Purified water preparation Since the use of reverse osmosis (RO) method in the second half of the 1980s, after more than 20 years of evolution and development, we have absorbed advanced foreign water production from the efforts of pharmaceutical manufacturers and technicians of purified water equipment manufacturing enterprises. The process, from the manufacture and assembly of single-piece, single-unit equipment to the complete set of purified water preparation processes currently in use, can be composed of five parts: pretreatment (also known as pretreatment unit), primary demineralizer, depth Desalination device, post-treatment device, purified water delivery and distribution system.
1 Common Purified Water Preparation Process 1.1 Pretreatment Unit As the raw water, the city tap water has reached the drinking water standard, but a small amount of suspended particles, organic matter and residual chlorine, calcium and magnesium ions remain. In order to remove these impurities, the raw water needs to be removed. Pretreatment. The conventional configuration in this group of power devices consists of a raw water pump, a fine sand filter, an activated carbon filter, and a softener.
1.1.1 The raw water pump transports the raw water into the pretreatment system, which is the power source for the fluid movement of the pretreatment device.
1.1.2 Fine sand filter The filter medium is quartz sand with different particle diameters. It can be loaded with a certain thickness to remove the suspended particulate matter in the water. When the pore size of the filter material is blocked, it can be washed and regenerated by backflushing.
1.1.3 Activated carbon filter It is a filter made of porous granular activated carbon as a filter material. It acts as an adsorbent to remove organic matter and residual chlorine in raw water. The activated carbon has large adsorption capacity and high specific surface area, and can reach 500-2000 m2/g, which can remove organic matter, free residual chlorine, odor and color in water.
1.1.4 The softening device is usually a sodium ion softener. The hardness of raw water is mainly composed of Ca++ and Mg++. The sodium ions in the cation exchanger in the softener are exchanged with Ca++ and Mg++ in the water to soften the water. The exchange principle is as follows:
2RNa++Ca++→R2Ca+2Na+
2RNa++Mg++→R2Mg+2Na+
When the Na+ of the cation resin in the softener is completely replaced, the exchange capacity is lost. After the resin fails, the regeneration treatment should be carried out in order to restore the exchange capacity. The regenerant can be selected from NaCl (sodium chloride), which has a wide range of sources and is convenient to use. Cheap and good results. The principle of regeneration is as follows:
R2Ca+2Nacl→2RNa+CaCl2
R2Mg+2Nacl→2RNa+MgCl2
The Ca++ and Mg++ ions in the raw water easily form scale, which blocks the reverse osmosis membrane element and affects the flux of water. In addition to the use of an exchanger, it is also possible to use a reagent to convert Ca++, Mg++ in water into a water-insoluble compound to precipitate or filter out.
Combining the equipment used in the above several unit operations to form a separate system becomes a pretreatment device for preparing purified water.
1.2 Primary demineralization device The primary demineralization function is to remove salt by the first-stage RO method. It is composed of a precision filter (security filter), a high pressure pump, a reverse osmosis casing, a membrane element, and an operation control box.
1.2.1 Precision filter In order to prevent the fine particles in the quartz sand filter and the activated carbon filter from flowing into the reverse osmosis membrane, the filter medium has a pore diameter of 1 μm to 5 μm, which can effectively ensure the influent SDI value. Thereby protecting the membrane element from damage.
1.2.2 High-pressure pump provides power for the device, and the vertical multi-stage high-pressure pump is often used to increase the water pressure.
1.2.3 Reverse osmosis system device (RO device)
The reverse osmosis unit is reported to use a primary RO, which can effectively remove pathogenic microorganisms in the water, such as: various types of bacteria and viruses; 100% remove low molecular organic compounds; 95% to 99% remove monovalent ions in water, effluent conductance The rate can be around 30 μs/cm.
The quality indicators of the influent water quality of the first-stage reverse osmosis (RO) unit can be referred to the following items, as shown in Table 1.
The main components of the primary sterilization system consist of a housing, a membrane element, a pipe joint, a valve, a pressure gauge, and a flow meter.
Under a certain pressure, the water is selectively purified by selectively permeating the water molecules by means of a semipermeable membrane to separate the solute from the solvent. The composition of the secondary RO device disposed after the primary RO is the same as that of the primary RO, but after the secondary RO treatment, the conductivity of the purified water can reach 1 to 30 μs/cm.
1.2.4 Operation Control Box The entire primary desalination (level 1 RO) can be controlled by PLC and realized automatically. There is pressure control before and after the high pressure pump. The membrane element can be cleaned automatically. The system can monitor the quality of the purified water and various process parameters online, such as: flow, pressure, conductivity, valve opening and closing, the entire state can be displayed and controlled.
The whole set of primary demineralizers are connected by pipes and combined into a modular system for transportation, installation, and convenience.
1.3 After the primary desalination treatment (after the first stage RO), the conductivity of the purified water is 30μs/cm, and the water quality can be improved after the two RO treatment, and the conductivity is 1~5μs/cm. In order to further remove traces of ions remaining in the water, deep desalination is required. Purified water with a conductivity range of 0.1 to 0.06 μs/cm can be obtained. Currently, there are several methods for deep demineralization: adding a mixed bed (ion exchange resin) after reverse osmosis (RO) treatment, An EDI device is added after reverse osmosis (RO), and a polishing mixed bed device is added after reverse osmosis (RO).
1.3.1 Mixed bed filled with ordinary anion and cation exchange resin (mixed bed)
A mixed bed is a method that is often used in the preparation of purified water to be installed at the end of a water system to improve water quality. A mixed bed can be added after the first stage RO, or a mixed bed can be added after the second stage RO, and the conductivity of the purified water can be increased to 1 μs/cm (ie, 10 MΩ·cm) or more.
1.3.2 Polishing the mixed bed The two kinds of densely packed male and female resins are mixed and packed in an exchange column and placed behind reverse osmosis (RO) to increase the conductivity of the purified water to 0.06 μs/cm. That is, 18 MΩ·cm). This method is a good way to carry out deep desalination and improve the quality of purified water. Because the two resins are similar in density, they are difficult to separate and cannot be recycled. After the failure, they are discarded and replaced with new resin. This method is often used in small-capacity water systems.
1.3.3 EDI device (1) EDI is an electrodeionization technology whose basic principle is to achieve deep desalination by means of ion exchange of resin and the function of selective exchange of anion and cation in water. The whole separation process is to complete the directional migration of ions under the direct action of the direct current electric field, thereby removing the residual ions of water and increasing the conductivity of the purified water.
(2) EDI technology combines electrodialysis technology and ion exchange technology organically, and is a new type of membrane separation technology. It can effectively remove trace ions in water, so that the resistivity of purified water can reach 15MΩ·cm or more. No chemicals need to be added during the whole desalination process, no environmental pollution occurs, and water utilization rate is high. Purified water was continuously prepared.
(3) During the deep desalination process of EDI, traces of cations and cations are removed by the exchange electric field under the action of DC electric field, and the water molecules are decomposed into H+ and OH- under the action of electric field. In addition, the exchange resin is regenerated in situ, so that the ion exchange resin is always in a good exchange state, thereby achieving the purpose of deep demineralization.
(4) The EDI device is used for deep desalination in the preparation process of purified water. In order to ensure the normal operation of the EDI device, the EDI system should also be equipped with a circulating flushing device, also known as an EDI regeneration device, in order to ensure the smooth operation of the EDI function. get on.
(5) Several items that can be referred to for entering the water quality conditions of the EDI device (unit), as shown in Fig. 2.
(6) The EDI device has compact structure, low energy consumption, low concentration of concentrated water, saves water, does not require any chemical regeneration, does not pollute the environment, and can remove various trace ions in water in depth. The more pharmaceutical manufacturers use it.
(7) There are two types of EDI devices on the market: roll and diaphragm (also known as membrane stack), which can be combined according to the amount of water produced.
1.4 Post-Processing Module The post-processing unit is also an integral part of the entire purified water preparation process. Commonly used equipment is a combination of a purified water delivery pump, an ultraviolet sterilization device (UV), an ozone generator, and a microporous filter.
The purified water storage tank can determine the volume according to the amount of water produced and the amount of water used, which is also attributed to the post-treatment module.
1.5 Purified water delivery and distribution system As the finished purified water is a clean and hygienic fluid, the quality of which will directly affect the intrinsic quality of the drug. Therefore, it is necessary to pay attention to the delivery and distribution of purified water during the use process. In order to prevent microbial contamination, take necessary precautions in accordance with the requirements of the GMP regulations.
1.6 Process summary in the preparation of purified water The above several functional systems can be easily summarized into three modular devices.
(1) Pretreatment module: It consists of raw water pump, sand filter, carbon filter, softener and so on.
(2) Main processing module: consists of high pressure pump, security filter, RO housing, RO component, EDI device, mixed bed, and purified water tank.
(3) Post-processing module: It consists of a purified water pump, an ozone generator, a gas-liquid mixture, an ultraviolet sterilizer, and a precision filter.
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2 Combination scheme of the purified water preparation process in the pharmaceutical industry 2.1 Commonly used purified water preparation schemes There are often four process schemes widely used in the pharmaceutical industry, namely secondary RO, (level 1 RO+EDI), (secondary RO) +EDI) and (secondary RO+ mixed bed) process schemes, the comparison between them is shown in Table 3.
2.2 Reasonable modular combination process for purified water preparation With the wide application of membrane technology and the application of EDI technology in the preparation process of purified water in the past decade, a purified water preparation without chemical reagent regeneration, no pollution to the environment and low operating cost The process is gradually being adopted by more and more pharmaceutical manufacturers. The following two modular combination processes (as shown in Table 4) can produce purified water with a water quality of 10 to 17 MΩ·cm.
(1) Process I is a process for preparing purified water used by many pharmaceutical companies. The membrane separation technology is adopted to reduce the daily operation cost, prolong the use period of the mixed bed resin, reduce the amount of acid and alkali during regeneration, and ensure the quality of the purified water.
(2) Process II has been adopted in some enterprises. After using EDI deionization technology and equipment, the daily water production operation cost is lower, the water production is more, and no chemical reagent (acid, alkali) is needed to pollute the environment. It is a purified water preparation process that is both energy-saving and environmentally friendly. . This modular process is worth promoting.
(3) An optimized modular combination process for the preparation of purified water, as shown in Table 5.
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1 Common Purified Water Preparation Process 1.1 Pretreatment Unit As the raw water, the city tap water has reached the drinking water standard, but a small amount of suspended particles, organic matter and residual chlorine, calcium and magnesium ions remain. In order to remove these impurities, the raw water needs to be removed. Pretreatment. The conventional configuration in this group of power devices consists of a raw water pump, a fine sand filter, an activated carbon filter, and a softener.
1.1.1 The raw water pump transports the raw water into the pretreatment system, which is the power source for the fluid movement of the pretreatment device.
1.1.2 Fine sand filter The filter medium is quartz sand with different particle diameters. It can be loaded with a certain thickness to remove the suspended particulate matter in the water. When the pore size of the filter material is blocked, it can be washed and regenerated by backflushing.
1.1.3 Activated carbon filter It is a filter made of porous granular activated carbon as a filter material. It acts as an adsorbent to remove organic matter and residual chlorine in raw water. The activated carbon has large adsorption capacity and high specific surface area, and can reach 500-2000 m2/g, which can remove organic matter, free residual chlorine, odor and color in water.
1.1.4 The softening device is usually a sodium ion softener. The hardness of raw water is mainly composed of Ca++ and Mg++. The sodium ions in the cation exchanger in the softener are exchanged with Ca++ and Mg++ in the water to soften the water. The exchange principle is as follows:
2RNa++Ca++→R2Ca+2Na+
2RNa++Mg++→R2Mg+2Na+
When the Na+ of the cation resin in the softener is completely replaced, the exchange capacity is lost. After the resin fails, the regeneration treatment should be carried out in order to restore the exchange capacity. The regenerant can be selected from NaCl (sodium chloride), which has a wide range of sources and is convenient to use. Cheap and good results. The principle of regeneration is as follows:
R2Ca+2Nacl→2RNa+CaCl2
R2Mg+2Nacl→2RNa+MgCl2
The Ca++ and Mg++ ions in the raw water easily form scale, which blocks the reverse osmosis membrane element and affects the flux of water. In addition to the use of an exchanger, it is also possible to use a reagent to convert Ca++, Mg++ in water into a water-insoluble compound to precipitate or filter out.
Combining the equipment used in the above several unit operations to form a separate system becomes a pretreatment device for preparing purified water.
1.2 Primary demineralization device The primary demineralization function is to remove salt by the first-stage RO method. It is composed of a precision filter (security filter), a high pressure pump, a reverse osmosis casing, a membrane element, and an operation control box.
1.2.1 Precision filter In order to prevent the fine particles in the quartz sand filter and the activated carbon filter from flowing into the reverse osmosis membrane, the filter medium has a pore diameter of 1 μm to 5 μm, which can effectively ensure the influent SDI value. Thereby protecting the membrane element from damage.
1.2.2 High-pressure pump provides power for the device, and the vertical multi-stage high-pressure pump is often used to increase the water pressure.
1.2.3 Reverse osmosis system device (RO device)
The reverse osmosis unit is reported to use a primary RO, which can effectively remove pathogenic microorganisms in the water, such as: various types of bacteria and viruses; 100% remove low molecular organic compounds; 95% to 99% remove monovalent ions in water, effluent conductance The rate can be around 30 μs/cm.
Table 1 Level 1 (RO) device water quality technical quality indicators | |||
SDI | Residual chlorine | pH | temperature |
≤5.0 | ≤0.1μg/L | 3 to 10 | 5～45°C |
The quality indicators of the influent water quality of the first-stage reverse osmosis (RO) unit can be referred to the following items, as shown in Table 1.
The main components of the primary sterilization system consist of a housing, a membrane element, a pipe joint, a valve, a pressure gauge, and a flow meter.
Under a certain pressure, the water is selectively purified by selectively permeating the water molecules by means of a semipermeable membrane to separate the solute from the solvent. The composition of the secondary RO device disposed after the primary RO is the same as that of the primary RO, but after the secondary RO treatment, the conductivity of the purified water can reach 1 to 30 μs/cm.
1.2.4 Operation Control Box The entire primary desalination (level 1 RO) can be controlled by PLC and realized automatically. There is pressure control before and after the high pressure pump. The membrane element can be cleaned automatically. The system can monitor the quality of the purified water and various process parameters online, such as: flow, pressure, conductivity, valve opening and closing, the entire state can be displayed and controlled.
The whole set of primary demineralizers are connected by pipes and combined into a modular system for transportation, installation, and convenience.
1.3 After the primary desalination treatment (after the first stage RO), the conductivity of the purified water is 30μs/cm, and the water quality can be improved after the two RO treatment, and the conductivity is 1~5μs/cm. In order to further remove traces of ions remaining in the water, deep desalination is required. Purified water with a conductivity range of 0.1 to 0.06 μs/cm can be obtained. Currently, there are several methods for deep demineralization: adding a mixed bed (ion exchange resin) after reverse osmosis (RO) treatment, An EDI device is added after reverse osmosis (RO), and a polishing mixed bed device is added after reverse osmosis (RO).
1.3.1 Mixed bed filled with ordinary anion and cation exchange resin (mixed bed)
A mixed bed is a method that is often used in the preparation of purified water to be installed at the end of a water system to improve water quality. A mixed bed can be added after the first stage RO, or a mixed bed can be added after the second stage RO, and the conductivity of the purified water can be increased to 1 μs/cm (ie, 10 MΩ·cm) or more.
1.3.2 Polishing the mixed bed The two kinds of densely packed male and female resins are mixed and packed in an exchange column and placed behind reverse osmosis (RO) to increase the conductivity of the purified water to 0.06 μs/cm. That is, 18 MΩ·cm). This method is a good way to carry out deep desalination and improve the quality of purified water. Because the two resins are similar in density, they are difficult to separate and cannot be recycled. After the failure, they are discarded and replaced with new resin. This method is often used in small-capacity water systems.
1.3.3 EDI device (1) EDI is an electrodeionization technology whose basic principle is to achieve deep desalination by means of ion exchange of resin and the function of selective exchange of anion and cation in water. The whole separation process is to complete the directional migration of ions under the direct action of the direct current electric field, thereby removing the residual ions of water and increasing the conductivity of the purified water.
(2) EDI technology combines electrodialysis technology and ion exchange technology organically, and is a new type of membrane separation technology. It can effectively remove trace ions in water, so that the resistivity of purified water can reach 15MΩ·cm or more. No chemicals need to be added during the whole desalination process, no environmental pollution occurs, and water utilization rate is high. Purified water was continuously prepared.
(3) During the deep desalination process of EDI, traces of cations and cations are removed by the exchange electric field under the action of DC electric field, and the water molecules are decomposed into H+ and OH- under the action of electric field. In addition, the exchange resin is regenerated in situ, so that the ion exchange resin is always in a good exchange state, thereby achieving the purpose of deep demineralization.
(4) The EDI device is used for deep desalination in the preparation process of purified water. In order to ensure the normal operation of the EDI device, the EDI system should also be equipped with a circulating flushing device, also known as an EDI regeneration device, in order to ensure the smooth operation of the EDI function. get on.
(5) Several items that can be referred to for entering the water quality conditions of the EDI device (unit), as shown in Fig. 2.
Table 2 Water quality conditions for entering the EDI unit (unit) | |||||
hardness | Conductivity | Residual chlorine | SIO 2 | Fe ++ | Toc |
≤0.1mg/L | 50μs/cm | ≤0.05mg/L | ≤0.5mg/L | ≤0.01mg/L | ≤0.5mg/L |
Power supply conditions applied to the EDI unit: voltage 380 ~ 400V current 2 ~ 50A | |||||
(6) The EDI device has compact structure, low energy consumption, low concentration of concentrated water, saves water, does not require any chemical regeneration, does not pollute the environment, and can remove various trace ions in water in depth. The more pharmaceutical manufacturers use it.
(7) There are two types of EDI devices on the market: roll and diaphragm (also known as membrane stack), which can be combined according to the amount of water produced.
1.4 Post-Processing Module The post-processing unit is also an integral part of the entire purified water preparation process. Commonly used equipment is a combination of a purified water delivery pump, an ultraviolet sterilization device (UV), an ozone generator, and a microporous filter.
The purified water storage tank can determine the volume according to the amount of water produced and the amount of water used, which is also attributed to the post-treatment module.
1.5 Purified water delivery and distribution system As the finished purified water is a clean and hygienic fluid, the quality of which will directly affect the intrinsic quality of the drug. Therefore, it is necessary to pay attention to the delivery and distribution of purified water during the use process. In order to prevent microbial contamination, take necessary precautions in accordance with the requirements of the GMP regulations.
1.6 Process summary in the preparation of purified water The above several functional systems can be easily summarized into three modular devices.
(1) Pretreatment module: It consists of raw water pump, sand filter, carbon filter, softener and so on.
(2) Main processing module: consists of high pressure pump, security filter, RO housing, RO component, EDI device, mixed bed, and purified water tank.
(3) Post-processing module: It consists of a purified water pump, an ozone generator, a gas-liquid mixture, an ultraviolet sterilizer, and a precision filter.
2 Combination scheme of the purified water preparation process in the pharmaceutical industry 2.1 Commonly used purified water preparation schemes There are often four process schemes widely used in the pharmaceutical industry, namely secondary RO, (level 1 RO+EDI), (secondary RO) +EDI) and (secondary RO+ mixed bed) process schemes, the comparison between them is shown in Table 3.
2.2 Reasonable modular combination process for purified water preparation With the wide application of membrane technology and the application of EDI technology in the preparation process of purified water in the past decade, a purified water preparation without chemical reagent regeneration, no pollution to the environment and low operating cost The process is gradually being adopted by more and more pharmaceutical manufacturers. The following two modular combination processes (as shown in Table 4) can produce purified water with a water quality of 10 to 17 MΩ·cm.
(1) Process I is a process for preparing purified water used by many pharmaceutical companies. The membrane separation technology is adopted to reduce the daily operation cost, prolong the use period of the mixed bed resin, reduce the amount of acid and alkali during regeneration, and ensure the quality of the purified water.
(2) Process II has been adopted in some enterprises. After using EDI deionization technology and equipment, the daily water production operation cost is lower, the water production is more, and no chemical reagent (acid, alkali) is needed to pollute the environment. It is a purified water preparation process that is both energy-saving and environmentally friendly. . This modular process is worth promoting.
(3) An optimized modular combination process for the preparation of purified water, as shown in Table 5.
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