Understanding Laboratory Water Purification: A Step-by-Step Guide and Flowchart.

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Have you ever wondered what it takes to produce the ultra-pure water essential for laboratory work? Whether you're running sensitive analytical tests or preparing critical solutions, water purity can make or break your experiments. This comprehensive flowchart breaks down the sophisticated process of laboratory water purification from raw water to Type I ultrapure water, detailing each crucial step and its specific parameters.

Laboratory-water-flowchart

Stage 1: Raw Water Pretreatment

Coarse Particle Filtration

Utilizes 5 μm and 1 μm polypropylene filters in series and operates at 2-3 bar pressure to effectively remove sediment, sand, and larger particles.

Dechlorination

Water flows through a stainless-steel column filled with granular activated carbon (particle size 0.5-1 mm) at a rate of 10-15 L/min per m³ of bed, with a contact time of 5-7 minutes to remove residual chlorine.

Decalcification

Reduces water hardness to <1 mg/L CaCO3 using sulfonated polystyrene resin in sodium form.

Stage 2: Primary Purification Treatment

Reverse Osmosis (RO)

Removes dissolved solids and contaminants using a polyamide membrane at 15-20 bar and 15-25°C (optimal 20°C), with a salt rejection of 98-99%.

Mixed Bed Deionization

This process effectively removes virtually all dissolved ions from the water, producing highly purified water suitable for laboratories and industrial applications. The system contains two key components:

  • A Cation exchange resin with sulfonic groups that carries a negative charge
  • An anion exchange resin with ammonium groups that carries a positive charge

When water flows through this mixed bed, two reactions happen at the same time:

  1. The cation resin captures positive ions like calcium, magnesium and sodium from the water, releasing hydrogen ions (H+) in exchange
  2. The anion resin traps negative ions like chloride, sulfate and nitrate, releasing hydroxide ions (OH-) in return

The released H+ and OH- ions then combine to form pure water molecules (H2O).

Stage 3: Final Polishing Treatments

Continuous Electrodeionization (EDI)

EDI is a water purification technology that uses electricity, ion-exchange membranes and resins to remove ionized species from water without chemical regeneration. The process operates at specific voltage (300-600V DC) and current (1-5A) conditions, where an electric field forces ions through resins and selective membranes, continuously producing high-purity water (>15 MΩ·cm) while collecting impurities in concentrate streams.

UV Radiation Treatment

UV Radiation Treatment serves two critical purposes in water purification: breaking down organic compounds and eliminating microorganisms. The system uses a dual-wavelength mercury lamp that simultaneously emits UV light at 185 nm and 254 nm by 10-15 seconds of exposure.

A 185 nm wavelength to oxidize and break down organic contaminants, reducing Total Organic Carbon (TOC) to <5 ppb whilst a 254 nm wavelength destroys bacteria and other microorganisms.

 Terminal Ultrafiltration

Terminal Ultrafiltration is the final polishing step in water purification that removes the smallest contaminants through a specialized membrane system. This process ensures the highest level of water purity by eliminating endotoxins, bacteria, viruses, and other microscopic particles.

The system operates using polysulfone membranes with a molecular weight cut-off of 10 kDa. The water passes through these membranes under a controlled pressure of 0.5-1.5 bar, effectively retaining pyrogens and particles larger than 0.03 micrometers.

 

Now very few secrets escape you about water purification for laboratory use.