China Library Classification Number: R658 Document Identification Number: A Document Number:1672-3791(2012) 07 (a)-0195-01.
Medical purified water has a far-reaching impact on drug production. Purified water is not only used as a cleaning agent, but also as a raw material for drug production, so the quality of purified water directly affects the quality of drugs. Therefore, the preparation of purified water that meets the requirements of pharmaceutical water is the primary guarantee for the production of qualified drugs, and the design of pharmaceutical purified water system is the premise of everything. Therefore, this paper briefly analyzes the design of purified water preparation system.
Overview of 1 purified water preparation system
With the rapid development of science and technology, the purified water preparation system has also been greatly improved. Its treatment technology has experienced distillation, ion exchange technology, membrane separation, reverse osmosis (RO) and electrodeionization (EDI), and its equipment has also developed from a single preparation unit to a set of modular preparation processes. Due to the increasing concern about drug safety around the world, pharmacopoeias of various countries have clear regulations and requirements on the quality standards and uses of drug water. In order to meet the international standards and strictly control the water production system, the mainstream two-stage RO+EDI preparation process is adopted to meet the requirements of production water and ensure the water quality meets the GMP requirements of various countries.
Design of pure water preparation system
From drinking water that meets certain requirements to pure water that meets pharmacopoeia standards, the whole preparation process can be composed of pretreatment, primary desalination system and deep desalination system.
2. 1 pretreatment
Pretreatment is the first step to prepare purified water. Its main function is to remove microorganisms and chemicals in water under different influent conditions, so that the two-stage RO system can obtain stable and qualified influent quality, mainly including: multi-media filter, activated carbon filter and softener.
2. 1. 1 multimedia filter
Generally, quartz sand or anthracite is used as the multi-media filter material, and it is filled in the filter from top to bottom according to the particle size, so as to intercept the large particles, suspended solids, colloids and sediments in the water, so that the SDI value is less than 5 and the turbidity of the effluent is less than 1, ensuring that the subsequent water inflow requirements can be met. With the continuous operation of the equipment, the pressure difference will increase continuously. Backwashing with 3 ~ 10 times the flow of clean raw water can remove the filter material deposits, reduce the filtration pressure and regenerate the filter material.
2. 1.2 activated carbon filter
The filter medium is usually composed of fixed layers of granular activated carbon such as coconut shell charcoal and anthracite, which can not only effectively adsorb some organic substances in water (the adsorption rate is about ` 60%), but also make the adsorption surface area of activated carbon reach 500 ~ 2000m2/g due to a large number of micropores and particle gaps with an average pore diameter of 2mm~5nm, which has strong dechlorination ability for residual chloride ions in water, and can also effectively remove odor and chromaticity in water. After comprehensive treatment, the residual chlorine in the effluent should be ensured to be < 0. 1ppm, SDI. Because of the large internal surface area and slow flow rate of activated carbon, microorganisms are easy to breed. In order to ensure the adsorption activity of activated carbon, pasteurization should be used regularly to control microbial pollution.
2. 1.3 softener
The hardness of raw water is mainly composed of Ca2+ and Mg2+. If scaling occurs on the surface of RO membrane, it will block the reverse osmosis membrane and affect the water flux. Therefore, in order to prevent the deposition and scaling of calcium and magnesium salts, sodium cation resin is currently used in the softener, and exchangeable Na+ in the resin is used to exchange Ca2+ and Mg2+ in the water, so that the raw water is softened into softened water, the hardness of the water is reduced, and the service life of the subsequent reverse osmosis membrane is prolonged. In production, one softener is usually used for standby, and the other is automatically controlled by PLC to complete resin conversion and salt absorption regeneration.
2.2 Primary demineralization system
As a primary desalting, the secondary RO system is the main desalting equipment in the whole preparation process, which mainly includes membrane safety filter, high-pressure pump, NaOH dosing box and secondary RO device.
2.2. 1 membrane safety filter
The small particle filter material in the pretreatment stage may enter the reverse osmosis device with the pipeline due to leakage and block the reverse osmosis membrane. As the last filter barrier for raw water to enter the desalination system, the membrane safety filter can filter out particles with particle size ≥5μm in raw water and provide reliable water source for subsequent desalination system. Therefore, membrane safety filtration is also called fine filtration.
high pressure pump
Reverse osmosis needs high pressure to make raw water flow from concentrated solution side to dilute solution side. The high-pressure pump provides a stable power source for the system and ensures the continuous and stable operation of the secondary reverse osmosis system. As the high-pressure pump runs continuously, it should be equipped with high-low pressure protection and overheating protection to prevent the pump from being damaged.
NaOH metering box
Dissolving carbon dioxide in water will increase the conductivity of pure water. For the two-stage RO system, NaOH dosing box is placed after the first-stage reverse osmosis, and the pH value of the first-stage effluent is adjusted, so that CO2 gas molecules in the water are converted into CO32- ions, which are dissolved in the water in an alkaline environment, thus increasing the second-stage desalination effect.
2.2.4 Two-stage reverse osmosis device
The two-stage reverse osmosis process is a physical desalination process, which uses the selective permeability of semi-permeable membrane to make water molecules in raw water flow from the concentrated solution side to the dilute solution side under pressure, and then enter the subsequent EDI unit after merging. However, microorganisms, endotoxin, colloid and various salts in raw water are intercepted and discharged with concentrated water, and the desalination rate of the system can reach above 98%. The discharged concentrated water can be used as supplementary water for cooling tower or factory greening.
2.3 Deep Desalination System
EDI is the deep desalination after two-stage RO. It is a treatment technology combining electrodialysis and ion exchange. Under the action of external electric field, anion and cation selectively permeate through the membrane to achieve the purpose of deep desalination. The resistivity of the prepared pure water can reach more than15mΩ cm. In the whole desalination process, the system does not use acid-base reagents, but uses the continuous electrolysis of H+ and OH- to regeneration of resin, which ensures the continuity, stability and pollution-free of the preparation process.
3 Conclusion
To sum up, the two-stage RO+EDI purified water preparation method provides purified water that meets GMP standards for pharmaceutical production, and the whole preparation process is energy-saving and environmentally friendly, which conforms to the development trend of pharmaceutical purified water preparation today and provides a better guarantee for pharmaceutical production.