Preliminary design of permeable reactive wall based on column studies

摘要

In this study, a total of eight columns were set up, in which two columns were used as the control columns and the other six were used for investigating the effects of hardness on the dehalogenation of TCE and PCE. The results from column tests show that the degradation process of TCE and PCE is a pseudo first order reaction. If normalized the surface area to solution volume ratio to 1 m~2/cm~3, the half-lives of TCE and PCE in distilled water condition without hardness are 12.03 hours and 12.47 hours, respectively. In the cases when the contaminated groundwater containing hardness of 250 mg/L as CaCO_3, the half-lives of TCE and PCE are slightly increased to 12.18 hours and 12.64 hours, respectively. When the hardness was further increased from 250 mg/L to 500 mg/L as CaCO_3, the half-lives of TCE and PCE (12.77 hours and 12.92 hours) are increased correspondently by 4.8% and 2.2%. Besides, it is found by X-Ray Photoelectron Spec-troscopy that magnesium oxide was detected on the surface of iron samples. Based on the column flow-through studies under different groundwater geochemistry, the details in designing the thickness of a perme-able barrier are presented. Depending on the desired removal efficiency of TCE and PCE, the required thick-ness varies from about 60 cm to 90 cm for 95% and 99% removal efficiency.