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What are the components and function of a "typical" septic system?
What is a Soil Absorption System (SAS)?
What are the different types of soil absorption?
What are the possible signs and causes of a failing septic system?
What is a septic
system?
The privately owned
wastewater treatment system (POWTS) is an effective, long-standing method
for collecting, treating, and disposing of sewage from rural and suburban
homes and businesses. Septic systems are used in every country and in
the majority of Wisconsin rural homes. Simply put, the raw wastewater
from your home or business is being disposed of on the property rather
than being piped to a municipal sewage treatment plant.
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What are the components and function of a "typical" septic
system?
In a typical modern
system, wastewater flows from a house or building to a septic tank and
finally to an absorption area (In certain situations a dosing tank is
required when the effluent from the septic tank can not be fed to the
absorption field by way of gravity).
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The Septic Tank Component.
The modern tank is
normally constructed of prefabricated reinforced concrete. The tank (assuming
watertight integrity) is normally "full" of liquid and waste all the time.
Therefore, if 100 gallons of water is discharged to the septic tank, it
will push 100 gallons of effluent (clarified wastewater) out of the tank
to the absorption area (or pump chamber). After entering a properly sized
tank, the wastewater separates as either floating debris (i.e. greases)
referred to as the "scum layer", more dense solids which settle to the
bottom commonly called "sludge" and effluent the clarified wastewater
between the scum and sludge layers. Minimal treatment does occur in the
septic tank, anaerobic bacterial action and the conversion of organic
nitrogen to ammonia. The anaerobic treatment is slow and incomplete and
therefore the tank requires pumping (performed only by a licensed septage
hauler) a minimum of every three years. Finally, something should be said
of the baffles and/or outlet filter (if present). The baffles, which are
probably the most important component of the tank, cover both the inlet
and outlet openings inside of the tank. The baffles direct the flow so
that only the clarified effluent flows to the absorption area (again a
pump chamber may be necessary). Systems installed after July of 2000 require
a filter be placed at the outlet of the tank. The filter replaces the
outlet baffle and prevents an additional 10-25% of suspended particles
from leaving the tank. Under "normal" usage the filters are cleaned every
three years.
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What is a Soil Absorption System (SAS)?
The SAS (commonly referred
to as the drainfield) is a component consisting of sands and/or other
textural material and gravel which serves as the final stage of the wastewater
treatment process. Typically, in this region four types of absorption
components are commonly installed: conventional below grade (non-pressurized),
below-grade (pressurized), at-grade and mound. In any instance, the absorption
areas basically work under the same concept. Clarified liquid waste (effluent)
is dispersed either by gravity (trickle flow) or via a pumping system
(dosing) into the soil absorption system. Refer to each individual system
for more detailed information.
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Different types of Soil Absorption System (SAS)
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Non-Pressurized Below Grade "Conventional Component"
The modern conventional soil absorption system (SAS) is a trench design
using either perforated pipe and gravel or graveless leaching chambers.
The aggregate trench distributes the effluent by gravity through a four-inch
perforated distribution pipe. A more recent alternative to the aggregate
trench is the graveless leaching chamber commonly called a "turtle shell".
The chambers is buried at least 12" below the ground leaving an open void.
Effluent is discharged in an opening at one end of the chamber. The uses
for either type of conventional SAS vary and you should consult with a
qualified licensed professional for the best application.
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Pressurized Below Grade "In-Ground Pressure Component"
The in-ground pressure is another type of below-grade SAS. The major distinction
between this system and the non-pressurized conventional is that the effluent
is supplied through a distribution network by pressure dosing from a pump
tank. Pressure dosing allows for more even distribution of the effluent
over the entire system area during each dosing period. All Pressure distribution
systems require special plan approval from the Wisconsin Department of
Commerce - Safety & Building Division.
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At-Grade Component
As the name implies, the system is installed at the surface of the ground.
As with below-grade pressurized systems, the at-grade system is also a
pressure distribution system. At-grade system designs tend to be long
and narrow and therefore require additional site considerations when testing
for and placing one on a site.
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Mound Component
The mound system is in effect the same system as the at-grade. The major
difference is that this system requires washed sand below the aggregate
or leaching chambers. The effluent is supplied by a pump through a pressurized
piping network. The purpose of the sand is to create the necessary separation
above a limiting condition in the soil beneath. The separation is necessary
for the proper removal of bacteria and viruses from the untreated wastewater.
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Aerobic Treatment Highly-Treated Effluent
Today's technology has allowed for more innovative solutions to the above
mentioned components. As shown above the "in-situ........... soil at the
site is tasked with the job of treating the wastewater. Highly treated
effluent completes much of the treatment before the wastewater is discharged
to the ground and the soil serves only as a final polishing agent. The
advantages to this type of treatment are many; including massive reduction
in the amount of area needed verses untreated systems, possibly eliminating
the need for unsightly mound systems and unlimited life expectancy. Certain
aerobically treated wastewater has >95% contaminant removal, which eliminates
the need for replacing a failed system. In many situations a failing systems
can be reclaimed through the proper use of aerobic treatment. Odors are
drastically reduced or completely eliminated through proper design and
installation.
The arguments
against aerobic treatment are few. The most common being the initial cost.
It is true, aerobic treatment is more expensive "initially". However,
over time when a system using raw wastewater is failing, the aerobic treatment
unit is actually cleaning the SAS (drainfield). Eventually the untreated
system fails and needs to be replaced. Who knows what codes changes and
regulations will be requiring in the future - possibly aerobic treatment!
Not to mention the cost of re-landscaping, possible septage back-ups and
other inconveniences - all with associated costs. Maybe even worse, the
property may no longer have enough suitable area for a septic system and
you are forced into installing a holding tank!
Another argument
is that these systems require maintenance or they don't work like they
are supposed to! Well more than likely these two go hand in hand. Homeowners
who don't properly maintain these systems will experience problems. However,
with proper attention aerobic treatment has proven time and time again
that it can and does work.
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Possible Signs and Causes of a Failing Septic System
The following is a
common list of signs and possible reasons of a failing septic system.
· Sewage at the ground surface
· Sewage backing in dwelling
· Improper/poor system location
· Improper/poor construction techniques
· System installed in "unsuitable" soils
· Inadequate sizing "overloading" the system
· Frequent freezing problems
· Driving/paving over system
· Use of additives
· Baffles missing from septic tank
· Old age (systems eventually fail)
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Contacting local regulators
Chippewa
County Zoning & Solid Waste
711 N Bridge
Chippewa Falls, WI 54729
715-726-7940
Dunn
County Zoning Department
800 Wilson
Menomonie, WI 54751
715-232-1401
Eau
Claire County Health Department
920 2nd Ave.
Eau Claire, WI 54701
715-839-4718
District
Wastewater Specialist -
Mr. Leroy Jansky
3 E Spruce St.
Chippewa Falls, WI 54729
715-726-2544
