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When looking at water sampling in general, there are a variety of different methods that you can follow to obtain a high-quality sample. It can be quite easy to collect and test these sorts of samples when the water resides on the surface. However, when looking at groundwater, one such method that has become increasingly approved in the industry over time is that of low flow groundwater sampling. If you are searching for the most accurate representation of the water that you intend to sample, then this may be the best option for you.

In this article from ECO Environmental, we aim to explain how you can use low flow groundwater sampling techniques to accurately monitor the condition of your groundwater. 

What is low flow groundwater sampling? 

The process of low flow groundwater sampling usually involves collecting water samples from a groundwater monitoring bore. Traditional well volume purging can cause substantial bias and error in groundwater sample data. Using low flow groundwater sampling can help to overcome many of the issues that are associated with well volume purging, and obtain accurate data for your water quality. 

Compared to high flow sampling, which uses various methods including bailers and high volume pumps to sample water from the ground at a much faster rate, low flow groundwater sampling extracts water at a slower rate, usually below 500 millilitres per minute. This means that low flow sampling extracts less water, leading to lower purging volumes and thus smaller amounts of wastewater disposal, which greatly reduces costs, particularly if there’s contaminated groundwater present. 

Low flow groundwater sampling also takes less time to complete than traditional methods, making this approach a cost effective sampling technique to pursue. This sampling method reduces sample turbidity, increases the accuracy of dissolved concentrations, and provides a better estimate of the mobile contaminant load.

How do you collect groundwater samples? 

There are a number of different groundwater sampling equipment options that you could choose, with each having their own unique benefits. This particular sampling method involves purging water from the aquifer at a slow rate using a sampling pump. To obtain that water you’ll need to choose the most suitable sampling pump for your particular job, with factors such as the depth of the water, the size of your borehole, and purpose of the sampling, all being aspects you need to consider. You’ll also want a pump with an adjustable flow, allowing you to match the purge rate to well yield.

There are different types of pumps that you could use, including the Geotech Low Flow Bladder Pump, which can sample water as deep as 305m to give you a high quality representative sample. These bladder pumps help to obtain water with minimal agitation and drawdown, making them a suitable choice for low flow groundwater sampling. A bladder pump offers the user the optimal combination of sample accuracy, reliability and the depth capabilities for low flow sampling. 

Another type of pump that could be used is a peristaltic pump, whereby water is obtained by running tubes through a number of rollers. The rollers exhibit pressure on the tubes, creating a vacuum that draws in the water for purging or sampling. 

The Geotech Peristaltic Pump, for example, is the perfect choice for shallow low flow groundwater applications up to 8m deep. It is important to note that peristaltic pumps are not suitable for deepwater well sampling. 

One sampling technique that doesn’t involve a pump is the non-purge method of using a HydraSleeve sampler. These are incredibly easy to use, due to their size and lack of components associated with other sampling equipment. 

ECO Environmental – groundwater sampling equipment in Perth 

Low flow groundwater sampling is a highly beneficial method to use when seeking accurate information on the water quality of your groundwater. ECO Environmental offers quality groundwater sampling equipment and consultations. We provide affordable water monitoring equipment for both purchase and rental. If you require a customised piece of equipment, we also have experience in customising both dedicated and portable sampling systems, to more appropriately help with your projects.

If you are unsure of what equipment may be best for your specific situation, please contact one of our environmental specialists today and we can advise on a suitable solution for you.