Not only does sewage treatment squander drinkable water but it also creates a lot of pollution in the form of waste solids. These aren't new discoveries. Ecological sanitation has been widely successful in Africa and Asia, particularly as a method of transforming shit into soil in places where there are high rates of waterborne illnesses and potable water is scarce. The world as a whole is already faced with major sanitation problems. Almost half of people globally don't have access to a sanitation system¹. The effect of global climate change is that these issues will become a reality for even more people around the world. A great place to read a little about this is an organization called Sustainable Organic Integrated Livelihoods (SOIL). They advocate for "ecological sanitation" too, although I prefer the term shit composting.
¹ "Ecological Sanitation;" Sustainable Organic Integrated Livelihoods (SOIL);