Abstract
Dicyandiamide (DCD) is widely used as nitrification inhibitor in soil. In order to examine the influence of DCD application on pollutant removals through soil infiltration treatment (SIT), three soil columns with different constituents were run under hydraulic loading rate of 0.01–0.02 m3/m2/d in parallel in laboratory. The results indicated that effective removals of COD (90.68–92.11%), TP (>99%), and NH3–N (98.96–99.72%) maintained during 1.5 mg/l of DCD application. The performance of TN removal differed among columns: little detrimental effects observed on two columns (B and C) with TN removal being 86.87–93.10%, while detrimental to one column (A) with only 26.19% of TN removal achieved. Enzyme activity assay showed that DCD application inhibited the expression of urease activity at all depths of soil in the three columns, and the inhibition effect of DCD on activities of nitrate reductase (NAR) and nitrite reductase (NIR) differed among the three columns. An unbalanced nitrification/denitrification process occurred in the column (A) with deteriorated TN removal, resulting from DCD inhibition on both NAR and NIR activities at all soil depths. The relationship was also disclosed between the activity of urease, NIR, NAR, or catalase and influencing factors including influent COD/TN, soil C/N, and TN removal.
