Is wastewater drainage possible in the basement?

At what height is the backwater level or what are the individual specifications?

The backwater level is usually = street surface level. Rhine regards

Question for understanding:
Is it about leading the household wastewater into the sewer, or water that collects via a floor drain in the basement?
Is there a modern sewer system with separate foul and rainwater?

For a floor drain, I might understand a lifting system because of the backwater level, but not for household wastewater discharged through a closed pipe system. If there is sufficient slope to the sewer pipe, the pipes can also be routed below the basement floor and drain properly. Purely physically speaking, I don't know the regulations about that.
In general, all wastewater pipes leaving a building are frost-proof deep below street level. However, very few houses have a lifting system. Therefore, I do not understand the statement about the backwater level here.

To protect against backwater, check valves can be used; this is often recommended or even required.

My question was whether it would be possible to install a toilet and shower in the basement without a lifting unit. Or rather, to prepare this. And whether this can be determined with the help of the terrain section plan and the sewer plan. Yes, there are separate foul water and stormwater sewers.

Then I would see no objection, provided that the sewer in the street is deep enough. In heavy rain, there is no risk to the basement, as the rainwater is discharged separately and there must be no connection from the toilet or shower to the rainwater sewer. A lifting station can be omitted in this case. Unfortunately, I also cannot say from the plan how deep the sewer pipes are laid. I would recommend asking the responsible authority for that.

Then I would see no obstacle, provided the channel lies deep enough in the street.

That is always a matter of how "we" see it and how it can be implemented in reality. In recent years, I have overseen just 2 construction projects where your approach was allowed; however, these were on slight slopes. All other construction projects where a basement bathroom was planned had to be drained above the backwater level. So they had to be planned with a lifting station. So in any case, _beforehand_ double-check whether and what can be approved. Rhineland regards

How is that supposed to work when the backwater level is practically at street level, but the pipes are laid well about 1m below ground level? And with separate drainage, there is no risk if the work is done properly.