The Do's and Don'ts of Ammonia Monitoring

15th June 2021
Jon Penn,
Global Product Line Manager - CWA
Measurement & Analytics

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While we’re all used to the benefits of ammonia as a cleansing agent in the home, in the wider environment excessive concentrations can be potentially catastrophic, especially in streams and rivers.

Naturally occurring in the environment, ammonia is simply a compound of nitrogen and hydrogen with the formula NH3. It is usually found in low concentrations in many natural water sources.

Ammonia can enter watercourses in several ways. While the main sources of ammonia are natural, including human and animal waste and decaying organic matter, levels can be increased by human activities, specifically agricultural fertilisers, waste disposal and industrial processes.

Ammonia is commonly used for cleaning in the home (Picture credit: Shutterstock.com)

Ammonia levels higher than around 0.1 mg/L are an indicator of a polluted water source and can cause harm. It can also overstimulate plant growth or cause algal blooms, leading to a drastic reduction in the oxygen needed to support aquatic life. You would think perhaps that more plant life means more oxygen, but the problem here is twofold; the additional algal blooms can restrict sunlight reaching other organisms that need it for photosynthesis, but also the algae switches from photosynthesis during the day to respiration at night which is why oxygen levels decrease.

In addition to this, in a concentrated form, ammonia is both a caustic and hazardous substance and is toxic to both fish and other aquatic organisms. The result is dead rivers and lakes, devoid of fish.

So, monitoring ammonia levels is vital, but how can we ensure the best results? Where should you monitor, how often should samples be taken, what technologies can you use and what should you look for in an instrument?

Decide where to monitor

At which stage in the water use and treatment cycle will you be measuring ammonia – water intake, chloramination, effluent from industrial sites, aeration, filtration and final discharge of water to the environment. For what purpose - assessment of river water quality, disinfection control, compliance and consent monitoring, or optimization of treatment processes. Once you have assessed where you will be measuring, and for what purpose you can choose a solution that is suitable for the intended use. Accuracy, monitoring frequency and how the data is read and communicated will all play a part in your decision.

Close control of ammonia and other substances can avoid algal blooms and ensure a healthy aquatic environment in streams, rivers and lakes relies on. (Picture credit: Shutterstock.com)

Choose the right technology

You will need a good idea of the level of ammonia you’ll be looking at so you can choose the right technology. One popular monitor uses Ion Selective Electrode (ISE) technology to measure levels of 0.050 to 1000 mg/L, but some applications may demand a device capable of a lower range. Another monitor from the same vendor uses colorimetric technology to achieve reliable and highly accurate measurement of low-level ammonia concentrations from 0 to 3 mg/L. Also, do you need continuous measurement or will a few measurements per hour suffice? The ISE meter offers continuous monitoring, while the colorimetric version can provide up to four measurements per hour.

ABB Aztec Ammonia Analysers

Ensure you get maximum accuracy

Temperature variations can lead to significant measurement errors. To avoid this, ensure the device you choose can control both the sample and electrode temperature. The ammonia electrode should be housed in a fully enclosed temperature-controlled cell ensuring a constant temperature is maintained during both calibration and measurement. Some monitors will use a buffer reagent to provide a true measurement of the total sample concentration.

Set it up right

Of course, accuracy also depends on accurate calibration. Monitors with automatic two-point calibration use a low sample based on deionized water and a high sample based on 0.35 ppm NH3. This provides calibration by calculating the calibration gradient and comparing to theoretical values

LED calibration involves the instrument checking it is achieving the optimum span on the detector and automatically adjusting if required. This process accounts for any drift or cell fouling that may have occurred.

Make maintenance easy

After doing all the above, don’t make the mistake of choosing a monitor that is difficult or expensive to maintain. Look for ones that can work for months without the need to change reagent and which make annual analyser servicing easy. Also look out for low maintenance electrodes and inbuilt diagnostics.

Look for vendors that supply annual maintenance kits, which should provide all the necessary consumables, complete with step-by-step guidance on what to do.

Keep it clean

Part of achieving the accurate results you need is keeping the measuring components clean. Some ammonia monitors can continually clean their measurement cell as a normal part of their action. Cell rinsing can also be conducted, using a sample to clean the cell before measurement takes place. In some devices, additional cleaning sequences can be commanded by the user.

For both ISE & colorimetric ammonia analyzers, regular inspection and cleaning of the main components will also help. This includes probe membrane and the reference solution level, the side sample pot, the sample handling pipework and the ample pre-filtration system. Most of these should be cleaned monthly. Replace reagents as required, typically every 40 to 240 days.

Follow the steps for a healthy environment

Ammonia is a problematic chemical that needs to be minimized in our water supplies and water sources – choosing a good analyzer and following these tips should put you on the path to keeping it under control.