RO/NF Pretreatment Reference for what feeds the membrane train, with KPI targets, chemistry, and instrumentation. The 80 % rule: most RO/NF/EDI problems originate upstream. Convention markers: - — likely bug or incorrect assumption in calling code - — enhancement opportunity (new alert, new monitoring point, new dosing logic) --- §1 — Pretreatment Chain Overview 1.1 SWRO open intake 1.2 SWRO beach well (subsurface intake) Subsurface intakes naturally deliver SDI₁₅ < 3 in most geologies → skip coagulation and media filtration. Yield (m³/h per well) and risk of Fe/Mn intrusion from anoxic strat…