Continuous nitrite and nitrate monitoring of recirculating aquaculture systems using a deployable ion chromatography-based analyser

Water quality and the management of nitrogenous compounds are of key importance within aquaculture. In this paper, automated and portable analysers for in situ analysis of nitrite and nitrate in water were deployed in freshwater and saline recirculating aquaculture systems (RAS). The analysers were based upon ion chromatography (IC) and employed a NaCl eluent with an anion exchange guard column for low backpressure anion separation, in combination with selective 235 nm ultra-violet light-emitting diode (UV-LED) based absorbance detection. The analysers were monitored and delivered real-time concentration data using a cellular internet of things (IoT) module and cloud-based dashboard. Overall performance and chromatographic repeatability were tested across various temperature profiles and 500 sequential runs within the laboratory. Deployments in freshwater and saline RAS, with concentrations ranging between 0.1-3.6 mg L-1 nitrite and 0.6-392 mg L-1 nitrate, were successful and the analytical performance was comparable to that of accredited lab-based instrumentation.