Efficiency of Nitrogen Removal in a Simulated Overland Flow Waste Water Treatment System1
- R. L. Chen and
- W. H. Patrick2
In a simulated overland flow waste water treatment system, vertical measurements of redox potential indicated the presence of both oxidized and reduced zones that provided favorable conditions for simultaneous nitrification-denitrification reactions. Addition of C sources substantially reduced the redox potential and enhanced the rate of nitrate reduction. Nitrogen transformation rates were examined by the use of labeled 15N under controlled laboratory conditions.
Adsorption and retention of NH4+-N in soil matrix accounted for approximately 70–90% of the NH4+-N applied in simulated waste water. Nitrification occurred in surface oxidized soil layers, resulting in conversion of waste water N to nitrate and nitrite. The downward movement of nitrate to the reduced soil layers in the overland flow model during subsequent application of waste water lead to denitrification and assimilatory nitrate reduction.
Estimation of N balance in this study indicated that the overland flow system was capable of removing 80–90% of the added NH4+-N within the N concentration range commonly found in municipal waste waters. However, labeled 15N data showed that an average of 11–21% of the N was taken up by vegetation and approximately 5–10% was immobilized and incorporated into soil organic N. Thus, the net loss of N is much less than would be predicted by nonlabeled N mass balance calculations. Overall, only 66–80% of the added labeled N was removed from the simulated overland flow model under laboratory conditions.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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