Numerical simulation of leaching contaminants from ash field of thermal power plant on groundwater pollution

摘要

Better understanding of the transport of leaching contaminants from fly ash in soil and groundwater important to remediation of soil and groundwater systems. Based on column leaching experiments, the concentration of leaching contaminants at different liquid to solid ratios is studied. Results shows with exception heavy metal As, the evolution of the concentration of leaching contaminants show a sharp decrease during the first liquid to solid (US) ratios 10mg/g of leaching volume before attaining a steady concentration. The concentration of leaching contaminants in the leachates was found to decrease almost in proportion to the L/S ratio. And pH is an important parameter affecting the leaching rate of contaminants from ash. A numerical model has been developed, which predict the temporal and spatial distribution features and distribution range of contaminant concentration. Solutions to the coupled model are accomplished by finite difference method and splitting operator method. Taking sulphate pollution as an example, the approach has been used for the simulation of groundwater flow and contaminant transport. Numerical simulation results indicate the subsurface pollution range has a trend of increase with time, namely with the increase of pollution area, the pollution area concentration values increase in the same location. A very good agreement was achieved for sulphate between the monitored data and modeled breakthrough curves. It provides theoretical instruction for making decision the disposal filed and pollution control and prevention.