What Are the Water Quality Requirements? A Cross-Industry Guide

Although water is the source of all life, in industry, it is anything but simply "pure". Water specifications are defined at many different grades of purity depending on the industry and application, including purity to very specific levels of remaining ions, organics, particles, microbes and gases, each with the potential to interfere with your manufacturing processes, product quality and overall efficiency. Alfa Chemistry is a leading global supplier of high-performance ion exchange resins and ion exchange membranes to these markets and applications.

What Exactly is "Pure Water"?

In a true scientific sense, pure water (H2O) contains no other impurities. However, in real-world manufacturing settings, it is often both unnecessary and technically difficult to create truly 100% pure water. Instead, the standard for "pure water" is the near-total removal of a combination of specific target impurities (ions, organics, particles, microbes, and gases) to levels that will not negatively impact an intended use or process. These specifications are most often defined by Electrical Conductivity (EC) or its reciprocal Resistivity, as this indicates the level of remaining ionized impurities. The following is a general guideline of water types used in many industries.

• Industrial Pure Water: Conductivity 1 - 10 μS/cm; Resistivity 0.1 - 1 MΩ·cm (TDS<1 mg/L)
• High-Purity Water (HPW): Conductivity 0.1 - 1.0 μS/cm; Resistivity 1 - 10 MΩ·cm (TDS<0.3 mg/L)
• Ultrapure Water (UPW): Conductivity 0.055 - 0.1 μS/cm; Resistivity 10 - 18.25 MΩ·cm (TDS<0.1 mg/L)
• Pharmaceutical Purified Water (PW) - USP: ≤ 1.3 μS/cm @ 25°C (typically stricter than this limit); Resistivity: ≥ 0.77 MΩ·cm (often much higher in practice).
• Drinking Water: Conductivity 20-500 μS/cm; Resistivity 2-50 MΩ·cm

Why Industrial Pure Water Matters?

Industrial water: With the rapid development trend of industry, industrial production and manufacturing have increasingly stringent requirements for water quality. For example, in the fields of industrial electronic devices, semiconductor materials, semiconductor devices, components, printed circuit boards, integrated circuit chips, etc., high (ultra) pure water must be used for production and manufacturing, food, beverages, and drinking water must use high (ultra) pure water, biochemistry and precision courses must use high (ultra) pure water, other industries need industrial pure water, and the pharmaceutical industry must use industrial processing water. Eliminate sea surface and brackish water, clean water injection, injection, tablet pressing, biochemical products and equipment in the pharmaceutical industry, eliminate sea surface and brackish water, and spraying of automobiles, home appliances, glass coatings, cosmetics, and fine chemical products must use high (ultra) pure water.

Domestic water & drinking water: Compared with mineral water, spring water, and natural water, which are limited by resources, purified water is produced by tap water through a certain production process. Therefore, the most popular water in the market is purified water, and the quality of purified water is closely related to the lives of the people. The pure water in life mainly includes FDA 21 CFR §165.110 (Bottled Water Standards) and IBWA Model Code (International Bottled Water Association). In these two standards, there are sensory indicators (taste, odor, color, clarity), physical and chemical indicators (TDS, pH, conductivity, heavy metals), and sanitary indicators (coliforms, E. coli, cryptosporidium, disinfection byproducts). The standard of pure water in life is more comprehensive and complex than that of industrial pure water.

The following table lists the adverse effects that impurities in water may bring in different industries.

Industry-Specific Water Purity Requirements & Solutions

Technical terms:

• Reverse Osmosis (RO): Uses semi-permeable membranes to remove >95-99% of dissolved ions and organics. Often the primary workhorse.
• Ion Exchange (IX): Employs cation exchange resins and anion exchange resins to remove specific ions via exchange. Used as primary demineralization (post-RO) and polishing (mixed bed resins - MB).
• Electrodeionization (EDI): Combines ion exchange resins and selective ion exchange membranes with an electrical current to continuously remove ions and regenerate the resin without chemicals. Common post-RO polishing.
• Type I/II/III: ASTM standards for laboratory reagent water (ASTM D1193-91).

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