** Counties must apply to the State for Experimental Concurrence Approval.
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"Protecting You and the Environment"
The Presby Maze® for Septic Tanks
The Presby Maze® is a simple plastic device inserted inside a septic tank and designed to trap suspended solids before they reach the leach area. The Presby Maze® may be used residentially but is primarily used for commercial systems. 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 and form 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 and to the liquid surface.
Solid end walls have openings positioned to direct liquid back and forth inside the tank. This increases the distance traveled by the liquid and prevents liquid and suspended solids from flowing directly from the inlet to the outlet. Increasing liquid travel distance provides more time for solids to naturally separate from the liquid and for the Presby Maze® to collect them.
The Mesh panels of the Presby Maze® provide a large bacterial surface covered with solids. Solids on the mesh are then more efficiently 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 addition 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 and drop to the bottom of the tank due to the lack of buoyancy and are pumped out.
A number of tests have been conducted on Presby Mazes in secondary tanks of a 20,000 gallon per day commercial system that includes a restaurant 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 New Hampshire allows up to a 25% reduction in commercial leach area. This is the only commercial reduction ever allowed for passive systems by the State.
