An integrated approach to quantifying the efficiency of plants and algae in water purification and bioethanol production

The inadequate sanitation, global warming, and dwindling natural oil reserves pose significant threats to global sustainable growth. With this objective, biomass availability for bioenergy production could be ensured alternately by exploring non-conventional plant species and algae. This idea was examined by growing divergent plants and algae species separately in horizontal subsurface flow constructed wetlands and raceway ponds, later collected their biomass for bioethanol determination. Through this approach, sewage was fed to constructed wetlands and raceway ponds as influent and passed through these cultivated systems for wastewater treatment. Although all the four plant and algae species showed efficient results in sewage treatment, however, Ipomoea aquatica and Spirogyra were statistically superior to the others and produced the highest biomass yield of 4.5 and 4.1 kg m⁻², respectively. For bioethanol production, alkali–autohydrolysis combined pretreatment followed by enzymatic hydrolysis with two successive incubation periods (12 and 24 h) were employed. Results suggested that Spirogyra biomass rendered greater carbohydrate and ethanol concentration (3.7 and 1.9 mg L⁻¹, respectively) during 24 hours of incubation, whereas Oryza sativa acquired similar carbohydrate concentration as Spirogyra but slightly lower bioethanol yield. This study postulates, Spirogyra is promising for wastewater treatment coupled with bioethanol production.