Sustainable Reuse of Dairy Wastewater Treated in Constructed Wetlands for Radish Production

Abstract The reuse of treated dairy cattle wastewater represents a sustainable alternative for agriculture, reducing environmental impacts and promoting resource efficiency and circular nutrient use. In this context, the objective of the present study was to evaluate the production of radishes ( Raphanus sativus L.) fertigated with different doses of treated dairy cattle wastewater (DWW) in comparison with conventional fertilization. The experiment was conducted in a greenhouse located at Gragoatá – UFF, in Niterói, Rio de Janeiro State, Brazil, during two seasons, winter and spring. Different doses of DWW treated in constructed wetlands cultivated with vetiver grass were used: 0%, 50%, 100%, and 200% of the crop nitrogen requirement, in addition to a treatment with nitrogen addition through conventional fertilization. The experimental design used was completely randomized. Morphological characteristics (plant height, bulb diameter and length, number of leaves) and productive characteristics (fresh and dry mass of leaves and bulbs) were evaluated. The results showed no statistically significant differences among treatments for most growth and productivity variables, indicating that treated DWW did not significantly reduce radish agronomic performance under the experimental conditions evaluates. Furthermore, the reuse of treated wastewater contributes to reducing freshwater demand and enhances nutrient recycling, supporting more sustainable agricultural practices. Microbiological analyses showed E. coli levels below the detection limit and the absence of Salmonella spp. in the analyzed samples, indicating compliance with the microbiological criteria evaluated under the experimental conditions. These findings highlight the potential of constructed wetlands as a nature-based solution for wastewater treatment and reinforce the feasibility of integrating treated effluents into sustainable agricultural systems.