Alternative septic system information needed

My mother has a lakeshore home on Lake Mille Lacs near the town of Isle, Minnesota. We are attempting to replace the twenty year old septic system (a septic tank and holding tank requiring periodic pumping) with some type of mound system. I have noticed several mound systems in our neighborhood (they all look alike to me).
Our lot is small and Mille Lacs county is telling us the typical sand mound system is a little too large to fit on the lot. I understand there are alternative mound type systems that do not require as much space as the typical sand mound system. On the Internet I have encountered the terms "textile filter technology" describing a smaller mound system and also "aerobic treatment" describing another smaller system. If anyone has any experience with either of these two types of septic systems, I would appreciate your analysis of them.
Also, if anyone has encountered a similar situation as ours, I am interested in the solution you found and the type of septic system you used.
Approximate costs of these alternative septic systems are also appreciated, if possible.
TIA, Terry
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