Processes of Generating Pharmacopeia Grade Purified Water

Process water (council water) comes in off the mains supply and the filtration process is underway. The treatment process is started by ensuring the chlorine content is right to kill off any bacteria. There may possibly be a chlorine detector at the start, and it doses chlorine to keep that concentration right. As water is pumped through the carbon bed, organic compounds and pollutants are removed as they are absorbed by the carbon. Subsequently chlorine residues are removed at this stage. (Simazaki, D et al 2008).

Water softeners follows then as this is where salt water is used to substitute the Calcium and Magnesium ions with Sodium (soft) ions - the calcium ions make the water hard and u get calcites forming on your equipment. During reverse osmosis the carbonate is removed. A mixer guarantees adequate mixing and homogenous dosing. The reaction to convert CO2 to carbonate decreases the pH of the water back to a slightly acidic or neutral pH (Van (Dijk J.C et al, 2000). This is the final step which utilises chemicals to neutralise or remove contaminants in the water treatment system.

After water softener, you go into carbon filters – essentially a charcoal filter bed which takes out organic impurities – removes the chlorine which was thrown in at the start. In order to filter water, charcoal carbon filters are most effective in eliminating chlorine, particles similar to sediment, volatile organic compounds (VOCs), odor and taste. By using a filter rating of 5μm, this leads to 95% of material larger than 5μm will be held by the filter. This will physically eliminate dirt or silt but will have partial effect on the microbes that are naturally smaller than 5μm in size.

Additionally, an Ultra Violet lamp can be placed at the end of each carbon filter in order to kill any bacteria. UV light treatment is cheap, effective and a simple way to disinfect the water. The water will be passed through a thin channel where the Ultra Violet light, at 254nm, passes through the water and penetrates the microbial cell walls. Ultra Violet radiation then disturbs the cell DNA stopping reproduction (TroganUV, 2018).

Process continues after carbon filters & UV lamps to Reverse Osmosis (RO) train. (RO) is a water treatment process that eliminates contaminants from the water by forcing the water molecules through a semipermeable membrane using pressure. During this procedure, contaminants are filtered out and flushed away, resulting in clean drinkable water. Osmosis is the procedure whereby the molecules of a solvent lead through a semi permeable membrane from a higher concentrate of solution to a less solution of less concentration, thus balancing the concentration on either side of the membrane (Baumgarten,C et al 2012).

Continuous Deionisation is achieved, after RO, using as a polishing step in order to remove any ions that were not removed. Conventional Ion Exchange uses a polymer resin to attract and bind ions which in turn removes them from the water. In return this consumes the resin which must be replaced, leading to both expense and downtime of the system (Wychwood Water Systems Ltd, 2015).

Fitting a 0.22μm filter bank to act as a final barrier to microbes entering the WFI system is installed. It is at this point where Purified Water has been produced and this can take 3 different routes – 1) Act as feed water to produce Water for Injection (WFI) and Clean Steam, 2) Re-process through the Reverse Osmosis units to keep them in operation or 3) Send to drain in the case of excessive water. (DPS, 2018).

In terms of storing, it’s made on demand. There are recirc loops between the end of PW trains and the user points so there is always a flow ready to go. As its generated, it will be dumped to drain until it meets parameters specified in pharmacopeia, and will then be in production, used for WFI (Water for Injection) generation.

References

• Baumgarten,C ,Feher, J. (2012). Osmosis. Available: https://www.sciencedirect.com/topics/neuroscience/osmosis. Last accessed 3rd Oct 2019.
• DPS. (2018). Design of Purified Water and Water for Injection Systems. Available: https://www.dpsgroupglobal.com/contentFiles/newsImages/PUW%20and%20WFI%20Systems%20Design%20H%20Hodkinson.pdf. Last accessed 9th Oct 2019.
• Simazaki,D, Fujiwara J,Manabe S,Matsuda,M, Asami,M, Kunikane,S. (2008). Removal of selected pharmaceuticals by chlorination, coagulation-sedimentation and powdered activated carbon treatment. Available: https://www.ncbi.nlm.nih.gov/pubmed/18824814. Last accessed 18th Oct 2019
• TROJAN UV. (2018). UV Disinfection for Drinking Water. Available: https://info.trojanuv.com/1834_TROJAN_c-dw_UK-Systems-Landing-Page_en_LP-ApplicationProductInformation.html?utm_medium=cpc&utm_source=google&utm_campaign=1919359578&gclid=CjwKCAjw3c_tBRA4EiwAICs8CriBi. Last accessed 2nd Oct 2019.
• Van Dijk J.C., Wilms D.A. (2000). Specialised and advanced water treatment processes. Available: https://www.sciencedirect.com/science/article/pii/B9780340720189500102. Last accessed 4th Oct 2019.
• Wychwood Water Systems Ltd, (2015). Continuous Electro Deionisation (CDI). Available: https://www.wychwood-water.com/process/continous-electro-deionisation/. Last accessed 21st Oct 2019.