In order to evaluate the influence of the deep water discharged from the sewage on the marine environment accurately, numerical simulation of the deep water discharge is of great significance. Considering the effect of the buoyant jet caused by different salinity and sediment, three-dimensional RNG κ-ε turbulence model was developed, including sediment scour equation and salinity advection equation. The mechanism experiment was carried out to verify the flow field and salinity field of the mathematical model. It showed that the simulation results are in good agreement with the experiment data. The simulation for a specific discharge case was conducted to predict the hydraulic characteristics, the distribution of the salinity and suspended sediment after the sandy water discharge with low salinity was discharged into the sea at a certain depth. It demonstrated that the sewage discharged into the sea shows buoyant jet feature due to the difference of the density between the inflow and the sea water. The axis of the buoyant jet exhibits a parabolic form in the vertical plane. After the buoyant jet having reached the surface of the sea water, the salinity in the butterfly-shaped diffusion zone decreased gradually while the sediment concentration increased gradually. With the time went on, the impact of the sediment discharge on the sea water was more and more serious. In the beginning, the diffusion rate of the pollution zone was relatively faster, and it was gradually slowing down with time.
