Permeate is the purified water that passes through a reverse-osmosis or nanofiltration membrane. It contains a small fraction of the feed water's dissolved solids — typically <500 ppm TDS for SWRO permeate from a 35,000 ppm feed. As pressurized feed flows across the membrane surface, water molecules diffuse through the polyamide active layer and exit as permeate. Dissolved salts, organics, and particulates are rejected and exit as concentrate. Permeate quality is the primary product specification for any RO system. It determines whether the output is suitable for potable use, boiler feed, semiconductor rinse, pharmaceutical USP, or beverage formulation. Typical SWRO permeate is 150–400 ppm TDS from a 35,000 ppm seawater feed, well below the WHO 600 ppm potable guideline. RO permeate is microbiologically safe and meets potable TDS standards, but it is often remineralized post-RO to restore palatability and protect downstream piping. Rising permeate TDS indicates membrane fouling, o-ring damage, or membrane oxidation (chlorine contact). Inspect interconnectors and check chlorine in feed. ForeverPure has supplied desalination, high-pressure pumps, and energy-recovery devices to commercial and industrial customers since 2003. Contact our engineers for sizing, quotes, or technical support.Permeate
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