IDEXX have announced that South West Water has selected the Colilert-18 method to detect the presence of E. coli and coliforms in its drinking water. The switch to Colilert-18 from the traditional agar plate method followed a six-month comparison study between the two. The study concluded that Colilert-18 was faster, more accurate and met the goals of the laboratory and operational scientists.

South West Water supplies a customer base of 1.7 million people throughout Cornwall and Devon and in small areas of Dorset and Somerset, and welcomes over 7.0 million visitors during the peak summer tourism months. Accurate and timely microbiological analysis is essential in delivering their goal of supplying good, safe drinking water that has the trust of their consumers. South West Water merged with Bournemouth Water in 2016, which supplies drinking water to nearly half a million people in parts of Dorset, Hampshire and Wiltshire.

South West Water is the latest major UK utility to adopt the Colilert-18 test which is also used extensively by Thames Water, South East Water and Essex & Suffolk Water. Providing confirmed results in 18 hours compared to the 48 hours it takes to run agar based tests and requiring no confirmation steps, Colilert-18 was made the ISO 9308-2 standard for the enumeration of E. coli and coliform bacteria in all types of water in 2012 and was added to the European Drinking Water Directive in 2015, where it is now included as one of only two reference methods for coliform and E. coli detection.

“The quality of our water and safety of our customers is of paramount importance at South West Water,” commented Claire Coppin, South West Water’s Laboratory Manager. Claire added, “Switching to the Coliert-18 test enables us to get water quality results in half the time compared to the agar tests that we ran previously. It is quick and simple to use and our studies showed it to be more accurate.” Chris Rockey, South West Water's Head of Water Quality added “Having confirmed results in a more timely manner helps us make confident decisions to ensure our consumers can have trust in their tap water; which is our (and their) number one priority”.

Andrew Headland, Senior Business Manager for IDEXX EMEA said, “Colilert-18 has again demonstrated real value to a water operations team, providing accurate, rapid and cost effective results which facilitate confident decision making. The value of a long shelf life also means that South West Water will only need to order 2 to 3 batches per year compared to 2 to 3 batches per week for the agar based test. We are seeing significant interest in Colilert-18 from other major UK utilities as result of its speed, accuracy and ease-of-use.”

Colilert-18 consists of a reagent powder, which is added to a standard 100ml water sample and then incubated for 18 hours in the case of presence/absence determination. This step takes less than 1 minute of hands-on time. The presence of E. coli and total coliforms is subsequently determined following incubation, with coliforms indicated by the sample turning yellow, and fluorescence indicating the presence of E. coli. Where quantification of a sample is required, IDEXX has developed a simple device known as a Quanti-Tray®, which consists of 51 individually sealable cells. The Quanti-Tray can also be incubated for 18 hours after which the fluorescent cells can be counted and quantified.

For more information visit www.idexx.com/water