AquaSynch: A Feasibility-Aware Closed-Loop Water-Quality Management Framework for Energy-Efficient Agricultural Desalination

Conventional desalination-to-agriculture water management produces water to a fixed high purity regardless of actual crop, soil, and drainage conditions. This paper presents AquaSynch, reconstructed here as its third development generation, around a central engineering insight not present in its earlier versions: treatment intensity should be adaptively controlled only WITHIN a feasibility envelope determined independently of the controller. A devil's-advocate audit of the prior generation's root-zone salinity model found that its real-time control formula disagreed with an internally built numerical benchmark by 2.2-2.6x; root-causing this established that the benchmark was correct, while the formula used for control failed a basic physical limiting-case test. Replacing the control formula with the corrected one changes every downstream quantitative result: single-season energy reduction versus a fixed-maximum-purity baseline falls from previously reported values of 53-88% to a more conservative, defensible 11.7% (boron-sensitive crop), 52.0% (moderately sensitive), and 81.9% (tolerant), now achieved with zero simulated safety violations. All results are computationally simulated under explicitly typed parameters; no field, pilot, or hardware validation has been performed.