Estimation of states in photosynthetic systems via chained observers:design for a tertiary wastewater treatment by using Spirulina maxima on photobiorreactor

The cultivation of microalgae has currently shown a growth in interest because it has shown significant contributions to the production of energy, high-quality food and as agents for tertiary treatment of wastewater. Microalgae culture are carried out on photobioreactors, which are often very complex. Therefore, the automatic control of these devices can be very difficult and the lack of in-line sensors makes it difficult to control them. For this purpose, state observers have proven to be an excellent tool for measuring variables that cannot be measured online. In this work, we propose the theoretical design of a robust linear type observer, the so-called Chained Observer. Stability is demonstrated through Lyapunov functions and an observer is didactically designed for the study of tertiary wastewater treatment by demonstrating that under certain conditions, the Chained Observer presents better yields than even more sophisticated observers. A simple technique is presented for multi-disciplinary researchers.

Keywords: Spirulina maxima, observers, photobioreactor, Lyapunov.