CALAGUA group is studying an alternative to the conventional treatment for nutrient removal based on cultivating microalgae in photobioreactors and separating them from the effluent by membranes (membrane photobioreactors or MPBR). Membranes can be used to obtain good quality reusable water.

Microalgae eliminate the nutrients present in the wastewater using Sunlight as energy source and while fixing atmospheric CO₂ , which presents beneficial effects on the environment.

The generated microalgae biomass can be used to generate energy by anaerobic digestion. Also, eliminating nutrients from the wastewater and recirculating the microalgae to an anaerobic digestion system promotes nitrogen and phosphorus enrichment in the sludge created by the system, thereby increasing its value as an agricultural fertiliser.

This means that using anaerobic processes and microalgae in a WWTP allows the recovery of nutrients from the water and energy generation in the form of biogas. One of the most important aspects of this research field consists of ensuring that the amount of biogas generated will compensate for the energy cost involved in the process, mostly due to stirring and filtration.