Introduction 

Water purification is the process of removing contaminants including, biological contaminants, suspended solids and gases from water. 

Water contains numerous different contaminants and even trace levels of impurities can affect a variety of scientific experiments. It is vital for getting good, reliable, accurate scientific data from experiments that you use water for making up buffers or rinsing glassware which has had these impurities removed.   

When it comes to choosing your water purification system it is important to know what both your application and impurities are.  

Fistreem International have designed economical water purification systems that guarantee pure water for all your laboratory needs.  

Technologies 

There are several different methods of water purification that you can use to create pure water from potable water supplies. The technology best suited for your needs depends on the application you require it for, as well as the grade of water needed

Distillation 

Distillation is a long-established method that separates water from contaminants by changing the state of water from liquid phase to a gas phase then back to a liquid phase. 

Water is first heated to boiling point and water vapour rises to a condenser where cooling water lowers the temperature so that the water vapour is condensed, collected, and stored. 

Distillation removes the following water impurities 

• Organic compounds 
• Inorganic salts 
• Microrganisms and biomolecules
• Pyrogens 

Reverse Osmosis (RO) 

The process of osmosis, a solvent naturally moves from an area of low solute concentration (high water potential) through a membrane to an area of high solute concentration (low water potential). 

Reverse osmosis an applied pressure is used to overcome osmotic pressure. The solute is retained on the pressurised side of the membrane and the pure solvent is allowed to pass to the other side. 

Reverse Osmosis removes the following water impurities 

• Organic compounds  
• Inorganic salts 
• Microorganisms and Biomolecules 
• Pyrogens 

Deionisation 

Deionisation uses synthetic ion-exchange resins to chemically remove ions from feedwater. As the water passes through the ion exchange of hydrogen and hydroxide ions for dissolved minerals and then recombine to form water.  

Deionisation resin beds or columns are typically made from cation-exchange resins and anion-exchange resins either in separate beds or packaged together. There are three types of deionisation: cocurrent, counter-current and mixed bed. 

Co-current deionisation refers to the original downflow process where both input water and regeneration chemicals enter at top of an ion exchange column and exit at the bottom.  

Counter current deionisation comes in two forms the first form is up flow columns where input water enters from the bottom and regenerants enter from the top of the exchange column. Second form is up flow regeneration where water enters from the top and regenerants enter from the bottom. 

Mixed bed deionisation is a 50/50 mixture of carbon and anion resin combined in a single ion-exchange column. 

Deionisation removes the following water impurities 

• Inorganic ions 

Ultra-Violet (UV) 

UV is used to disinfect water. Two wavelengths are commonly used 185nm and 254nm.  

254nm UV has a strong bacterial action as it damages DNA and RNA polymerase at low doses preventing replication. UV light at 185nm has a strong oxidising action which breaks down large organic molecules into smaller ionised components ultimately CO2. 

A UV chamber typically consists of a UV lamp mounted in a quartz tube in the centre of a stainless-steel tube, water then flows through the zone between the quartz and the steel tubes. 

Ultra-Violet removes the following water impurities 

• Trace organic compounds 
• Inactivates micro-organisms and biomolecules