Science of greywater treatment?

Hi everybody

Still on my quest to design a home made greywater treatment system, I have come across virtually no specific science on the efficiency and effectiveness of greywater treatment systems.
Permies seem to apply mulch beds, carbon, gravel, sand, reed beds etc. They show off a glass filled with greywater before treatment, and greywater after treatment. Of course, the treated greywater is clearER, meaning the turbidity was reduced. Everything else remains a mistery: contents of N and P, heavy metals, tensides, salts, soap, bacteria, viruses, acidity/alkanility etc.

I have come about one review paper on greywater treatment systems, which emphasizes that it investigated  only industrial scale systems and thus would NOT be applicable to home made systems- still useful informations about the beforementioned mehtods. here is the link:
https://link.springer.com/article/10.1007/s11270-018-3909-8

What science do you base your design on?
Please feel free to share other articles!
cheerio
Lukas

This is a different system it's 0 discharge so there is no "end" product other than coppiced willow/alder.
 the text on the picture is in Danish, but basically it's settling tanks leading to a sealed basin planted with willow/alder that is coppiced in rotation every 3 years, the whole thing takes up around 2500 sqr ft


This might be what you are after. there are 5 more references at the bottom of that link

Thanks for the reply, indeed this sort of information is what I am interested in!
Keep coming