There appears to be a myth that mound systems do not work. Mound systems work every bit as well as an in-ground (conventional) POWTS.
The primary difference between the two systems is that mound systems are pressurized above-ground systems, and the conventional in-ground system is below ground and typically not pressurized. As far as system performance is concerned, a pressurized system typically will perform better than one that is not. The wastewater is dosed over the entire absorption area versus being distributed over a small area as in the conventional gravity system.