Uranium in the Upper Republican Natural Resources District’s Groundwater

Uranium in the Upper Republican Natural Resources District’s Groundwater

In the summer of 2020, Upper Republican Natural Resources District (URNRD) staff collected water samples from 144 irrigation wells throughout the URNRD and sent them to a certified laboratory to determine the uranium concentration in the water. The figure titled Uranium Concentration in the URNRD in 2020 shows the test results and the location of the sampled wells. The uranium concentration in the groundwater exceeded the US Environmental Protection Agency’s (EPA) drinking water standard in several locations in the Republican River valley, and in general, the groundwater uranium concentration beneath the Republican River valley in southern Dundy County was higher than the remainder of the URNRD. The City of Benkelman recently drilled new municipal wells and installed a water-delivery pipeline from the wells to the city, because of the high arsenic and uranium levels in their previous water supply.

Source of Uranium in Groundwater

Uranium is a naturally occurring, radioactive mineral present in low amounts in certain types of rocks and soil. Radioactivity means the mineral can produce its own energy. Uranium releases energy as it decays.

Glaciers and volcanic ash deposited uranium all across Nebraska at varying levels, but it is found primarily in river valleys and floodplains where erosion has caused it to settle. Rivers and streams flowing from Wyoming and Colorado also carry the mineral from those states into Nebraska.

Monitoring has shown that while groundwater in most areas of the state contains low levels of uranium, higher levels can be found in the groundwater beneath the Republican, North Platte and portions of the Platte River valleys. As water containing oxygen and nitrate passes through and over rock and soil formations, many compounds and minerals, including uranium, dissolve and go into the groundwater.

Uranium also occurs in some of Nebraska’s surface waters. In 2001, Nebraska Department of Health and Human Services (DHHS) personnel collected samples from the Republican and Platte Rivers. Uranium concentrations in the rivers at the sampling locations were just below or exceeded the current uranium limit for drinking water.

Indications of Uranium in Water

Uranium cannot be detected by taste, sight, or smell. The only way to know the concentration is through sampling and testing, which is described in greater detail in a subsequent section.

Potential Health Effects

Alpha particles released by uranium cannot penetrate the skin, so natural uranium that is outside the body is less harmful than that which is inhaled, swallowed, or enters through the skin. About 99 percent of the uranium ingested in food or water will leave a person’s body in the feces, and the remainder will enter the blood. The kidneys remove most of this uranium, and it is excreted in the urine within a few

days. A small amount of the uranium in the bloodstream will be deposited in a person’s bones, where it remains for several years.

At the levels occurring naturally in the URNRD, the main health risk of uranium is not cancer, but its impact on the kidneys when ingested over a long time. The health effects of uranium in drinking water are chronic (the delayed result of continuous consumption over a long time) rather than acute (the immediate result of consumption). Individual risk depends on the concentration, how much water was consumed and for how long, and the age and general health of the individual.

EPA Drinking Water Standard for Uranium

In regulating a contaminant, the EPA first sets a maximum contaminant level goal (MCLG), which establishes the contaminant level at which no known or expected adverse health effects occur. MCLGs are non-enforceable health goals. For uranium, EPA set the MCLG at zero. The EPA then set an enforceable maximum contaminant level (MCL) as close as technologically possible to the MCLG. In addition, the EPA used its discretion in setting the MCL by choosing an MCL that is protective of public health while also ensuring that the quantified and non-quantified costs are justified by the quantified and non-quantified benefits of the drinking water standard. For uranium, EPA has set an MCL of 0.03 mg/L (0.03 ppm). Water supplies containing more than 0.03 mg/L violate the Environmental Protection Agency’s drinking water standard, although ingesting water containing uranium of up to 0.06 mg/L is considered safe for a year or two. The EPA standard is based on 70 years of consuming two liters of contaminated water each day. The EPA’s MCL is very conservative and meant to protect the most fragile populations — the elderly, the very young, and those already suffering from kidney disorders.

Water Treatment Methods

Options for Public Water Supplies

Community water systems (CWS) serve at least 15 service connections or 25 residents year-round. They include such entities as mobile home parks, rural water districts, and sanitary improvement districts, as well as municipalities. CWS in Nebraska have five options for removing or reducing uranium concentrations in drinking water. They include:

· locating and developing a new source of drinking water,

· purchasing drinking water from another water system,

· blending water from a contaminated source with water from an uncontaminated source(s),

· building and operating a treatment plant to remove uranium, and

· installing and maintaining point-of-use (POU) treatment devices at each drinking water tap.

Nebraska DHHS suggests the system investigate the first three options before reviewing treatment options. Community treatment options may require expensive waste disposal. Treatment processes available to CWS for uranium removal include, but are not limited to, reverse osmosis, anion exchange, special adsorbent media or lime softening. Water users wishing to reduce uranium levels prior to a community achieving compliance can treat water as described below.

Options for Public Noncommunity Water Supplies

Noncommunity water systems serve at least 25 people over six months of the year but not year-round. Examples include a manufacturing company with its own well, a rural school with over 25 students, a café beside the highway which has its own well, and the water systems at interstate rest areas and state parks. Noncommunity water systems (NCWS) in Nebraska are not required to meet the uranium standard. However, those systems wishing to do so should consider the same five options listed above for public community water supplies. Some municipal treatment methods, including lime softening, may not be viable treatment alternatives for public noncommunity water suppliers.

Depending on the size of the facility or facilities being served, treatment to remove uranium at a NCWS might be accomplished safely and economically with a point-of-entry (POE) system. A POE system is a small-scale water treatment unit that treats all the water that enters the facility or building. POE systems for uranium removal often make use of anion exchange technology because of its comparatively lower cost. However, reverse osmosis POE systems are becoming more affordable and provide another option. Treatment options can remove an array of contaminants that may be present in the water supply besides uranium. The waste stream produced by the treatment unit should be considered before making any decision. While unlikely, it is possible that uranium and other contaminants removed from the water by a POE unit could result in waste that is regulated by various agencies as hazardous waste or low-level radioactive waste.

It is strongly recommended that noncommunity water systems consult with Nebraska DHHS and the Nebraska Department of Environmental Quality regarding the latest scientific and regulatory data related to the waste stream generated through water treatment and its proper disposal. In addition, a NCWS should work with reliable and competent professionals to select the best option for their situation.

Options for Private Water Supplies

For private water supplies with a high uranium concentration, it may be possible to obtain a satisfactory alternate water supply by drilling a new well in a different location; however, drilling a new well does not guarantee a satisfactory water supply will be found. Another alternative source of water is bottled water that can be purchased in stores or direct from bottling companies.

Uranium treatment systems for private water supplies come in Point-of-Entry (POE) and Point-of-Use (POU) systems. POE systems treat water before it enters the home, so all the home’s water will be treated, and POU systems treat water where it is used. A POU system is usually placed under or near a faucet and treats only the water coming out of that tap for drinking or cooking.

Typically, the most feasible treatment alternative to remove uranium in private water supplies is the Point-of-Use (POU) system. While no POU system is certified to remove uranium at this time, documentary proof exists to show that reverse osmosis, distillation, special adsorbent media (such as titanium dioxide) and anion exchange remove uranium and a variety of other contaminants. Boiling water is not an effective means of removing uranium. Pour-through, faucet-mounted, and POU activated carbon filters also are not an effective means of removing uranium.

Residential point-of-use treatment methods are:

· Strong Base Anion Exchange Resins (Clform),

· Reverse Osmosis, and

· Distillation

For more information on these treatment options see University of Nebraska-Lincoln NebGuides Drinking Water Treatment: Reverse Osmosis (G1490) and Drinking Water Treatment: Distillation (G1493). Treatment options used to remove uranium likely will remove an array of additional contaminants if they are present in the water supply. Nebraska regulations allow homeowners with private wells to send the waste collected from water treatment filters or adsorbent material to a licensed landfill.

Strong base anion exchange resins, Type I and Type II, have a strong affinity for the uranium complexes and can remove them effectively to meet the MCL requirement. Cation exchange resins are not effective for the removal of uranium. Reverse osmosis and distillation are also potentially effective techniques for reducing uranium levels. There are presently no protocols in any of the NSF/ANSI Standards for reducing the uranium levels from water. Thus, the treatment methods listed are recognized as techniques that can effectively reduce uranium sufficiently to meet or exceed the MCL. However, this list does not reflect the fact that POU/POE devices and systems currently on the market may differ widely in their effectiveness in treating specific contaminants and performance may vary from application to application. Selection of a particular device or system for uranium reduction should be made only after a careful investigation of its performance capabilities based on results from competent equipment validation testing for the specific contaminant to be reduced. As part of the installation procedure, system performance characteristics should be verified by tests conducted under established test procedures and water analysis. The resulting water should be monitored periodically to verify continued performance. The application of the water treatment equipment must be controlled diligently to ensure that acceptable feedwater conditions and equipment capacity are not exceeded.

The treatment system or combination of systems that will be best for a private well user depends on several factors, including the uranium concentration in the water, desired level of uranium removal, the quantity of water to be treated, and the chemistry of the water. Whenever possible, assistance from a water professional or expert should be sought in the selection, installation, and operation of a chosen technique. Visit WQA.org to locate water professionals in your area. Note that Certified Water Specialists have passed the water treatment education program with the Water Quality Association and continue their education with recertification every 3 years.