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:

General Tips

1. Analyze samples as soon as possible after collection.

2. Consistency is key! Make a habit of using similar timing between collection and analyses.

3. Test samples within 4 hours of collection for greatest accuracy.

4. Use the same sample point as what is used for other tests (i.e. TSS).

5. Fill sample bottles 2/3 full and cap loosely to avoid suffocation.

6. For samples obtained using a dipper, use a consistent depth. Some bioreactors (i.e. anaerobic digesters) have stratified levels with varying biological activity

7. For bioreactors experiencing non-uniform flow patterns and/or dead zones, perform tests at multiple locations.

8. Never artificially settle samples (i.e. centrifuge).

9. Sterile bottles are not necessary. However, ensure that bottles are washed out and free of residual disinfectant.

10. Mix samples thoroughly prior to analyses. However, vigorous mixing can be stressful to the population. Five inversions is generally sufficient.

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.