Septage: What is it and where does it go?

By Valerie Prax, University of Minnesota Extension
ST. PAUL, Minn. (3/26/2007) – Have you ever driven by an open field and noticed the land application of septage, believing there was cause for great concern? In reality, it's a safe practice that can produce environmental and economic benefits.

Septage is the material pumped from residential and small business septic tanks. In Minnesota, septage is either land-applied or transferred to a publicly owned treatment facility, such as a municipal wastewater treatment plant.

About 70 percent of Minnesota's septage is land-applied. In many parts of the state, municipal plants have limitations on how much septage they can accept. Therefore, the practical solution for most septic pumpers is to apply the septage to land.

Individual or onsite septic systems usually consist of a septic tank and a soil treatment area. The septic tank is designed to collect the wastewater from the home and separate the liquids from the solids – the septage. The liquids go to the soil treatment area where harmful bacteria and other pathogens are destroyed and some nutrients removed. When done properly, the soil treatment area and land-application of septage returns cleaned, safe water to the ground water.

Septic pumpers must follow guidelines developed by the Environmental Protection Agency and Minnesota Pollution Control Agency to protect public safety and water quality. These guidelines include specified distances from property lines, waterways, wells, surface waters and residential or commercial sites. The septic pumper must also document what crops are grown and how they are managed, meet guidelines for how much and how often septage is applied to each site, and keep complete records. Lime must be added to destroy harmful pathogens and help control odors.

The proper land-application of septage has many advantages. Farmers are able to utilize a natural fertilizer source, reducing the amount of commercial fertilizers they use, such as nitrogen. Applying septage locally and limiting travel distances helps control costs for pumpers and homeowners. As fuel prices rise, the cost of septage disposal rises.

According to Minnesota state codes, all rural property owners must have their septic tanks evaluated a minimum of every three years, and pumped if needed. It is the homeowner's responsibility to ensure their septic system is working properly as it recycles used water and replaces it in the ground water.