Automated micro Loop Flow Reactor technology to measure nutrients in coastal water: State of the art and field application

Nutrient pollution is one of worldwide most diffused, expensive and challenging environmental issues. The monitoring of nutrients in coastal areas is a complex task, due to the fact that the available methods reaching the required sensitivity are based on optical wet chemistry measurements. In order to be representative, a reliable water sample collection for further laboratory analysis requires a very strict protocol and sample handling. Because of this, most of the scientists agree in affirming that the best and practical solution is to measure nutrients directly on field. SYSTEA S.p.A. has been working in the last two decades to improve automated solutions for on-line nutrient monitoring. The micro Loop Flow Reactor (μLFR) technology was presented in 2009 in Oceans conference in Biloxi (USA) and is currently a consolidated technique allowing the field measurement of nutrients in different environmental conditions. Fast growing urbanization and industrialization of river basins and coastal areas in China are imposing the local Government to improve large water quality monitoring networks; during the last few years, around one hundred in-situ nutrient multi-parameter probes (NPA pro and WIZ) were installed and provided extensive long term data to support the environmental control and related decisions making policy. The WIZ probe is an advanced real time instrument to measure the nutrient concentrations in aquatic environments. In particular, it is the only portable and submersible equipment able to measure the total concentrations of both phosphorus and nitrogen. The uniqueness of this probe is given by the fact that the unit performing the sample digestion, required for the analysis of both total phosphorus and nitrogen, was downscaled to fit within the probe. The efficiency of NPA pro and WIZ probes in measuring the concentrations of ammonia, nitrate, phosphate and nitrite was evaluated on field deployments in coastal waters, in China and South Korea, respectively. Importantly, the probe results were found to be highly correlated with laboratory measurements. The μLFR technology was also applied to the design and manufacturing of μLFA modules, on-line nutrient analyzers integrated in Ferrybox systems for the measurement of ammonia and orthophosphates. In situ results obtained in Ferrybox installations were compared and correlated with laboratory analysis of grab samples. Finally, a number of practical solutions for the improvement of NPA pro and WIZ probes in terms of instrument robustness, data reproducibility, deployment life and reliability, were, for the first time, presented and discussed. The Alliance for Coastal Technologies (ACT) is a US partnership of research organizations, water stakeholders and private companies competent in the field of nutrient management which, by means of dedicated market surveys, were able to catalogue the most frequently requested specifications for nutrient analyzers. This record was used as a guide to assess the current performance level of μLFR-based probes and modules with respect to market expectations. In conclusion, the main factors which facilitated the global diffusion of this technology were lower equipment costs than analogous products and the ability of providing highly experienced timely technical support at the local level.