Electrophoretic repair of impoundment leaks: Analysis and verification with experimental data

Sealing leaks which have developed in liquid surface impoundments with geom embrane liners may be difficult due to aged liner material. A technique uti lizing electrophoresis which causes clay particles to be attracted toward l eaks when an electric field is applied provides a cost-effective method for repair. This study presents an experimentally verified methodology to pred ict electrophoretic sealing of in-service geomembrane liners. The methodolo gy includes a procedure to simulate axis-symmetric electrophoretic cake for mation and a numerical technique to solve the electric field for voltage gr adients. Path lines of solid particles are generated by superposing electro phoretic and Stokes' settling velocities. A numerical method to obtain a st eady-state cake profile by conserving solids mass and an approach which use s path lines to simulate transient cake formation are described. For an ini tially uniform suspension, final and transient cake profiles are obtained u nder varying conditions. The effects of voltage difference, surface electro de size, and initial bentonite concentration on cake formation are discusse d. In general, a higher Voltage difference or a wider surface electrode acc elerates the cake formation process. For efficient cake formation, the surf ace electrode should be located close to the water surface over the leak. A comparison of theoretical predictions with previously obtained experimenta l data shows a reasonable agreement. The analysis presented in the study pr ovides a relatively inexpensive and useful tool in the implentation of an i n situ field operation.