Abstract
The detection of nitrate pollutants is a widely used strategy for protecting water sources. Although ion-selective electrodes (ISEs) have been considered for the determination of ion concentrations in water, the accuracy of ISE technology decreases owing to the signal drift and decreasing sensitivity over time. The objectives of the present study were: (1) to develop an online water monitoring system mainly consisting of an Arduino board-based Internet-of-Things (IoT) device and nitrate ISEs; and (2) to propose a self-diagnostic function for monitoring and reporting the condition of the ISEs. The developed system communicates with the cloud server by using the message queuing telemetry transport (MQTT) protocol and provides monitoring information through the developed cloud-based webpage. In addition, the online monitoring system provides information on the electrode status, which is determined based on a self-diagnostic index (SDI, with a range of 0–100) of the electrode drift and sensitivity. The diagnostic method for monitoring and reporting the electrode status was validated in a one-month-long laboratory test followed by a field test in a stream near an agricultural facility. Moreover, a self-diagnostic index (SDI) was applied in the final field experiments with an accuracy of 0.77.
Highlights
In many parts of the world, rapid industrialization and population growth in urban areas have increased the water demand and gradually worsened the water quality owing to the depletion of the water volumes in rivers
The effectiveness of the developed online monitoring system and self-diagnostic algorithm was tested by continuously measuring a sample in the laboratory setting for three days
This paper proposes an algorithm that diagnoses the status of ion-selective electrodes (ISEs), displays the replacement time, and verifies its own effectiveness
Summary
In many parts of the world, rapid industrialization and population growth in urban areas have increased the water demand and gradually worsened the water quality owing to the depletion of the water volumes in rivers. The dams and reservoirs, which have been constructed to retain and manage such water resources efficiently, slow down the cycling of the water volumes in the river systems; the pollutants cannot be fully removed, and the water quality degenerates. The excessive inflow of nutrient salts such as nitrates and phosphates causes multiple problems such as eutrophication, which results in the growth of algal blooms and reduced water availability. Managing these pollutants requires special government-driven management programs [1,2]. Monitoring systems for aquatic environments play a crucial role in various water uses such as human usage, aquaculture, livestock watering, irrigation, and agricultural fertigation. Accurately measuring ionic concentrations can provide useful information on the biogeochemistry of aquatic ecosystems [5]
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