About Septic Systems

Background:

Wisconsin has had a Sanitary Code in place regulating sewage disposal since the early 1900’s.  Those early codes were very general, hard to find, and were essentially voluntary as there was very little governmental administration or enforcement.
With the rise of environmental awareness in the 1960’s and ’70’s, sanitary codes dealing with sewage disposal were clarified and amended.  A state wide administration program was developed and implemented in an attempt to protect ground water and to prevent associated health hazards.
Wisconsin now has a state wide uniform sanitary code that is administered by “designated agents” – typically County Zoning and/or health Departments.  These agents are tasked with insuring that all state codes pertaining to septic system design, installation, use and maintenance are adhered to.

 

Purpose of septic systems:

A septic system has two primary functions to preform.  The first is to treat and clean sewage by removing harmful bacteria, viruses and nutrients from the waste stream, which is necessary to protect our drinking water and to prevent the spread of communicable diseases.  This is typically accomplished by filtering the waste through a minimum of 3′ of soil suitable for cleaning sewage.  The second function of a septic system is to get rid of sewage wastes and prevent discharges to the ground surface or back-ups into the house.

 

Types of septic systems:

  • Conventional Systems.  A conventional septic system is one that transmits wastes from the house by gravity through a 4″ building sewer.  Those wastes are deposited into a septic tank which separates out the heavier solid materials, greases, soaps, etc.  The clarified effluent passes through a filter on its way out of the tank and flows out to a below ground dispersal cell where it drains away through the underlying soil.  A minimum of 3′ of suitable soil is required below the dispersal cell in order to properly treat the sewage effluent and remove any harmful bacterial and viruses that may be present.
  • Dose-Conventional Systems.  Similar to a conventional system, however the dispersal cell is at a higher elevation than the septic tank outlet, so gravity flow cannot be attained.  A pump chamber, otherwise know as a lift station, is installed with an effluent pump to lift, or dose, the effluent up and into the below ground dispersal cell.  Again, 3′ of suitable soil is required below the dispersal cell for effluent purification.
  • At-Grade & Mound Systems.  Sites that do not have at least 3′ of suitable natural soil require that the system be built at or above the ground surface.  An At-grade system consists of a septic tank that clarifies the effluent, a pump chamber to dose the effluent up into the dispersal cell, and a dispersal cell that is built by plowing the native soil, laying gravel and pipe on the ground surface and covering with topsoil.  A mound system is similar to an At-grade system, but with a sand blanket laid on top of the ground surface before the gravel and piping are put in place.
  • Drip Irrigation Systems.  Drip Irrigation Systems can sometimes be installed to service sites with very difficult topography or other physical limitations where more standard types of systems are not a viable option.  They can be installed on steep hillsides or otherwise inaccessible areas by installing irrigation tubing just below the ground surface.  The flexible tubing does not need to remain at a constant elevation and does not require a straight linear installation.  Tubing can be installed to avoid objects by simply going around rather than through them.  Pressurized effluent is pushed through the distribution lines and dispersed through drip emitters into the soil, where it evaporates, is taken up by plants and drains away through the underlying soil.
  • Aeration Treatment Unit (ATU) Systems.  Traditional septic systems rely on anaerobic bacteria to break down the sewage wastes that pass through the system.  An ATU system provides a steady and consistent oxygen supply into the waste stream where aerobic bacteria have been introduced.  Aerobic bacteria thrive in the oxygen rich sewage and are very efficient at breaking down and cleaning up wastes in a short time.  Because the sewage is treated to a much higher quality in the tank, a smaller dispersal cell is needed and requires only 2′ of suitable soil beneath the dispersal cell.  ATU units are typically installed to serve commercial properties such as restaurants where wastes strength and volumes are typically very high.  ATU units are expensive to install and have annual maintenance costs throughout the life of the system, but they are a “top of the line” system, are more environmentally friendly and, if properly maintained, will last many more years than a standard system.