2018 Volume 41 Issue 2 Pages 35-42
Field observation was conducted to study the influence of nitrification restrained water in an estuary. In particular, the transport of ammonium nitrogen before and after nitrification restraint was investigated. It was found that the mixing and dispersion along the flow in a semitidal period dilute the concentration of ammonium nitrogen; therefore, the increase in nutrient concentration in the downstream area was not clear under the restrained nitrification treatment at the sewage treatment plant. On the other hand, the effluent water body flowed out to near the seaweed cultivation area. Then, the effluent water body moved upstream near the upper tidal area of 4 to 5 km from the river mouth. In addition, on the basis of past research regarding the effects of the removal of ammonium nitrogen on salinity and suspended solids, the transport of ammonium nitrogen in estuaries was considered. The results indicate that high salinity blocks the adsorption of ammonium nitrogen on suspended solids, and the potential for the accumulation of deposits including ammonium nitrogen out of a tidal river was shown. Consequently, ammonium nitrogen derived from the effluent water may be transported offshore without removal by adsorption on suspended solids.
