am worried about, not dirt but industrial chemicals and fluoride dumped in our water which is from the manufacturing of aluminum. It is not naturally occurring fluoride, both are deadly if taken in large amounts, one is beneficial in small amounts the other from aluminum manufacturing accumulates in the body, ruining our very fragile hormonal system and causes brittle bones and bad teeth.