Biomass productivity of Chlorella vulgaris cultivated in fish and dairy cattle wastewaters

Abstract

The biomass productivity and nutrient composition of microalgae, such as Chlorella vulgaris, depend on the cultivation process and the nutrient content of growth media. Thus, in this study aimed to investigate the biomass productivity of C. vulgaris cultivated in fish and dairy cattle wastewaters. Thirty wastewater samples (2.5 L) were collected from system of production. Microalgae were cultivated in Erlenmeyer flasks containing 10 mL of microalgae and 1,790 mL of wastewater under constant light of 5,000 lux for 16 days at 25 ± 2.0 °C. Wastewater samples differed in composition. Biomass productivity was 47 % higher (P<0.0001) in dairy cattle than in fish wastewater, reaching 67.61 g m?3 day?1 (dry matter basis, DM) when compared by Student’s t-test (P<0.05). Cultivation media also had an effect on biomass chemical composition. The C. vulgaris grown in dairy cattle wastewater was higher in crude protein and ash contents (359.6 g kg?1 DM and 230.4 g kg?1 DM, respectively), whereas microalgae grown in fish wastewater had higher nitrogen-free extract content (347.8 g kg?1 DM). Crude fat content did not vary greatly (mean of 313.15 g kg?1 DM). The pH (8.0 – 8.7) and ammonia concentration (0.07 to 0.4 mg L?1) in fish wastewater was stable throughout the 16-day experimental period. In dairy wastewater, pH increased up (6.3 to 8.9) to the fourth day and remained constant thereafter, and ammonia concentration increased up (24.3 to 28.7 mg L?1) to the eighth day and then it declined (2.1 mg L?1). The C. vulgaris was successfully grown in both wastewaters, but productivity was higher in dairy cattle wastewater.

Keywords

• Chemical composition
• Runoff
• Microalgae.