Importance of Water Purification System in Laboratory

Tap Water contents paving way for  Lab Water Purification System

In the laboratory, water is the most used reagent. However, it is not respected and its purity is not being taken care of. This leads to a negative impact on laboratory experiments. The accuracy and precision of the experiments are getting lost due to impure water. For each type of experiment, there is a need for a certain purity or grade of water. Using tap water for all laboratory purposes kills the aim of getting good results. To obtain better purity in water, it is necessary to have a lab water purification system. Water purification system for laboratory helps in maintaining purity of water in the laboratory. The water purification system for the laboratory serves as a one-stop solution for getting the desired amount of quality and quantity of laboratory water at the desired level. 

Tap water usually contains microorganisms, dissolved gases, ions, organic and inorganic compounds, and particles. Most of these contaminants will influence the results of the experiments. Hence, usage of tap water as such is impossible in the laboratory for sensitive experiments.

Types of Lab Water

There are three types of water -  Type 1 water, Type 2 water and Type 3 water.

• Type 1 Water - Type 1 water is ultrapure water. There are very low levels of ions, particles, and bacteria present. It is prepared by a combination of purification techniques, namely membrane filtration, deionization, ion exchange resins, ultraviolet photo-oxidation, and reverse osmosis. This water is used in the fields of cell biology and molecular biology for the preparation of laboratory reagents. It is also used in sophisticated analytical instruments like gas chromatography, high-performance liquid chromatography, and inductively coupled plasma mass spectrometry. This water has maximum precision and minimum interference.
• Type 2 Water - Type 2 water is pure water. It consists of some organic molecules, ions and bacteria. This kind of water is used for preparing buffers and reagents used every day in the lab. 
• Type 3 Water - Type 3 water is the water prepared by the ion exchange process. This type of water finds its usage in less sensitive operations like water baths, rinsing of glassware and qualitative analyses. It is used for general washing. Based on needs, laboratories require one or two types of water. 

Need of water purification system for laboratory

Tuned to the laboratory's needs, it is necessary to design a water purification system for the laboratory. The purification process should be available in the minimum time in the lab water purification system. Demand for lab water systems has increased drastically over the years because parts-per-million was a lesser level of contamination. But nowadays, even parts per trillion have been seen as major contamination in water. A few years ago, only ionic contaminants were given importance. But these days, gases and organics are also carefully watched in water.

Different methods of Water Purification

Eight methods are usually used to purify water. They are 

• Electrodialysis, 
• Ultraviolet oxidation, 
• Ultrafiltration, 
• Microporous filtration, 
• Activated carbon filtration, 
• Distillation,
• Deionization  
• Reverse osmosis.

• Distillation is a comparatively lower cost process compared to some methods. It is usually used in colleges and schools. Hence, a water distillation unit for the laboratory is a must in every laboratory because it is not acceptable to use high pure water to wash basic glassware. It will increase the financial burden. It is better to avoid high pure water for washing laboratory glassware and should be used for instruments like inductively-coupled plasma mass spectrometry. However, distillation requires a huge amount of water for the recirculation purpose in the condensing section.
• Demineralization or deionization is performed using ion exchange resins, it is comparatively inexpensive. Yet, it is ineffective in the removal of suspended particles, bacteria, and organics. Also, column regeneration is essential once saturation of ion exchange sites occurs.

• Adsorption occurs through activated carbon packed columns. It is useful in the removal of chloramines, organics and chlorine. It aids to mitigate the total organic carbon. However, it is not possible for all organics. Some soluble compounds can’t be filtered using this process.
• Ultraviolet radiation at 185 nm helps in breaking down large organic molecules into tiny ionic molecules, which will be easily removed by the deionization process. Radiation at 254 nm is used to eradicate bacteria in water. But, the process is not able to remove particulates, colloids, and ions. The reduction of total organic carbon is lesser only.
• Membrane filtration is an effective technique in the removal of bacteria, suspended impurities, and particulates that are greater than the pore size of the filter. Microporous filtration, ultrafiltration, nanofiltration, and reverse osmosis are the techniques that come under membrane filtration. Depending on the technique, operating pressure, efficiency, and cost will vary. It is capable of providing high pure water to the laboratory. The process is advantageous as it removes endotoxins (pyrogens). The con of the process is filtered get choked after prolonged usage. For damaged filters, regeneration is impossible. In addition, dissolved organics can’t be removed during the process.

Initially, tap water has to be converted into pure water. Then the water system should be converted into ultrapure water. Thus, extracting ultrapure water from tap water is a minimum two-step process, which demands much time, finance and energy. As the number of treatment steps increases, the loss of water also increases as in each step, some water is lost as an impurity. Additionally, there is a need for pre-treatment before the passed into major purification technology. Pre-treatment removes larger suspended molecules, which will block the filters in membrane filtration. Post-treatment chlorination is used for the prevention of bacterial growth during the storage of water in larger tanks. High pure water is reactive to minute molecules. Hence, the storage time of filtered water should be kept minimal. 

Conclusion

The success of a laboratory depends on the reliability of pure water as it impacts the repeatability and accuracy of results. Desired purity of water is different for different methods and instruments. One should look carefully at the purity and conductivity of water needed for each experiment and accordingly, run the required combo of purification methods. It will help to optimize the expenditure needed for running the process. For quantity of water, quality can’t be traded off and vice-versa. One can’t use low grade water for sophisticated equipment. Also, it is not advisable to utilize pure water for washing the glassware initially. However, after the experiment, high pure water should be used for washing.