Purification Systems | Laboratory Water

Importance And Need For Lab Water Purification

The water purification system for laboratory use is vital and is usually purified from drinking water. The unique ability of water is to dissolve substances that support every form of life. This means that drinking water contains many substances like minerals, chemical compounds, microorganisms, and gases. The additional impurities in the drinking water or natural water are removed during the drinking water purification process. The water purity may vary from one geographical region to another and from season to season.

Usually, purified water is used in most laboratory and clinical applications. Domestic consumers consider tap water to be pure. But laboratory scientists regard it as highly contaminated. Analytical and experimental scientists are more concerned with the elements and compounds concentration in parts per billion (ppb) or lower. As the elements and compounds have a tendency to interact with other substances and many of these contaminants can have a negative effect on application under analysis.

The ultrapure water system for laboratories is considered in an analytical laboratory that can substantially reduce the time spent on troubleshooting issues. Lab water purification system delivers highly purified water to enhance the quality of lab applications.

Generally, there are 5 types of impurities found in natural and drinking water:

  • Suspended particles
  • Dissolved inorganic compounds
  • Dissolved organic compounds
  • Microorganisms & biomolecules
  • Dissolved gases

The main objective of water purification methods is to remove drinking water impurities that minimize contamination from purification system components and bacterial growth.

Contaminants in Potable Water

Inorganic Ions Sodium chloride Calcium bicarbonateCations Na+Ca+2Anions Cl-HCO-3
OrganicsNatural Tannic AcidHumic AcidMan-Made PesticidesHerbicides
Particles (Colloids)                                  Non-Dissolved Solid Matter (Small deformable solids with a net negative charge)
Microorganisms  (Endotoxin)Bacteria , Algae , Microfungi (Lipopolysaccharide fragment of Gram-negative bacterial cell wall)
Dissolved gasesHydrogen Sulphide, Methane, Nitrogen, Oxygen

  Measurement of Contaminant level

Inorganic IonsConductivity (Resistivity)μs/cmMΩ.cm
OrganicsTotal Oxidizable Carbon (T.O.C)ppb (μg/L)
Particles (Colloids)Silt Density Index / Fouling Index0.45 μm membrane.
EndotoxinRabbit Inoculation testLAL TestEndotoxin units/ml

There are different types of water purification systems for laboratories generally  referred to as Type 1, Type 2, and Type 3.

Lab Water Purification System – TYPE 1 (Ultrapure/ Reagent grade)

It is also referred to as an ultrapure water system for laboratories. This grade of water purification system for laboratory is required  for most water critical applications such as

Buffer for

  • HPLC (High-Performance Liquid Chromatography)
  • GC (Gas Chromatography)
  • AAS (Atomic Absorption Spectrophotometry)
  • ICP-MS(Inductively Coupled Plasma Mass Spectrometry)

 Culture Media for

  •  Mammalian cell culture
  •  IVF ( In Vitro Fertilization)

Reagents for Microbiology applications

Lab Water Purification System –Type 2 ( Pure / Analytical grade)

This grade of a water purification system laboratory is used for standard applications such as buffers, media preparation, pH solutions, certain clinical analyzers, and weather meters feed. It is a common practice to feed Type2 water purification systems to Type1 water purification systems.

Lab Water purification System-Type 3 (Pure/ Laboratory-grade)

This grade of a water purification system laboratory is used for general laboratory applications (non-critical work) such as glassware rinsing, heating baths, humidifiers, autoclaves filling, disinfector feed as well as environmental chambers, and plant growth rooms. This system can also be used as a feed to the Type 2 lab water purification system.

ASTM Standards for Laboratory Reagent Water

ASTM: American Society for Testing and Materials

ContaminantParameter (units)Type 1Type 2Type 3
IonsResistivity (MW-cm)> 18.0> 1.0> 4.0
 Silica  (ppb)< 3< 3< 500
OrganicsTOC (ppb)< 50< 50< 200
Particlesparticles > 0.2 um (#/ml) < 1NANA
BacteriaBacteria (cfu/ml)10/1000 ml10/100ml100/10ml
 Endotoxin (EU/ml)< 0.030.25NA

CLSI Standards for Laboratory Reagent Water

CLSI: Clinical and Laboratory Standard Institute

ContaminantParameter and UnitType 3Type 2Type 1CLRW
IonsResistivity (MΩ-cm)> 0.05 (50 KΩ)> 1> 18> 10
OrganicsTotal Organic Carbon (TOC) ppb< 200< 50< 10< 500
Pyrogens(Eu/ML)N/AN/A< 0.03---
ParticlesParticles > 0.2 µm (units/mL)N/AN/A< 1 (0.22 µ filtration required)Include 0.22 µ filtration
ColloidsSilica (ppb)< 1000< 100< 10---
BacteriaBacteria (cfu/mL)< 1000< 100< 1< 10

ISO 3696 Standard

ISO: International Organization for Standardization

ParameterType 1Type 2Type  3
Conductivity µS/cm (temp corrected)< 0.1< 1< 5
pH at 25°CN/AN/A5.0 - 7.0
Oxidizable matter Oxygen (02) content mg/LN/A< 0.08< 0.4
Absorbance at 254 nm and 1 cm optical path length, absorbance units< 0.001< 0.01N/A
Residue after evaporation on heating at 110°C mg/kgN/A< 1< 2
Silica (Si02) mg/L< 0.01< 0.02< N/A

Methods of lab water purification

The water purification process with a pretreatment purification stage to reduce the damage of subsequent water purification components. This pretreatment purification stage ensures reliable operation and decreases the operational cost preventing the damage of expensive components in the major laboratory water purification process. Different technologies are used in the water purification process and are listed below.

Water pretreatment technologies

  • Microporous depth filters
  • Activated Carbon (AC)- in pretreatment media

Major Water Purification Technologies

  • Reverse Osmosis (RO)
  • Ion Exchange (IX)
  • Electrodeionization(EDI)
  • Distillation 
  • Activated carbon
  • Microporous filters
  • Ultrafilters
  • Vent filters
  • Degassing membranes
  • UV light

Challenges In Ultrapure Water System for laboratory

The main challenge for an ultrapure water purification system laboratory is the bacteria as they enter unprotected water purification systems or any openings in the system. This will grow as biofilms on all wet surfaces of purification components, storage tanks, and the plumbing of distribution systems and multiply even when the contraction of nutrition in the water is very low. This biofilm layer will protect the organisms from the periodic treatment of biocides. These biofilms and their by-products are potential contaminants of water.

It is more important to remove the bacteria present in the feed water and ensure that minimal bacteria is present after each stage of purification. Prevent bacteria from entering the water purification system and recontaminating it. The system design and periodic sanitization should inhibit the growth of bacteria in the system.


Here, we understand the necessity of a water purification system for laboratories. A general overview of different types of impurities present in the water and different grades of water purification systems and their laboratory applications is made. Several organizations like ASTM, CLSI, ISO have published the laboratory water quality standards. Had a general idea of methods and technologies used for water purification system laboratory and the challenges faced in the ultrapure water purification system. 

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