Release and Transformation of Nitrogen from Sediments during In-situ Treatment with Calcium Nitrate Injection for Odor Control

Sediments sampled from the Pearl River tributary inlet, with seriously black and odor problem, was treated with calcium nitrate injection in the river simulator. During the course, release and transformation of nitrogen from sediments was investigated. The results showed that calcium nitrate injection is one kind of feasible approaches for sediments odor control. Removal rate of sulfide in sediments reached up to 99% in a month, the color of sediments turned to light brown from black, and the odor disappeared. However, release of NH4+-N and NO3--N was accelerated with calcium nitrate injection, the maximum release concentration of NH4+-N and NO3--N was close to 48 mg/L and 417.4 mg/L with injecting dosing of 8%(W/W, dry-weight). Furthermore, continued aeration to overlying water seemed not to be a good way for NO3--N removal. Contrastively, under low DO condition, both concentration of NH4+-N and NO3--N took increasing-decrease trends. In this work, TN concentration decreased from 97.7 mg/L to 27.4 mg/L. That is, by maintaining low DO concentration in sediment-water interface, the extra release of nitrogen caused by calcium nitrate injection could be well controlled.