Clogging by ochre may be considered a major threat in the performance of filters and drainage systems. The environmental conditions including the chemo-microbiological aspects involved for the ochre formation and clogging of geotextile filters used in drainage systems are discussed. Column tests are being carried on using samples of geotextiles as filters with the inoculation of iron bacteria under three different filter submersion conditions. The concentration of dissolved oxygen, pH, and iron reten-tion rate are being monitored during the column tests. Biofilm formation on the geotextile filters is being evaluated through the analysis of EDS (Energy Dispersive X-ray detector) and scanning electron micros-copy.