First thing I would do is reach out to all the cleaning material suppliers. I use Saati and their chemicals can be put into the sewerage system, I’m not sure about septic tanks. Ask them.
Second thing is have a good filter system, I have something based on Pierre’s system. All the water for opening and cleaning screens runs through 3 tanks that flow one into the other. All the heavy stuff stays in the tanks. Once every few months I put what’s in the tanks into used emulsion buckets, I put these on the roof in the sun and after a few weeks get a hard cake of old plastisol and emulsion that I can throw in the garbage.
After the last of these tanks I run the water into a bath with a pump that works automatically as the bath fills up. The water gets pumped through a filter into the sewerage system.
If you are interested I can send you photographs.
