Wichita Falls, Texas actually piped their treated sewage outflow directly into their treatment plants for a short while because if a drought. Usually it gets dumped in a river after treatment but they were running out of water.

https://practical.engineering/blog/2025/6/17/how-sewage-recycling-works

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.

As a fellow South Australian, I had the same thought. This is NOT an Australian issue, this is a Sydney issue.

You really should not.

Waste water treatment, in order to reach human consumption grade, undergoes several stages of treatment.

• preliminary

Removes solids, largely unsoluble, be it organic or inorganic

• primary

Forced oxygenization, to activate micro organism capable of digesting the organic matter present. This stage is the most crucial for the entire process.

• secondary

Waters are allowed to settle, in order to separate solids, now highly rich organic mud, from the water, in large pools or tanks, that are continually fed. Entering water displaces already clarified and mostly depleted of oxygen water, which can safely be returned to nature.

• terciary

Previously clarified water undergoes UV treatment and/or has added minute quantities of sodium hypochlorite, for disinfection purposes. Microfiltering can be added subsequently.

This water is safe for use in street cleaning, irrigation, industrial uses, fire fighting, etc.

• quarternary

Obligatory microfiltering, followed by reverse osmosis process, to remove heavy metals and trace chemicals, followed by filtering through activated charcoal filters. Mineral (sand and rock) filters are then used to give back minerals to the water, to give it an organoleptic profile.

Stabilization of pH and final clarification can be done, before being reintroduced to the supply network.

Funny story there (well, not "haha" funny). I recently finished my bachelors in Architectual Technologies and Construction Management in Denmark. The exam for this bachelors is defending a project you've worked on for 4-ish months. It's a construction project, where you alone have to design a building of a decent size while making sure you don't break a bunch of laws or building codes. My exam was a catastrophe. Part of what made it so incredibly bad, was that I insisted on making a building that was good for the end-user. Unfortunately, part of our building codes here in Denmark is that we have to build a building that is good for the customer, not the end-user. This meant that I went directly against code, by e.g. soundproofing the building better than the nationally agreed minimum soundproofing, because that would be more expensive for the customer, or by insulating the building more than legally required, because we live in fucking Denmark, and heating of a building is a big environmental factor.

According to our codes (apparently), you have to only ever do the absolutely legal minimum when designing a construction project, unless the customer has expressly stated otherwise, because if not, you're not securing your customer's interest. So in other words, the quality of the building isn't important, only the cost of it.