Use of geotextiles as filters in decanting wells of ash ponds

Disposal of fly-ash, a residue of burning coal in thermal power stations, is carried out in the form of ash slurry by mixing the fly-ash with water. Initially, the fly-ash slurry is stored in an ash pond and the water in the slurry is drained out through filters in the embankment, over the spillway and from decanting wells. The current design of decanting wells used to discharge water from ash pond has been found ineffective. This is because the vents on decanting wells are clear openings without filters and hence a considerable amount of ash also flows with the water. This results in pollution and creates problems in the drainage system of the decanting wells. This paper presents the test procedure and results of a set of experiments carried out on model decanting wells using a geotextile lining. The tests were conducted using different fly-ash to water ratios and different grades of geotextiles. The results indicated that the use of geotextiles is potentially very effective for improving the efficiency of decanting wells used in thermal power stations.