Environmental Water Testing

PRINCIPLE OF TEST:

Testing of environmental water requires a range of microbiological tests to be performed. These tests are as shown below. 
 

Heterotrophic Plate Count (HPC)

Pour plates are performed on the sample at a suitable dilution range. 2 temperatures are employed since many waterborne micro-organisms will not grow at elevated temperatures. Conversely micro-organisms indicating poor hygiene will generally grow well at higher temperatures. Incubating plates at both temperatures gives a better overall picture of the water quality. 

Test for E. coli and Thermo-tolerant Coliforms

These micro-organisms are useful indicators of possible faecal contamination of water and also suggest that there may be other pathogenic bacteria, parasites or viruses present. A suitable dilution, or range, is filtered and the membrane transferred to a selective agar plate and incubated at an elevated temperature (44°C). Following incubation suspect colonies are counted and confirmed.

The thermotolerant coliforms group includes E.coli and number of other similar bacteria. 

Test for Coliforms

The test for the presence of coliforms is a more general test than that for E. coli and Thermo-tolerant Coliforms and includes many non-pathogenic species. However, being a broader test it has the potential to detect contamination in water where pathogenic species are present in only very small numbers.

A suitable dilution, or range, is filtered and the membrane transferred to a selective agar plate and incubated at 37°C. Following incubation suspect colonies are counted and confirmed. 

Test for Enterococci

These micro-organisms are useful indicators of possible faecal contamination of water and also suggest that there may be other pathogenic bacteria, parasites or viruses present.

A suitable dilution, or range, is filtered and the membrane transferred to a selective agar plate and incubated at 44°C. Following incubation suspect colonies are counted and confirmed. 

Test for Pseudomonas aeruginosa

P. aeruginosa is an opportunistic pathogen commonly found in soil and water. It is able to tolerate and grow in a very wide variety of conditions. In poorly or untreated water it has the potential to cause skin and ear infections and is of particular concern in spa water where the elevated temperature serves to reduce competition.

A suitable dilution, or range, is filtered and the membrane transferred to a selective agar plate and incubated at 42°C. Following incubation suspect colonies are counted and confirmed. 

Test for Pseudomonads

This test includes members of the Pseudomonas genus, as well as several other genera which have similar growth characteristics. Some of these were previously classified in the genus Pseudomonas, but have since been removed. 
Pseudomonads are commonly found in soil and water. The group includes opportunistic animal and plant pathogens such as P. aeruginosa and Burkholderia cepacia, a number of causative agents of spoilage and some species have uses as biocontrol and bioremediation agents. 
A suitable dilution, or range, is filtered and the membrane transferred to a selective agar plate and incubated at 21°C. Following incubation suspect colonies are counted and confirmed by a number of steps. 

SAMPLE REQUIREMENTS:

Sample size is dependent on the quality of the water to be tested. As a general guide, at least 100mL per test should be submitted.

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