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NC Department of Health and Human Services
State Laboratory of Public Health
N.C. Public Health Home

Microbiology Sample Collection

Water Sample Test Results

Milk Sample Test Results

Public Water System Results


Environmental Sciences: Environmental Microbiology

Water Sample Testing

The Environmental Microbiology Unit performs bacteriological analyses on water samples from both public and private water systems. Samples are examined for the presence of the coliform group of bacteria (including E. coli), which are indicators of fecal contamination. Water is not examined for additional pathogenic bacteria, as the prospect of isolating these from water is generally very remote.

Public Water Systems

Public water system samples are submitted to this Laboratory by the Regional Office staff of the Public Water Supply Section.

Private Wells

Samples from existing or new private wells will be analyzed for coliform bacteria only if the sample is submitted through a local health department. The well should be inspected at the time the sample is collected by a health department representative.

Refer to the water sample collection recommendations from the DHHS, DPH, Environmental Health Section On-Site Water Protection Branch.

Preparing Your Well for the Next Flood (PDF, 293 KB)

Non-Drinking Water

Samples of non-drinking water, such as those from lakes, streams, rivers, and ponds, that are submitted by health departments may also be examined for total and fecal coliform bacteria to determine the degree of contamination.

Milk Microbiology

The Environmental Microbiology Unit provides analyses of milk and dairy products on reference samples received from the Milk Sanitation Branch. Proper shipping measures must be observed to maintain integrity of samples and to meet the regulatory requirements of the National Conference of Interstate Milk Shippers (NCIMS). Dairy products may be analyzed by the following procedures:

  1. Pretrifilm Aerobic Plate Count
  2. Petrifilm Coliform County and Petrifilm High-Sensitivity Coliform Count
  3. Inhibitory Substances Test
  4. Direct Microscopic Somatic Cell Count
  5. Alkaline Phosphatase Test
  6. Milk Containers

Reporting and Interpretation

Test results for drinking water analyses are sent within two working days after the sample is received by the Laboratory. If coliform bacteria are present, the water is considered unsafe for drinking purposes. Results are reported as the presence or absence of both Total Coliform and E-coli bacteria. An analysis refers only to the sample as received and should not be regarded as a complete report on the water source. Non-drinking water sample results are forwarded as soon as complete, typically 4-5 days after receipt of the sample and initiation of testing.

Environmental Sciences Information