Obtaining mutant Chlorella vulgaris strains with excellent self-flocculation properties and high wastewater treatment efficiency via atmospheric and room temperature plasma technique

In this study, atmospheric and room temperature plasma technique (ARTP) was applied to generate mutants of Chlorella vulgaris to improve its self-flocculation. Four high self-flocculation mutant strains named SDJZM-1, SDJZM-2, SDJZM-3 and SDJZM-4 were obtained. Among them, SDJZM-1showed the highest self-flocculation efficiency of 92.34 %, and the lowest self-flocculation efficiency of SDJZM-2 was still increased by 78.85 % compared to the original type. In addition, four mutants showed high capability to uptake nutrients from wastewater. Especially, mutant SDJZM-4 increased the removal of total nitrogen, phosphorus and ammonia nitrogen by 29.39 %, 22.72 % and 14.82 %, respectively, in comparison with wild-type strain. Three-dimensional excitation and emission matrix fluorescence spectroscopy analysis showed that more protein was found in mutant strains, and a significant correlation between the protein content in bound extracellular polymeric substances (B-EPS) and flocculation efficiency was observed. The main self-flocculation mechanism of mutant strains was the bridging and sweeping made by B-EPS.