Hi Dean, Recent research here in Ireland showed that where the soil conditions are suitable and the distribution system works well - a septic tank/percolation system can be a very good, low cost, zero
energy way to filter your sewage before it hits the groundwater. About 50% of Irish systems are built in soils that are suitable. Excellent. It's the other half that has us in
hot water with the EU courts and in dirty water at home
Anyway, if your soil is suitable - chances are it's working fine.
If you want the
permie ideal of obtaining a yield, then an obvious yield from the people living on your plot are humic material and nutrients. If you are happy to flush these away with precious Arizona water, then that's fine, welcome to the comfortable majority. If on the other hand you would rather
save water, save those nutrients and get biomass back on your land, then have a good look at the dry toilet information that's out there and start putting pencil to paper with your designs. That's it in a nutshell really.