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Understanding Purified Water for Pharmaceutical Applications

In the pharmaceutical industry, purified water is a crucial ingredient in the processing, formulating and manufacturing of pharmaceuticals and APIs.

What is Purified Water in Pharma?

Purified water is a pharmaceutical grade of water that is extensively used as an excipient in the preparation of sterile and apyrogenic medicines. It is usually produced on-site from potable water, which also must meet stringent quality thresholds.

What Are The Uses of Purified Water?

Applications of purified water in pharmaceuticals range from rinsing equipment to being one of the main constituents in several products and processes. Some of these include:

  • Production of oral and topical products
  • Granulation process for tablets and capsules
  • Being the feed water for WFI (Water for Injection)
  • Being the feed water for pharmaceutical grade clean steam
  • Preparation of cleaning solutions

The Process to Produce Purified Water in Pharma


In this initial stage, the water is made to pass through multimedia filters to eliminate suspended matter like mineral salts. This process is referred to as ultrafiltration. Following ultrafiltration, different additives are also introduced to perform specific roles.

Processes of Pre-Treatment


An anti-oxidant such as chlorine is added to the water to eliminate bacteria and viruses. 


Salts of magnesium and calcium render the water hard. Additives like hydrogen peroxide and sodium hypochlorite are introduced to the water, usually at 80 degrees Celsius, turning the hard water into soft water. Softening also aids in the process of electro de-ionization.

Dosing System

The process of dosing has three main objectives. Anti-scalent dosing is performed to break up the silica, sulfates, and other precipitates in the water, which may lead to fouling the filter membranes. It is achieved by adding sodium hexametaphosphates. Next, acids like hydrochloric acid and acetic acid are added to eliminate carbon dioxide in the water. This is called pH correction dosing. SMBS or sodium metabisulfite is also added to the water to eliminate the chlorine that was added during the process of chlorination, as it may be corrosive to the RO membranes in the piping. 

Post Treatment Stage

After treating the water with different additives and making it flow through multimedia filters, the water now enters the post-treatment stage, where other processes are carried out to ensure proper purification. This qualifies the water to meet the stringent standards set for purified water by different regulatory bodies.

There are several processes to manufacture purified water. Depending on the plant capacities and the end user application, a combination of one or more of the following processes is used to manufacture pharma-grade purified water. 

Reverse Osmosis

It is widely considered one of the most effective ways to purify water. It is extensively used in pharmaceuticals and industries where water is an essential resource and raw material. 

The word ‘osmosis’ comes from the Greek word ‘osmos’, which means ‘push’. During reverse osmosis, the natural osmotic flow of the water is disrupted using semi-permeable membranes which force the water to the diluted side. 

The membranes used in reverse osmosis are usually made of cellulose acetate with very small pore sizes, letting the water flow but trapping the microorganisms. When a high-pressure using pump is applied to the water, and it is made to pass through the membranes, it rejects the contaminants on its way. It is also essential to ensure that the membranes used in the process require specific sanitization methods. While rinsing the membranes with hot water at 80 degrees, Celsius eliminates microbial contaminants. Acids such as citric acid are used to eliminate the inorganic impurities that may compromise the quality of the water being passed through the membranes.

Reverse osmosis effectively removes salts, sugars, dyes, bacteria, other particles, microorganisms, trihalomethanes, pesticides, and volatile organic compounds. However, it cannot eliminate the dissolved gases in the water, such as carbon dioxide.


It is another popular method used in the pharmaceutical industry to obtain purified water. It is comparatively more cost-effective than the other methods and is thus preferred by many.

The principle of the de-ionization procedure relies on ion exchange and electrolysis. Its main objective is to eliminate specific ions from the water and replace them with more desirable ions. 

Water has different ions or differently charged molecules and atoms in it. Ions with a positive charge are called ‘cations,’ and the ions with a negative charge are called ‘anions’. The EDI module is set up using ion exchange resin beds and separated by ion- exchanging membranes which are basically high surface electrodes with positive and negative charges. When an electric current is passed through the water at right angles, the positively charged cation moves toward the negatively charged anode and the negatively charged anions move toward the positively charged cathode rendering the water de-ionized.

De-ionization effectively removes dissolved particles such as salts, minerals, and organic contaminants from the water. 


It is yet another popular way to manufacture purified water. Distillation uses the process of difference in vapour pressures (volatility) of water and impurities suspended in the water. The water is boiled in a specially designed multi-column distillation plant. The vapours are then condensed to obtain sterile and purified water. 

One of the primary uses of the purified water obtained through the process of distillation is Water for Injection (WFI). It is a grade of pharmaceutical water which is fit for delivering medicines or drugs directly into the bloodstream of patients. 

Ultraviolet Disinfection

UV disinfection is a simple and inexpensive method of water purification. In this process, the water is exposed to UV rays of specific wavelengths using a UV lamp to eliminate pathogens such as bacteria, viruses, algae, molds, etc. 

One of the main applications of UV disinfection apart from manufacturing healthcare products is Cleaning in Place (CIP), which is a method used in the pharmaceutical industry and is implemented to make sure the vessels, equipment, pipes, filters, and other paraphernalia are safe to be used for different pharma operations.

In conclusion, pharmaceutical-grade purified water based on specific pharmacopoeia requirements can be achieved through different methods. TSA has almost 20 years of experience delivering optimized purified water solutions at the lowest cost per litre. Our team can support you at every stage, from design and installation and validation to after-sales support. 

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