And that’s partly my point.

“Safe to drink” means: you can drink this and not immediately die or get sick/poisoned from it.

“Drinking water quality” means: if you drink nothing but this water for your whole life, it won’t harm you. (as far as our scientific understanding goes)

That’s a bit of a gap.

Do you mind sharing which part of the world you’re in?

I made my degree in Germany (and Switzerland for a small part) and there are a few assumptions that come with that. We mostly have combined sewers here (i.e. wastewater and rainwater runoff through the same pipe) and local regulations of course.

Maybe you have different circumstances where you live?

Also on a side note: I consider solar panels as a kind of a cheat as well, because they are not in any way reliant on the water treatment process and could be installed regardless and fed into the grid. Though the dual usage of the area is much appreciated and using their energy at the source is a good idea.

How do you know so much about waste water treatment and why are you so optimistic about what could be done?

I’ve got a relevant university degree, and I’m way less optimistic about most of these topics.

For example:

Muds can be harvested for digestion, in order to produce methane for generating electricity. Depending on the scale, it can be used to power the plant alone or to inject into the wide power grid.

This is usually not a net gain. Wastewater treatment plans consume more energy than can be harvested from the wastewater. The only WWTP I know that claims to produce more than they require for operation can only do so, because they accept additional organic material from a nearby slaughterhouse into their sludge fermentation stage, which is a bit of a cheat.

The same plant is btw also burning their treated sludge because it contains too many pollutants to be used in agriculture.

Citation needed.

I highly doubt that. There would be absolutely no reason to clean the water up to tap water quality and then discharge it into the river, instead of using it as tap water. That’s just not economically feasible.

I know a part of the Danube near Vienna is a valuable nature reserve, but even then tap water quality is not necessary.

If you have a source that proves your claim, I’d be highly interested to learn why and how they do that. I have a degree in environmental engineering, and I want to know when I’m wrong about something like this.