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Coliforms and E-Coli

EColi testing

Stansted Laboratories can test for Coliforms and E.Coli using the Colilert-18 Quanti-Tray Method

The test for coliform organisms and E. coli is the most important routine bacteriological examination carried out on drinking water, as it provides the most sensitive method for detecting faecal contamination. The Quanti-Tray is a multi-well, most probable number method.


This method gives a confirmed result in 22 hours time.

Ecoli testing
Where Can Stansted Laboratories test for Coliforms and E.Coli? 

Using UKAS approved testing methods we can test for Coliforms and E.coli from the following samples:

  • Drinking Tap Non-reg

  • Drinking Bottled Water

  • Drinking Bowser/ Tanker

  • Recreational-Swimming Pool

  • Recreational- Hydrotherapy

  • Recreational-Spa*

* are in-house non UKAS methods

Our method is suitable for the examination of drinking and recreational waters, including samples from all stages of treatment and distribution, and those source waters of moderate to high turbidity.

Water testing for Ecoli
Ecoli identification

Samples are collected in previously sterilized bottles. For chlorinated potable waters the sample bottles are pre-dosed with 1.8% sodium thiosulphate solution. During transit and when in storage, samples should be kept cool (2°C – 8º C).


Samples should be analysed as soon as practicable on the day of collection. In the event of exceptional circumstances, storage under the above conditions should not exceed 24 hours before the commencement of analysis.

Samples likely to contain excessive chlorine (strong chlorine smell) are likely to affect the result since the sodium thiosulphate used in the Colilert bottles is unlikely to be at a concentration strong enough to neutralise the chlorine. In this case let laboratory manager know immediately.


1 The Microbiology of Drinking Water (2016) – Part 4 – Methods for the isolation and enumeration of coliform bacteria and Escherichia coli (including E. coli 0157:H7) Part D

2 Idexx laboratories – Product codes 98/21373/00 and 98/06161/00, 98/21378/00

3 PHLS Methods for Water. Enumeration of coliforms and E. coli by IDEXX Quanti-tray – Standard Method

4 Colorimetric Enumeration of Escherichia coli  based on β- glucuronidase activity: Applied and Environmental Microbiology, July 1990, p 2021-2024; M. R. Adams, S.M Grub, A.Hamer, M.N. Clifford.

5 Identification of Escherichia coli by colilert β- glucuronidase assay: Sensitivity, Specificity and implications for water testing: EPA American Water Works Association

6 The Microbiology of Recreational and Environmental waters (2016) Part 3- Methods for the isolation and enumeration of Escherichia coli.

7  This is in-house method based on colilert 250 test kit IDEXX p/a comparator catalog WPI04

8  Pool water treatment advisory group: swimming pool water(treatment and quality standards for pools + SPA)

9 Wikipedia

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