Microalgae photobioreactors: A resource for tertiary wastewater treatment

Los fotobiorreactores de microalgas: Un recurso para el tratamiento terciario de aguas residuales

Abstract

Microalgae are photosynthetic organisms and are found in nature with a wide diversity of taxonomies. Multiple industrial applications have been reported that are based on a series of advances in the development of the field of biotechnology of these organisms. These developments range from the production of biofuels, fertilizers, supplements for human nutrition and breeding animals to the contribution of inputs for the pharmaceutical industry. One of the best documented applications of these cultures is their use for wastewater treatment in the final stages of the purification process. The cultivation of microalgae at an industrial level presents a series of difficulties due to the high cost of the process and the instability of the cultures due to the variable conditions of the environment and the contamination of the nutrient medium with other microorganisms. An alternative to overcome some of these problems is the use of photobioreactors. A photobioreactor is a closed device designed to produce photosynthetic microorganisms with a high biomass yield as long as optimal requirements are met. Growing algae in a photobioreactor reduces the risk of contamination, improves reproducibility under cultivation conditions, provides greater control of hydrodynamic and temperature conditions, and allows for appropriate technical design. Technological advances in the design of these systems have significantly improved the productivity and therefore the economy of crops for different purposes. This article aims to critically present information about the different designs of photobioreactors, as well as the factors that affect the cultivation of microalgae in this type of devices and will focus on the tertiary treatment of wastewater. From the information collected in this work we can suggest the use of these devices and in particular those that are built on a small scale as a resource to reduce the pollution of wastewater from industrial and urban sources.