Factors And Optimization Research Of Pump-and-Treat Technology In Contaminated Site

Pump-and-Treat systems is an important technology in emergency treatment of groundwater contaminated sites, which has been widely used. Because optimizating pump-and-treat technology can remove pollutants effectively and control plume spread, reaching the hydraulic control requirements, and also cost-effectively. So this article started from the basic theory of groundwater flow and solute transport, set up a groundwater flow and solute transport coupled model for a typical contaminated sites with the limited difference simulation software VisualMODFLOW, and simulated a single-factor scenario on the hydro-geological conditions of the aquifer, the layout of pumping wells, pumping of pumping wells and other factors on the pump and treat optimization programs. Followed by a homogeneous unconfined and the confined space aquifer Optimization of the various programs. The objective function is that the percentage of pump pollutants is 95% and the decision variables are the pumping time, the total pumping capacity and the number of wells. Based on the decision variables weighted average, the program has been optimized.In single-factor effects, permeability, porosity, aquifer thickness, well layout, well distances are the most important factors. Simulation results show that the total pumping times and the total pumping capacity increases with the permeability coefficient,porosity and the thickness of confined aquifer increasing. With the confined aquifer head increasing, the total pumping volume and the total pumping time are almost unchanged. With the unconfined aquifer water table increasing, the total pumping time and the total pumping capacity decreas. Under the same interval, taking the percentage content of pollutants increased with the increase over time, but not the amplitude increased, but showed decreasing trends have increased, and the decreasing rate of fast. The best well layout is in the axial line of pollution plume.Optimizations in different locations are gotten combinating a site simulation with the weighted average.Homogeneous unconfined aquifer simulation results show that the total pumping capacity concentrate in 154000m3-170000m3 and the total pumping time mostly concentrate from 70 days to 120 days. After using four weighted averages to get the most optimazational solution that five wells, well distence of 40m and single-well pumping capacity of 400m3/ d. Homogeneous confined aquifer simulation results show that the total pumping capacity concentrate in 100000m3-160000m3, the total pumping time mostly concentrate in 70 days to110 days. After using four weighted averages to get the optimal solution for the five wells, well distence of 40m, single-well pumping capacity 300m3/d.Heterogeneous unconfined aquifer simulation results show that the total pumping capacity concentrate in 154000m3-170000m3 and the total pumping time mostly concentrate from 70 days to 120 days. After using four weighted averages to get the most optimazational solution that five wells, well distence of 40m and single-well pumping capacity of 400m3/d. Heterogeneous confined aquifer simulation results show that the total pumping capacity concentrate in 100000m3-160000m3, the total pumping time mostly concentrate in 70 days to110 days. After using four weighted averages to get the optimal solution for the five wells, well distence of 40m, single-well pumping capacity 300m3/d . When the site similar, regardless of the nature of aquifers, as long as the pollution plume shape similar ,so to the pumping wells layout can be same, the pumping wells distants can be same and the number of wells can be same.Using the weighted average method can simplify the calculation, without complicated formulas, and can also distribute different weight to different factors depending on different situation ,with greater flexibility. But this method can only be a rough calculation, randomnessly. When the pumping time between 30 days and 40 days and the amount of pumping pollution between 70% and 80%, the pumping efficiency significantly reduced. Therefore, in the project the paper relied on the pumping pollutions reaching 95% is unreasonable.