Recovery of nutrients from aquaculture wastewater: Effects of light quality on the growth, biochemical composition, and nutrient removal of Chlorella sorokiniana

Light quality is known to affect microalgal growth and biochemical composition. However, there are few reports about its multiple effects in the nutrient recovery process of aquaculture wastewater. This study investigated the effects of light quality (white light, red light, blue light, and mixed red and blue lights) on the growth, nutrient removal and biochemical composition of Chlorella sorokiniana CMBB276 in aquaculture wastewater. The results showed that C. sorokiniana CMBB276 could rapidly adapt to aquaculture wastewater with high nutrient removal. White light could maximize biomass production, with the highest dry weight of 1.93 g L-1; the productivity of biomass (0.22 g L-1 d-1) and carbohydrates, lipids and proteins (121.26, 64.79 and 38.85 mg L-1 d-1); during 8-day cultivation. Red light and blue light could finely tune the specific biochemical components of C. sorokiniana CMBB276. Red light promoted the production of carbohydrates (130.54 mg L-1 d-1) and proteins (47.26 mg L-1 d-1) in the first 4 days of cultivation. Blue light was beneficial for obtaining the highest contents of pigments, including chlorophyll a, chlorophyll b and carotenoids (5.13, 3.53 and 1.46 mg g- 1), as well as proteins (21.54 % DW) and fatty acids (13.56 % DW). The highest degradation of TOC (82.27 %) was achieved under blue light, and the highest removals of TN (86.42 %) and NH3-N (93.25 %) were achieved under the mixed red and blue lights. The removal of TOC, TN and NH3-N was mainly stimulated by nonmicroalgal pathways (bacterial degradation, photolysis, etc.). This study provided insights into the impacts of light quality on the process of microalgae-based aquaculture wastewater treatment to contribute to the nutrient recovery and sustainable development of aquaculture.

Automated summary

Light quality has significant effects on the growth, nutrient removal, and biochemical composition of Chlorella sorokiniana in aquaculture wastewater. White light maximizes biomass production, while red light and blue light finely tune the specific biochemical components. Blue light is particularly beneficial for pigment content and the removal of TOC, TN, and NH3-N is mainly driven by nonmicroalgal pathways.