Biological Incrustation occurs when wells are populated with slime bacteria or one of several genera of iron related bacteria (IRB). These organisms form a slimy gelatinous matrix of polysaccharide polymer material that enhances the attachment to the surface, nutrient capture and protection of the cells. They feed off dissolved iron in the water that is ultimately deposited in the form of a hydroxide. The organic slime matrix combined with iron deposits can greatly reduce the pumping capacity of a well in a short period of time. Although many microorganisms in a well are considered free swimmers and are easy to remove, the main concern must be the attached or embedded organisms in the biofilm.
Wells with slime and IRB’s require complete cleaning from the static water level to the bottom of the well. Wire brushing or high pressure jetting with simultaneous pumping will remove most debris inside the screen and casing. The microbial debris must be removed from the well prior to chemical treatment. The chemicals used for cleaning must be capable of removing and killing live bacteria and decaying debris.