The Presby Maze® is a simple plastic device inserted inside a septic tank designed to trap suspended solids before they reach the leach area. Suspended solids are those solids that are tiny enough or of a certain density, so as to remain suspended in septic tank effluent. Solids in effluent exit the tank where they can pollute the soil and groundwater or cause costly leach area failure. The Presby Maze® uses a network of vertical mesh panels to provide a large surface area for naturally sticky suspended solids to collect on. Solids on the mesh attract other solids forming globules (a collection of solids). Globules gradually change size and density either becoming more dense, slithering down the mesh panels, sinking to the bottom of the tank or more buoyant, creeping up the mesh panels to the liquid surface.
In addition the Presby Maze® provides for a substantial increase in liquid retention time inside the tank. Solid end walls have openings positioned to direct liquid back and forth inside the tank increasing the retention time and preventing liquid from flowing directly from inlet to outlet. Increasing liquid retention time provides more time for solids to naturally separate from the liquid and for the Presby Maze® to collect the more resistant solids.
The Mesh panels of the Presby Maze® provide a large bacterial surface covered with solids. Solids on the mesh are more effiecently broken down by anaerobic bacteria naturally present in the septic tank. Increased bacterial breakdown, increased retention time, and trapping suspended solids allows the Presby Maze® to pretreat effluent in the septic tank before it reaches the leach area. Effluent pretreatment provides for smaller, less expensive, longer lasting, leach areas in addion to protecting soil and groundwater.
The Presby Maze® never needs any special maintenance or cleaning. During normal septic tank pumping when liquid is removed from the tank, solids separate from the mesh due to the lack of buoyancy and are pumped out.
A number of recent tests have been conducted on Presby Mazes in secondary tanks of a 20,000 gallon per day commercial system, which includes a resturaunt and hotel. In these tests the Presby Maze® tanks have trapped a minimum of 92% percent of the suspended solids. Some states are allowing reduction of commercial and/or residential leach area sizes when using the Presby Maze®. The percentage of reduction varies depending on the state. Currently Maine allows up to a 35% reduction in commercial leach area.