Fate of nitrogen in land application systems

Land application of wastewater has been considered as one of the processes that can be used to reduce the pressure on fresh water resources for irrigation use. Over ten years of research on the conversion, movement, and utilization of the various forms of nitrogen applied to land application systems is presented as it relates to the system design based upon the water, nutrient, and salt balance processes. This research modeled the quality and quantity of leachate water passing through root zone. Deep percolate water was collected in lysimeter type samplers and analyzed for quality constituents. The data shows that the total nitrogen concentration in the leachate is less than 5 mg/L and typically less than 2 mg/L. Salt concentration varies with designed leaching ranging from 1100 to 2500 μS/cm. The variance of soil TKN was investigated within three types of soils at two different depth ranges over a 12-month period while the denitrification rate was measured within three soils in three different months of that period and in the lab. This research confirmed that the denitrification process prefers higher temperatures and soil moisture levels above 10%. Soil moisture content was found to be the prerequisite condition for high denitrification. In addition, there was no significant difference (p<0.05) in the TKN in the soil at the two depths of 0 to 15 cm (0 to 6 in) and 46 to 61 cm (18 to 24 in) in the mass-balanced designed and operated system.