A Lab-on-a-Drone for turbidimetric and nephelometric analysis of environmental water samples with real-time data transmission

Abstract

This study reports the development and validation of a turbidimeter/nephelometer coupled to an unmanned aerial vehicle (UAV), constituting a Lab-on-a-Drone platform for real-time water analysis with data transmission via Wi-Fi. The system is based on turbidimetric and nephelometric detections using light-emitting diodes (LEDs) operating at 405 and 890 nm. Calibration curves were obtained for both detectors, and the 890 nm LED combined with infrared sensors exhibited superior performance and was therefore selected for validation. Linear working ranges of 0.50–40 (NTU, Nephelometric Turbidity Units) for nephelometry and 40–1000 (FAU, Formazin Attenuation Units) for turbidimetry were achieved, with limits of detection and quantification of 0.12 and 0.38 NTU and 11.13 and 37.12 FAU, respectively. The method was applied to turbidity determination in compliance with international and national regulations, including those of the United States Environmental Protection Agency (USEPA), which recommends turbidity values below 1.0 NTU; the World Health Organization (WHO) and the Brazilian Ministry of Health (MS), which establish limits of up to 5.0 NTU. Accuracy and precision were evaluated by comparison with a benchtop turbidimeter, and no statistically significant differences were observed at a 95% confidence level (n = 3) using t- and f-tests. The Lab-on-a-Drone system integrates a micropump, a solenoid valve, and an optical detector, is remotely controlled via a smartphone, is powered by solar energy, and represents a sustainable alternative for water quality monitoring.