Characteristics and Principles of Laboratory Ultra-Pure Water

Laboratory ultra-pure water is renowned for its exceptional purity, achieved by nearly eliminating conductive substances from water and reducing undissolved gases, colloids, and organic matter (including bacteria) to minimal levels. Its electrical conductivity typically ranges from 0.1 to 0.055 µS/cm, with a resistance of over 10×10^6 Ω/cm at 25°C. Ideally, pure water (theoretically) has an electrical conductivity of 0.055 µS/cm and a resistance of 18.3×10^6 Ω/cm at 25°C.

Principles of Laboratory Ultra-Pure Water Generation

Laboratory pure water systems operate on advanced technology, combining reverse osmosis (RO) and ion exchange techniques. These systems are controlled by microcomputer boards, offering automatic water quality monitoring and display, resulting in high-quality output water with an electrical resistance typically reaching 18 MΩ/cm. Imported components such as booster pumps, solenoid valves, high-capacity ion exchange resins, RO membranes, filters, piping connectors, control devices, and ultraviolet lamps are used in these systems.

Reverse Osmosis Principle

The reverse osmosis principle involves applying pressure greater than natural osmotic pressure to water, causing water molecules to move from a higher concentration side to a lower concentration side. Since the pore size of reverse osmosis membranes is much smaller than viruses and bacteria, by several hundred to even thousands of times, various contaminants such as viruses, bacteria, heavy metals, solid soluble substances, organic pollutants, calcium, magnesium ions, and more cannot pass through the reverse osmosis membrane. This process effectively purifies the water.

Characteristics of Laboratory Ultra-Pure Water Systems:

  1. High Operating Pressure and Leak Resistance: The module employs multi-layer rubber O-ring seals, ensuring high pressure resistance and preventing leaks.
  2. No Chemical Usage: Due to the presence of technical resins in the concentrate, reducing membrane resistance, there is no need for concentrate recirculation or salt injection into the freshwater chamber. This setup is advantageous for the removal of weak electrolytes.
  3. Simplicity in System Design: The system is straightforward, with only three piping connections (inlet, product water, and concentrate). It does not require circulation pumps, salt injection systems, or PLC program controllers, resulting in lower construction and maintenance costs.
  4. Concentrate Recovery: The concentrate’s water quality (20-100 µS/cm) is better than that of the feedwater and can be recycled for further use before the RO unit.
  5. Other Advantages: The system does not require salt injection, thus avoiding chlorine gas damage to the module’s internal structure and contamination of the surrounding environment. Each module has an independent power control, and maintenance of one module does not affect the normal operation of others.

Laboratory Ultra-Pure Water Production Processes:

  1. Ion Exchange Method: This process involves the following stages: Raw Water → Raw Water Booster Pump → Multi-Media Filter → Activated Carbon Filter → Water Softener → Precision Filter → Cation Resin Filter → Anion Resin Filter → Mixed-Bed Resin → Microporous Filter → Point of Use.
  2. Two-Stage Reverse Osmosis: The process includes Raw Water → Raw Water Booster Pump → Multi-Media Filter → Activated Carbon Filter → Water Softener → Precision Filter → First-Stage Reverse Osmosis → pH Adjustment → Intermediate Water Tank → Second-Stage Reverse Osmosis → Purified Water Tank → Pure Water Pump → Microporous Filter → Point of Use.
  3. Electrodeionization (EDI) Method: This method involves Raw Water → Raw Water Booster Pump → Multi-Media Filter → Activated Carbon Filter → Water Softener → Precision Filter → First-Stage Reverse Osmosis Unit → Intermediate Water Tank → Intermediate Water Pump → EDI System → Microporous Filter → Point of Use.
  4. Alternative Process: Raw Water → Multi-Media Filter → Activated Carbon Filter → Water Softening Unit → Intermediate Water Tank → Low-Pressure Pump → pH Adjustment → High-Efficiency Mixer → Precision Filter → High-Efficiency Reverse Osmosis → Intermediate Water Tank → EDI Water Pump → EDI System → Microporous Filter → Point of Use.


Laboratory ultra-pure water is characterized by its exceptionally high purity achieved through advanced water treatment technologies such as reverse osmosis and electrodeionization. These systems provide researchers with the reliable and pure water required for laboratory experiments and analytical processes, contributing to the success of various scientific endeavors.

Xi’an CHIWATEC Water Treatment Technology is a high-tech enterprise specialized in various water processing devices. Aside from these individual products, which cover a number of types and series, we can also help with related comprehensive engineering projects. Thanks to our hard work and dedication upon our founding, we are now one of the fastest-developing water treatment equipment manufacturers in Western China.

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