Numerical Simulation of Tidal Current for Combined Dilution and Diffusion of Effluent Sewage at Radial Sandbank in Northern Jiangsu Province

A two-dimensional mathematical model for the simulation of tidal current for combined dilution and diffusion of effluent sewage was proposed. The dilution and diffusion behavior of near field and far field were studied. An orthogonal curvilinear coordinate system is used, greatly increasing model efficiency in treating irregularly shaped coastlines and in meeting requirements for high resolution at desired locations. The computed hydrodynamic field consistently supports the observed short-term data. A comparison of the behavior for the dilution and diffusion was made between 3000 m³/h and 5400 m ³/h of the two typical planned discharges. The far field for dilution and diffusion of sewage resulted from the planned discharge of the spring tide shows that wastewater is mixed with current over a large area. The area covered by the pollutant patch (Such as defined by the dilute contour of 100) is large, whereas the dilute contour of 20 still encloses the vicinity of outfalls.