Design Blueprint: Village Batch Reverse-Osmosis Desalination Unit — Build Specification Derived from the Osmotic-Curve Batch RO Paper

DESIGN BLUEPRINT — SIMULATED, NOT MEASURED — NOT BUILT. A complete build specification for a village seawater desalination unit that desalinates in batches, ramping its feed pressure to follow the osmotic curve of the concentrating charge at a constant net driving pressure of 5.0 bar. Derived from the source paper: https://doi.org/10.5281/zenodo.24108571. Design basis: seawater at 35 g/L, 50% recovery, specific energy 1.814 kWh/m3 against 2.318 kWh/m3 for a continuous plant with isobaric recovery computed on the same basis, set pressure rising from 33.61 bar to a peak of 61.23 bar, and no energy-recovery device. The unit is sized at 10 m3 of permeate per day in five cycles of 4.5 hours: a batch tank of 4.4 m3 nominal volume (1.78 m diameter as specified), 33.3 m2 of membrane at a flux of 15 litres per square metre per hour, a product blending tank of 11.0 m3 nominal volume, a high-pressure pump peaking at 1.00 kW, and a circulation pump of 0.083 kW. The blueprint gives dimensions and layout, a bill of materials in generic specification classes, an assembly sequence, the operating envelope and its limits, critical fits tied to the source figures, failure modes and mitigations, a cycle-based maintenance schedule, and the measurements a first build must make to verify or falsify the claimed saving. Nothing has been built or measured; every derived quantity is reproducible from the accompanying compute.py.