Efficient treatment of phenol wastewater by co-culture of Chlorella vulgaris and Candida tropicalis

The increased water contamination with phenolic compounds has emerged as an important environmental concern due to their considerable ecotoxicities and associated health issues. Here, a co-cultured microalgae/ microorganism system, Chlorella vulgaris and Candida tropicalis, has been developed for efficient treatment of phenol and microalgal biomass accumulation. Our results show that the Chlorella vulgaris and Candida tropicalis co-culture system can achieve the highest phenol removal rate as 233.3 mg/L/d and the total chlorophyll accumulation as 23.0 mg/L with the initial volume ratio of Chlorella vulgaris and Candida tropicalis at 1:3, which are 5.2 and 7.2 times higher than that of Chlorella vulgaris monoculture respectively. The maximum phenol removal ability of the constructed co-culture system was tested as 1500 mg/L within 6 days. Transcriptome analysis suggested that the co-cultured microalgae/microorganism can utilize phenol as a carbon source for its growth and metabolism, and the removal mechanism of phenol was mainly due to the biodegradation process other than bio-absorption. Simulated wastewater experiment shows that the co-culture system can not only efficient remove the phenol compounds, also can significantly decrease the ammonia nitrogen (NH3-N), total phosphorus (TP) and chemical oxygen demand (COD) of wastewater with removal efficiencies as high as 93%, 92%, 80% and 100%, respectively. Our work provided a promising way for the treatment of phenol compounds and then promoting the growth of Chlorella vulgaris using phenol containing wastewater.