Inoculating Water with Thermotolerant Coliforms?
I'm looking for advice on how to reliably inoculate water with thermotolerant coliforms (preferably E. coli), for the purpose of quality control testing the ceramic filters that my organisation, Abundant Water, makes and distributes across Laos for treating water.
I am specifically after a good starter culture (tried horse poo and nasty canal water already, not enough coliforms) to work with. Is there a commercially available starter culture available or if not which animals faeces would be the best starting point??
I am not sure why you are looking to test with coliforms other than by culturing at temperature you can evaluate. To get a starter culture that is calibrated and you know how many there are you probably need to look at bacteriophages. These are widely used in testing membrane and other filters and UV systems for validation purposes and cultures are commercially available. There is also a difference between validation testing for getting approval and QC testing of production samples. The former really needs to be done by an outside agency to have the validity and protocol required. Routine QC testing is a more in house activity but I would suggest does not need to involve bacteria. For safety reasons if nothing else try either using a dust of suitable size or even depending on the type of filter and the arrangement bubble point testing of a filter assembly using low pressure air on a wetted filter is quick cheap and effective and results are readily recorded.
Are you sure you did your testing correctly? Water quality E.coli testing is so sensitive that normally there is no such thing as "not enough".
Although I could imagine the horse-poo was older and and mixed with urine (driving up pH and thus killing bacteria)?
In most cases I worked on we used fresh municipal waste water, but that might not be available in at your site. For animal poo I would look for as fresh as possible one... maybe chicken litter would work? With chicken you can easily keep a steady supply close at hand.
The commercially available E.coli cultures are probably not suitable for this, as they are typically not very environmentally resistant strains. Think of lab-rat vs. street rat.
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