No abstract

Considering the diffusion, adsorption or desorption, and microbial degradation of petroleum hydrocarbons (PHs) in the soil–water system, the numerical model describing the migration and transportation of PHs is estabilished and it is simulated by HYDRUS-1D model. The degradation effect of time and depth variation of PHs is gained by numerical simulation. The results show that the degradation ability of indigenous microbial of PHs is poor. The HYDRUS-1D software is feasible in simulating and predicting the migration and transformation of PHs in soils.

The water diversion project from Luanhe River to Tianjin is a large-scale project eliminating the water shortage of Tianjin city. Because the long water supply open channel along highroads, the traffic emergent incidents bring great potential dangers to the water supply of Tianjin. In this paper, the prediction model of traffic emergent incidents was built and the transportation of pollutants in Yinluan open channel with the effects of wind was simulated by EFDC model. The evolution and affective area of pollutant in Yinluan open channel was obtained. The results showed that the effects of wind on the transportation of pollutant in Yinluan open channel are strong when the wind direction is along the channel.

The optimization effects of the particle swarm optimization (PSO) on the parameters of Van Genuchten (VG) equation for the soil water characteristic curve were investigated. The results indicated that the VG parameters determined by the PSO were very close to those of experiments with a very high accuracy. The PSO was proven to be used as an optimization method for estimating VG parameters for the soil water characteristic curve. The PSO had the higher parameter precision than the damped least squares method and the nonlinear simplex method. The particle swarm optimization was improved and its convergence accuracy was higher than that of constriction factor particle swarm optimization (CFPSO) and PSO of Filedsend.

The velocity and sludge distribution in the aerobic tank of step-feed A/O process were simulated by the two-phase flow model. The aeration process was simulated by the discrete phase model and the influence of the aeration on the sludge distribution was studied. The space distribution of the wastewater-sludge-bubble in the aerobic tank was determined. The results showed that the sludge age is hard to be control led as the eddies in the aerobic tank have a strong influence on the sludge retention time. The impact of the aeration on the mean sludge concentration is neglectable. The uniformity of sludge distribution along the vertical direction and the sludge sedimentation on the bottom layer are improved by the process of aeration. The results have great theoretical significance and guidance for the optimal design of the aerobic tank of step-feed A/O process.