Many residential homeowners rely on the use of private wells to supply water to their home. Likewise, many farmers rely on the use of wells to supply water to irrigate crops or to keep animals hydrated. Private water wells are a common feature in areas where municipal or city water services are unavailable or where surface supplies are not sufficient or accessible. Water wells are commonly used to source groundwater where naturally occurring groundwater exists in spaces between rocks and/or sand. The wells themselves are bore holes either drilled or pressed into or through the ground into which casing pipes, screens, pumps and other water plumbing are installed. Groundwater seeps through openings in the casing pipe called screens. Water can be pumped via these wells, either with an above ground vacuum pump or, where the water is deeper than 30 feet, with a submersed pump that creates upward pressure to move the water to the surface.
A conventional well typically includes a borehole from the surface to a required depth to reach the groundwater. A casing pipe is inserted into the borehole and grout is used to seal the space between the casing pipe and the earth. A pump (either submersed or above the groundwater surface, depending on depth) is attached to the water pipe for transportation of water from the well to the point of use. The well is capped at the wellhead on the ground surface with a well cap. Typically, information which may include a service contractor's phone number and a date of service may be recorded on the well cap.
Water well construction and sometimes site selection or location advisement is done by a well driller, who takes care to design the well to meet the needs of those who will use the water. The well driller, in the process of planning and drilling, will determine where there is ample groundwater, and will size the length and diameter of the well and casing pipe and the capacity and location of the pump accordingly. The well driller will take special care to know the top elevation and the productivity of the groundwater table. Elevation is often found by measuring down from the wellhead (top of the well) to the water surface. Productivity of the well is inferred by measuring the elevation of the water and time it takes to return to a resting level after a pumping event has removed water from the well. Together with elevation and productivity, the final pump selection is made and construction can be completed.
In addition to locating a well in a correct location and at the correct depth to maximize the groundwater productivity of the well, the well also needs to produce groundwater of acceptable quality for use by the well owner. Water quality is important to the well owner because only water of sufficiently high quality may be used safely for human consumption and other domestic and agricultural uses. A well that is contaminated by either natural or human impacts may cause water from the well to be unacceptable and not usable to the well owner. The United States Environmental Protection Agency (EPA) sets maximum contaminant levels (MCLs) for many natural and human introduced contaminants in the environment which serve as human health benchmarks for drinking water. The well owner may also establish specific quality standards based on the use of the well water including human consumption, animal consumption, crop watering, manufacturing and processing requirements, and the like. If the water from the well does not meet the EPA's or the well owner's water quality standards, the well owner may need to remediate or abandon the well. These actions are often expensive and could limit the amount of water the well owner is able to draw from the land.
When commissioning or repairing a well, a well driller may also perform an initial water quality indicator test of the well to determine whether the well location will produce acceptable water quality. In the event a certain water quality indicator, or concentration of a chemical is detected, the well driller may notify the well owner to determine if the well water is acceptable to the well owner.
There are many water quality indicators which the well owner may wish to detect and monitor, especially substances which are harmful to the well owner's health and property. Some non-limiting examples of these substances are volatile organic compounds (VOC), radon, radiation, natural gas, oil, and the like.
One method used to measure the water quality of the well water is by taking physical samples of the water. Such water samples can be taken from the well by removing the wellhead cap and using equipment to take water samples from the well. Removal of a well cap and direct sampling of well water requires specialized training and certification due to the possibility of groundwater contamination and therefore incurs a high cost to the well owner. Alternately, water samples can be taken from the water pumped from the well. Testing for certain substances from water samples pumped from the well can be disadvantageous due to changes in water properties during pumping and transport of the water. Both of these two processes require samples to be sent to an offsite laboratory which incurs high costs and substantial wait times for information. Submersible devices are available that can monitor water quality indicators in well water, log these data through time, and provide accurate information at a high temporal frequency. These devices and methods are generally extremely costly and often require specialized training to calibrate the submerged sensors, as well as to download and interpret data. In addition, these devices require manual data retrieval which does not provide the ability to take immediate action due to a rapid change in water quality and can lead to the loss of data if the device fails without the owner's knowledge.
There are many water quality indicators and contaminants which the well owner may wish to detect and monitor, especially substances that are harmful to the well owner's health and property. Examples of water quality indicators are the concentration of total dissolved solids, chloride, dissolved oxygen, trace metals such as iron and manganese, the pH level, the specific conductance, and turbidity. Substances that are of interest as they impact human health are nitrate, sulfate, volatile organic compounds (VOCs), radon and other radionuclides, arsenic, natural gas, pesticides microbial contaminants, and the like.
Another way to measure water quality indicators is by measuring water quality indicators in the air in the well above the groundwater level. Air is present within the well between the groundwater level and the well cap. Certain volatile water quality indicators and contaminants such as VOCs, radon, natural gas, certain pesticides, and the like, are present within this air due to the exchanges of substances across the air-water interface. These volatile substances may accumulate in the wellhead air space due to the minimal exchange of air between the wellhead space and the outside of the well, ambient air. The transfer of volatile compounds across the air-water interface is controlled by the solubility of the dissolved gas in water, which is often dependent on water temperature, molecular diffusion at the air-water interface, and turbulent diffusion in both the air and water columns. Accordingly, the detection of volatile water quality indicators in the well air, and tracking their change in time, provides an indication of their presence in the well water and provide important information to the well owner of well water contamination and the need for further testing.
As such, there is a need for a device that continuously monitors water quality indicators present in and around a well. What is also needed is a way to monitor the water quality indicators present in a well without repeatedly removing the well cap and subjecting the well owner to the expense of manual well water sampling, laboratory analysis requiring long wait times, and the purchase of expensive equipment which requires specialized training to operate and interpret data. Further, what is needed is a way to retrofit existing wells with a device that monitors water quality indicators in a well without repeatedly removing the well cap or physically removing water from the well for analysis unless it is necessary. Heretofore, these requirements have not been fully met without incurring various disadvantages.
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