If you own a septic tank system you are an operator of a highly efficient wastewater treatment system! A properly designed, constructed and operated septic tank system treats your wastewater more completely than a conventional municipal treatment plant and returns it safely to the ground water resource. Your system represents a significant investment that you will want to protect. Proper operation and regular maintenance will increase its life and effectiveness. Use this guide to understand how to properly care for your onsite wastewater treatment system.
An onsite wastewater treatment system typically consists of a septic tank and subsurface infiltration field or drainfield. It is designed to treat both black water (toilet wastes) and gray water (wastewater from sinks, baths, laundry and water softener brines) so that they may be safely discharged to the soil for recharge to the ground water.
When wastewater is discharged from your home, it enters the septic tank. This tank provides partial treatment of the wastewater. It is a watertight tank that holds the wastewater for up to a day or more. During this time, solid particles suspended in the wastewater are removed. Heavier solids settle to the bottom of the tank to form a sludge layer. Buoyant solids such as greases and oils float to the top to form a scum layer. If not removed, these solids could clog the infiltration field.
The sludge and scum are stored in the tank and undergo digestion or reduction in volume by facultative and anaerobic microorganisms that can thrive without oxygen.
In the process, methane, carbon dioxide, hydrogen sulfide and other gases are released that are vented from the tank through the plumbing stack vent on your house roof. Only about 40% of the sludge and scum volume can be reduced through digestion so the contents of the tank must be pumped periodically and disposed of at a treatment plant or licensed land spreading site.
The subsurface infiltration field absorbs the septic tank effluent and completes the treatment as the liquid percolates through the soil to the ground water. The field typically consists of a series of trenches or a bed. They are excavations in permeable soil that have been partially filled with large gravel. A perforated pipe is buried in the gravel to distribute the septic tank effluent onto the infiltrative surface of the soil. The gravel is covered with natural soil.
Other subsurface infiltration fields may be used for different site characteristics. At-grades and mounds are similar infiltration fields except that they are built on or above the natural soil surface. They provide additional soil materials where there is insufficient depth of unsaturated soil to insure satisfactory treatment.
The infiltration system provides excellent treatment. The soil acts as a biological filter that removes nearly all harmful parasites, bacterial and viruses. It is also very effective in removing toxic organics that may be in the wastewater from household cleaning products. It will not remove nitrate nitrogen, however. Elevated nitrates in the ground water can raise health concerns if found in wells used for drinking water supplies. However, agricultural practices are usually the source of the nitrates rather than properly silted onsite treatment systems.
Proper care and regular maintenance will increase the effectiveness and life of your system. The two most important things you can do are to use water wisely and regularly pump your septic tank. Some helpful suggestions are provided below.
If your toilet does not seem to flush properly, your drains are backing up or you notice wastewater on the ground surface you have symptoms of a hydraulic failure. When you first notice any of these, do the following:
Eliminate all unnecessary water use immediately
Call a licensed pumper to pump the tank and empty the infiltration field if possible
Hire a professional to advise you of appropriate corrective measures
*This information is provided courtesy of the Cass County Minnesota Environmental Services Department.