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Healthy Water, Healthy People Testing Kit Support
FAQ’s for Healthy Water, Healthy People
Rivers, Streams, Ponds, and Lakes
Testing Kit #7
Alkalinity
- After I added the phenolphthalein, the sample did not turn pink, what should I do?
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This is common and will happen whenever the starting pH of the sample is less than 8.3. This means that there is no
phenolphthalein alkalinity in the sample. Continue with the test by adding the bromcresol-green methyl red indicator
and titrate to the endpoint for total alkalinity.
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My sample turns light pink when I add the bromcresol-green methyl red indicator, not a blue-green color, what is wrong?
- If chlorine is in the sample, it will bleach the indicator. Start with a fresh sample and add one drop 0.1 N sodium thiosulfate per
100 mL sample to remove chlorine. Then begin the test as usual.
- How do I know whether to use the High Range or Low Range procedure?
- If you don’t know what the approximate alkalinity of your sample will be, use the high range procedure.
If your results are below 100 mg/L, you can increase your accuracy by repeating the test using a fresh sample
and the low range procedure.
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Biological Oxygen Demand (BOD) and Dissolved Oxygen (DO)
What happens if I have an air bubble in my BOD bottle?
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If there is an air bubble in the bottle used to measure dissolved oxygen, the DO result will be higher
than it actually is. This will make the final calculation for BOD incorrect. If the bottle that is incubated has a bubble, there will be more oxygen available to the sample than there should be, and results will also be incorrect.
- Does the order in which I add the manganous sulfate and alkaline iodide-azide powder pillows affect the test results?
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It is best to add the manganous sulfate first and then the alkaline iodide-azide.
- My final DO is always zero. What can I do?
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Note that the result in this case is not initial – final DO. You can only say that the result is greater than the initial – final DO difference, because there is no way to know how much more oxygen the sample would have consumed if more oxygen had been available. You can start over and dilute your sample with distilled water, for instance one part sample to one part distilled water, to try and get a final DO concentration that is not zero. Then multiply the initial – final DO difference by the dilution factor to get the BOD result.
- How does this modified procedure compare to the Standard Methods procedure?
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The Standard Methods BOD procedure is more complicated and involves making sample dilutions, adding microorganisms and nutrients, and incubating at a carefully controlled temperature of 20 oC (68 oF) for 5 days. There are also specific instructions for cleaning the bottles and preparing dilution water that is not contaminated. The procedure in your kit is simplified and therefore the results will not match those from the Standard Methods procedure.
- What is Standard Methods?
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Standard Methods is a reference book used for water testing in all drinking water and wastewater plants. It contains step-by-step procedures that are to be followed for measuring all aspects of water quality.
- How can I use the BOD glucose plus glutamic acid standard solution?
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This standard solution should only be used with the Standard Methods procedure because you must add microorganisms and nutrients, make dilutions, and incubate for 5 days at a carefully controlled temperature to get the correct result.
Conductivity
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How often do I have to calibrate the tester?
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For the best results, calibrate the tester every day that you use it to be sure it is reading correctly.
- Which conductivity standard should I use for calibration?
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Choose a standard that has a conductivity that is similar to the conductivity of your samples. If you do not know what the approximate conductivity of your samples will be, start with the 1000 uS/cm standard. If you find that your samples have a much higher or lower conductivity than this standard, choose a standard with a different conductivity for future calibrations.
- How do I store the tester?
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Rinse the electrode with distilled water and store dry with the cap on.
Nitrate
- When I repeat the test on the same sample, I get different results. What is wrong?
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This is likely due to the way the sample is shaken after the NitraVer5 or NitraVer6 reagent has been added. It is important to be consistent when shaking the sample, and it may be necessary to change the shaking time. The longer and more vigorously the sample is shaken, the higher the result.
To find what the best shaking time is, run the test with a nitrate standard solution instead of your sample. If your results are lower than expected, repeat the test by increasing the shaking time by 30 seconds or 1 minute until your results are close to the concentration of the standard. If your results using the standard are higher than expected, reduce the shaking time. Then use that shaking time for all your samples. Remember to measure and subtract the reagent blank when using the standard solution. When you receive a new lot of NitraVer reagent, you may need to adjust the shaking time again.
- How do I dispose of cadmium waste from the NitraVer reagents?
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It is important to follow hazardous waste regulations for disposal of waste from this test. Federal regulations may be superseded by state and local regulations, so it is important to check with a regulatory agency in your area for disposal instructions. The Environmental Protection Agency maintains a hotline where you can find local regulatory contact information; this hotline is 800-424-9346.
- I’m not getting any results. How can I tell if this test is working correctly?
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Open a Test Yes packet and dissolve in 1 liter of distilled water. Pour 10 mL of this solution into the sample cell and run the test as usual (add the reagents and wait the reaction time.) You will get a result using this solution.
For greater accuracy, you can use a sample of known nitrate concentration, called a nitrate standard solution. Run the test using the standard solution in place of your sample. If your result is close to the concentration of the standard solution, you can be sure that your reagents and instrument are working properly, and that you are performing the test correctly.
pH
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How often do I have to calibrate?
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For the best results, calibrate the tester every day that you use it to be sure it is reading correctly.
- Which buffers should I use for calibration?
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Two buffers should be used for calibration of a pH tester. If the expected pH of the sample is below 7, use pH 4 and 7 buffers. If the expected pH is above 7, use pH 7 and 10 buffers.
- How should I store the tester?
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During everyday use between sample measurements, store the electrode in either a pH 4 or 7 buffer solution. If storing for several weeks, rinse the electrode with distilled water and store dry. After long-term storage, let stand in pH 4 or 7 buffer solution for 30 minutes before using.
Phosphate
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Why do I have to multiply my results for total phosphorus by 1.2?
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This factor corrects for the increase in volume from adding sulfuric acid and sodium hydroxide to the sample. After 2 mL of sulfuric acid plus 2 mL sodium hydroxide are added to the sample, the volume changes from 25 mL to 29 mL. The dilution factor = 29 ÷ 25, or 1.2.
In the traditional digestion procedure, the sample is boiled and much of the sample evaporates. Distilled water is added at the end so that the final volume is exactly 25 mL, therefore no multiplication factor is required.
- I’m comparing my results with another group and my results are 3 times higher. What is wrong?
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Most likely you are comparing results that are not in the same chemical form. Many labs report phosphorus as mg/L P, which has a concentration that is approximately 1/3 the concentration as PO43-. This test kit reports results as mg/L PO43-, which is phosphorus as phosphate.
The same amount of color is measured in the test regardless of which form is used, but when this color is converted to concentration, different conversions are used for the different forms. The conversion to mg/L PO43- uses the weight of PO43-, whereas the conversion to mg/L P uses the weight of P, which is approximately 1/3 the weight of PO43-.
- I’m not getting any results. How can I tell if this test is working correctly?
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Open a Test Yes packet and dissolve in 1 liter of distilled water. Pour this solution into the mixing bottle or sample tube and run the test as usual (add the PhosVer3 and wait the reaction time.) You will get a positive result using this solution.
For greater accuracy, you can use a sample of known phosphate concentration, called a phosphate standard solution. Run the test using the standard solution in place of your sample. If your result is close to the concentration of the standard solution, you can be sure that your reagents and instrument are working properly, and that you are performing the test correctly.
- What is the long path viewing adapter?
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This is the small mirror that comes with the kit, and changes the orientation of looking at the tube from looking through the diameter to looking through the length of the tube. By looking through the length of the tube, more color can be seen. This is used for low concentration samples where not much color is formed.
- How do I know whether I should follow the low range, medium range, or high range procedure?
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If measuring water from a river, stream, or lake, use the low range procedure. Drinking water usually has low levels of phosphorus as well. Wastewater usually has higher concentrations. If you find that your sample measures above the range of the test, start with a fresh sample and repeat the test using a procedure for a different range.
Turbidity Tube
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Does it matter if I record the height when the disc disappears when I’m filling the tube vs. when the disc appears when letting the water
drain?
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Recording the height when the disc becomes visible as the water drains tends to give more reproducible results.
- A lot of bubbles form when I fill the tube. Will bubbles affect my measurement?
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If a lot of bubbles form when filling the tube, the water may appear more turbid than it actually is. It is best to wait briefly to let bubbles dissipate before draining the tube.
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