WorldWide Drilling Resource

Notes from the Groundwater Guy by Thomas E. Ballard, P.G., C.H.G. Southeast Hydrogeology, PLLC Bacteria are Everywhere! Most often, we test for coliform bacteria in a well, and do not even look at other types of bacteria which can also cause problems. The simple fact of the matter is, you can’t get rid of all the bacteria in a well - they occur naturally and are always present. The important thing is to track to trend the total bacteria counts in a well. If bacteria counts are increasing, it means the well is providing a favorable environment for bacteria growth and reproduction. and some sort of control measures need to be undertaken to avoid the water becoming cloudy, tasting unpleasant, or smelling bad - generally unhealthy conditions even if the bacteria present in the well are not pathogenic. Keep in mind, for every bacteria detected in a water sample, there are usually one million bacteria attached to the casing, screen, or wellbore. Iron-related bacteria are very common throughout the United States and the world, and probably contribute to about 80% of all well plugging cases. They can form a slimy protective biofilm which, left untreated, can eventually fully plug a well. Sulfur-reducing bacteria can often be found in conjunction with iron-related bacteria, and tend to produce hydrogen sulfide gas - the rotten egg odor you can smell in some wells. Sulfur-reducing bacteria can also cause corrosion in steel-cased wells. There can be many other types of bacteria in a well, although most of them are harmless if present in low numbers. Laboratory testing using the adeno- sine triphosphate (ATP) method can give a reliable indication of the total bacteria count in the well. Increasing trends for total bacteria should signal that well reha- bilitation may be needed to address the issue. If increased levels of iron are seen in the water pumped from the well or if well performance is steadily declining, a simple biological activity reaction test (BART) for iron-related bacteria should be conducted. If a rotten egg odor is present, indicating the presence of hydrogen sulfide gas and sulfur-reduc- ing bacteria, then a BART test for sulfur- reducing bacteria should be conducted. If any of these tests indicates a problem with elevated levels of bacte- ria, appropriate wel l rehabi l i tat ion should be undertaken. Such remedia- tion should include some sort of brush- ing/swabbing to disrupt the bacterial growth, and an appropriate chemical application. Use of chlorine as a pri- mary means to control bacteria is not recommended, as it can often cause the bacter ia to “harden” down and make the problem more challenging for future cleaning efforts. Tom Tom Ballard may be contacted via e-mail to michele@ worldwidedrillingresource.com WTR 41 WorldWide Drilling Resource ® JUNE 2019