Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D6161-19 – Standard Test Method Technical Guide
📜 Introduction to ASTM D6161‑19 Terminology
ASTM D6161‑19 defines the standardized terminology used in the microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) membrane separation processes. Developed by Subcommittee D19.08 on Membranes and Ion Exchange Materials, this standard is essential for establishing a common language among manufacturers, consultants, and end‑users in the water treatment industry.
This terminology is designed to be independent of the source of manufacture, ensuring consistency across different systems and applications. It expands upon the foundational definitions provided in ASTM D1129 (Terminology Relating to Water) and is frequently referenced alongside practices such as D2035 (Coagulation‑Flocculation) and D3739 (Langelier Saturation Index).
🔬 Technical Note: The standard emphasizes that understanding the precise relationships found in membrane unit processes is critical for effective water treatment system design and operation. This terminology directly addresses the “inter‑process terminology confusion” that can arise between different membrane technologies.
⚙️ Significance in Membrane System Design & Water Chemistry
The scope of D6161‑19 covers the critical terms that define system performance, water quality, and component function. These definitions must be strictly interpreted to ensure accurate communication of system specifications, performance guarantees, and operational limits. Below are key terms from the standard organized by their relevance to system design and chemistry:
| 🟦 Term | 📏 Category | 📐 Definition (per D6161‑19) |
|---|---|---|
| Absolute Filter Rating | Filtration Performance | Particle size above which 100% of particles are trapped on or within the filter medium. |
| Accuracy | Measurement | Closeness of agreement between an observed value and an accepted reference value, including both precision and bias. |
| Aggressive Water | Feed Water Quality | Water having a high tendency to corrode pipes, usually indicated by a negative Langelier Index value. |
| Acidity | Water Chemistry | The quantitative capacity of aqueous media to react with hydroxyl ions. |
⚠️ Important Reference Note: The standard references Practice D4582 for the Stiff and Davis Stability Index. Note that D4582 was withdrawn in 2019. Practitioners should verify the current status and applicability of this calculation method for their specific RO system designs.
📖 Key Process Definitions: Components & Interactions
D6161‑19 provides critical distinctions between physical and chemical material interactions, as well as definitions for system components and pretreatment media:
| 🟦 Term | 📏 Category | 📐 Definition (per D6161‑19) |
|---|---|---|
| Absorption | Material Interaction | Release for desorption holding of a substance within a solid by cohesive or capillary forces. |
| Adsorption | Material Interaction | Holding of a substance onto the surface of a solid by chemical surface forces, without forming new chemical bonds. |
| Activated Carbon | Pretreatment Media | Granulated or powdered carbon used to remove tastes, odor, chlorine, chloramines, and some organics from water. |
| Accumulator | System Hardware | A pulsation dampener installed on suction/discharge lines of pumps to minimize pressure surges and provide flow uniformity. |
| Aerobic Bacteria | Biological Activity | Bacteria that require oxygen for growth. |
The standard also defines terms like aggregate (granular material such as sand, gravel, or crushed stone) and absolute filter rating, which are commonly used in the context of pre‑treatment and process performance guarantees.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D6161‑19?
This standard covers the use of microfiltration, ultrafiltration, nanofiltration, and reverse osmosis for membrane separation processes. It was developed in accordance with internationally recognized principles on standardization as established by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
💡 What is the difference between Absorption and Adsorption defined in the standard?
Absorption is defined as “the release for desorption holding of a substance within a solid by cohesive or capillary forces,” involving the bulk of the material. Adsorption is “the holding of a substance onto the surface of a solid by chemical surface forces, without forming new chemical bonds.” This distinction is crucial for understanding membrane fouling mechanisms.
⚡ How does D6161‑19 relate to ASTM D1129 (Terminology Relating to Water)?
D6161‑19 specifically states that it “expands the definitions found in Terminology D1129.” While D1129 covers general water-related terms, D6161 focuses specifically on the terminology for microfiltration, ultrafiltration, nanofiltration, and reverse osmosis processes.
📌 What does the term Absolute Filter Rating mean in the context of this standard?
It is defined as the “particle size above which 100 % of particles that are trapped on or within the filter medium.” This is a critical parameter for membrane and filter selection to ensure complete retention of particles above a specified size.