Ammonia in Water

Introduction

The amount of ammonia in a water sample will be found by using the TesTab^® color concentration method.

Concepts

• Concentration of ammonia
• Parts per million
• Water testing 

Background

When ammonia is intoduced to water it is converted to nitrates by the process of nitrification. Nitrification is the process during which nitrifying bacteria convert toxic ammonia to less harmful nitrates. By way of nitrification, ammonia is often the primary or secondary source of nitrates for plants. Ammonia is found in water from excretions of aquatic organisms and from bacterial decomposition of organic waste. Ammonia is generally found in very low amounts in water that is non-polluted and in water that contains a high amount of oxygen.

The amount of ammonia aquatic life can withstand is highly dependent on the pH and temperature of the water. As pH and temperature decrease, more total ammonia can be tolerated. The following table is an example of how pH and ammonia can affect aquatic life (specifically salmon in this study). Lethal concentrations were derived form levels at which half the exposed individuals died.

Water that contains 5 to 10 parts per million of ammonia indicates that there is a high amount of decaying matter and low dissolved oxygen in the water. Ammonia is an essential nutrient for life but high levels may also cause changes in the metabolism and pH levels of organisms.

Materials

Safety Precautions

Ammonia #1 TesTabs^® and Ammonia #2 TesTabs contain chemicals that may be harmful and irritating if absorbed through the skin or if swallowed. Ammonia #2 TesTabs contain less than 0.5% lithium carbonate. The TesTab reagents used in this kit were designed with safety in mind. The single-use, foil-packaged TesTabs are easy to dispense. Store TesTabs in a cool, dry place and only open when ready to use the tablet. A single tablet, either alone or reacted with a sample, is a very low health hazard; however, TesTabs should not be ingested. Wear chemical splash goggles and chemical-resistant gloves. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. In the field, reacted samples may be poured into a container for later treatment. Reacted samples may be flushed down the drain with excess water according to Flinn Suggested Disposal Method #26b.

Procedure

1. Fill the water sample tube to the 5-mL line with the water sample.
2. Add one Ammonia #1 TesTab^® to the tube.
3. Cap the tube and mix the solution until the tablet has dissolved.
4. Add one Ammonia #2 TesTab to the tube.
5. Cap the tube once again and mix the solution until the tablet has dissolved.
6. Wait for five minutes.
7. Compare the color of the water sample to the Ammonia color comparison chart.
8. Dispose of the reacted sample according to the instructor.

Teacher Tips

• Enough materials are provided for 15 tests.
• It’s a good idea to collect several samples from each site that is tested. It is also wise to test the samples within one hour of collection if possible.
• Ammonia #1 TesTabs^® and Ammonia #2 TesTabs contain lithium hypochlorite and sodium salicylate. Ammonia reacts with salicylate at high pH in the presence of a chlorine donor and an iron catalyst to form an indophenol dye in proportion to the amount of ammonia in the sample.
• A wait of five minutes is required to allow time for the overall reaction to take place.
• The range of the ammonia TesTab test is between 0 and 4 ppm.

References

U.S. Environmental Protection Agency. Ambient Water Quality Criteria for Ammonia. (EPA 440/5–85–001) January 1985.