Desarrollo de un sensor virtual basado en la medición de la conductividad para la monitorización de nutrientes en cultivos de microalgas.Un estudio preliminar

Abstract

Microalgae are photosynthetic organisms that can grow under light and convert CO2 into valuable biomass. Nowadays, microalgae biomass is attracting the interest of new merging industrial sectors such as biofuels, biopesticides, human nutrition, cosmetics and aquaculture. One of the key parameters for optimal microalgae growing is adequate nutrient supply. Microalgae, apart from light, carbon, and water, need macronutrients such as nitrogen (N) and phosphorus (P) to grow. In microalgae production with clean water, these nutrients are supplied in the form nitrates (NO3-) and phosphates (PO4 3-), respectively. However, the nutrients are generally provided by fertilizers, representing a high cost of the overall production. For this reason, optimizing the overall salts' contribution to the culture is fundamental not limiting their groth and reducing costs. In this framework, it was developed an online sensor for the nutrients (NO3 -, PO4 3-) tracing in a microalgal culture using a conductivity probe. Using the signal provided by the sensor, it was possible to determine the concentration of salts in the culture from a mathematical correlation and by measuring theconductivity constants in the laboratory. The described correlation was determined first in small lab scales and then in real systems (Raceways reactor, 12 m3) with a high accuracy (R2=0.8). The results obtained are promising as they may allow to reach a good mathematical approximation to estimate the salts' concentration using the conductivity measure.