Simulation of Nitrification and Denitrification Processes in a Tidal River

Abstract

Nitrification and denitrification processes in a well mixed tidal river in Japan are modeled, based on results of long term field observation on water quality and sediments in the river. Laboratory test results and values in references are used for the determination of parameters and coefficients in the model. In modeling of the processes, sediments, suspended solids, and overlying water are taken as elements and in computation a Lagrangian reference frame in terms of accumulated water volume is employed for reduction in numerical dispersion. Simulation results on ammonium and nitrate nitrogen, showing good agreement with long term field observation results, qualitatively explain well the processes in the river. The results indicate some countermeasures to reduce nitrate more such as the increase in the area of sediment surface. The simulation model is available for the estimation of water quality in well mixed tidal rivers and applicable for water quality control.

Effect of Nitrification on Nitrogen Flux Across Sediment‐Water Interface

“…As shown in Table 1, at the end of the incubation experiment, the bacteria densities in the surface layers of sediment cores were much higher than in the water columns (the bacteria densities in the sediment cores could not be detected during the incubation experiments, because sampling will destroy the sediment cores). Therefore, ammonification and nitrification occurred mainly at the sedimentwater interface, as found in previous studies (Kusuda et al, 1994;Lau, 1990;Pauer and Auer, 2000).…”

Effect of Suspended-Sediment Concentration on Nitrification in River Water: Importance of Suspended Sediment−Water Interface

“…Previous studies indicate that nitrifying bacteria tend to grow by attaching to the surface of sediment particles (5,6,12). This is especially true in shallow streams (13)(14)(15). Increasing evidence has demonstrated the important roles of sediment-based nitrification in rivers and lakes (16)(17)(18).…”