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You are here: EPA Home Radiation Protection Programs Naturally-Occurring Radiation 

TENORM Drinking Water Treatment Wastes

Drinking Water Treatment Wastes 

Certain rock types naturally contain radioactive elements 

referred to as NORM (Naturally Occurring Radioactive 

Materials). When a source of drinking water comes in contact 

with NORM-bearing rocks, radionuclides may accumulate in 

the water to levels of concern. The predominant radionuclides 

found in water include: 

radium (and its decay products) 

thorium (and its decay products) 

uranium (and its decay products) 

As water is treated to remove impurities, radionuclides may 

collect and eventually build up in filters, tanks, and pipes at 

treatment plants. The small amounts of NORM present in the 

source water may concentrate in sediment or sludges. Because 

the NORM is concentrated due to human activity, it is classified as TENORM (Technologically 

Enhanced Radioactive Material). Most of this waste is disposed in landfills and lagoons, or is 

applied to agricultural fields.

Most drinking water treatment sludges are thought to contain radium (Ra-226) levels 

comparable to typical concentrations in soils. However, some water supply systems, primarily 

those relying on groundwater sources, may generate sludge with much higher Ra-226 levels. 

Furthermore, some water treatment systems are more effective than others in removing 

naturally-occurring radionuclides from the water. 

The table below lists the current radionuclide standards for drinking water. 

Radionuclide Maximum Contaminant 

Level (MCL) Allowed 

by EPA

combined radium 

226/228

5 pCi/L

uranium 30 μg/L

beta emitters 4 mrems

gross alpha 

standard

15 pCi/L

Radiation Protection 

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Radionuclide Maximum Contaminant 

Level (MCL) Allowed 

by EPA

radon 300 pCi/L (proposed 

standard)

On this page: 

Radiation Levels

Waste Generation 

Lime Softening

Ion-Exchange and Activated Charcoal

Disposal and Reuse

Lagoons

Landfills

Sewer Systems

Deepwell Injection

Landspreading and Soil Conditioning

What is being done about these wastes?

Radiation Levels

Of the 160,000 public water systems serving the U.S., approximately 700 of these systems 

treat water with elevated TENORM levels. The National Inorganics and Radionuclide Survey

(NIRS), performed by the EPA, found large numbers of water treatment plants in the 

midwestern and southeastern states processing water with radium concentrations in excess 

of EPA's Maximum Contaminant Levels (MCLs). The concentration and distribution of 

radionuclides in drinking water varies from one area to another depending on location 

variables:

geological location 

groundwater pH

redox potential 

radionuclide solubility and half-life

water withdrawal rates

amount of sludge produced per unit volume of water processed. 

Radium levels are typically found in higher concentrations in groundwater than in surface 

water. Concentrations in groundwater typically range from 0.5-25 pCi/L compared to 0.01-1 

pCi/L for surface water. Radium concentrations as high as 200 pCi/L have been reported, 

although this is rare; levels are seldom seen above 50pci/L.

Ra-226 average concentration in community drinking water supplies is estimated to range 

from 0.3 to 0.8 pCi/L . The results of the National Inorganics and Radionuclide Survey 

(NIRS), performed by the U.S. EPA's Office of Drinking Water, indicate a higher weighted 

average of 0.905 pCi/L. Five states—Georgia, Illinois, Minnesota,Missouri, and Wisconsin— 

have been noted to have still higher average concentrations, ranging from 1.27 to 5.29 

pCi/L .

Uranium activity as high as 652 pCi/L has been observed in both surface and groundwater 

samples. The average uranium concentrations in surface and groundwater are believed to be 

about 1 and 3 pCi/L, respectively. The population-weighted average uranium concentration in 

community drinking water supplies is estimated to range from 0.3 to 2.0 pCi/L . 

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The presence of radon in groundwater is known to vary significantly, with the concentration 

being over six orders of magnitude different from that of Ra-226. The geometric mean of 

groundwater radon concentrations is nearly 1,000 pCi/L. For radon, the population-weighted 

average is believed to range from 194 to 780 pCi/L.

Waste Generation

Approximately 260,000 metric tons (MT) of TENORM wastes are generated each year by U.S. 

water treatment facilities. This is equivalent to 600 MT of TENORM per utility. Eighty-three 

percent of the contaminated waste is filter sludge and the remaining 17 percent is ion 

exchange resins and charcoal.

The table below lists typical radiation levels in drinking water treatment residuals:

Wastes Radiation Level [pCi/g]

 low average high

Treatment Sludge 

[pCi/l] 1.3 11 11,686

Treatment Plant 

Filters 40,000 

The Radiation in TENORM Summary Table provides a range of reported concentrations, and 

average concentration measurements of NORM associated with various waste types and 

materials. 

Not all treatment facilities produce TENORM wastes. The degree of contamination varies 

according to the natural abundance of radionuclides in the water and on the treatment 

methods employed. Only 28 percent of water treatment processes remove radionuclides from 

water. Those of most concern are lime softening and ion exchange and activated charcoal. 

Lime softening

Lime softening is used on large water supply systems to soften water by the addition of 

calcium hydroxide. Calcium hydroxide raises the pH of water causing calcium and magnesium 

to settle out and form a solid sludge. 80 to 90 percent of the radium in the water becomes 

trapped in the sludge, which is removed by sedimentation and filtration. This process 

typically produces about 4 cubic yards (3.1 m3) of dewatered sludge per million gallons of 

processed water.

Ion-Exchange and Activated Charcoal 

Ion-exchange resins are used on smaller water supply systems to soften water by replacing 

Ca2+ and Mg2+ ions with Na+ ions. In the process, about 95 percent of the radium is also 

removed . However, the resins are usually back washed for reuse rather than being disposed. 

The backwash water, which contains radium, is typically discharged to storm sewers, 

underground injection wells or septic tanks, or is back washed to another ion-exchange 

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column for the selective removal of radium. Radionuclide content eventually builds up in the 

resin after prolonged usage.

Disposal and Reuse

A variety of methods are employed for disposing of drinking-water treatment sludge, 

including lagoons, landfills, sewer systems, deep well injection, and land spreading/soil 

conditioning. 

Lagoons

Approximately 42 percent of sludge is disposed of in lagoons. Any radium present in the 

sludge will settle in bottom sediments which may have to be periodically dredged and 

properly disposed of. 

Landfills

Approximately 30 percent of generated sludge is disposed of in landfills. Contaminated 

materials are typically covered and compacted on a daily basis. Features such as clay layers 

are emplaced above and below the buried waste to prevent radon emissions and 

radionuclides from leaching into the groundwater.

Sewer Systems 

Approximately five percent of sludge is discharged into sewer systems. Sludge and other 

wastes released into sanitary sewers are ultimately treated at sewage treatment facilities. 

Some of the discharged sludge may wind up in storm sewers where it is typically routed to 

natural bodies of water where sludge may accumulate in aquatic sediments.

Deep-Well Injection

Deep-well injection involves the pumping of sludge into a stable geologic formation. Deepwell injection is not commonly used and is specifically prohibited in the states of Wisconsin 

and Illinois. Because of its potential adverse impact on groundwater aquifers, EPA uses its 

authority under the Safe Drinking Water Act to control and also discourage this practice.

Land Spreading/Soil Conditioning

About 20 percent of sludge is disposed of by land application to improve soil conditions or to 

fertilize the soil. The sludge is plowed directly into the soil to limit water runoff and for 

sanitary reasons. Recently proposed rules may prohibit this practice on agriculture land. 

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What is Being Done About These wastes?

EPA 

EPA has developed guidance on managing drinking water treatment waste and is conducting 

a study to learn more about the levels of radioactivity in these wastes. 

A Regulators' Guide to the Management of Radioactive Residuals from Drinking Water 

Technologies (PDF) (81 pp, 561K [about pdf format] )[EPA 816-R-04-005] 

This report includes guidance on managing water treatment wastes and other topics: 

technologies for treating and removing radionuclides from drinking water

general principles of radioactivity 

recommendations for occupational safety of workers at the Community Water 

Systems (CWS) including guidance for radiation protection and protection from radon

regulatory requirements governing the radioactive wastes generated by the CWSs.

Study of the Levels of Radioactivity in Drinking Water Wastes

In a limited radiation study at several Community Water Systems around the country, EPA is 

evaluating radiation levels and concentrations of radionuclides in facilities which treat water 

for radionuclides. The study will measure radiation levels the facilities: 

tanks, filters, and other equipment

piping and possibly pipe scales 

source water

finished drinking water

sludges and sediments 

Programs  Topics  References

http://www.epa.gov/rpdweb00/tenorm/drinking-water.html

Last updated on Friday, July 08, 2011

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