How to Design A Laboratory Water Purification System

Your current applications and future testing methods or equipment expansions determine the type of water you need. According to international standards, laboratory water is classified into three tiers: ultrapure, pure, and reverse osmosis.

Laboratory feed water may contain organic compounds, dissolved inorganic ions, microorganisms, and other contaminants. To ensure you have the right water grade needed for your workflow, the water system should use the correct purification technologies.

1. Prefiltration and Activated Carbon - A mechanical filter traps large suspended elements, such as silt, clay, and rust. Granular or block-activated carbon beds reduce free chlorine, chloramines, and large organic compounds. 

2. Reverse Osmosis - A semi-permeable membrane functions as a physical barrier that blocks anything larger than water molecules. These include dissolved organic ions, organic molecules, bacteria, viruses, and other environmental particulates. 

3. Deionization / Ion Exchange - Synthetic spherical resins exchange the ions of dissolved inorganic ions that slip through the RO membrane. Cation resins swap positively charged ions for hydrogen ions, while anion resins swap negatively charged ions for hydroxyl ions. The released ions combine to form pure water.

4. Ultraviolet Photo-oxidation - A 254 nm wavelength UV lamp destroys bacterial DNA, rendering the water bacteriologically sterile. The other lamp, emitting light at 185 nm, breaks down trace organic molecules, lowering total organic carbon (TOC) levels to less than 5 parts per billion.

5. Ultrafiltration - Hollow-fiber membranes with a 1 to 10 nm pore size physically filter out macromolecular biological contaminants. Pyrogens, RNase, and DNase will be blocked, as water molecules are allowed to pass through.

An oversized or undersized water purification system causes issues, such as increased biofilm development, workflow bottlenecks, and unnecessary capital expenditure. Follow these tips to avoid these problems and ensure your setup can sustain your daily processes.

• Use a small, point-of-use system that purifies water directly from a pretreated line if your lab requires small volumes of water at inconsistent intervals.

• Pair your system with an appropriate storage reservoir if your applications require large volumes of water within a short window.

• Use a tank with a vent filter when using a storage reservoir for Type 2 or RO water to block airborne particles, carbon dioxide, and volatile organic compounds.

• Add an automated recirculation loop with a UV lamp to prevent biofilm growth within the stagnant water.

Most laboratories are shifting from centralized water systems to point-of-use systems and wall-mounted filter holders. Not only are these alternative setups more cost-effective, but they also offer better flexibility and are easier to scale. Adaptable water systems are ideal for labs with changing project scopes, limited space, or localized high-purity demands.