Environmental Impacts

Improperly functioning and overloaded septic systems are major sources of water pollution. Failing septic systems leak harmful pollutants, like bacteria and excess nutrients (nitrogen and phosphorus), into groundwater. From there, pollutants make their way into lakes, streams, rivers, and coastal waterbodies.

Malfunctioning septic systems add excess nutrients (nitrogen and phosphorus) to nearby waters. In coastal ecosystems, nitrogen is the nutrient of greatest concern; whereas, in lakes, rivers and streams, phosphorus is the biggest threat.

Lake Contamination
Failing Septic Systems are the source of 5-10% of the phosphorus that reaches lakes. In a lake, increased phosphorus nourishes algae. When phosphorus levels rise, even by a small amount, algae multiply. The water becomes cloudy and green, leading to taste and odor problems, and dissolved oxygen levels are reduced, resulting in impacts to fish and other organisms that live there. As a result, lake use may decrease and property values can plummet.

About half of the phosphorus reaching a septic system is from household cleaners. Much of this phosphorus will be removed by a properly functioning system. But, if the leach field is clogged, for example, effluent may surface and flow over land to nearby streams and lakes. Or, if the soil cleansing process does not work properly, phosphorus may flow underground to nearby streams, lakes through groundwater.

Groundwater Contamination
The chemicals and organisms in untreated septic waste can be dangerous. Wastewater contains nitrates, which are particularly toxic to infants, and disease-causing bacteria and viruses. Wastewater also contains toxic chemicals from household products such as cleaners, spot removers, solvents, furniture polish, silver polish, bleach and pesticides. These chemicals and organisms may migrate through groundwater and threaten nearby wells.

Even the chemicals used in commercial septic system cleaners can be dangerous. Organic solvents travel through groundwater and can contaminate wells. Biological cleaners can plug up the disposal area and ruin the system.

Coastal Contamination
Nitrogen loading from failing septic systems can adversely affect Maine's coastal ecosystems. When too much nitrogen gets into the water, it disturbs the natural balance by allowing too much algae (microscopic plants) to grow. The algae cloud the water and block vital sunlight to underwater plants. When the algae die and decay, they use up much of the oxygen needed by fish and shellfish, often killing them. Special "denitrifying" septic systems designed to reduce nitrogen loading to nearby coastal waters are available.