Nitrogen Release Performance of Sediments in Drainage Pipeline

The effects of soil and water ratio, pH, temperature and rotation on the nitrogen transformation of sediment in drainage pipeline were investigated in this study. The experimental results for the four impact factors indicated that ammonia nitrogen was the main existing form for nitrogen release from the sediment to the overlying water, the concentration of ammonia nitrogen was uptrend, reaching the maximum in four to six days, and it went down till to the end of experiments. While the variation trend of nitrate nitrogen concentration was opposite to that of ammonia nitrogen. The factor of pH influenced most in the release of ammonia nitrogen among the four factors, then was the disturbance, and the temperature had a minimal impact. The release of ammonia nitrogen followed the descending order of pH 6.3 > pH 8.0 > pH 9.6, and the maximum concentrations were 54.0, 30.9 and 26.7 mg x L(-1) respectively. The higher soil and water ratio and the longer agitation time under the same agitation speed were, the higher ammonia nitrogen concentration was obtained. An increase in temperature promoted the conversion of ammonia nitrogen to the nitrate nitrogen, and speeded up the decrease of total nitrogen in the overlying water.