Floating treatment wetland for nutrient removal and acute ecotoxicity improvement of untreated urban wastewater

Wastewater treatments are often expensive, and the resulting effluent can still harm the environment. Floating treatment wetland is an alternative low-cost eco-technology in which a hydroponic root network remediates polluted waters. This system has been broadly studied as a secondary treatment to remove nutrients and pollutants, but its application to improve raw wastewater quality is still incipient. Moreover, few studies have assessed acute ecotoxicity toward fish after treatment. Thus, this study aimed to evaluate the efficiency of a mesocosm floating treatment wetland to improve the raw wastewater quality from a university campus in South Brazil. Efficiency was assessed based on the improvement of physicochemical parameters (conductivity, pH, turbidity, color), nutrients (nitrogen and phosphorus), and heavy metals (zinc, chromium, copper, lead, and cadmium); Typha domingensis adaptability; and acute fish ecotoxicity reduction after wastewater treatment. Influent was treated with macrophytes tanks and their respective controls. T test was used to compare influent versus effluent samples, and macrophytes tanks versus controls. A Principal Component Analysis identified the main explanatory variables on the system, and a Two-way Cluster Analysis grouped samples before and after treatment. The results show floating mats efficiency in reducing most parameters compared to the influent, except phosphorus and zinc. Control tanks were also effective in improving wastewater quality due to microalgae and duckweed proliferation. In conclusion, floating treatment wetlands with Typha domingensis have the potential to treat raw wastewater. Further nitrogen removal in wastewater might improve acute ecotoxicity toward fish.

Automated summary

Floating treatment wetlands with Typha domingensis are a potential low-cost eco-technology to treat raw wastewater and improve its quality. Results showed high efficiency in reducing most parameters, except for phosphorus and zinc. Further research on improving nitrogen removal in wastewater may help enhance acute ecotoxicity reduction toward fish.