It's probably septic or an aerobic system.

Mold is anaerobic so once you paint over it, you've given it a motel 6....perfect place to thrive.Microban is the industry standard for treating, killing and cleaning mold.

I have a park in my sites with an aerobic septic system in it.

Is it an aerobic or spray system? 

If it is an aerobic treatment system there's usually an air pump, but it uses a relatively small amount of electricity.

For an aerobic system you need around 5800 sq ft for the spray area for 3 bedroom home.

They claim their system converts the anaerobic septic system to an aerobic system which supposedly can fix failed septic systems and drain fields.

They produce the same anaerobic response as lifting weights, thus enabling burning calories throughout the day.To conclude, I believe in diet and exercise to support you physically and mentally which in turn will help your work performance.  

Just need to be aware of the unique differences in maintenance requirements.I've had multiple properties with septic systems new and old, lateral lines - anaerobic - etc...