You can see a video of his process below. The experimentation started with fish tank clarifier, which is — apparently — mostly alum. Alum’s been used to treat wastewater for a long time.

One important note: the tests were done with pure aluminum sulfate (the right name for alum). If you buy alum at the store, it is likely to have potassium or other additives and that might change ...

Chandler explained how this process worked to help reduce turbidity at North Fork. “In the treatment process, liquid aluminum sulfate reacts with hydroxide ions to become a large solid that ...