This study investigated the potential of indigenous endophytic bacteria to improve the efficiency of the wetland helophyte Juncus acutus to deal with a mixed pollution consisting of emerging organic contaminants (EOCs) and metals. The beneficial effect of bioaugmentation with selected endophytic bacteria was more prominent in case of high contamination: most of the inoculated plants (especially those inoculated with the mixed culture) removed higher percentages of organics and metals from the liquid phase in shorter times compared to the non-inoculated plants without exhibiting significant oxidative stress. When exposed to the lower concentrations, the tailored mixed culture enhanced the performance of the plants to decrease the organics and metals from the water. The composition of the root endophytic community changed in response to increased levels of contaminants while the inoculated bacteria did not modify the community structure. Our results indicate that the synergistic relationships between endophytes and the macrophyte enhance plants’ performance and may be exploited in constructed wetlands treating water with mixed contaminations. Taking into account that the concentrations of EOCs used in this study are much higher than the average contents of typical wastewaters, we can conclude that the macrophyte J. acutus with the aid of a mixed culture of tailored endophytic bacteria represents a suitable environmentally friendly alternative for treating pharmaceuticals and metals.

BACKGROUND: Emerging organic contaminants include a large group of compounds that are frequently detected in wastewater along with heavy metals, due to incomplete removal or limitations in conventional and advanced treatment processes. In this work, the efficiency of Juncus acutus L. on the removal of mixed contamination; ciprofloxacin (CIP), sulfamethoxazole (SMX), bisphenol A (BPA) and heavy metals (chromium (Cr), nickel (Ni), cadmium (Cd) and zinc (Zn)), was investigated in a hydroponic experiment in order to evaluate its potential for use in the alternative remediation technology of constructed wetland (CW) systems. Concentrations of the compounds ranged from g L −1 to well beyond environmentally relevant values (50 mg L −1 for the organics and more than 1000 mg L −1 in the case of Zn and Cr). (CIP and SMX), BPA and heavy metals were efficiently removed after 28 days, without J. acutus exhibiting perceptible phytotoxicity symptoms, in concentrations even higher than those that are generally detected in industrial or hospital wastewater. Extremely high concentrations of heavy metals induced severe physiological damage to the plants. RESULTS: Antibiotics CONCLUSION:The remarkable efficiency of the halophyte J. acutus was revealed, regarding all the contaminants tested at environmentally relevant concentrations. In higher concentrations of antibiotics and mixtures of organic and inorganic contaminants, the contribution of the plant was also demonstrated. Findings from this work suggest that J. acutus plants are an ideal candidate for phytoremediation applications in CW systems, targeting urban, industrial or pharmaceutical wastewater treatment. Data AnalysisStatistical analysis was performed with a t-test, using the Add-In statistical package in Microsoft Excel (significance level set at P < 0.05).