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ExtremeSTP Cold Climate Sewage Treatment Plants

Typical Site Conditions for an ExtremeSTP

ExtremeSTPs are simple, fully functional, aerobic sewage treatment plants and are consequently more expensive than septic systems. From a cost perspective, if a septic system will work, use one. It will probably be your least cost solution. However, if site conditions prohibit use of a septic system or make it likely that a septic system will fail in a few years and have to be replaced, or if the home or business owner wants to achieve better treatment than can be obtained from a septic system, then an ExtremeSTP is a great alternative.

Permafrost

Permafrost presents several engineering challenges to on-site sewage treatment system designers. Some permafrost is thaw-stable, meaning that if heat is put into it causing it to thaw, no settlement will occur. Unfortunately most permafrost is not thaw-stable. In most cases, if some natural or man-induced change causes permafrost to thaw, ground movement will occur. Ground movement is a common cause of failure of on-site systems in which separate components are connected together by pipes. Examples of such systems are a septic tank connected to a leach field; or a pretreatment tank connected to a separate aerobic treatment tank, connected to a lift station, connected to a leach field. ExtremeSTPs eliminate the problem of differential movement between components in two ways:

• Above ground models minimize the chances of the permafrost thawing by minimizing the amount of heat that is put into the ground.
• ExtremeSTPs consist of one multi-compartment tank so if movement occurs, all parts move together (the exception to one multi-compartment tank is when multiple tanks are required for larger systems or because manufacturing or transportation constraints restrict tank size)

Low Permeability or Saturated Soils

Sometimes an impermeable layer such as clay, bedrock, or permafrost restricts the downward flow of water, or the ground may even be naturally saturated. In such cases, it is very difficult or impossible to get water to flow into the ground. ExtremeSTPs have been used at sites like this to provide a good quality effluent that can be discharged either directly to the ground surface or into a mounded leach field, or directly to a surface water body. In the case of a hillside home near Palmer, Alaska on a low permeability, saturated site a below ground model was used with surface discharge. In this case an effluent pump was not needed because the slope of the hill allowed the outlet pipe to daylight, allowing effluent to flow out of the unit by gravity. As is typically done for surface discharge, a dosing siphon was used to prevent freezing during winter conditions.

Shallow Groundwater

When the groundwater level is naturally close to the surface, the soil will not provide adsorption or filtration of the particulate matter which is contained in the effluent of a septic system. In these cases, regulations do not allow discharge into the soil without a mounded leach field or a higher degree of treatment than can be provided by a septic system. Depending on site-specific conditions, regulators may allow less than 4 feet of separation to groundwater if you have a good quality, aerobic, disinfected effluent such as comes from an ExtremeSTP. In the case of a fishing lodge near Lake Iliamna, Alaska, the separation to groundwater was reduced to 1.5 feet.

Close Proximity to Surface Water

Depending on site-specific conditions, regulators may allow less than 100 feet separation to surface water if you have a good quality, aerobic, disinfected effluent such as is produced by an ExtremeSTP. In the case of a summer home near Big Lake, Alaska, a separation of 60 feet to surface water was approved. In other cases, direct discharge to surface water has been approved.

Small Lot without Room for a Replacement Leach Field

ExtremeSTPs can be used to help prolong the life of a leach field because ExtremeSTPs produce oxygen-rich (aerobic) effluent, which encourages aerobic microbes to grow in the leach field. Aerobic microbes can decompose contaminants faster and more thoroughly than anaerobic microbes.

Site with a Failing Leach Field

For the same reason as above, ExtremeSTPs can help restore the life of a failing leach field. At a site near Fairbanks, Alaska a RetroFAST® unit is being used to restore function to a failed leach field. Further information about this application of FAST® technology can be found in the "Bio-Microbics FAST® (Fixed Activated Sludge Treatment) Insert Information" section.

Nitrate Reduction is Desired

The standard Bio-Microbics FAST® treatment inserts that are used in ExtremeSTPs provide good nitrate reduction. However, in cases where a higher degree of nitrate reduction is required, Bio-Microbics NitriFAST® units or ABC-N™ units can be used.

Lagoon Discharge

Bio-Microbics FAST® treatment systems are available in a floating configuration for treating the contents of a lagoon prior to discharge. These floating units can be winterized for use in cold climates, or an ExtremeSTP can be used to treat the contents of a lagoon for discharge.