Indigenous fungi derived from a municipal wastewater treatment plant with rapid flocculation of Chlorella sp.: Convenience, mechanisms, and conditions optimization

Few indigenous fungi species that can flocculate microalgae in wastewater treatment plants (WWTPs) have been reported, and more effective fungi strains for microalgal flocculation remain to be identified. In this research, a flocculating fungi strain was screened from a WWTP. The flocculation performance and properties were assessed. The underlying mechanisms were elucidated through extracellular polymeric substances (EPS) analysis. The flocculation conditions were optimized by the response surface method (RSM). The findings indicated that the isolated strain Curvularia moringae J-26 flocculated Chlorella sp. with an efficiency of up to 97.3 % within 120 min. Curvularia moringae J-26 flocculated Chlorella sp. mainly via mycelium absorption, attributed to the protein-like (PN) and soluble microbial byproduct-like substances contained in the EPS. The optimal conditions to flocculate Chlorella sp. were the mycelium pellets dosage of 2.25 g/L at 160 rpm for 4.8 h. Curvularia moringae J-26 flocculated Chlorella sp. with good performance, which had the potential to reduce the cost of Chlorella sp. harvesting. This research provided a technical reference for Chlorella sp. harvesting and fungi application in wastewater treatment.