Comparison of oleaginous microalgal growth and lipid accumulation in saline-alkali leachate: a case from Shandong Province

In this study, the feasibility of using the saline-alkali leachate from Shandong Province to culture three oleaginous microalgae (Chlorella sp. HQ, Chlorella vulgaris, and Scenedesmus sp. LX1) for biomass and lipid production were explored. The results showed that all the three microalgae could grow in the leachates, among which, Chlorella sp. HQ kept the maximal density of 1.65 ± 0.05 × 10 7 cells mL –1 , largest lipid yield (69.90 ± 6.89 mg L –1 ) and content (50.53 ± 5.00%) after 25 d of cultivation. During the cultivation, the total organic carbon (TOC), inorganic carbon (IC), total nitrogen, and salinity of the leachates decreased in different degrees. The carbon source utilized by microalgae was mainly IC but not TOC, and the IC removal rate by Chlorella sp. HQ was the highest, reaching 89.85 ± 5.48%. The application potential of using saline-alkali leachates for Chlorella sp. HQ cultivation was investigated. The results showed that the pH values of five kinds of water [including L1 (salinity of 0.18%), L2 (salinity of 0.25%), tap water, reclaimed water, and SE standard medium] gradually increased during the cultivation and finally were stable at around eight. After 45 d of cultivation, the order of algal density was L2 (19.13 ± 0.70 × 10 7 cells mL –1 ) > L1 (13.55 ± 0.46 × 10 7 cells mL –1 ) > SE medium (10.99 ± 0.03 × 10 7 cells mL –1 ) > reclaimed water (5.45 ± 0.46 × 10 7 cells mL –1 ) > tap water (4.08 ± 0.33 × 10 7 cells mL –1 ). Compared with SE medium, the lipid yield, and content of Chlorella in the saline-alkali leachates were higher, but lower than those of tap water and reclaimed water, which may be due to nutrient deficiency of the latter two. Based on the comprehensive comparison, Chlorella sp. HQ was more suitable to cultivate in leachate in the view of not only biomass but also lipid content. Hence, using saline-alkali leachate for the cultivation of oleaginous microalgae is a promising alternative not only to purify leachates but also to serve as the large-scale applications for cost-saving.