Modeling Sewage Sludge Decomposition in Soil: II. Nitrogen Transformations
1981
Hsieh, Y. P. | Douglas, Lowell A. | Motto, Harry L.
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.
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