The University of Minnesota Extension Services conducts research, provides education, and makes recommendations for Lawn Care and Nutrient Management for agriculture. Contact the Drinking Water Protection Program: health.
Nitrate in Drinking Water Nitrate is a compound that naturally occurs and has many human-made sources. How to Protect Yourself and Your Family.
If you have a private well The following types of wells are the most vulnerable to nitrate contamination, especially if they are near septic tanks or areas with agricultural activities: Shallow wells Wells in sand aquifers Dug wells with casings that are not watertight Wells with damaged or leaking casings or fittings Below are recommendations on how to prevent and address nitrate contamination.
Keep nitrate sources away from your well. Sources may include fertilizer, septic systems , and animal waste. Regularly inspect your well for damage see Protect Your Well for guidance. Contact a licensed Well Contractor if you find any damage. Test for nitrate every other year. You are responsible for keeping your private well water safe and testing it as needed. Contact an accredited laboratory to get a sample container and instructions, or ask your county environmental or public health services if they provide well water testing services.
Address Contamination If nitrate is detected in your well water, there may be other contaminants in the water as well. This is especially important if there are any babies under six months old drinking the water or formula made with water. Boiled water is not a safe alternative if there is nitrate in your water; boiling water will make nitrate more concentrated.
Have a Licensed Well Contractor inspect your well for damage. Find and remove potential sources of nitrate contamination on your property. Protecting Your Well can help you identify sources to check. Nitrate can occur naturally in surface and groundwater at a level that does not generally cause health problems. High levels of nitrate in well water often result from improper well construction, well location, overuse of chemical fertilizers, or improper disposal of human and animal waste.
Sources of nitrate that can enter your well include fertilizers, septic systems, animal feedlots, industrial waste, and food processing waste.
Wells may be more vulnerable to such contamination after flooding, particularly if the wells are shallow, have been dug or bored, or have been submerged by floodwater for long periods of time. If you suspect a problem and your drinking water comes from a private well, you may contact your state certification officer external icon for a list of laboratories in your area that will perform tests on drinking water for a fee. Nitrate may be successfully removed from water using treatment processes such as ion exchange, distillation, and reverse osmosis.
Contact your local health department for recommended procedures. Heating or boiling your water will not remove nitrate. Because some of the water will evaporate during the boiling process, the nitrate levels of water can actually increase slightly in concentration if the water is boiled.
Remember to have your well water tested regularly , at least once a year, after installing a treatment system to make sure the problem is controlled. The cadmium reduction method is a colorimetric method that involves contact of the nitrate in the sample with cadmium particles, which cause nitrates to be converted to nitrites. The nitrites then react with another reagent to form a red color whose intensity is proportional to the original amount of nitrate.
The red color is then measured either by comparison to a color wheel with a scale in milligrams per liter that increases with the increase in color hue, or by use of an electronic spectrophotometer that measures the amount of light absorbed by the treated sample at a nanometer wavelength.
The absorbance value is then converted to the equivalent concentration of nitrate by using a standard curve. Methods for making standard solutions and standard curves are presented at the end of this section. This curve should be created by the program advisor before each sampling run. The curve is developed by making a set of standard concentrations of nitrate, reacting them and developing the corresponding color, and then plotting the absorbance value for each concentration against concentration.
A standard curve could also be generated for the color wheel. Matching the color of a treated sample at low concentrations to a color wheel or cubes can be very subjective and can lead to variable results. Color comparators can, however, be effectively used to identify sites with high nitrates. This method requires that the samples being treated are clear.
If a sample is turbid, it should be filtered through a 0. Be sure to test whether the filter is nitrate-free. The reagents used for this method are often prepackaged for different ranges, depending on the expected concentration of nitrate in the stream. For example, the Hach Company provides reagents for the following ranges: low 0 to 0. You should determine the appropriate range for the stream being monitored. A nitrate electrode used with a meter is similar in function to a dissolved oxygen meter.
It consists of a probe with a sensor that measures nitrate activity in the water; this activity affects the electric potential of a solution in the probe.
This change is then transmitted to the meter, which converts the electric signal to a scale that is read in millivolts. The accuracy of the electrode can be affected by high concentrations of chloride or bicarbonate ions in the sample water. Fluctuating pH levels can also affect the reading by the meter. Nitrate electrodes and meters are expensive compared to field kits that employ the cadmium reduction method.
The expense is comparable, however, if a spectrophotometer is used rather than a color wheel. If the program has a pH meter that displays readings in millivolts, it can be used with a nitrate probe and no separate nitrate meter is needed. Results are read directly as milligrams per liter. Although nitrate electrodes and spectrophotometers can be used in the field, they have certain disadvantages.
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