The Mayans figured it out thousands of years ago. Constructed wetlands with filters, plants, insects, and animals all work together if given the proper formulation to provide a healthy, clean, safe water source which is low maintenance (do not confuse with no maintenance) and inexpensive over the life of the system.
Basically think sand mounds for sceptic systems, but better.
I maintain similar systems to filter contamination from coal mines for work, so it’s nice to see research related to agriculture, permaculture, or growing plants as the focus.
Some limestone ponds in operation /maintenance as a reference point for how things might be done on a small scale.
I wouldn’t consider using it as a source for drinking water, but if I could use greywater to fill and replenish a constructed wetlands water feature then that would be nice. The author of the series of books on the subject of greywater suggested that it was not an efficient use of resources to pump the wastewater uphill in order to put it to use. He much preferred to design systems that would use gravity to distribute it.
The systems I work on are all gravity drained. It definitely doesn’t make sense to me to pump water for treatment unless it’s the only option available. That said… in some areas electricity is more abundant/available than water.
This is definitely true, and I’ve wondered where the tipping point is.
Some people can do fine just harvesting the water that is already being moved by the pump in their laundry washing machine (reportedly the worst offender for septic systems, given the clothing fibers released in the washing process), but others might be willing to pay to split the wastewater system of their house into greywater (low incidences of E. coli) separate from their blackwater discharge, and then pump what is useful uphill to the point of use.