Novel Microelectrode-Based Online System for Monitoring N2O Gas Emissions during Wastewater Treatment

Marques, Ricardo; Oehmen, Adrian; Pijuan, Maite

Novel Microelectrode-Based Online System for Monitoring N2O Gas Emissions during Wastewater Treatment

2014

Marques, Ricardo | Oehmen, Adrian | Pijuan, Maite

Clark-type nitrous oxide (N₂O) microelectrodes are commonly used for measuring dissolved N₂O levels, but have not previously been tested for gas-phase applications, where the N₂O emitted from wastewater systems can be directly quantified. In this study, N₂O microelectrodes were tested and validated for online gas measurements, and assessed with respect to their temperature, gas flow, composition dependence, gas pressure, and humidity. An exponential correlation between temperature and sensor signal was found, whereas gas flow, composition, pressure, and humidity did not have any influence on the signal. Two of the sensors were tested at different N₂O concentration ranges (0–422.3, 0–50, 0–10, and 0–2 ppmv N₂O) and exhibited a linear response over each range. The N₂O emission dynamics from two laboratory scale sequencing batch reactors performing ammonia or nitrite oxidation were also monitored using one of the microsensors and results were compared with two other analytical methods. Results show that N₂O emissions were accurately described with these microelectrodes and support their application for assessing gaseous N₂O emissions from wastewater treatment systems. Advantages of the sensors as compared to conventional measurement techniques include a wider quantification range of N₂O fluxes, and a single measurement system that can assess both liquid and gas-phase N₂O dynamics.

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