Choramines and nitrification: Aquamonitrix® is being used in the US by water-utilities to control nitrification (nitrite-formation) in chloraminated drinking-water supplies.
Aquamonitrix® is a next-generation autonomous, real-time nitrite and nitrate analyzer that can reliably deliver the accuracy, specificity and extremely low limits of detection required to provide water reservoir and pipeline managers a timely warning of nitrification events in drinking water distribution systems.
Case Study: Nitrification control with Aquamonitrix®
As disinfectants, chloramines offer many benefits. One of the downsides, however, is the risk of nitrification, which can lead to a range of problems for drinking water providers.
These include the risks of exceeding maximum allowable concentrations of nitrate & nitrite; disinfectant depletion; an increase in heterotrophic plate count; dissolved oxygen depletion; reduced pH and alkalinity leading to corrosion problems; and the formation of disinfection by-products due to mitigation techniques.
One of our clients, a utility in a southwestern state of the US, had been experiencing nitrification problems in open-air drinking water storage reservoirs, leading to odour and taste issues at the customers’ taps.
The graph below illustrates how they used Aquamonitrix® to track increasing nitrite levels, allowing them to temporarily switch from chloramine to chlorine disinfection at the optimum time, to achieve a rapid fall-off in nitrification.
Nitrite limits were set using the accompanying Datamonitrix portal so that instantaneous alarms are sent directly to specified users’ PCs when levels are breached, allowing for real-time alerts.
How Aquamonitrix outperforms alternatives
Compared with hit-and-miss grab sampling and laboratory analysis, automated, real-time detection enables more proactive and precise nitrification control.
In the past, however, many utilities have struggled to achieve the desired performance with conventional real-time, autonomous nitrite analyzers based on UV, UV-LED, wet chemistry or ion-selective electrode techniques.
But Aquamonitrix® is fundamentally different in the way it works.
- Aquamonitrix® incorporates ion chromatography – the gold standard for laboratory analysis of nitrite (and nitrate) – in combination with UV-LED detection. This provides exceptional sensitivity, delivering the low levels of detection required for early identification of nitrification events.
- The separation capabilities of the ion chromatography column also ensure exceptional selectivity so that nitrite measurement accuracy is not impacted when nitrate levels are also high.
- The column acts as a ‘trap’ for air bubbles, turbidity and organics, resolving common sources of interference that affect other techniques in real-world environments.
- Only microfluidic volumes of eluent (reagent) are used, and the eluent is low-cost and non-hazardous, minimising handling, sample disposal and lifetime costs.
Reliable solution for utilities that have switched to chloramines
A reliable, autonomous, real-time alert system for nitrification is a major boon for the many utilities that have switched from chlorine to chloramine for secondary and/or primary disinfection. As a result of ever-tightening US EPA limits on disinfection by-products (DBPs), this switch has meant that, today, over 20% of the US population drinks water disinfected with chloramine.