“Big Layer Cake” is an example of a saturated layered system. Saturation is maintained in the sand/sawdust layer to promote anoxic (no/low dissolved oxygen) conditions.
The treatment area is basically a leach field that is placed in layers, using materials that allow for the successive nitrification and denitrification of septic tank effluent as it percolates through the layers.
This layered soil absorption system is something MASSTC has been experimenting with for years to investigate the possibility of passively removing nitrogen from wastewater as it passes through successive layers of material on its way to the groundwater.
Learn more about layer cake systems here.
Additional links to learn more about MASSTC’s collaborations with towns on Layer Cake systems:
EASTHAM: The Town of Eastham and a property on State Highway received piloting approval for a system. The Provincetown Independent wrote all about it here.
BUZZARD’S BAY: Solutions to Nitrogen Pollution: Installation of Nitrogen Reducing Septic Systems Layer Cake Demonstration Project in the Buzzards Bay Watershed project here.
FALMOUTH: Innovative and Alternative Septic Systems for the West Falmouth Nitrogen-Reducing Septic System Demonstration Project. Read more here.