Abstract:
Four species of green algae, Chlamydomonas sp., Pandorina sp., Scenedesmus quadricauda and Scenedesmus dimorphus were tested for wastewater treatment from biodiesel production plant. S. dimorphus with the highest specific growth rates of 0.62 ± 0.12 day[superscript -1], was the most effective algae for reducing nitrate, phosphate, BOD and COD in wastewater with the removal rate of 95.78%, 16.02%, 50.58% and 45.08%, respectively. However, the efficiency of ammonia removal between S. dimorphus and S. quadricauda were not significantly different (p value > 0.05). The result indicated that only nitrate concentration could affect growth and the efficiency of water treatment. S. dimorphus grown in nitrate-adjusted wastewater (40 mg/l nitrate) had the highest specific growth rates of 0.81 ± 0.08 day[superscript -1] and was more effective in wastewater treatment than microalgae grown in non-adjusted nitrate concentration wastewater. The remove rates were on follow: phosphate 42.25%, BOD 67.54% and COD 60.65%. Moreover, culture of S. dimorphus in 80 mg/l nitrate-adjusted wastewater had high efficiency of wastewater treatment but the concentration of nitrate left at the end of the experiment was still high (51.43 mg/l). The culture conducted under natural sunlight (312 μmol.m[superscript -2].s[superscript -1]) gave high growth rate of 1.07 ± 0.32 day[superscript -1] which was higher than culture under control light (60 μmol.m[superscript -2].s[superscript -1]) and the reduction of ammonia 99.81%, nitrate 96.11%, phosphate 56.72%, BOD 76.50% and COD 67.48%. The biochemical compositions of this S. dimorphus contained high protein content, 27.44 ± 1.83 %DW, lipid content 13.89 ± 1.12 %DW and carbohydrate 11.02 ± 1.98 %DW. The pattern of fatty acid in S. dimorphus is very rich Palmitic acid (C16:0) and Linoleic acid (C18:2).