CONTENTS INVESTIGATIVE PARAMETERS

Bacteria Count

Water quality is also measured by investigating the nature and abundunce of microbes found in the freshwater ecosystem. Of special interest are the bacteria. Recall that the higher the organic chemicals / substances contained within the freshwater, the greater the microbial population potentially supported. The greater the microbial population, the greater the biological oxygen demand and consequently the greater the threat on the freshwater ecosystem. Analysis of the microbial population could focus on total bacterial count (TBC) or, specifically, a coliform bacterial count (CBC).

Procedure

  1. Quantitative analysis of bacterial levels by using bacterial samplers is a much safer and less-complicated process. Bacterial samplers give a very reliable semi-quantitative result. Although costly, the results are excellent. Most scientific suppliers sell the samplers in bulk. In the case of Petrifilm samplers (3M), the samples once inoculated can be placed in a zip-lock bag and incubated with no need to open and have contact with the sample.
  2. Qualitative bacterial monitoring can be conducted using nutrient media in a sterilised test-tube or petri-plate. The sterile growth media is inoculated with the stream water by immersing the test-tube or plate into the freshwater at the investigative site. The water is allowed to be in contact with the media for one minute. The water is then poured out and the vials resealed and incubated for 48 hours. Bacterial colonies are glistening and translucent in appearance. A wide variety of bacterial colony colours may be evident. This procedure is NOT RECOMMENDED because of the health and safety implications associated with working in such close contact with potentially pathogenic bacteria.

Fecal coliform are found in animal excrement and although not normally pathenogenic, their presence indicates the presence of inadequately treated waste and poor water quality.


© 2004 Manitoba Waterways Project
Site Developed by: J. Cook
Questions or comments: Contact the Manitoba Waterways Project
Many files on this site are best viewed with the Adobe Reader.
To download the Adobe reader, visit the Adobe website.