## 6 Specific Applications of Wastewater Bioprocessing with Simultaneous Biofuel Production  
### Municipal Wastewater and Bioethanol/Bidiesel Production  
In the context of investigating the production of bioethanol from microalgae in municipal effluent substrate, the study of Onay [43] evaluated Hindakia tetrachotoma ME03 at various wastewater concentrations. The waste, after sterilization, was mixed with Bold's Basal Medium (BBM) in concentrations of 0%, 25%, 50%, 75%, and 100%. The maximum biomass productivity (0.097 g/L/d) was observed in the 25% sample, but the 50% sample had the highest specific growth rate (m) = 4.89/d, compared to the value of the 25% sample of 4.74/d, with slightly lower biomass productivity (0.090 g/L/d). In addition, the 50% sample had the highest carbohydrate content (23.6 \(\pm\) 0.4%). With these criteria, the 50% waste concentration sample was selected to be tested for bioethanol production through fermentation. The maximum bioethanol concentration (11.2 \(\pm\) 0.3 g/L) was observed at 36 h of incubation with Saccharomyces cerevisiae, with a percentage yield of 94 \(\pm\) 2.2%. The conclusions of the study showed that the selected strain H. tetrachotoma ME03 can be considered a type of mycoalgae for bioethanol production in municipal wastewater substrate, giving satisfactory results, after solving bacterial and fungal contamination problems through specialized technologies [43]. Satisfactory yields in biodiesel production and simultaneous treatment of municipal waste are recorded in the study of [PERSON] et al. [44]. The effluent samples examined came from inputs to wastewater treatment facilities near New Delhi, India. They were diluted to concentrations of 25, 50, and 100%, after being sterilized with synthetic substrate BG-11. The strain used was Scenedesmus sp. ISTGA1, isolated from the rock surface of a marble mining area adjacent to New Delhi. The crops lasted 14 days and the results showed satisfactory removal of heavy metals and a plethora of organic substances. The strain performed better on all three wastewater samples than on the reference sample artificial substrate (BG-11). Indicatively, concentration reductions of 91.50, 92.09, and 82.30% were recorded for Zn, Fe, and Al, and complete removal of Cd, Ni, Pb, and Co. At the same time, there were large decreases in BOD and COD values, of 86.74% and 88.82%, respectively, while nitrates and phosphates were completely removed. In relation to lipid production, the maximum production was achieved by the 100% waste sample. According to the above, the strain _Scenedesmus_ sp. ISTGA1 can be used for the development of municipal effluent bioremediation technology with simultaneous sustainable biodiesel production [44]. The study by [PERSON] and [PERSON] [45] evaluated the potential of microalgae of marine origin of _Tetraselmis indica_, in relation to three other freshwater plants, for the treatment of municipal waste for the production of fatty acids for conversion to biodiesel with simultaneous bioremediation. Samples were taken from primary and secondary treatments of local municipal wastewater treatment facilities at a university site in India and the crops lasted 14 days. Bioremediation in all samples was satisfactory, as both organic carbon (71.16-85.70%) and the nutrients nitrogen (63.6-78.24%) and phosphorus (60.90-65.97%) were removed. The measurements showed that _Tetraselmis indica_ had the most satisfactory yields compared to the others, and the highest biomass yield amounted to 0.6533 g/L, while lipid productivity amounted to 25.44 mg/L/d, in the secondary sample. The profile of fatty acids produced from the biomass met the specifications for biodiesel production and use in internal combustion engines, as it included myristic (1.2%), pentadecyclic (0.28%), palmitic (10.32%), oleic (34.59%), linoleic (12.38%), and eicosanoic acids (14.88%) [45].