It also removes many of the nutrients in wastewater. Drainfields recycle some water and nutrients to grass and trees. The remainder percolates downward into the groundwater. Nitrates from a septic system are rarely a problem when a properly cased well is more than 50 feet deep and meets setback requirements. When properly designed, installed, operated and maintained, a septic system treats sewage as well or better than municipal treatment plants.
More information is available in other INFO-U messages.