| Summary: | Microalgae have been in the center of research for several years due to their high production rates. The use of fresh-water algae in the production of biofuels coupled with wastewater treatment has become a topic of modern research. While most algal farming is performed in warm and sunny climate, this project focused on naturally occurring microalgae in Northern Sweden and their ability to reclaim wastewater and produce lipids. The four microalgae Chlorococcum sp. (MC1), Scotiellopsis reticulata (UFA-2), Coelastrella sp. (3-4) and Chlorella vulgaris (13-1) were grown under mixotrophic conditions in municipal wastewater (MWW), pulp and paper wastewater (PnP) and mixtures of both. Except of UFA-2, I found the growth of the tested species to be limited in pure PnP, however, mixtures of PnP and MWW were suitable for algal growth. The removal rates of total nitrogen achieved the goals regulated by the Swedish government for wastewater reclamation. Phosphorus, of which maximal levels according the Swedish regulations need to be below 0.5 mg/L, was efficiently removed by the strain 3-4 in PnP and in MWW + PnP (ratio 3+1) as well as by the strain 13-1 in MWW + PnP (ratio 3+1). The tested microalgae are therefore appropriate candidates to be used in sustainable wastewater treatment. The algal biomass composition was determined with the help of Fourier-transform infrared spectroscopy and an increase in the spectra for biomass grown in wastewaters within the fingerprint region (800 – 1800 cm-1) was observed. From this, I conclude that the lipid content was elevated in the biomass received after growth in PnP and all mixtures of MWW and PnP compared to the in BG11 grown biomass, which acts as a control group. A quantitative lipid analysis performed on the biomass of the strains UFA-2 and 3-4 confirmed higher lipid amounts after growth in PnP wastewater compared to growth in BG11. These findings show that the examined microalgae might have the potential to be used as a potential feedstock for biofuel productions after ...
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