The photos below show a community sewage treatment project that uses Pura-Flo peat filters manufactured by an Irish firm, Bord-na-Mona. Pura-Flow peat filters are approved for use in Virginia.
This was a community project serving 20 homes. The cost of $6,000 per home includes new 1000 gallon septic tanks for each home. Cost was kept down by the labor of community members, who applied "sweat equity" to construct the piping that collects septic effluent from each home and brings it to the central treatment location.
Each septic tank contains a chamber with a pump that pumps sewage effluent through a piping system to the Pura-Flo units. Because septic effluent, not raw sewage, is being pumped, pipes may be used that are smaller than what would be used in a typical sewage system. This arrangement is known as a "STEP" system (Septic Tank Effluent Pumping).
The STEP effluent is delivered to large subsurface tanks that provide storage and recirculation. A 50 percent recirculation ratio is used in this project (which means that each volume of effluent is circulated through the peat filtration system twice, on average), although the peat filtration system can be used without recirculation. The 50 percent recirculation provides an extra factor of safety to ensure adequate treatment in this high water-table area.
Above are the Pura-Flo units. Each unit
is approximately 7' x 4' x 30" in size, and contains built-in piping as
well as the peat filter. Four banks of 10 units each were set up
to treat septage from 20 homes. A typical Pura-Flo installation in Virginia
will use one unit per bedroom.
Above are two more banks of Pura-Flo units.
The banks were installed on top of a gravel bed, which was placed on top
of the existing soil. The soil fill placed over the gravel bed and surrounding
the Pura-Flo units has not yet been graded smooth or revegetated. Effluent
from the peat filters enters the gravel bed and is dispersed over the underlying
natural soil. This type of arrangement allows for cost-effective effluent
dispersal despite the high water table conditions that prevent use of conventional
septic drainfields on this site.
Above and below are close-up views of the
Pura-Flo units. The built-in piping that distributes wastewater is visible
through the peat. The peat itself is very coarse textured, much more coarse
than peat products that can be purchased in retail stores for landscaping
and other purposes. The manufacturer states that the coarse-textured peat
is able to retain permeability and its capability to treat septic wastewaters
effectively for more than 10 years without replacement. The peat's acidic
nature is an asset to its capability to reduce wastewater pathogens. The
Pura-Flo units' lids can be closed and secured with the built-in metal
fasteners that are visible in the photo above.
This page created and maintained by Carl
26 October 01