In the previous article, we saw the fundamentals of water and the properties of water due to its molecular structure. So, how does it affect the water used in pharma industry?
| Kishor Datar |
It is evident and clear that when a drug is administered to a patient it is importantto ensure that only the drug having therapeutic use and the excipients required to ensure that the drug is administered properly are present in the product.
Hence, in the pharma industry it is important to ensure that contamination of the product is avoided. This means that the materials forming part of product or used in the process are assuredly free of contamination or it is kept within a limit prescribed for such a product type.
As we learnt, water is a universal solvent and will have contamination. However, it is used in the pharma industry for various process steps, including cleaning. So, it is essential to see that the water used in such processes must have contamination within limits.
Thus, evidently it is necessary to have a treatment system to ensure that such contaminations are removed from water to make it usable in the pharma industry.
However, let us first understand the type of contaminations which can be present in water, before we move on to handling them. This will enable you to understand the further subject with better clarity.
Generally contaminants found in water are divided as follows:
Suspended
These are the particles suspended in water and don’t have any other chemical bonding with water molecules. Normally they are dirt, dust, fibres, colloids etc. The particles which are not chemically bonded or dissolved but are suspended in liquid are called as suspended contaminations. Water will have suspended particles in the form of dirt/fibre etc. The sources for these contaminants are from atmosphere, surface etc. These contaminants are easy to remove by filtration method. However suspended particles also have colloidal material. They carry a slight negative charge, which causes them to repel each other like two south poles of a magnet. Although they do not readily dissolve in the water, they repel each other and form a stable suspension in water. Since these are very tiny particles and are slightly charged negative, repelling each other, makes evenly distributed suspension. Colloids are the one which are most difficult silts to be removed.Also these particles, being tinny in nature, if not removed, clog the physical filtration mechanism and hence are very important aspect in purification.
Bacteria
Gases
Water can dissolve gases though not in large quantities but enough to make it non-compliant to pharma specifications. Most common gases which are found dissolved in water are O2 and CO2.
Dissolved ions/ inorganic salts
Many ions/ inorganic salts are dissolved in water. The maximum limit for each ion in dissolved condition depends on the temperature, pH etc.
With above contaminants known, it is clear, that water if it is to be used in any process, needs to be purified to remove contaminants which are not acceptable for the process or its end use.
The type of methods used to remove such contaminants depends on the water analysis and end use requirement. However, generally the following systems are used:
To reduce suspended particles: Filtration, a process of trapping the suspended particles using filter media.
To reduce colloidal: Agglomeration, a process of using natural or poly electrolyte material to react with colloids and neutralise negative charge on them so as to agglomerate them to precipitate out.
To reduce dissolved gases: To reduce dissolved gases various methods are used, like changing pH value of water. For e.g. at pH more than 8.2, CO2 can’t remain in dissolved condition in water. Degasser units are also used for reducing the dissolved gases.
To reduce dissolved solids: Chemical method of using charged particles of opposite charge to adsorb cations/ anions and removing these adsorbed during wash cycle. Physical filtration method using cross flow filtration membrane to remove due to porosity of membrane.
To reduce bacteria: Bacteria are living organism. They are organic compounds and hence generally following methods are used:
- Chemical method to oxidise – This is used by dosing higher reducing agents like Cl2/ Ozone. Which provides Nascent Oxygen to react with organic cells to reduce them.
- Temperature – Bacteria decompose at higher temperatures. This physical property is used to reduce bacteria by heating water above 60° C temperature.
- Using membrane filters – Membrane filters have ultra low porosity. The size of bacteria are higher than these porosity and hence gets removed from water stream.
Sources of water
We took a brief look at water contaminants and most commonly used treatment methods for reducing contaminants. Now let us try and look at the natural sources of water and how the source affects the contamination. This will probably bring in further clarity regarding the basics to understand further series of articles.
We all know the water cycle. Water is available naturally through rains/ snow falls. During sunny days, this water evaporates and forms a water vapour. These vapours, in turn, form clouds and during rainy/ snow fall season, water reaches to earth again. The water stored on earth surface, penetrates through layers of earth and gets stored below the earth surfaces. These are natural resources of water that are available to us.
During earlier days of human life, human developed the colonies near the natural water sources like lake, river etc.
As the colonies started increasing it was not possible for humans to remain close to such natural sources. However, water was need for life and hence during the process of urbanisation, using technology, humans developed two basic methods of water sources. Even today these are used as main sources of water.
Surface water: Water available on surface of earth is referred as “surface water” This can be through rivers, natural lakes. Humans have developed the method of blocking water during rainy season in the form of dams and utilising the same throughout the year. Water, available through natural sources like rain/ snow fall, is transported on the earth surface due to natural slopes etc. and by constructing dams, this water is blocked in going to river and sea. Such water travels on the earth surface for long distances and carries dirt/ dust/ fibres/ organic compounds etc. on earth. This also is referred to, as surface water. Surface water has higher degree of contamination of dirt, dust, fibres, colloidal, biological and vegetative organic contaminants and lower degree of contamination of dissolved ions and gases.
Ground water: Water is also stored inside the earth surface in the form of dam, river, lakes etc. penetrates through surface of earth. It is referred to as ground water This penetration action takes place due to a physical process called ‘Osmosis’. While the Osmosis takes place, water, as we learned, due to polar nature, captures the metals, solids in the earth layers and hence becomes vulnerable to such dissolved contamination. However since it gets stored in the earth surface due to Osmosis process, it has limited ways to have dirt/ dust/ fibres/ organic compounds etc. By drilling hole in the earth surface to the required depth, this water can be sourced.
Ground water has higher degree of contamination of dissolved ions and gases: especially Calcium, other divalent salts and silica salts while there is a lower degree of contamination of dirt, dust, fibres, colloidal, biological contaminants.
The author can be reached at kd.datar@tppl.net.in