Water Well Journal
Issue link: http://read.dmtmag.com/i/692787
The implementation of coliform testing has addressed the need for timely and affordable testing related to the presence of potentially harmful bacteria. But the knowledge of other bi- ological fouling mechanisms implores us to expand our hori- zons to other types of bacteria which can influence our wells. Quantifying the total bacterial population offers a good starting point in monitoring biologically based fouling by es- sentially illustrating the overall biological load within a well. A variety of methods, including heterotrophic plate counts (HPC) and adenosine triphosphate (ATP), are available and offer quick, relatively inexpensive approaches to determining the level of bacteria present. An additional benefit of ATP test- ing is it is non-reliant on culturing the available bacteria, which often proves to be unconducive to a large percentage of the available bacteria in a laboratory setting. Once the population size is determined, it can be further dissected into subgroups much in the way a census is con- ducted. In the world of biological testing this can be done in a number of ways with varying degrees of detail. But in sticking with the approach of gaining the most bang for our buck, a simple designation to begin with is the differentiation between potentially harmful organisms and those that do not pose health risks but can cause other fouling issues. The latter of these we could term "nuisance" bacteria. Ex- amples of nuisance bacteria include the previously discussed slime-forming bacteria, iron-oxidizing bacteria, and sulfate- reducing bacteria. These groups of bacteria are important to account for—not because they can make water supplies un- safe, but because they can be damaging to the infrastructure of a well, drastically change the quality of water being produced, and cause increased maintenance and treatment costs. Detection of many of these bacteria can be accomplished through relatively simple scientific testing. Microscopy can be used to not only observe active bacteria, but also detect masses of biofilm accumulations and in some cases actually identify bacteria themselves. One such example of this is iron- oxidizing bacteria, many of which are easily identifiable by the structure of the stalks they produce. Simple nutrient characterization assays are also available to assess anaerobic bacteria, including SRBs. Other tests used to identify specific bacteria include polymerase chain reac- tion, DNA sequencing, and phenotype microarrays. These methods vary greatly in time and cost which should be considered in determining if they are suitable for your needs. Conclusion In order to decipher which biological tests are most appropriate for a well sys- tem, it is necessary to first obtain a basic understanding about the microorganisms themselves which inhabit groundwater. Bacteria are an extremely diverse do- main of single-celled organisms that can be found in nearly every environment on Earth. Testing for bacteria within water sup- plies has increased in notoriety, accu- racy, and availability in a relatively short time span. Yet understanding which methods offer the best approach for evaluating the biological activity within a well is often overlooked due to the requirement of coliform testing prominence of the Bac-T (coliform) test within the industry. However, the need The heterotrophic plate count testing method provides an assess- ment of viable biological growth in response to a specific agar. waterwelljournal.com TESTING from page 20 PROBES WINCHES LOGGERS SOFTW ARE OUTSTANDING IN OUR FIELD mount sopris ins truments is a leading manufacturer of slimline bor ehole geophysical logging systems f or downhole groundwater applications. Learn more at mountsopris.com or call 303-279-3211 22 July 2016 WWJ