Location criteria for rapid wastewater infiltration basins based on hydrogeological modeling supported by sensibility analysis

ABSTRACT Rapid wastewater infiltration basins (RWIBs) offer a sustainable alternative for wastewater disposal and aquifer recharge, especially in regions with limited surface water availability. This study employs numerical modeling (MODFLOW) to evaluate RWIB performance and refine site selection criteria by analyzing the relationship between infiltration capacity and key hydrogeological parameters. Results demonstrate that infiltration flow does not scale linearly with basin surface area, contrary to assumptions in standard design approaches. Simulations showed that beyond doubling the initial application area, infiltration efficiency declines – from 100 to 67, 36, 24, and 20% – indicating a lack of proportional response between geometric expansion and effective recharge. Sensitivity analyses revealed that soils with hydraulic conductivity ≥10−4 m/s sustain infiltration regardless of increased recharge flows, while values ≤10−5 m/s significantly restrict it. The model indicated low sensitivity to porosity due to the area's low hydraulic gradient. These findings highlight the importance of considering both vertical and lateral hydrogeological conditions when designing RWIBs, particularly in heterogeneous or coastal aquifer systems. The study warns against relying on geometric design criteria, which may overestimate infiltration capacity and increase environmental risk. The insights support improved planning of managed aquifer recharge systems and reinforce the role of modeling in sustainable groundwater management.