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The system has two things to deal with: liquids and solids. The latter means maintenance-free is bullshit.
One of my colleagues had a house with an anaerobic digestion system under the lawn. The liquid overflow was routed into a perforated pipe under the hedge lining the (slightly downhill) driveway, which was hence permanently "watered" and fertilised. The bacteria digesting the waste produced a flammable gas which was captured in a tank for his heating system. Even with the bacteria breaking stuff down, he still had to get the solids emptied occasionally, but a local farmer did this for free, since the remaining solids were reasonably sterile and nitrogen-rich.
Very common in the US but they are NOT maintenance free. You will need to ensure your loo roll is septic tank safe, amongst other things. Should be loads of stuff on Google from the US. Ask about the last time the tank was pumped and make sure you know how/when it was built. Could get expensive quick if it's wrong.