Pine sawdust as algal biofilm biocarrier for wastewater treatment and algae-based byproducts production

Abstract

Currently, excellent algal biofilm carriers were costly and difficult to be obtained, their nutrients removal capacities have also not been valued. In this study, pine sawdust was utilized as algal biofilm biocarriers for wastewater treatment in a self-designed photo-bioreactor. Treatment by suspended culture was conducted as control. The nutrient removal efficiency, algal biomass production and biochemical composition were characterized. Carrier behavior before and after treatment was also evaluated. Results indicated that 96.95% of chemical oxygen demand (COD) and 97.16% of total phosphorus (TP) in synthetic wastewater as well as 95.54% of total nitrogen (TN) and 96.10% of NH4+-N in real wastewater were removed by Chlorella vulgaris biofilm. Chlorella vulgaris performed the best in the production of biomass (8.10 g‧m−2‧day−1) and value-added products (lipid: 1.08 g‧m−2‧day−1, biodiesel: 0.081 g‧m−2‧day−1) during synthetic wastewater treatment. Meanwhile, Chlorella vulgaris biofilm performed better in biomass production (5.53 vs. 2.36 g‧m−2‧day−1), nutrients removal and biodiesel production (186.33 vs. 44.57 mg‧m−2‧day−1) than its suspended culture during the real wastewater treatment. In addition, pine sawdust was not only a biocarrier for the robust growth of algal biofilm, but also a bio-sorbent for nutrients removal (23.60%, 37.30%, 41.08% and 17.07% for COD, TN, NH4+-N and TP removal) from wastewater. The biocarrier itself could also be pretreated by the treatment process and be beneficial to its energy conversion. The results of the present study fully illustrated the feasibility and broad applicability of using this biocarrier based biofilm technology for algal biomass and value-added byproducts production and wastewater treatment.