Process Development and Optimization of Wastewater Derived Integrated Biorefinery for Production of Bio-Based Energy Carriers Employing Spirodela polyrhiza

The excesssive use of agrochemicals to fulfill the high demand of agricultural products has been imposing numerous negative impacts on the environment for decades worldwide. Untreated wastewater with high chemical load and unutilized nutrients of fertilizers and pesticides released from agricultural farms results in contamination and intoxication of clean water bodies. Giant duckweed specifically Spirodela polyrhiza specie has shown the potential to efficiently uptake nutrients from nutrient rich waters thus, it can be employed cost-effective approach for phytoremediation of agricultural runoff. S. polyrhiza biomass also serves as an alternative feedstock for the production of biofuels which is another precedence of using this method. In this study, the potential of S. polyrhiza for removing nitrogen and phosphates from the agricultural runoff was determined by growing it in the agricultural runoff under lab conditions. Upto 70% and 78% removal of nitrogen and phosphates respectively was achieved during the treatment of agricultural runoff by Spirodela polyrhiza. The starch content of Spirodela polyrhiza was elevated 58% during 10–12 days of nutrient starvation at the end of the agricultural runoff treatment process. The biomass obtained was pretreated with dilute acid that liberated 96.4% glucose from the starch-rich biomass. This glucose was used as a substrate for the fermentation process carried out by Saccharomyces cerevisiae QG1 MK788210 yeast strain which yielded 99% volumetric conversion of glucose into bioethanol. The remaining fermentation vinnasse was anaerobically digested and 589 Nml/g VS biogas yield was obtained. To the best of our knowledge this is the first study that develops a lab-scale bioprocess in terms of integrated wastewater derived S. polyrhiza biorefinery.