A decline in groundwater recharge due to increased runoff and excessive groundwater pumping has led to the use of artificial recharge to restore and maintain the water level in aquifers. One of the methods used to recharge these aquifers is the installation of drywells. These gravity-fed wells with perforated linings facilitate groundwater recharge and stormwater infiltration by penetrating layers of soil to access the permeable soil in the vadose zone. Over time, the soil surrounding drywells may become clogged due to the release and mobilization of colloidal clays. This phenomenon is evident through varying solution chemistries between injected water and infiltrated stormwater. Previous studies demonstrated the effectiveness of applying a polymer, polyacrylamide (PAM) to soil to stabilize soil aggregates, control soil erosion, and increase filtration. PAM is an organic polymer synthesized as either a simple linear-chain or cross-linked structure formed from acrylamide subunits. Based on the properties of the polymer and the soil composition, PAM has exhibited a significant impact on stabilizing the clay particles in the soil. Our study was conducted to evaluate the effects on the transport behavior of in situ mobilized clay colloids in Ottawa sand. A column experiment was designed in two phases. The first was to simulate clogging, induced by the release of natural clays in the packed column. This occurred when the column was subjected to a sequence of solution variations in ionic strength, pH, and cation exchange from DI water, 1 mM NaCl, 10 mM NaCl, 100 mM NaCl, and pH 10. The second phase was to stabilize the sand and prevent the release and mobilization of clay colloids under steady-flow conditions using the polymer PAM. The results of this study will provide a better understanding of the performance of PAM as a soil conditioner to mitigate the release, transport, and clogging of colloidal clays around drywells.
|Commitee:||Leij, Feike, Bradford, Scott, Sasidharan, Salini|
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 81/4(E), Masters Abstracts International|
|Subjects:||Water Resources Management, Civil engineering, Hydraulic engineering|
|Keywords:||cation bridge, clogging, colloidal clay release, column experiment, PAM, Polyacrylamide|
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