Treated Wastewater Use for Fertigation: A Distance-Based and Sodium-Constrained Deterministic Allocation Model in the Semi-Arid Region of Minas Gerais, Brazil

The use of treated wastewater constitutes a strategic alternative for agriculture in water-scarce regions. This study developed and applied a distance-based and sodium-constrained deterministic allocation model integrating geoprocessing tools with environmental and logistical constraints to optimize the spatial distribution of treated effluent from 48 wastewater treatment plants (WWTPs) in the semi-arid region of Minas Gerais, Brazil. The deterministic allocation algorithm prioritizes geographic proximity and favorable topographic differences as a proxy for reducing potential pumping requirements. Two scenarios were evaluated: (1) full effluent availability and (2) sodium-regulated allocation limited to 300 kg ha−1 year−1 of Na, in accordance with Normative Deliberation CERH-MG 65/2020. Under Scenario 1, cotton demand exceeded (184%), while coffee and sugarcane reached 69% and 24% of annual demand, respectively. Under the sodium-constrained Scenario 2, demand fulfillment changed to 37% for coffee and 42% for sugarcane, while cotton remained above full demand (108%). The proposed model differs from previous deterministic spatial allocation applications by integrating regulatory sodium constraints and dual-scenario regional assessment, providing a spatially explicit and regulation-compliant decision-support tool for sustainable wastewater reuse in semi-arid agricultural systems.