The most common way to treat household waste in rural Wisconsin is with an on-site disposal system or septic system. These systems treat most waste through a natural process, the balance of the waste must be periodically pumped out.

There are three main stages in the treatment of household waste. The first is the septic tank. Wastewater exits the house via a sewer pipe and enters the septic tank. The septic tank acts as a holding tank allowing the solids to settle-out. The larger solids sink to the bottom where naturally occurring anaerobic bacteria begin breaking them down and destroying pathogens. The lighter solids, like grease, float to the top and form a scum layer. The relatively clear layer in the middle is the effluent.

Next, liquid effluent flows from the tank through the distribution box to the absorption area. The inlet and outlet to the septic tank are covered by baffles which prevent the scum layer from entering the absorption area where it would clog the field. A hydraulic pump is sometimes needed if the absorption site is higher than the septic tank, or if an elevated sand mound is used.

Finally the effluent arrives at the absorption field or drainfield where it is distributed to the soil for treatment. The drainfield field consists of several lateral pipes either in a rectangular bed or in individual trenches partially filled with gravel and covered with topsoil. Holes positioned along the length of the pipe allow the effluent to slowly flow out. As the effluent enters the drainfield it percolates through the gravel bed where a large portion of the pathogens are destroyed. As the effluent exits the drainfield microorganisms in the natural soil consume the organic pollutants and complete the treatment process. This percolation process is a natural biological one that can safely treat the liquid before it reaches groundwater, if the system has been properly designed and maintained.