Alternatives to the Mound System

We are looking at building a house and are required to install a mound type system. I had heard of an alternate to the mound system that had been approved in other states. I cant rememeber what its called by the way I understand it is that it works as its own mini wastewater treatment system. Does any know what I am talking about? What are the pros & cons of this new system.Any help is greatly appreciated. Thanks