I have read about and seen pictures of some decentralized wastewater treatment systems, but it was only on January 30th that I had an opportunity to visit one in person.
The system being used was developed by a man named Stanislaw, and is known as the ReVive. It features two tanks, one where the initial wastewater (which isn’t separated) flows and settles while it mineralizes, and a second one where the water is moved around, oxygenated and airlifted until it reaches a biological area, where plants are grown and where an ecosystem flourishes. While the system looked a bit down given that it is currently winter where it is located (Sweden), the quality of the water leaving the system was remarkable given that it only has a biological treatment. Below follow some of the pictures:
First tank where the wastewater settles
Overview of the system, with the decaying organic mater visible underwater, as well as some surviving grass, and some foam from the greywater use of soap in the house the system is servicing.
Outlet pipe for the treated water as well as recirculating hose. The system never floods since there is a floater which regulates the water level.
Treated water exiting the system
From what I was able to gather, the whole system runs on only one water pump and one air pump and seemed extremely well designed. The fact that it is designed to handle a family of 20 with daily use on such a small size was also remarkable. The system is technically an anthroponics system without the need for urine/feces separation, since it doesn’t use soil. The fact that it is possible to scale down a treatment unit to this size is most promissing.
While I have my doubts that it would be possible to grow edible plants in this particular system, due to the risk of pathogen contamination, I believe it would be possible to grow other useful non-edible crops (ex: rapeseed, sunflower or hemp for biodiesel production). Then again, I don’t know the details of the design of the system, so it is possible it could have been designed so that the water touching the plants is already pathogen-free.