Optimisation Of Permeable Reactive Barriers For Contaminated Groundwater In Liguan Source Field Based On Numerical Simulation

Shenyang is a city with larger groundwater exploitation in our country, Liguanwater source is one of the main water supply sources in Shenyang, which is located inthe north shore of the Hun River. In recent years, the discharge of the municipalsewage and industrial wastewater to surface rivers cause serious pollution,deteriorating the quality of groundwater close to Hun River.Permeable reactive barrier (PRB) originated in the1990s is a in-situ remediationtechnology for contaminated groundwater, with the advantage of low cost, highefficiency. The PRB technology can effectively remove heavy metals, inorganicanions, organic matter and other pollutants in the groundwater. The PRB system cancapture the target polluted water and remove polluted water, the hydraulic capturewidth and residence time are the two most basic parameters in the design process.The study analyzed the temporal and spatial distribution of the nitrogen in thestudy area. From the entire study area, three nitrogen concentration in water wellsclose to Hun River is relatively high, Three nitrogen concentrations tend to decreasewith the increase in the distance of Hun River. According to groundwater qualitymonitoring data from1998to2009,NH4+-N and NO3-N concentration showed anupward trend over time, the concentration of rain season is generally higher than theconcentration of dry season, because large quantities of pollutants in rain seasoninfiltrate into groundwater with rain.In this paper, the numerical simulation method was used to analyse the influenceof the permeability coefficient ratio and the thickness of the PRB system and thepumping capacity of the pumping well and the hydraulic gradient on the width of thecapture zone and residence time. The increase in the permeability coefficient ratio andthe pumping capacity can increase the width of the capture zone, but will reduce theresidence time. The increase in the thickness of the PRB system can increase theresidence time, but the influence on the capture zone width is very limited, theincrease in the hydraulic gradient will lead to the rapid reduction in the residence time. According to the analysis of various factors, the variation in the residence time of thetransverse direction are proposed to analysis in the actual design of the PRB to ensurecontaminated groundwater captured by the PRB system can be effectively removed.Numerical simulation method was used to compare treatment effect on differentsize of PRB,and determined the optimal design size of PRB in the field conditions,PRB with the width of25m and the thickness of1m, the maximum allowablepumping capacity of200m3/d.