Based on the principles of fairness and feasibility, a nonlinear optimization allocation method for pollutants was developed based on controlled section water quality standards, considering the synergetic influence of point and surface sources. The maximum allowable emission of pollutants from point and surface sources were taken as the objective function. The water quality attainment rate of controlled sections, the control requirements of pollution sources, and technical parameters of pollution control engineering were taken as constraints. A nonlinear optimization allocation model was established, and a genetic algorithm was used to solve the problem. As an example, the model was applied to a certain area in the Taihu Lake basin, southern Jiangsu province, China. The analysis results showed that the annual number of days for ammonia-nitrogen and total phosphorus meeting the standard were 334 and 332 days, respectively, under maximum allowable emissions for each pollutant, and the water quality compliance rates of the control section were 91.5% and 91%, respectively. The ammonia-nitrogen and total phosphorus concentrations in the controlled section achieved related water quality compliance rate targets of 90%. These all met the water quality compliance rate requirements of the control section. The results indicate that this method reflects the feasibility of optimizing the total allocation results systematically and intuitively, overcomes the insufficiency in the feasibility of the optimized allocation method, and provides effective and reliable technical support for control and management of the total pollutant amount based on water quality improvement.

A mathematical model for simulating hydrodynamics and pollutants migration in a tidal river network was constructed, which takes the temporal and spatial distribution of rainfall runoff and non-point pollutants into consideration. Under the design hydrologic conditions of a typical hydrological year, the daily concentration change process for the control section is obtained. Aiming at the uncertainty of hydrology and water quality parameters such as flow direction, flow rate and concentration change in tidal river network area, a statistical analysis method is used to obtain the maximum allowable concentration of pollutants in the control section under the condition of the water quality standard assurance rate of. Then, a formula for calculating the pollutions emission intensity of point and non-point sources is derived. The method was applied to the pollution source control in a typical region like Taihu in China.

Simulations of water flow in channel networks require estimated values of roughness for all the individual channel segments that make up a network. When the number of individual channel segments is large, the parameter calibration workload is substantial and a high level of uncertainty in estimated roughness cannot be avoided. In this study, all the individual channel segments are graded according to the factors determining the value of roughness. It is assumed that channel segments with the same grade have the same value of roughness. Based on observed hydrological data, an optimal model for roughness estimation is built. The procedure of solving the optimal problem using the optimal model is described. In a test of its efficacy, this estimation method was applied successfully in the simulation of tidal water flow in a large complicated channel network in the lower reach of the Yangtze River in China

Ji, H., Pan, S. and Han, X., 2012. Effect of wastewater discharge on Jiangsu coastal environment, China To meet the needs of the rapid economic development in the coastal area of Qidong City in Jiangsu Province of China, a new wastewater treatment plant and a reclaimed water plant have been planned. The preliminarily treated wastewater will be discharged to the coastal area in the Yellow Sea near Dayang Port. Due to the complex tidal regime in the area, the impacts of the outfall from the treatment plant can be important for the surrounding marine environment. The present study aims to investigate the impacts of the discharge of the treated wastewater into the Yellow Sea under three operational conditions using the TELEMAC software. The computational domain covers a large coastal area (~2800 km2). TELEMAC2D is used to compute the depth-averaged currents, and the convection and diffusion of the pollutants, namely CODMn and Inorganic Nitrogen, which are treated as the neutral buoyancy tracers, but ...

The natural dispersion of oil depends on the oil types, wave-mixing energy, and the temperature and salinity of water. Laboratory experiments were conducted to investigate the effects of these factors on oil dispersion. The results demonstrated that the increase in temperature significantly enhanced the oil dispersion efficiency, particularly for low-viscosity oils. At 30 °C, the dispersion efficiency is 2 times higher than that at 15 °C, while salinity has no significant effect on dispersion efficiency. Nonlinear fitting results revealed an exponential increase in dispersion efficiency with the energy dissipation rate. Furthermore, partial correlation analysis was employed to examine the effects of oil density, viscosity, and surface tension on dispersion efficiency. The results indicated a high correlation between density, viscosity, and dispersion efficiency (r = −0.801, r = −0.812), whereas the correlation coefficient of surface tension was low (r = −0.286). Based on these findings, linear and nonlinear regression models were established between dispersion efficiency and density and viscosity, enabling a rough estimation of oil spill dispersion efficiency under low sea state conditions.

Accidentally spilled oil can cause great harm to the ecological balance of water once it enters the environmental waters. Clarifying its movement behavior and migration law in water has been the focus of environmental hydraulics research. This review starts from the mechanism of the oil spill migration process, and firstly reviews the kinematic characteristics of the smallest moving unit of the oil spill, the individual oil droplet, as well as focusing on several key aspects such as droplet shape, trajectory, terminal velocity and drag coefficient. Subsequently, considering the commonalities and differences between inland riverine and oceanic environments, different aspects of oil droplet collision, coalescence, breakage, particle size distribution, and vertical diffusion are discussed separately. Finally, the current status of research on the migration laws of accidental oil spills in environmental waters is summarized, and feasible future research directions are proposed to address the emerging research problems and research gaps.