After clearing it with our local health officer, when we built our house and homestead, one of our ideas was
a non-traditional hybrid septic/grey water system that actually will produce a clean useful composted material
that can be used in the garden or elsewhere to build soil fertility.
We buried a small 300 gal. plastic septic tank near our house and then down stream from that,
a 30 gallon siphon and finally a 40 foot long by 4 foot wide trench, we call it the chip bed, that has a perforated pipe held above the trench a couple of feet.
Then the whole trench and pipe is covered with 4 feet of wood chips, planer shavings, sawdust or some other convenient carbon source.
The way it works is the septic tank fills with black/grey water. When full, the liquid flows from the tank to the siphon.
When the siphon is full, the 30 gallon slug of liquid is released and flows into the chip bed and is distributed evenly by the perforated pipe.
We have had this system for nearly 30 years and had the septic tank pumped only once during that period and the pump man said that our tank was healthy and working perfectly.
The key to proper septic tank management is never putting chemicals or other stuff that will kill the beneficial bacteria in the tank that breaks down the solids.
We do have some maintenance on the chip bed yearly, replenishing the carbon material, flushing the pipes and removing some of the composted material.