Simulation Of Migration Of Municipal Solid Waste Landfill Organic Pollutant In Aquifers

Landfill leachate is high concentration of hazardous liquid by precipitation, the process of compaction, fermentation and biochemical degradation. The main pollutants are organic pollutant, nitrogen and heavy metal ions, with some characteristics: complexity of the type, fatalness, concealment, long-term, difficulty to reverse and so on. Once the landfill leachate entering the aquifer, the aquifer will be contaminated. Most landfill leachate contains benzene. Benzene is a toxic carcinogen, and is also a soluble material, with strong ability to migrate that it can easily into the groundwater system and pollute underground water. Therefore, this choice of benzene of Chang-an Landfill Leachate as a object to study its migration, will take on important theoretical and practical significance.Through field survey, combined with previous geological and hydro-geological data, this paper analyze the characteristics of the aquifer of the study area. Through indoor static assay of benzene, we found that Kd is 0.5873 when the solid-liquid ratio is 1:1; Kd is 0.85 in the condition of the solid-liquid ratio is 2:1. Through three soil columns, with the columns'K value are 0.4m/d, 0.4m/d and 1.2m/d respectively, and columns'height are 30cm, 30cm, 60cm respectively, we found that sorption capacity of clay is 0.15mg / l larger than sand, in the condition of same height soil column, with two different media of clay and sand. The peak of breakthrough curves of clay is 76 minutes behind sand with the same way of infiltration. In the same medium, through different height of the soil column: 20cm, 40cm, 60cm, the adsorption of benzene are 0.07 mg/l, 1.19 mg/l, 1.42 mg/l respectively. Setting up mathematical model which is based on the physical model of benzene migration, we simulate groundwater flow of study area by MODFLOW software, and use the MT3D software to forecast 10 days, 100 days, 1000 days, 5000 days, 20,000 days migration of benzene of landfill leachate in the aquifer, and found that as time goes by, benzene in groundwater is increasing, so do the pollution, and the pollution path strips were gradually migration from south to the north area. The longitudinal migration of contamination will expand to 6500m or so, and the concentration will reach Chang-an River in 20,000 days'time.