Design and Feasibility Evaluation of a Prototype Setup for Contemporary Easy Nitrates and Nitrites UV Detection in Water for Agriculture

Nitrates and nitrites are inorganic anions which, beyond specific concentration threshold, are classified as water pollutants. Nitrate compounds are commonly used as fertilizers; however, their high concentration in soil and in wastewater, as well as their reduction to nitrites, pose serious environmental and human health risks. Therefore, detecting these ions in water intended for human consumption, zootechnical use, and agricultural applications is essential. This work presents a proof of concept for a spectroscopic prototype setup enabling simple, direct, and simultaneous detection of nitrates and nitrites in water. The device employs solid-state sensor technology and requires no sample pretreatment or chemicals. Ultimately, this apparatus will allow real-time, in-line process analysis. UV absorption bands centered at approximately 302 nm and 355 nm were selected for detecting nitrates and nitrites, respectively. Because nitrite exhibits a slight absorption at 302 nm as well, a straightforward method for simultaneous nitrate and nitrite detection is proposed. The proposed system incorporates a UV deuterium lamp, a 10 cm path length optical cuvette, and a custom home-built silicon carbide detector. This configuration enables testing various concentrations, achieving detection limits of 2.2 mg/L for nitrates and 0.5 mg/L for nitrites. Potential interferences from substances commonly found in drinking and treated agricultural wastewaters, including sodium bicarbonate, sodium sulfate, ammonium chloride, hydrogen peroxide, and sodium hypochlorite, were also investigated. Finally, a compact on-site and online monitoring future device is illustrated.