Modeling Sewage Sludge Decomposition in Soil: II. Nitrogen Transformations1
- Y. P. Hsieh,
- Lowell A. Douglas and
- Harry L. Motto2
Laboratory incubations were conducted to study N transformations in two sewage sludge-soil systems. The duration of the lag phase of nitrification was related to the active organic C content and moisture level of the system. The N mineralization potential was found to be 30% and 38% of the organic N in the activated sludge and digested sludge respectively. The mineralization rate constant was 0.026 day−1 at 21°C which corresponded to a half life of 27 days. Moisture levels of 0.06 and 0.33 bars had no significant effect on the N mineralization rate. Denitrification might be an important pathway of N transformation in sewage sludge-soil systems. Denitrification and nitrification could proceed either simultaneously or alternatively in the systems in an unsaturated condition. The N transformations of the sewage sludge-soil systems were described in a model assuming either first or zero order kinetics. The model can predict the amount of NH4+, NO3−, NO1−, organic N, and their rate of production. The values from the model usually fit the observed values.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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