Semi-permeable membrane forces water through under pressure, rejecting dissolved solids, salts, and contaminants (PFAS, nitrates, heavy metals) that filtration and UV alone don't remove, the highest achievable water-quality ceiling of any option in this catalog. Trade-off: significant electricity draw, a reject-water stream (often 3-4x the product volume), and a membrane needing periodic professional-grade replacement rather than a field repair.
Note: Cost, carbon and footprint are rated against the other options for this same need, not in absolute terms.
No sizing or quantities: how much a technique yields, and how much a household needs, both depend on the build and the people, so the catalogue compares options rather than dimensioning them. It carries no bill of materials and no build sequence, and it is written for an oceanic, clay-soil climate (Normandy, France). Regulatory notes are indicative and need confirming locally.