Follow NEMC
 |
 |
 |
Approaches to the Detection of Fecal Coliforms
Oral Presentation
Prepared by C. Fricker
CRF Consulting LTD, Child's Acre Church Lane, Reading, Berkshire, RG7 1HD
Contact Information: colinfricker@aol.com; 774-029-2101
ABSTRACT
While the term “fecal coliform” is misinterpreted by many, the examination of materials for the presence of fecal coliforms remains a widely applied test for some waters and biosolids. Fecal coliforms are generally defined as total coliform organisms that are able to grow at elevated temperature (e.g. 44oC) and the group was first used as a surrogate for E. coli. Now that robust methods are available for the detection of E. coli specifically the use of fecal coliforms as indicators has declined. Nonetheless, there remain regulations that rely upon the detection of fecal coliforms.
Traditionally, fecal coliforms have been detected using membrane filtration techniques that utilise fermentation of lactose as the indicator pathway with elevated temperature of incubation inhibiting those coliforms thought not to be of fecal origin. Unfortunately there are many coliforms that are not of fecal origin that are able to ferment lactose at 44oC. However, until regulations are changed there is still a requirement to test. Membrane filtration techniques are being utilized less and less due to the high labor requirement and the time taken to obtain a confirmed result and other methods that utilize β-D-galactosidase as the indicator nutrient are being used more frequently.
Membrane filtration suffers, in particular when samples with high particulate concentrations are examined as the membranes can block and reading of membranes containing high numbers of large particles can be problematic. For this reason, most probably number techniques are often favoured. A comparison of the two approaches will be presented together with discussion on the relative merits of both and guidance on the interpretation of both. The benefits and cost savings of utilizing most probable number techniques will be highlighted.
Oral Presentation
Prepared by C. Fricker
CRF Consulting LTD, Child's Acre Church Lane, Reading, Berkshire, RG7 1HD
Contact Information: colinfricker@aol.com; 774-029-2101
ABSTRACT
While the term “fecal coliform” is misinterpreted by many, the examination of materials for the presence of fecal coliforms remains a widely applied test for some waters and biosolids. Fecal coliforms are generally defined as total coliform organisms that are able to grow at elevated temperature (e.g. 44oC) and the group was first used as a surrogate for E. coli. Now that robust methods are available for the detection of E. coli specifically the use of fecal coliforms as indicators has declined. Nonetheless, there remain regulations that rely upon the detection of fecal coliforms.
Traditionally, fecal coliforms have been detected using membrane filtration techniques that utilise fermentation of lactose as the indicator pathway with elevated temperature of incubation inhibiting those coliforms thought not to be of fecal origin. Unfortunately there are many coliforms that are not of fecal origin that are able to ferment lactose at 44oC. However, until regulations are changed there is still a requirement to test. Membrane filtration techniques are being utilized less and less due to the high labor requirement and the time taken to obtain a confirmed result and other methods that utilize β-D-galactosidase as the indicator nutrient are being used more frequently.
Membrane filtration suffers, in particular when samples with high particulate concentrations are examined as the membranes can block and reading of membranes containing high numbers of large particles can be problematic. For this reason, most probably number techniques are often favoured. A comparison of the two approaches will be presented together with discussion on the relative merits of both and guidance on the interpretation of both. The benefits and cost savings of utilizing most probable number techniques will be highlighted.