Chloramines & Nitrification Problems : Aquamonitrix Provides a Solution

Background

Nitrification is a microbial process that converts ammonia and similar nitrogen compounds into nitrite (NO2–) and then nitrate (NO3–). Nitrification can occur in water systems that contain chloramines. The problem is greatest when temperatures are warm and water usage is low. Monitoring of nitrite and nitrate is traditionally carried out using lab analysis. The long lead time and degradation of sample before lab analysis means that traditional methods are limited when considering nitrification events. Water companies are starting to use real time online monitoring to allow automatic mitigation of nitrification by, for example, chlorine dosing in the network. Accurate real-time in-situ monitoring of nitrite and nitrate across all distribution systems is now possible through the Aquamonitrix® analyser.

Using NO2– and NO3– data to monitor nitrification in chloraminated water.

Water supply systems using chloramine disinfection can often experience water quality problems caused by biological nitrification. Resulting from the decay of chloramine, ammonia nitrogen can be released into the water, and incomplete nitrification can lead to the accumulation of nitrite, bringing about potential human health hazards. Biological nitrification can also promote the growth of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) and promote the formation of pipe network biofilm or sediment, providing an environment for large-scale reproduction of bacteria, reducing the biological stability of drinking water. Finally, nitrification can result in a large amount of dissolved oxygen, lower the pH value, and accelerate pipeline corrosion (Liu et al. 2020, Int. J. Environ. Res. Public Health. 17(3): 772) According to the WHO, Guidelines for Drinking-water Quality, chloramination often gives rise to the formation of nitrite within water distribution systems, and the concentration of nitrite may increase as the water moves towards the extremities of the system. Nitrification in distribution systems can increase nitrite levels, usually by 0.2 – 1.5 mg of nitrite per litre, but potentially by more than 3 mg of nitrite per litre. The Aquamonitrix® analyser provides, for the first time, a means to obtain real-time accurate nitrite and nitrate data within chloraminated water systems. Through this real-time data, nitrification events can be identified early, and action can be taken to stop the event. An example of this data is illustrated in Figure 1. A photograph of the analyser installed in-situ within the drinking water facility is shown in Figure 2, with photographs of analyser shown inset. This data highlights an example from a drinking water facility in the United States where real-time nitrite data, delivered by the Aquamonitrix® analyser, was used to identify nitrification events, enabling operators to take action to address the event.

Figure 1: Real-time nitrite and nitrate data delivered by Aquamonitrix® analyser within a chloraminated water system.

Figure 1: Real-time nitrite and nitrate data delivered by Aquamonitrix® analyser within a chloraminated water system.

Summary

The Aquamonitrix® analyser is a valuable tool for the real time online determination of nitrite and nitrate in chloraminated water systems. The real time data allows for early intervention should an issue arise. This is particularly important in systems with warmer water temperature, higher levels of organic matter and longer water ages which have a higher nitrification risk.