Bacteria create biofilms as a habitat to live in a location which challenges their survival. Biofilms allow bacteria to take in and store nutrients from their surroundings, be protected, and continue reproducing. You may wonder, “Are biofilms a health hazard because they contain bacteria?”. Biofilms develop in countless locations, such as the plaque on your teeth, medical devices implanted in the body, water systems. The main danger with biofilms in water systems is when they contain harmful bacteria (ex. E. coli, Legionella), cause microbial-induced corrosion, or create taste and/or odor issues. We are surrounded by bacteria and they are necessary for life to continue.

We often see biofilms that are gelatinous, slimy, and appear to be a combination between a liquid and a solid. This week, our lab saw an example of a different type of biofilm, one which was hard, crusty, and was originally thought to be mineral scale build up. This example of biofilm proves bacteria are resilient and thrive in many types of environments. It also means some types of biofilm are much more difficult to remove than others.

Sometimes, we recommend well cleaning and rehabilitation for our clients if their water tests indicate to us that this is necessary. You may be familiar with shock chlorination in wells. This is a process where bleach is put in the well and plumbing system, then sits until it is pumped off to waste. This type of treatment is used to kill bacteria and clean the system.

What happens when biofilm is actually the reason behind positive bacteria tests or other water quality issues? A shock chlorination may be temporarily effective or it may not be effective at all. All biofilms are different due to well construction, nutrients and bacteria present, the aquifer (area underground supplying the well with water), and more. The hard, crusty biofilm mentioned earlier, and other types of biofilm would likely not be controlled by a round of shock chlorination. In these cases, an acid treatment is likely necessary to remove as much biofilm as possible prior to shock chlorinating to kill the bacteria. Typically, a solution containing hydrochloric acid is used for acid treatment.

The test tube on the left (red-brown color) contains the hard, crusty biofilm when it was covered by hydrochloric acid. While the acid broke the biofilm apart, it did not destroy it completely. As an experiment, we transferred some of the remaining biofilm from the hydrochloric acid treatment and combined it with nitric acid. This acid created the green liquid in the right test tube. Analysis under the microscope indicated the biofilm had broken apart more and did not contain its original structure. 

It is important to recognize the strength and resiliency of biofilms, and It is critical that we consider the role biofilm has in causing water quality issues. By treating the source of the problem instead of the symptoms, we have a greater chance of success in removing and controlling water quality issues.