Coupled cultivation and pre-harvesting of microalgae in a membrane photobioreactor (MPBR).

A new and effective concept is proposed for microalgae cultivation and pre-harvesting using a membrane photobioreactor (MPBR), in which the bioreactor is coupled to membrane filtration by cultivating Chlorella vulgaris. A basic simulation was first performed to understand the behavior of the hybrid system. The effectiveness of the MPBR for cultivation and pre-harvesting was proven. The membrane completely retained the biomass, which then was partly recycled into the bioreactor to maintain a high biomass concentration, thus enhancing flexibility and robustness of the system. The MPBR can operate at both higher dilution and higher growth rates, resulting in a 9× higher biomass productivity. In addition, pre-harvesting can be achieved by applying variable concentration factors in the filtration stage. The membrane permeate was recycled to the reactor as feed medium without affecting the algae growth, which offers a substantial reduction of 77% in the water footprint.