Why test for Total Ammonia in drinking water if testing for mono chlorimines, free chlorine and free ammonia?
Published on by David Tooley, Water/Wastewater Operator at US Water corp in Technology
Taxonomy
- Standards & Quality
- Drinking Water Treatment
- Test & Measurement
- Chlorine Dioxide Treatment
- Testing Kit
- Annamox
4 Answers
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Long Answer: Not all of you ammonia will necessarily be present as monochloramine. A while back I was involved in a large study that was tracking monochloramine along a 800km (500 mile) pipeline. At the beginning of the process the total ammonia and total chlorine agreed with each other, however, as time passed they started to fall further and further apart indicating that the monochloramine system was failing.
Short Answer: It is a good check to do to confirm that your system is operating as expected.
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Depending on what analyzer or lab test you are using, one definition of 'total ammonia' is sum of the monochloramine concentration (in mg/L as N ) + the free ammonia concentration (mg/L as N). Since monochloramine is typically expressed in mg/L of Cl2, total ammonia is a means of tracking the total amount of nitrogen a utility is putting out into their distribution system, and can ultimately help if there are issues with excess biofilm growth, chlorine demand/residual loss or nitrification in the distribution system.
It should be noted that another common definition of total ammonia is the sum of ionized ammonia, aka ammonium (NH3+) and unionized ammonia (NH3). Some methods of analysis covert all of the species to the same form before analysis. The proportions of ammonia in water existing in either of these states depends on the pH of the water. I presumed it's the monochloramine-focused definition you were looking for since you're chloraminating.
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Total ammonia will be a predictor for total Cl2 dosage to get you to breakpoint chlorination. If you are just going to up your dose chlorine dose until you measure "free" then you probably don't need total.