Characterization of wastewater from sand pits and evaluation of its use in the cultivation of bioenergy species.
Sand Mining, Helianthus annuus, irrigation water quality index.
The world faces recurring water crises, intensified by climate change and the expansion of agriculture. In this context, water reuse is a fundamental strategy for water sustainability. At the same time, the intense sand mining in the Seropédica-Itaguaí-RJ region has generated extensive lagoons in abandoned pits, which represent an environmental liability. The volume of water in these pits has increased significantly, creating a reservoir that lacks productive use. Given the need for alternative water sources and the growing demand for sustainable solutions to reduce greenhouse gas emissions, this study proposes an innovative approach to sustainable agriculture and the energy transition. The overall objective is to evaluate the potential for reusing wastewater from sand pits (WWP) in irrigation and cultivation of a bioenergy species, sunflower (Helianthus annuus L.). The study methodology is divided into two main stages. In the first, the physicochemical characterization of the WWP will be carried out, collected bimonthly over a year in active and inactive pits. The samples will be analyzed to determine parameters such as pH, electrical conductivity, total solids, and the concentrations of macro and microelements, including ions such as sodium, potassium, calcium, and magnesium. Based on these data, the quality of the WWP will be classified using indicators that consider its risks and potential for the soil and plant. The objective is to determine the viability of the WWP for use in irrigation. The second stage consists of evaluating the viability of using ARA in sunflower cultivation through germination tests and a greenhouse experiment. Sunflowers will be grown in pots with ARA application, using a randomized block design with four irrigation levels. Morphophysiological and productive parameters of the crop will be evaluated, such as plant height, head diameter, grain yield, dry mass, and oil content. In addition, water use efficiency (WUE) and the water deficit response coefficient (Ky) will also be calculated. It is expected that the results of this study will demonstrate the potential of ARA for agricultural production, promoting the recovery of degraded areas and offering a sustainable alternative for family farming in the region.