The field of supply and disposal in settlement structures is currently undergoing major changes. On the one side, the focus is on the user's supply with energy, water, and food/goods and on the other side it is on the disposal of wastewater and waste. Thereby, disposal includes recycling and disposal processes with respective treatment processes prior to recycling and disposal. In the past, via the construction of sewer systems leading to conventional wastewater treatment plants (WWTPs) as end-of-pipe solutions for treating wastewater, fundamental interests of health and water protection have been met. The spread of diseases due to lacking sewers was most widely prevented, at least in the industrial nations. With the growing knowledge that wastewater ingredients, such as carbon, nitrogen, and phosphorus, lead to silting, oxygen consumption, and eutrophication of waterbodies, wastewater treatment plants were implemented, thus increasing the quality of waterbodies significantly. However, the question is whether the objectives of sustainable wastewater treatment have been achieved this way. Research results in the fields of health and water protection as well as changes in society's ecological awareness (climate and resource protection)