I have some basic experience of this. Some years ago we had a farm which for the main house had a Klargester, and for outbuildings effluent flowed to a reed bed of about a third of an acre, which was linked to a series of biggish ponds and eventually a stream. The Klargester rotating plate system also output clean water to the reed bed. The reed bed was fed from a trickle underground water supply I think as well, though I never found where , or proved that.
The ponds contained a large amount of wildlife and tench which were fine.
What I would say is that although it worked perfectly (I did not install it but it was only a year old when I bought it) it required strict care. This mainly revolved around the necessity to have strict control over disposal of sanitary products, non biodegradable toilet tissue, and grease traps in the kitchen and utility systems.
We saved a lot on waste water disposal. But to do it well, I suspect you need to balance reed bed size against inputs quite carefully.
