What is Nitrogen and how does it affect waste water?
Nitrogen in domestic sewage and sewage effluent exists in different chemical forms depending on the degree of oxidation. Fresh sewage is high in organic nitrogen. This will first break down into ammonia nitrogen. In the presence of oxygen, ammonia nitrogen is quite rapidly oxidized, first into nitrite nitrogen (NO2) and subsequently into nitrate nitrogen (NO3). This oxidation process primarily takes place near the infiltrative surface of the leaching system. Nitrate nitrogen is an essential nutrient for the growth of plants and algae, and is an end product of any properly functioning leaching system. Nitrates are not readily removed by filtration through soil, so that ground water underlying a leaching system would receive a certain amount of nitrate “fertilization”.
How much Nitrogen is Removed in a septic system?
Typically, septic systems remove approximately 30% of total nitrogen with the remaining 70% being discharged to the ground water. There are many other nitrogen sources in the environment which also will contribute nitrates to the ground water, such as fertilizers, rotting vegetation and the atmosphere itself. For this reason, it is usually not practical or necessary to try to design small subsurface sewage disposal systems for nitrate removal. An exception to this might be in heavy developed lakeside property where nitrates from subsurface sewage disposal systems could be a significant source of nitrate fertilization of the lake water, which would cause undesirable algae blooms. Excessive nitrate levels in drinking water wells could be a hazard to the health of infant children who consume the water regularly. However, it is extremely unlikely that domestic subsurface sewage disposal systems could ever produce hazardous nitrate levels in wells as long as the separating distances required by the Public Health Code are provided.
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