TABLE OF CONTENTS The removal of nitrogen in land treatment systems is complex and dynamic owing to the many forms of nitrogen (N 2, organic N, NH 3, NH 4, NO 2, NO 3) and the relative ease of changing from one oxidation state to the next. The nitrogen present in typical municipal wastewater is usually present as organic nitrogen (about 40 percent) and ammonia/ammonium ions (about 60 percent). Activated sludge and other high-rate biological processes can be designed to convert all of the ammonia ion to nitrate (nitrification). Typically only a portion of the ammonia nitrogen is nitrified, and the major fraction in most system effluents is still in the ammonium form (ammonia and ammonium are used interchangeably in this text).
It is important in the design of all three land treatment concepts to identify the total concentration of nitrogen in the wastewater to be treated as well as the specific forms (i.e., organic, ammonia, nitrate, etc.) expected. Experience with all three land treatment processes demonstrates that the less oxidized the nitrogen is when entering the land treatment system the more effective will be the retention and overall nitrogen removal.36
The soil plant system provides a number of interrelated responses to wastewater nitrogen. The organic N fraction usually associated with particulate matter is entrapped or filtered out of the applied liquid stream. The ammonia fraction can be lost by volatilization, taken up by the crop, or adsorbed by the clay minerals in...
