What is Nitrogen and Why Does it Matter in Your Septic System Design?
Why is California so concerned about nitrogen in groundwater?
California is particularly concerned about nitrogen contamination of groundwater due to its lack of available water, large agricultural industry, as well as its rapidly growing population and urbanization. To address these concerns, California has implemented strict regulations and programs aimed at reducing contamination and protecting groundwater quality.
Nitrogen is a common component of fertilizers, animal waste, and human sewage, which are all sources of nitrogen that can enter groundwater. When nitrogen enters groundwater, it can cause a variety of problems. Nitrogen in groundwater contributes to environmental problems such as eutrophication, which occurs when excess nutrients cause an overgrowth of algae and other aquatic plants, leading to decreased oxygen levels and harm to fish and other aquatic life, Blue baby syndrome etc.
How is nitrogen associated with Onsite Wastewater systems?
Nitrogen is commonly associated with Onsite Wastewater Treatment Systems (OWTS) because it is a major component of human and animal waste, which is typically treated by these systems. OWTS, also known as septic systems, are used to treat and dispose of wastewater in areas where centralized wastewater treatment (sewer) is not available or practical.
In septic systems, nitrogen is present in the form of organic and inorganic compounds, including proteins, ammonia, and nitrate. During the treatment process, bacteria in the septic tank break down organic matter, converting nitrogen-containing compounds into simpler forms such as ammonia and nitrate.
If the septic system is working properly, the effluent that exits the septic tank and enters the drain field should be relatively low in nitrogen. However, if the system is overloaded or malfunctioning, excess nitrogen can be discharged into the drain field and potentially contaminate nearby groundwater or surface water.
Graphic illustration of a nitrogen-reducing I/A septic system compared to a traditional septic system, modified from epa.gov.
How does denitrification in septic systems occur?
Denitrification in septic systems is a process by which bacteria convert nitrate (NO3-) in wastewater into nitrogen gas (N2) which is released into the atmosphere.
This process occurs in an anaerobic environment, which means that there is no oxygen present. In septic systems, wastewater flows into a septic tank where solids settle and the liquid portion (effluent) moves into a drain field. In the drain field, the effluent percolates through soil where it comes into contact with bacteria that are capable of denitrification.
These bacteria use the nitrate in the effluent as a source of oxygen instead of oxygen gas. They break down the nitrate, releasing nitrogen gas as a byproduct, which escapes into the atmosphere. This conversion of nitrate to nitrogen gas helps to reduce the amount of nitrogen that is released into the environment and can contribute to environmental problems such as eutrophication in bodies of water.
