Finally, domestic wastewater is a residue of interest for biofuels
production from microalgae. Microalgae ponds can be used in
secondary or tertiary treatment. This would bring advantages
such as cost effectiveness, low energy requirements, reduction
in sludge formations, greenhouse gas mitigation and the production
of useful microalgal biomass. Wastewater production by human
activity is ubiquitous, and the continuous increase in world population, particularly in developing countries, makes it an inexhaustible
resource. Because the use of microalgal biomass grown
in domestic wastewaters as a human and animal food supplement
faces toxicological problems, intensive research is being carried
out on the promotion of lipid accumulation for further biodiesel
production.