In drinking water, the common group of bacteria that has been described as potentially nuisance bacteria, include: Iron Bacteria, Slime Bacteria, Sulfate-Reducing Bacteria, standard plate count or heterotrophic bacteria (HPC), and pink bacteria. For the record, Pink Bacteria are not waterborne bacteria, but airborne bacteria that happen to grow in damp areas like bathroom tubs, showers, and toilets.
With the exception of a standard for standard plate count, these bacteria are not specifically regulated by a drinking water standard. However, their growth can create situations or problems that can result in the violation of a primary or secondary drinking water standard. Therefore, I tend to call these types of organisms nuisance bacteria, because they tend to create a nuisance problem before they create or facilitate a problem associated with a health concern or impact.
Slime bacteria are a group of bacteria that produce slime, but unlike iron bacteria they do not need to use iron or manganese in the process. The slime produced by slime-forming bacteria is typically gray, clear, and thicker than iron-related bacteria, but they can appear yellow or beige if other metals accumulate in the polysaccharide polymer slime layer. When the organism is stressed, it can create a thicker slime layer, something that is also promoted under aerobic conditions.
Iron-related bacteria that reduce iron or manganese (electron donors) to get energy, are called chemotrophs. These non-pathogenic (non health-threatening) bacteria occur in soil, shallow aquifers, and some surface waters.
Sulfate-related or reducing bacteria obtain energy by using a carbon source to reduce sulfate to hydrogen sulfide gas. Typically, these bacteria become established after the oxidizable oxygen, nitrate, iron, and manganese have been used up by other bacteria. For many water systems, the presence of this type of bacteria suggests a long-term microbiological problem with the water and not a short-term or recent condition.
We would have to say that there are no direct health risks, however, they are indicators of a potential health risk from other bacteria or microbiological agents. Ineffective disinfection of these bacteria can create conditions that result in increased or elevated levels of trace metals, such as: copper, lead, chromium, aluminum, and zinc. We have also seen a few cases where these bacteria appeared to be opportunistic pathogens for individuals under health stress or with a compromised immune system (Source).
With the exception of a standard plate count, there are no specific standards for nuisance bacteria. In 1989 the EPA set a non-health specific standard for standard plate count at a level of 500 colonies per ml and was proposing the use of this bacteria as a surrogate for total coliform bacteria. (Source) Standard plate count or HPC is commonly used in the bottle water industry and we tend to use this test as a surrogate for bacterial regrowth in distribution systems. We have found that increasing and elevated levels of HPC are associated with bacterial regrowth in the distribution system, increasing chlorine or oxidant demands within distribution systems, the likely presence of nuisance odors, and localized biochemical/chemical corrosion.
Some nuisance bacteria can create additional nuisances or conditions that can result in violating a primary or secondary drinking water standard. In most cases, the primary drinking water standard violations are related to the presence of metals associated with the plumbing and plumbing fixtures in the home or building or possibly an increased level of phthalates, because the bacteria use them as a carbon source. (Source)
Nuisance bacteria do create warning signs, but this commonly does not occur until the bacterial population gets high enough to create a problem the average person could smell, see, taste, or some other effect that is a "nuisance". You must be willing to look and take note of these early warning signs. In addition to nuisance issues, these bacteria can clog pipes and filters, cause premature failure or more frequent maintenance of water-using appliances and heat-exchange units, can cause a decrease in the pumping efficiency or yield of a water well, and be associated with intermittent odors, discolored water, and "off taste" to your drinking water. Nuisance bacteria can be a problem with all drinking water sources, even City Water.
Level 1 Testing is done with simple observations that an individual can make with their own senses such as sight, smell, and taste. These observations can be readily apparent or can be observed as they change over time. In addition, accessible related information about the home can also be used to narrow down the cause of your water issues.
You should check for the presence of a bacterial nuisance under the following conditions:
Level 2 Testing is Do-It-Yourself testing that can be done in your own home using a Testing Kit. After you’ve done Level 1 Testing, Level 2 Testing can confirm if your observations are correct. If your test results reveal the presence of a contaminant that is cause for concern, you can either proceed to determine the best treatment (see below) or continue to Level 3 Testing.
Most in-home water test kits are not designed for nuisance bacteria, but most kits are designed to test for the presence of total coliform and E. coli. The first step is to conduct a basic in-home water quality test for bacteria. If you have a sulfur odor, we also recommend the Sulfate-Reducing Bacteria Testing, but if you see slimy reddish, black, or brown films with little to no odor, but water with a metallic sheen, we also recommend testing for the Iron-Related Bacteria.
Level 3 Testing is done through an accredited Water Testing Laboratory. With Level 3 Testing, you can order a testing kit that is used to prepare your sample and submit it to the lab. By utilizing a lab, you have the assurance that a certified water expert had analyzed your water sample. If your test results reveal the presence of a contaminant that is cause for concern, you can either proceed to determine the best treatment options (see below) or continue to Level 4 Testing - Certified Testing.
A Level 4 Certified Test Test uses chain-of-custody with a water professional coming to your home to prepare the water sample and then works with an accredited laboratory in order to certify your test results. This type of testing not only gives you the highest level of assurance in the accuracy of your test results, but can also be used as a document in legal cases. For Baseline Testing, we recommend that you use Certified Testing.
If you identified or think there might be a bacterial problem, we suggest certified testing to document the actual number of colony forming units. Typically, this is best done using a local certified laboratory, because the holding time and sampling requirements have a very short holding time.