Low Flow Sampling
It is generaly accepted that groundwater wells should be purged before samples are taken as the water in a well is not representative of the formation water. Low-flow sampling (also known as low flow purging) has become the standard for obtaining representative groundwater samples.
Additional Equipment
The TROLL 9500 Multi-Parameter Water Quality Sonde is a required component of the Flow-Sense system, and the Rugged Reader provides the perfect solution to on-site setup and data monitoring.
Low Flow Sampling Increases Sampling Accuracy and Efficency
With the use of a submerged pump such as a bladder or peristaltic pump, groundwater can be pumped to the surface at a rate of between 100ml and 1000ml per minute. In the past, the problem with sampling groundwater has been that much larger samples (often contaminated) were taken which often contained stagnant water located above and below the screen. By abstracting much smaller samples, there is less stress and hence movement of water in the acquifer. The quanity of water being measured at the surface will be less than that entering the acquifer.
Today, it is possible to abstract just a few litres of water instead of older techniques which often required 10 times more IDW (Investigative Dervied Waste) from contaminated wells. The bladder pump and controller are located at the surface and the delivery hose is lowered down to the screened section of the monitoring well. The pump controller delivers a continuous sample to a flow cell and multiparameter instrument at the surface. Water levels will also be monitored continuously to ensure that the pumping causes no stress or drawdown within the well. Representative groundwater samples can be taken once the Troll 9500 multiparameter sonde and flow cell indicate that the measured parameters and turbidity have stabilised and at are at an acceptable level to the user.
Advantages of low-flow sampling
