A reader which I'm thankful to, incites me to go ahead and deepen the information regarding waste water treatment, I see that this area is raising interest for the lesser costs than other tecniques and several benefits can be obtained at the same time...
Let's say we want to treat the tricameral effluent of a household: two methods can be used according to the quantity of water to be treated: water recycle or effluent absorbtion.
Different designs are applied: the effluent absorbtion consists in excavating a trench, cover the inside with a layer of thick insulating material, fill back in the spoil and vegetate it with vetiver plants: the available moisture is distributed by a pipe underneath and totally absorbed by the plants. There is no output.
This application allows to grow biomasses with the discarted waters that can be easily converted in energy or fertility in the fields.
The other option consists in ponds(natural or constructed) where the waste water stay for at least ten hours, this period of time is subjected to change according with the seasonal temperatures. An interesting contribution to this can be viewed here.
Naturally by applicating these principles, we are creating an eco-system where many factors will gladly associate creating nuisances and benefits: mosquitoes, frogs, fish, ecc.
In Italy waste waters are disciplined by this laws.