Simultaneous removal of pollutants and high value biomaterials production by Chlorella variabilis TH03 from domestic wastewater

Abstract

Cultivation of microalgae in the domestic wastewater is an alternative approach over conventional activated sludge processes for simultaneous pollutants removal and biomaterials production for biorefinery. This study was aimed at growing a Chlorella variabilis TH03 in domestic wastewater using various closed photobioreactors and open-reactor systems for evaluation of the algal growth, pollutants removal efficiency, biomass productivity and characterization of the biomass. Results indicated that the C. variabilis TH03 exhibited an outstanding growth, achieving maximum biomass concentration of 1.52, 1.67, 1.54 and 1.72 g/L, with specific growth rate of 0.32/day, 0.27/day, 0.22/day and 0.34/day in PBR-5-R, PBR-5-S, T-50 and RW-500 reactor systems, respectively. Remarkably, additional supplement of CO2 significantly enhanced areal biomass productivity of C. variabilis TH03 grown in RW-500 from 13.1 to 38.5 g/m2 day. Pollutants in term of COD, total nitrogen and total phosphorous were removed by 74.8–89.8%, 93.8–96.1% and 97.1–99.9%, respectively, during 14–17 days cultivation of the C. variabilis TH03. The fatty acid methyl esters of the algal biomass was determined as 22.55–26.12% with the most abundant fatty acids of C16:0 (26.13–27.67%), C16:3n4 (20.07–22.24%) and C18:3n3 (34.83–36.79%) which were desirable fatty acids for biodiesel and bio-jet fuels synthesis. Moreover, total carbohydrates and proteins in the algal biomass were accumulated up to 31.56–35.23% and 33.67–37.34%, respectively. Our preliminary results demonstrated the cultivation technology of C. variabilis TH03 can sustainably replace the conventional activated sludge technologies for domestic wastewater treatment.