Nutrients removal from wastewater by microalga Chlorella sp. coupled to augmented lipid production with spent wastewater utilized by cyanobacterium Fischerella muscicola TISTR 8215 for hydrogen production

Wastewater from different sources with excessive nutrient loading, which is a major contributor to eutrophication, can be a promising medium alternative for microalgae cultivation with effective removal of NH4+-N, PO43--P and organic matter. In this study, three groups of synthetic wastewater (SWW), an ammonium-rich stream (60 to 250 mg L-1 NH4+) containing a specific type of organic matter, such as petroleum effluent (SWW1: 300 mg L-1 glucose and 10 mg L-1 phenol), molasses wastewater (SWW2: 600 mg L-1 glucose), and agro-industrial wastewater (SWW3: no organic matters) were used for growing Chlorella sp. and for investigating its potential for nutrient removal as well as the production of biomass and lipid. The findings showed that Chlorella sp. grown in SWW2 (i.e., the auto/mixotrophic culture with 14 days) served as efficient feedstock for lipid production, and showed the maximum lipid content and yield of 53 % DCW and 188 mg L-1, respectively. Additionally, the maximum removal of 76 % NH4+-N was observed under this condition. Higher removal of NH4+-N with 100 % efficiency was seen in Chlorella sp. under SWW1 and SWW3 conditions. However, under SWW2 the cells had higher NH4+ uptake rate than that under SWW1 and SWW3, resulting in highest biomass productivity in SWW2 grown cells. The spent media after Chlorella sp. cultivation were used for growing the N-2-fixing cyanobacterium Fischerella muscicola TISTR 8215 for the production of hydrogen. Among different spent media, F. muscicola TISTR 8215 cultivated in SWW1 spent medium obtained from 7-day Chlorella sp. cultivation had the highest hydrogen production of 200.8 mu mol H-2 mg(-1) chlorophyll a. Overall, the present study employed biorefinery approach using the microalga biomass as feedstock for lipid production with subsequent utilization of spent medium for growing the cyanobacterium for enhanced production of hydrogen.