Column test studies of chemical precipitation of calcium carbonate on geotextile filters

Chemical clogging can reduce geotextile permeability and obstruct drainage system. Calcium carbonate is a substance of low solubility which precipitates rapidly and forms the hard pan layer which results in clogging the drain envelope. The study was done on drain envelope in Abadan palm grove showed calcium carbonate was the main precipitated chemical in drain envelops. Laboratory column filter tests were conducted to simulate calcium carbonate precipitation on geotextile. Experiments performed with three types of geotextile including woven and nonwoven types. The result show that carbonate calcium precipitation decrease the ability to percolate water through the geotextile. Calcium carbonate precipitation was collected at an aerated/non-aerated interface in the filters and surrounded the fibers as a layer. Chemical precipitation in geotextile cover surrounds the fibers and increase thickness with time. Hydraulic conductivity was decreased about 30 percent by chemical precipitation. Results also show that according to laboratory conditions, clogging time for two kind of nonwoven geotextile is 4 and 6 years.