How to take groundwater samples?
Groundwater is used on a daily basis by millions of people for drinking water, industrial processes, agriculture and many other uses. Without groundwater the world would face a serious disaster situation without enough water to sustain the life and needs of the planet. It is therefore essential that groundwater is tested and monitored on a regular basis and any issues are contained and quickly cleaned up. Testing requires groundwater samples to be taken and processed by a laboratory to determine the chemicals and PH level of the water. In this article we discuss different methods of taking groundwater samples.
Gaining access to groundwater
In many situations the groundwater needs to be sampled where access does not currently exist in the form of a well. In these instances a bore hole needs to be drilled into the ground in order to penetrate the unsaturated zone and gain access to the saturated zone where the groundwater is contained. The best place to sample groundwater would be in an aquifer, this is a large pool of groundwater that sits below the ground. Aquifers are where the groundwater is most often extracted from for various uses. Bore holes need to be reinforced with steel to improve stability and therefore improve the longevity of the bore hole. If there is a well in place already this can be used to extract the groundwater for sampling.
Groundwater sampling methods
There are several different methods for sampling groundwater from a borehole or well, each of these methods uses slightly different equipment and yields slightly different results in terms of accuracy and what exactly is measured. We will be discussing two of the most common and accurate ways to sample groundwater, these are the recommended groundwater sampling methods for most industries and applications.
Passive groundwater sampling
Passive groundwater sampling is a method used to collect samples from the groundwater without extraction or pumping. It uses specially designed samplers which contain agents, when these agents are exposed to the water for a long period of time they react and can provide detailed information on what chemicals or contamination the water contains. The samplers need to be analyzed in a laboratory setting to get the final results. This process is good for showing up chemicals that may only be present in the water for short periods of time. They can be set and left without needing to monitor or revisit as long as they are set up correctly. It is important to set the equipment correctly, the sampler must be suspended in the water at all times. Water depth and changes such as tides or water table fluctuations should be considered as the sampler needs to be left in the water for a period of time that is relevant to the sampling objectives.
Low-flow purging and sampling
Low flow purging and sampling involves extracting groundwater at rates comparable to the natural groundwater flow (typically less than 500 ml/min). This enables the sample to take a true representation of the water at the given level and depth and avoids any disturbance from outside factors. It also minimizes the amount of water that needs to be taken from the aquifer, minimizing water wastage.
After the samples are taken, scientists, environmentalist agencies, and similar companies analyze and extract data from the samples. They use the data surrounding the quality of the water to inform others or make decisions. Decisions made might result in action needing to be taken to clean the water before it is used, or the water might be suitable and can be used for extracting for drinking water, or agricultural uses.
QED groundwater sampling equipment
At QED Environmental Systems we have a number of different groundwater sampling options available for all industries and uses. Our groundwater monitoring and sampling website section details out all of the information needed. Amongst our range of groundwater sampling equipment is the snap sampler, a dedicated passive sampling system that provides high accuracy. We also sell a number of low-flow purging and sampling solutions including the well-wizard dedicated groundwater sampling systems. This sampling system comes in a range of sizes, materials, and capabilities, including models for deep sampling wells, narrow or obstructed casings, and small-volume pumps for low-yield monitoring wells. For more help and advice contact our team of specialists.