Climate change and increasing world population call for careful utilization of water and energy sources. Microalgae to treat wastewater in a coupled process to produce biofuels and other value-added products for human consumption are promising solutions. An analysis of culture parameters and cultivation processes is presented as essential to achieve economical sustainability from the algae. Results of the activity of microalgal strains in detoxification of wastewater are compared and discussed, particularly in remediation of nitrogen and phosphorous compounds, heavy metal, pharmaceuticals and personal care products. Phycoremediation mechanisms and culture conditions to obtain optimal microalgal growth are discussed. Finally, valuable products that can be produced by microalgae and ecological problems of untreated wastewater are presented.

Carbon dioxide emissions are strongly related to climate change and increase of global temperature. Whilst a complete change in producing materials and energy and in traffic and transportation systems is already in progress and circular economy concepts are on working, Carbon Capture and Storage (CCS) and Carbon Capture and Utilisation (CCU) represent technically practicable operative strategies. Both technologies have main challenges related to high costs, so that further advanced research is required to obtain feasible options. In this article, the focus is mainly on CCU using microalgae that are able to use CO2 as building block for value-added products such as biofuels, EPS (Extracellular Polymeric Substances), biomaterials and electricity. The results of three strains (UTEX 90, CC 2656, and CC 1010) of the microalgal organism Chlamydomonas reinhardtii are discussed. The results about ideal culture conditions suggest incubation temperature of 30 °C, pH between 6.5 and 7.0, concentrations of acetate between 1.6 and 2.3 g L–1 and of ammonium chloride between 0.1 and 0.5 g L–1, the addition of glucose This green microalga is a valid model system to optimize the production of biomass, carbohydrates and lipids.