Sampling requires more than taking samples

Het Waterlaboratoirum is specialized in advanced sampling techniques. In addition to "normal" sampling by filling water bottles, we also perform more complex sampling. Examples are sampling of groundwater flows via monitoring wells, and sampling large volumes by using Grovols and Hemoflows.

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Sampling groundwater via monitoring wells with different diameters usually takes place in the dunes. By using various pumping techniques, water is pumped up from a few meters to a depth of more than a hundred meters. The applied pumping technique is determined by the environment and the groundwater level.

Before sampling, various parameters are measured, such as the electrical conductivity, turbidity and dissolved oxygen. As soon as these are stable, sampling is started. This kind of sampling is often used for the analysis of several chemical parameters in groundwater flows. However, it is also used for the analysis of microbiological parameters.

With large volume sampling, the change on finding bacteria increases. However, the applied filtering technique must be bacteria friendly. If the pressure for the filter becomes too high, bacteria might not survive. However, the filter cannot be too fine as clogging can become a problem. Therefore, the correct settings in terms of pressure, flow speed, and size of the filter are important. Every drop of water that has been pumped, has to permeate through the filter.

With Grovol sampling, a complete filtration is carried out at the location site. ‘Trapped’ bacteria from sampling are being cultured in the laboratory. This type of sampling is often used for a specific process to gain more knowledge into hygienic parameters.

Even more complex is Hemoflow sampling. Het Waterlaboratorium has developed a sampling method for investigating large volumes (50-3000 liters) of water over long periods for specific bacteria. At drinking water locations, even a few thousand liters can be sampled within 24 hours. The water is filtered through a so-called Hemofilter which is also used in the medical world, for example for dialysis. With this technique, microorganisms and/or viruses present are concentrated in the filter. The Hemoflow setup can be used for research on E. coli, Cryptosporidium, Giardia, Somatic and F-specific bacteriophages.