Collecting Samples

Because microorganisms are highly dynamic, it is recommended that when performing multiple analyses to collect samples within the same timeframe and to use the same collected samples for ATP and conventional analyses.

Make sure to test samples within 2 hours of collection for the greatest accuracy. In general, it is recommended that samples collected for ATP analyses are taken from the same location as typical samples for other analyses or ideally, the same samples are used for ATP measurements.

Good sampling practices are equally important for ATP analyses just like other monitoring parameters. When collecting samples, sterile bottles are not necessary because the analyses are completed before any microbial growth can occur. Also, contamination levels in bio-fouling application samples are usually much higher than would be present in a clean sample bottle.

Guidelines for Collecting Samples:

Equipment
► Prior to sampling water, remove any screens, aerators, swivel sprayers, etc. It is recommended to periodically remove and clean such devices in order to minimize the harboring of bacteria within the tap.

Biocide Sample Locations
► When dealing with systems dosed with biocides, sample location and sample collection timing are extremely important to assess biocide effectiveness. Factors to keep in mind are:

• Time required for the biocide to mix throughout the system and the fluid retention time

• Timing of associated plant operations

• Timing of peak challenges to the treatment program

• Biocide strength/kill rate

• The extent of system fouling prior to treatment (contamination recovery time is much shorter in a fouled system).

Similarly, location issues include:

• The distance of sample source from the point of biocide application

• The proximity to most vulnerable and important system components

• The proximity to suspected contamination sources

• The proximity to heat and aeration sources

Time
► The amount of time to let the water run depends on what part of the distribution system that is of interest.

• Within the faucet: Collect sample immediately

• Building Water Lines: Allow to run for 15 seconds

• Water Main: Allow to run for 5 minutes

Handling
► When handling the sample bottle, open the container without touching the inside of the cap or the mouth of the bottle. Fill the bottle to 2/3 full to allow sufficient headspace, provided that enough sample has been collected to complete the analysis.

Temperature
► Keep the sample cool until it can be analyzed (2 hours or less). The urgency is less for samples taken from low-nutrient environments. The urgency is higher in samples treated with biocide in which the timing of biocide action needs to be defined. Once samples are collected, they are taken out of their natural environment so they should be analyzed as soon as possible.

Mixing
► Mix samples thoroughly before subsamples for ATP analyses are removed. However, vigorous mixing is not required because dispersion of microbial clumps and flocs is not necessary. In fact, mixing that is too vigorous may be stressful to some species, especially anaerobes located within the particulate components of the sample.

Shipping
► When shipping samples to be analyzed at a different location, it is often useful to collect multiple samples to compare on a relative basis. For example, send additional samples that have been treated with biocide to compare to an untreated sample.