Treatment of Saline Organic-Rich Fermentation Wastewater by Marine Chlorella sp. for Value-Added Biomass Production

High-salt-concentration wastewater is an important pollution source for the ocean environment, and its ecological treatment is obligatory to meet the standard of discharge. In this study, an isolated Chlorella sp. from seawater was cultivated to treat salt organic-rich fermentation wastewater to simultaneously remove organic and inorganic nutrients. The results show that Chlorella sp. achieved the highest biomass (6.07 g/L) under a mixotrophic mode in a medium containing 50% fermentation wastewater. The removal rates of total organic carbon (TOC), ammonia-N, (NH3-N), total nitrogen (TN), and total phosphorus (TP) were 89, 95, 87, and 88%, respectively, after 10 days of cultivation. Lipid, carbohydrate, and protein contents in dry biomass were 33, 21, and 34% (w/w), respectively. Moreover, the produced biomass had 37.8 mg/g chlorophyll, 10 mg/g carotenoid, and 0.168 mg/g flavonoids. A flocculation efficiency of >90% was achieved in a medium containing 50% fermentation wastewater in 12 h of settling. The fatty acids composition analysis of the produced lipid shows that it is a suitable feedstock for biodiesel production. Taken together, mixotrophic cultivation of marine Chlorella sp. has the potential for the treatment of high salt organic-rich wastewater, as well as value-added biomass production.