This study investigated the effects of the light conditions on the productivity of scenedesmus dimorphus in the continuous mass cultivation system. To compare the algal productivity according to the light conditions, S. dimorphus was cultivated continuously under the wide range of light intensity(200-600 PPFD) and various light wavelength(white light and red-blue mixed light). After 100 days of cultivation under the different light intensity, the productivity of S. dimorphus increased as light intensity decreased. So, the productivity was maximized as 100 mg/L/d when light intensity was 200 PPFD. In case of light wavelength, the productivity of S. dimorphus was enhanced about 20% with the white light compared to that of the red-blue mixed light. Consequently, the optimal light conditions for the continuous mass cultivation of S. dimorphus were 200 PPFD as light intensity and white light as light wavelength.

This study investigated the effect of a co-culture of Scenedesmus dimorphus and nitrifiers using artificial wastewater on the removal of ammonium, nitrate and phosphate in the advanced treatment. To test the synergistic effect of the co-culture, we compared the co-culture treatment with the cultures using S. dimorphus-only and nitrifiers-only treatment as controls. After 6 days of incubation, nitrate was removed only in the co-culture treatment and total amount of N removal was 1.3 times and 1.6 times higher in the co-culture treatment compared to those in the S. dimorphus- and nitrifiers-only treatments, respectively. In case of total amount of P, co-culture treatment removed 1.2 times and 12 times more P than the S. dimorphus -and nitrifiers-only conditions, respectively. This indicates that the co-culture improved removal rates for ammonium, nitrate, and phosphate. This further implies that there was no need for denitrification of nitrate and luxury uptake of P processes because nitrate and phosphate can be removed from the uptake by S. dimorphus. In addition, co-culture condition maintained high DO above 7 mg/L without artificial aeration, which is enough for nitrification, implying that co-culture has a potential to decrease or remove aeration cost in the wastewater treatment plants.

This study investigates the effect of sodium bicarbonate (NaHCO3) on growth of S. dimorphus. NaHCO3 concentration was varied from 0 to 2 g-C/L. As a result, the increase in concentration of NaHCO3 up to 1.5 g-C/L increased dry weight of algae. The highest specific growth rate of S. dimorphus was 0.36 day-1 which was obtained at concentration of 0.5 g-C/L NaHCO3. pH showed a large variation range at the concentrations lower than 0.5 g-C/L NaHCO3 whereas inorganic carbon, nitrate and phosphorus removal rates were almost same at the concentrations higher than 0.5 g-C/L NaHCO3 (0.75, 1, 1.25, 1.5, 2 g-C/L NaHCO3). Their average inorganic carbon, nitrate and phosphorus removal rate were 70 mg-C/L/d, 11.3 mg-N/L/d, and 1.6 mg-P/L/d, respectively. Thus, NaHCO3 didn’t effect on inorganic carbon, nitrate and phosphorus removal rate of S. dimorphus.

This study aims to increase the organic carbon, nitrogen and phosphorus removal efficiencies than the conventional method and meet higher effluent water quality standards by co-culture with bacteria in activated sludge in the aeration tank. By the co-culture in mixotrophic conditions through metabolic characterization of Scenedesmus dimorphus and bacteria in the aeration activated sludge, assessed how the impact on the organic matter, nitrogen and phosphorus removal rate. In addition, the study was to determine if it is possible to supply the oxygen necessary for the bacteria through the photosynthesis of algae without aeration. To test the synergistic effects of the co-culture, we compared co culture with S. dimorphus - only, Bacteria - only as a controls. In the co-culture condition inoculation ratio is based on the TSS concentration S. dimorphus and bacteria 1 : 5 (w / w), 5 : 5 (w / w) at a ratio. The growth rate of S. dimorphus - only condition was higher, which was 10 times and 2 times lower compared to B : A (5 : 1), B : A (5 : 5) respectively. Organic carbon removal rate of S. dimorphus - only condition was lower than other conditions, the remaining conditions were consumed at a similar rate. In the co-culture of Mixed bacteria and S. dimorphus, ammonium and phosphate removal rate has been high. But, nitrate removal rate showed a tendency to decrease compared to the Bacteria-only condition. When considering the Ammonium, nitrate and phosphate removal rate, N, P removal efficiency which is most excellent in terms of bacteria, such as S. dimorphus ratio (5 : 5) were co-cultured in the conditions. DO was maintained at 3 mg/L or more under all conditions. So, implying co-culture has the potential to decrease aeration costs.

The most effective chemical pretreatment method for Scenedesmus dimorphus was evaluated based on solubilization rate and saccharification yield. When 1% of S. dimorphus with 0.5 N of chemicals such as HCl, H2SO4, HNO3, NaOH and KOH was autoclaved at 120oC and 1.1 atm for 60 min, the solubilization rate was high with alkali chemicals while the saccharification yield was low compared to that with acid chemicals. The pretreatment efficiency was significant in order in HNO3, HCl and H2SO4, however, HCl would be effective for field application considering the cost. The proper concentration and time to treat with HCl were concluded in 1 N and 10 min. In the conditions with 1 : 1 mixed acid chemicals such as H2SO4+ HNO3, HCl + HNO3 and HCl + H2SO4, the solubilization rate was similar to that with single acid treatment, while the saccharification yield was enhanced about 34% in the mixed condition with H2SO4 and HNO3 compared to that treated with H2SO4.