Novel bioconversions of municipal effluent and CO2 into protein riched Chlorella vulgaris biomass

► Three processes of treating municipal effluent by C. vulgaris were studied. ► C. vulgaris could establish and thrive with shorter lag phases and retention time. ► C. vulgaris can consume CO2 and efficiently remove N, P, CODCr and BOD5 in the ME. ► Protein content of C. vulgaris as feedstock is 550.0±30.0mg protein·g−1 dry cells. ► Algal protein was rich in eight kinds of essential amino acids (44.5% of the total). Batch, modified semi-continuous and continuous cultivations of Chlorella vulgaris C9-JN 2010 cells in municipal effluent were performed and analyzed. The experiments were carried out in 7.5-L photo-bioreactors, to which 2% of CO2 was supplied. Biomass and specific growth rate of C. vulgaris were 0.528–0.760gl−1 and 0.200–0.374d−1, respectively. Meanwhile, it could efficiently remove ammonia-N, total nitrogen, total phosphorus, CODCr and BOD5 by around 98.0%, 90.9–93.6%, 89.9–91.8%, 60.7–90.0% and 83.4–88.4%, respectively. Algal protein content was 550±30.0mgg−1 of the harvested biomass of C. vulgaris which was rich in eight kinds of essential amino acids (around 44.5% of the total). The processes of cultivation of C. vulgaris in municipal effluent could be proposed as dual-beneficial approaches, which could produce profitable byproducts and simultaneously reduce the contaminations to environment.