A new modeling method for estimation of the longevity of infiltration system was suggested in this study. The model was one-dimensional, based on results from long-term infiltration sites in Sweden, taking some physical and chemical parameters as controlling factors. It defines the longevity of infiltration systems as the time during which the P solution in effulent is under national criteria (1 mg/L in this study), and it aims at providing the longevity for any given point of the infiltration system. The soil in the model was assumed to be totally homogenous and isotropic and water flow was assumed to be unsaturated flow and constant continuous inflow. The flow rate was calculated from the Swedish criteria for infiltration systems. The dominant process in the model would be the solute transport process; however, retardation controlled by sorption would play a more important role than advection and dispersion in determining the longevity in the model. By using the definition of longevity in this study, the longevity of the three soil columns at 1 m depth (Knivingaryd, Ringamåla and Luvehult) were 1703 days, 1674 days and 2575 days. The exhaustion time of the three soil columns under inflow of 5 mg/L were 2531 days, 2709 days and 3673 days. The calculated sorbed phosphorus quantity for soil from sites Kn, Lu and Ri when they reach estimated longevity were 0.177, 0.288 and 0.168 mg/g, while the maximum sorption of Kn, Lu and Ri were 0.182, 0.293 and 0.176 mg/g separately. From the result of sensitivity study of the model, the sorption capacity and flow velocity were most important to the longevity of the infiltration system. Lower flow velocity and higher P sorption capacity extend the longevity of an infiltration bed. Due to the sorption isotherm selected in this study and the assumption of instant equilibrium, the sorption rate of the soil column was quite linear, although the estimated longevity was much shorter than the real exhaustion time of the soil column. In fact the soil has almost reached its sorption maximum when the system reaches its longevity.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-96097 |
| Date | January 2011 |
| Creators | Yu, Lin |
| Publisher | KTH, Miljögeokemi och ekoteknik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | TRITA-LWR Degree Project, 1651-064X ; LWR-EX-12-01 |
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