Nutrients from septic systems can impact well and surface water

Malfunctioning septic systems can result in the increased nutrients into local water wells and surface water.

Approximately thirty percent of homes and businesses in Michigan use septic systems to treat their wastewater. When a septic system is improperly managed, elevated nitrogen and phosphorus levels can be released into local water bodies or ground water. An estimated 10 to 20 percent of septic systems in the U.S. fail at some point in their operational lifetimes. Common causes of septic system failure include aging infrastructure, inappropriate design, overloading with too much wastewater in too short a period of time and poor maintenance.

In and around the home, fertilizers, yard and pet waste, and certain soaps and detergents contain nitrogen and phosphorus and can contribute to nutrient pollution if not properly used or disposed of. The amount of hard surfaces and type of landscaping can also increase the runoff of nitrogen and phosphorus during wet weather. The U.S. EPA has identified septic systems as one of the top 5 sources of pollutants in surface water bodies. Septic systems treat large quantities of waste and if these systems are not operating properly, they may not remove enough nitrogen and phosphorus before discharging into waterways.

When there are too many nutrients – nitrogen and phosphorus - in surface water, they act as a fertilizer for fast-growing bacteria and algae. This rapid growth can cause algal blooms that can reduce water quality, kill aquatic animals and plants, and form toxins in the water. This process is called eutrophication. Harmful algal blooms (HABs) in lakes and streams can be toxic to humans and animals. Each nutrient has a specific impact on water quality:

Phosphorus: Depending on your soil type, phosphorus from wastewater can be absorbed and retained in the soil. Unabsorbed phosphorus can travel in groundwater into wells or toward a waterbody and become a source of contamination. Freshwater is more vulnerable to phosphorus pollution.

Nitrogen: Some nitrogen may be removed as wastewater flows through the septic system and soil. The remaining nitrogen can enter the underlying groundwater and flow towards a surface water body. If there are many septic systems in a small area, the nitrogen flowing through groundwater could overload a waterbody, causing eutrophication. Saltwater is more vulnerable to nitrogen pollution. Infants are particularly vulnerable to a nitrogen-based compound called nitrates in drinking water that can reduce oxygen in the blood, resulting in a condition commonly known as “blue baby”.

Other contaminants, such as Escheri Coli (E. coli) and Salmonella, are carried into surface soils and ultimately surface waters from failed septic systems. These harmful bacteria cause flu-like symptoms and are a serious health concern when people are exposed to it in the water through swimming and wading activities.

Nutrient pollution in groundwater, which millions of people in the United States use as their drinking water source, can be harmful, even at low levels.


Michigan State University Michigan State University Close Menu button Menu and Search button Open Close