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D4194-23 – Standard Test Method Technical Guide
📖 Scope and Terminology
ASTM D4194-23 defines standardized test methods for determining the operating characteristics of reverse osmosis (RO) and nanofiltration (NF) devices. The standard is divided into three specific test methods: Brackish Water Reverse Osmosis Devices (Test Method A, Sections 8–14), Nanofiltration Devices (Sections 15–21), and Seawater Reverse Osmosis Devices (Sections 22–28). All values are mandated in SI units, and the methods are intended for evaluation under standard laboratory conditions rather than direct field application with natural waters.
Key terminology utilized in this standard is aligned with ASTM D1129 (Terminology Relating to Water) and D6161 (Terminology Used for Membrane Processes). Understanding these definitions is critical for accurate testing:
| 🟦 Term | 📏 Definition / Range |
|---|---|
| Brackish Water | Water containing dissolved solids from 1,000 to 30,000 mg/L. |
| Seawater | Water with total dissolved solids ranging from 30,000 to 60,000 mg/L. |
| Nanofiltration (NF) | A “loose RO” process designed to remove selected salts and most organics above a 300 molecular weight range, rejecting particles larger than 2 nm. |
| Reverse Osmosis (RO) | A pressure-driven process that removes ions based on electrochemical forces, colloids, and organics down to a 150 molecular weight. |
| Concentrate / Permeate | The stream exiting the device with concentrated solutes / the portion of the feed that passes through the membrane. |
© 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence.