High efficient treatment of citric acid effluent by Chlorella vulgaris and potential biomass utilization

The efficiency of treating citric acid effluent by green algae Chlorella was investigated. With the highest growth rate, Chlorella vulgaris C9-JN2010 that could efficiently remove nutrients in the citric acid effluent was selected for scale-up batch experiments under the optimal conditions, where its maximum biomass was 1.04 g l−1 and removal efficiencies of nutrients (nitrogen, phosphorus, total organic carbon, chemical oxygen demand and biochemical oxygen demand) were above 90.0%. Algal lipid and protein contents were around 340.0 and 500.0 mg·g−1 of the harvested biomass, respectively. Proportions of polyunsaturated fatty acids in the lipids and eight kinds of essential amino acids in algal protein were 74.0% and 40.0%, respectively. Three major fatty acids were hexadecanoic acid, eicosapentaenoic acid and docosadienoic acid. This specific effluent treatment process could be proposed as a dual-beneficial approach, which converts nutrients in the high strength citric acid effluent into profitable byproducts and reduces the contaminations.

► Chlorella vulgaris C9-JN2010 with the highest growth rate was screened out.
► Chlorella vulgaris C9-JN2010 could efficiently remove nutrients in the CAE.
► Under the optimal conditions, the removal efficiencies of nutrients were more than 90.0%.
► Content of algal protein was high (around 500.0 mg g−1 of the assayed biomass).
► Proportions of PUFAs in the lipids and essential amino acids in algal protein were fairly high.