Integrated nutrient removal and biogas production by Chlorella vulgaris cultures

Changes in global nutrient cycles as a result of industrialization affect both ecosystems and human well-being. A clear example of human manipulation on ecosystems is eutrophication; a phenomenon caused in receiving water bodies by discharge of urban sewage rich in nutrients such as nitrogen (N) and phosphorus (P). Microalgal nutrient removal is a viable alternative for biological wastewater treatment, considering high nutrient uptake capabilities of microalgae. These systems are also advantageous in terms of nutrient recycling and conversion into microalgal biomass, which, in turn, is a beneficial resource for biofuel production. In addition, microalgae can also aid reduction in atmospheric carbon dioxide levels, as a result of photosynthetic anabolism. In this study, a semi-continuous photobioreactor was operated for investigation of nutrient removal efficiency of unialgal culture, Chlorella vulgaris. Maximum N and P removal efficiencies of 99.6% and 91.2% were achieved in the photobioreactor. Biogas production from biomass obtained from semi-continuous photobioreactor was investigated via Biochemical Methane Potential assays. The results illustrated that maximum biogas yield of 442-ml/g Volatile Solids (VS) added could be achieved in anaerobic batch reactors fed with microalgal slurry.