In rural areas, one can often encounter off-grid houses disconnected from the central sewage system. They have to get regular visits from trucks that pump it off. Sometimes smaller villages have a central sewage collection site but digging a pipe to the next treatment plant would be too expensive so the truck visits that one collection site and doesn't have to collect from multiple tanks.
This isn't entirely true. Rural properties have septic tanks that are maintenance free for years at a time. The waste is digested by bacteria in the tank and effluents runs off into a septic field. The tank is pumped out only when there is a substantial amount of undigested sludge filling the tank.
Depending pn usage, septic tanks can sometimes go 20 years before being pumped. My house has heavy usage (lots of people), so it gets pumped every 2 years or so. It could maybe go longer, but it's not worth risking it getting over-filled.
It’s over 1/5 of homes in the US that aren’t connected to a public sewer system. That’s quite a bit more than what most people would interpret as “off grid”.
That means 4/5th are “on grid” for sewer. Solving a problem for 80% of the country seems good. Though it sounds like this tube system is economical for less than sewer.
