Halophilic archaea and their extracellular polymeric compounds in the treatment of high salt wastewater containing phenol

Phenol is one of the major organic pollutants in high salt industrial wastewaters. The biological treatment of such waste using microorganisms is considered to be a cost-effective and eco-friendly method. However, in this process, salt tolerance of microorganisms is one of the main limiting factors. Halophilic microorganisms, especially halophilic archaea are thought to be appropriate for such treatment. To develop a novel effective biological method for high salt phenol wastewater treatment, the influence of phenol in high salt phenol wastewater on halophilic archaea and their extracellular polymeric substances (EPS) should be investigated. In the present study, using phenol enrichment method, 75 halophilic archaeal strains were isolated from Wuyongbulake salt lake sediment sample. The majority of the identified strains were phenol-tolerant. Six strains with high phenol tolerance were chosen, and the phenol scavenging effect was observed in the microbial suspension, supernatant, and EPS. It was noticed that the phenol degradation rate of suspensions of both strains 869-1, and 121-1 in salt water exhibited the highest rates of 83.7%, while the supernatant of strain 869-1 reached the highest rate of 78.2%. When combined with the comprehensive analysis of the artificial wastewater simulation experiment, it was discovered that in the artificial wastewater containing phenol, the phenol degradation rate of suspension of strain A387 exhibited the highest rates of 55.74% both, and supernatant of strain 630-3 reached the highest rate of 62.3%. The EPS produced by strains A00135, 558-1, 869-1, 121-1 and A387 removed 100% phenol within 96 h, and the phenol removal efficiency of EPS produced by 869-1 reached 56.1% under an artificial wastewater simulation experiment with high salt (15%NaCl) condition. The present study suggests that halophilic archaea and their EPS play an important role in phenol degradation. This approach could be potentially used for industrial high-salt wastewater treatment.