Which is Best for Me?

Aerobic

• Uses bacteria that need air to live and prosper to digest the wastewater solids very rapidly, inside the tank.
• Treated water that is now harmless to plant or animal life leaves the tank and can be sprinkled on or drip-fed to the land. 
• The treated, odorless water does not damage the ecology, and in-tank objectionable odors are easy to control.

In some areas, aerobic septic systems are mandatory for new installations. On rocky terrain, the cost of installing a new aerobic septic system is lower than an anaerobic soil substitution system that will require building a leech field, provided the homeowner has enough land on which to do so. If the homeowner has a lot of land, with well-drained soil, initial installation of an anaerobic system might cost less, but the maintenance of an anaerobic (leech field) system could be higher if the soil becomes overwhelmed because it was unable to handle the load (terrain turned wet or marshy, or it was subjected to excessive organic loading).

Anaerobic

• Uses bacteria that live with little or no oxygen to prepare the wastewater for distribution on a ground-intensive leech (or leach) field.
• The leech field relies on ground bacteria to finish the job. 
• Objectionable odors can be controlled. If used beyond design limitations, repairs might be necessary for continued good performance. 
• Pumping is recommended to help avoid overwhelming the system and economy of operation.

In some areas, installation of a new anaerobic septic system is not allowed. Although components are less expensive for an anaerobic system, it is much more labor intensive. The leech field should be far from the house, to minimize objectionable odors. The soil under and around the leech field contribute to degrade the wastewater. Should the soil, topography, and local regulations allow it, an anaerobic system is less expensive than an aerobic one.