Chloramines & Nitrification Problems : Aquamonitrix Provides a Solution

The Aquamonitrix® Nitrite & Nitrate Analyzer enables water pipeline and reservoir managers to track nitrite (and nitrate) levels in real-time and receive an instantaneous alert when concentrations rise above their pre- set threshold levels at key points in the water distribution system

This allows for timely intervention (for example, temporarily switching from chloramine to chlorine disinfection) to halt the nitrification process, minimising impacts on the quality of water destined for customer’s taps.

Nitrite limits can be set using the proprietary Datamonitrix portal, with instantaneous alarms sent directly to specified users’ PCs when levels are breached, allowing for real-time alerts.

Chloramines are produced by mixing ammonia and chlorine.

They are recognized as safe disinfectants, used for their longer life- span within the water network and to avoid the formation of regulated disinfection by-products (DBPs).

However, nitrification can occur when bacteria ubiquitous in air, water
and soil (AOB/NOB bacteria) convert excess or released ammonia to nitrite and subsequently nitrate.

Problems associated with nitrification include

  • Risk of exceeding maximum allowable concentrations of nitrate & nitrite (methemoglobinemia /blue baby syndrome risk)
  • Disinfectant depletion (microbial problems)
  • An increase in AOB & NOB/ heterotrophic plate count (HPC)
  • Dissolved oxygen depletion • Reduced pH and alkalinity (corrosion problems)
  • DBP formation due to mitigation techniques.

Factors that can Influence nitrification include pH, flow, biofilms, water age, light and temperature.

Nitrification control with Aquamonitrix®

Our client, a utility in a southwestern state of the US, had been experiencing nitrification problems in open-air drinking water storage reservoirs, resulting in odor and taste issues at the customers’ taps.

By deploying a number of Aquamonitrix® Nitrite and Nitrate analyzers in the reservoirs, the utility has been able to track nitrite levels in real-time.
This has allowed the operators to intervene at the optimum point with break-through chlorination to rapidly halt the nitrification process before odor and taste become an issue for drinking water consumers. (See graph )

Compared with hit-and-miss grab sampling and laboratory analysis, real-time automated nitrite monitoring enables proactive nitrification control, allowing timely intervention so that drinking water providers can benefit from increased consumer confidence and satisfaction.

The graph shows how Aquamonitrix® has tracked increasing nitrite levels, alerting the operators and allowing them to temporarily switch from chloramine to chlorine disinfection at the optimum time point, to achieve a rapid fall off in nitrification (nitrite formation).

Why Aquamonitrix® outperforms existing nitrite analyzers

Utilities have struggled to achieve this performance with conventional real-time, autonomous nitrite analyzers based on UV, UV-LED, wet chemistry or ion selective electrode techniques.

But the Aquamonitrix® analyzer is fundamentally different in the way it works.

Aauamonitrix® incorporates ion chromatography – the gold standard for laboratory analysis of nitrite (and nitrate) – in combination with UV-LED detection.

 

  • This provides exception sensitivity, delivering the low levels of nitrite detection required for early identification of nitrification events.
  • The chromatography separation step (based on the lower ionic attraction of the nitrite ions to the column – (see illustration below) means the nitrite reaches the UV- LED detector first, enabling It to be measured accurately with high specificity – even when nitrate levels are also high.
  • The column also acts as a trap for air bubbles and condensation, which can cause interference with optical detection methods, such as conventional UV and UV-LED.
  • Only microfluidic volumes of eluent (reagent) are required – and the
    eluent is low-cost and non-hazardous, minimising handling, sample disposal and lifetime costs, compared with colorimetric methods.