Robust off-grid analyser for autonomous remote in-situ monitoring of nitrate and nitrite in water

Abstract

An off-grid, internet-of-things (IoT) connected ion chromatography analyser was developed for the real-time automated measurement of nitrate and nitrite levels in remote surface water applications. The system used KOH eluent with an AG15 guard column to achieve anion separation, in combination with a selective 235 nm UV-LED detector. A self-cleaning 3D printed Sediment Trap was developed to filter the sample before analysis, preventing silt and sediment from causing blockages and facilitating robust performance during long-term deployments. Laboratory tests showed reductions of up to 91% of total suspended solids and 61% of turbidity within the sample after a settling time of 5 min. In controlled temperature tests (7 to 40 °C), the average error in the detected concentration levels remained below 5%, indicating robust and repeatable performance of the analyser in varying environmental conditions. Two automated in-situ analysers were deployed at remote locations in West Cork, Ireland, for a period of one month. The deployments successfully demonstrated the capability of the system to detect transient pollution events, facilitating improved water-quality management of remote catchments. The analysers were monitored in real-time using a cellular IoT module and cloud-based dashboard.