Purification efficiency of Pyropia-processing wastewater and microalgal biomass production by the combination of Chlorella sp. C2 cultivated at different culture temperatures and chitosan

To elucidate the impacts of culture temperature on nutrient removal efficiency of Pyropia-processing wastewater (PPW) and microalgal biomass production, Chlorella sp. C2 was employed and cultivated in raw PPW under different temperatures. Results showed that, after incubating for 7 days, higher biomass (0.50 g/L) and total lipids (21.84 %) were attained at 35 °C. The maximal chemical oxygen demand (COD), phycobiliprotein, total nitrogen and total phosphorus removal rates were observed at 30-35 °C and separately reached 62.41 %, 92.61 %, 92.19 % and 98.33 %. Interestingly, COD removal efficiencies of Chlorella cells, cultivated for 3, 5 and 7 days at 30-35 °C, 15-25 °C and 10 °C respectively, could reach >75 % with assistance from 60-80 mg/L chitosan. Meanwhile, the clarification efficiency of chitosan on algal cells reached >95 %. It suggests that Chlorella strain cultured at altered temperatures could efficiently remove PPW nutrients assisted by moderate chitosan, simultaneously achieving the rapid harvest of microalgae.