The EDI (Electrodeionization) system utilizes mixed ion exchange resin to adsorb cations and anions in raw water. The adsorbed ions are then removed by passing through cation and anion exchange membranes under the action of direct current voltage. The EDI system typically consists of multiple pairs of alternating anion and cation exchange membranes and spacers, forming a concentrate compartment and a dilute compartment (i.e., cations can penetrate through cation exchange membrane, while anions can penetrate through anion exchange membrane).
In the dilute compartment, cations in the water migrate to the negative electrode and pass through the cation exchange membrane, where they are intercepted by the anion exchange membrane in the concentrate compartment; anions in the water migrate to the positive electrode and pass through the anion exchange membrane, where they are intercepted by the cation exchange membrane in the concentrate compartment. The number of ions in the water gradually decreases as it passes through the dilute compartment, resulting in purified water, while the concentration of the ionic species in the concentrate compartment continually increases, resulting in concentrated water.
Therefore, the EDI system achieves the goal of dilution, purification, concentration, or refinement. The ion exchange resin used in this process is continuously regenerated electrically, so it does not require regeneration with acid or alkali. This new technology in EDI purified water equipment can replace traditional ion exchange equipment to produce ultra-pure water up to 18 MΩ.cm.
Advantages of EDI Purified Water Equipment System:
1. No acid or alkali regeneration required: In a mixed bed system, the resin needs to be regenerated with chemical agents, while EDI eliminates the handling of these harmful substances and the tedious work. This protects the environment.
2. Continuous and simple operation: In a mixed bed system, the operational process becomes complicated due to the changing quality of the water with each regeneration, while the water production process in EDI is stable and continuous, and the water quality is constant. There are no complicated operational procedures, making operation much simpler.
3. Lower installation requirements: Compared to mixed bed systems that handle the same water volume, EDI systems have a smaller volume. They use a modular design that can be constructed flexibly based on the height and space of the installation site. The modular design also makes it easier to maintain the EDI system during production.
Organic matter pollution is a common problem in the RO industry, which reduces water production rates, increases inlet pressure, and lowers desalination rates, leading to the deterioration of the RO system's operation. If left untreated, membrane components will suffer permanent damage. Biofouling causes an increase in pressure differential, forming low-flow rate areas on the membrane surface, which intensify the formation of colloidal fouling, inorganic fouling, and microbial growth.
During the initial stages of biofouling, the standard water production rate decreases, the inlet pressure difference increases, and the desalination rate remains unchanged or slightly increased. As the biofilm gradually forms, the desalination rate begins to decrease, while colloidal fouling and inorganic fouling also increase.
Organic pollution can occur throughout the membrane system and under certain conditions, it can accelerate growth. Therefore, the biofouling situation in the pretreatment device should be checked, especially the relevant pipeline system of the pretreatment.
It is essential to detect and treat the pollutant in the early stages of organic matter pollution as it becomes much harder to deal with when the microbial biofilm has developed to a certain extent.
The specific steps for organic matter cleaning are:
Step 1: Add alkaline surfactants plus chelating agents, which can destroy organic blockages, causing the biofilm to age and rupture.
Cleaning conditions: pH 10.5, 30℃, cycle and soak for 4 hours.
Step 2: Use non-oxidizing agents to remove microorganisms, including bacteria, yeast, and fungi, and to eliminate organic matter.
Cleaning conditions: 30℃, cycling for 30 minutes to several hours (depending on the type of cleaner).
Step 3: Add alkaline surfactants plus chelating agents to remove microbial and organic matter fragments.
Cleaning conditions: pH 10.5, 30℃, cycle and soak for 4 hours.
Depending on the actual situation, an acidic cleaning agent can be used to remove residual inorganic fouling after Step 3. The order in which cleaning chemicals are used is critical, as some humic acids can be difficult to remove under acidic conditions. In the absence of determinate sediment properties, it is recommended to use an alkaline cleaning agent first.
Ultrafiltration is a membrane separation process based on the principle of sieve separation and driven by pressure. The filtration accuracy is within the range of 0.005-0.01μm. It can effectively remove particles, colloids, endotoxins, and high-molecular-weight organic substances in water. It can be widely used in material separation, concentration, and purification. The ultrafiltration process has no phase transformation, operates at room temperature, and is particularly suitable for the separation of heat-sensitive materials. It has good temperature resistance, acid-alkali resistance, and oxidation resistance, and can be used continuously under conditions of pH 2-11 and temperature below 60℃.
The outer diameter of the hollow fiber is 0.5-2.0mm, and the inner diameter is 0.3-1.4mm. The wall of the hollow fiber tube is covered with micropores, and the pore size is expressed in terms of the molecular weight of the substance that can be intercepted, with a molecular weight interception range of several thousand to several hundred thousand. Raw water flows under pressure on the outside or inside of the hollow fiber, respectively forming an external pressure type and an internal pressure type. Ultrafiltration is a dynamic filtration process, and the intercepted substances can be gradually discharged with concentration, without blocking the membrane surface, and can operate continuously for a long time.
Features of UF Ultrafiltration Membrane Filtration:
1. The UF system has a high recovery rate and a low operating pressure, which can achieve efficient purification, separation, purification, and concentration of materials.
2. The UF system separation process has no phase change, and does not affect the composition of materials. The separation, purification, and concentration processes are always at room temperature, especially suitable for the treatment of heat-sensitive materials, completely avoiding the disadvantage of high temperature damage to biological active substances, and effectively preserving the biological active substances and nutritional components in the original material system.
3. The UF system has low energy consumption, short production cycles, and low operating costs compared with traditional process equipment, which can effectively reduce production costs and improve the economic benefits of enterprises.
4. The UF system has advanced process design, high degree of integration, compact structure, small footprint, easy operation and maintenance, and low labor intensity of workers.
Application scope of UF ultrafiltration membrane filtration:
It is used for pre-treatment of purified water equipment, purification treatment of beverages, drinking water, and mineral water, separation, concentration, and purification of industrial products, industrial wastewater treatment, electrophoretic paint, and treatment of electroplating oily wastewater.
Variable frequency constant pressure water supply equipment is composed of variable frequency control cabinet, automation control system, water pump unit, remote monitoring system, pressure buffer tank, pressure sensor, etc. It can realize stable water pressure at the end of water use, stable water supply system, and energy saving.
Its performance and characteristics:
1. High degree of automation and intelligent operation: The equipment is controlled by an intelligent central processor, the operation and switching of the working pump and standby pump are fully automatic, and the faults are automatically reported, so that the user can quickly find out the cause of the fault from the human-machine interface. The PID closed-loop regulation is adopted, and the constant pressure accuracy is high, with small water pressure fluctuations. With various set functions, it can truly achieve unattended operation.
2. Reasonable control: Multi-pump circulation soft start control is adopted to reduce the impact and interference on the power grid caused by direct start. The working principle of the main pump start is: first open and then stop, first stop and then open, equal opportunities, which is conducive to extending the life of the unit.
3. Full functions: It has various automatic protection functions such as overload, short circuit, and overcurrent. The equipment runs stably, reliably, and is easy to use and maintain. It has functions such as stopping the pump in case of water shortage and automatically switching the water pump operation at a fixed time. In terms of timed water supply, it can be set as timed switch control through the central control unit in the system to achieve timed switch of the water pump. There are three working modes: manual, automatic, and single step (only available when there is a touch screen) to meet the needs under different working conditions.
4. Remote monitoring (optional function): Based on fully studying domestic and foreign products and user needs and combining with the automation experience of professional technical personnel for many years, the intelligent control system of water supply equipment is designed to monitor and monitor the system water volume, water pressure, liquid level, etc. through online remote monitoring, and directly monitor and record the system's working conditions and provide real-time feedback through powerful configuration software. The collected data is processed and provided for network database management of the entire system for query and analysis. It can also be operated and monitored remotely through the Internet, fault analysis and information sharing.
5. Hygiene and Energy Saving: By changing the motor speed through variable frequency control, the user's network pressure can be kept constant, and the energy-saving efficiency can reach 60%. The pressure flow during normal water supply can be controlled within ±0.01Mpa.
1. The sampling method for ultra-pure water varies depending on the testing project and required technical specifications.
For non-online testing: The water sample should be collected in advance and analyzed as soon as possible. The sampling point must be representative as it directly affects the test data results.
2. Container preparation:
For the sampling of silicon, cations, anions and particles, polyethylene plastic containers must be used.
For the sampling of total organic carbon and microorganisms, glass bottles with ground glass stoppers must be used.
3. Processing method for sampling bottles:
3.1 For cation and total silicon analysis: Soak 3 bottles of 500 mL of pure water bottles or hydrochloric acid bottles with a purity level higher than superior purity in 1mol hydrochloric acid overnight, wash with ultra-pure water more than 10 times (each time, shake vigorously for 1 minute with about 150 mL of pure water and then discard and repeat the cleaning), fill them with pure water, clean the bottle cap with ultra-pure water, seal it tightly, and let it stand overnight.
3.2 For anion and particle analysis: Soak 3 bottles of 500 mL of pure water bottles or H2O2 bottles with a purity level higher than superior purity in 1mol NaOH solution overnight, and clean them as in 3.1.
3.4 For the analysis of microorganisms and TOC: Fill 3 bottles of 50mL-100mL ground glass bottles with potassium dichromate sulfuric acid cleaning solution, cap them, soak them in acid overnight, wash them with ultra-pure water more than 10 times (each time, shake vigorously for 1 minute, discard, and repeat the cleaning), clean the bottle cap with ultra-pure water, and seal it tightly. Then put them in a high pressure ** pot for high-pressure steam for 30 minutes.
4. Sampling method:
4.1 For anion, cation and particle analysis, before taking a formal sample, pour out the water in the bottle and wash it more than 10 times with ultra-pure water, then inject 350-400mL of ultra-pure water in one go, clean the bottle cap with ultra-pure water and seal it tightly, and then seal it in a clean plastic bag.
4.2 For microorganism and TOC analysis, pour out the water in the bottle immediately before taking the formal sample, fill it with ultra-pure water, and seal it immediately with a sterilized bottle cap and then seal it in a clean plastic bag.
Polishing resin is mainly used to adsorb and exchange trace amounts of ions in water. The inlet electrical resistance value is generally greater than 15 megaohms, and the polishing resin filter is located at the end of the ultra-pure water treatment system (process: two-stage RO + EDI + polishing resin) to ensure that the system output water quality can meet water usage standards. Generally, the output water quality can be stabilized to above 18 megaohms, and has a certain control ability over TOC and SiO2. The ion types of polishing resin are H and OH, and they can be used directly after filling without regeneration. They are generally used in industries with high water quality requirements.
The following points should be noted when replacing polishing resin:
1. Use pure water to clean the filter tank before replacement. If water needs to be added to facilitate filling, pure water must be used and the water must be immediately drained or removed after the resin enters the resin tank to avoid resin stratification.
2. When filling the resin, the equipment in contact with the resin must be cleaned to prevent oil from entering the resin filter tank.
3. When replacing the filled resin, the center tube and water collector must be completely cleaned, and there must be no old resin residue on the bottom of the tank, otherwise these used resins will contaminate the water quality.
4. The O-ring seal ring used must be replaced regularly. At the same time, the relevant components must be checked and immediately replaced if damaged during each replacement.
5. When using an FRP filter tank (commonly known as a fiberglass tank) as a resin bed, the water collector should be left in the tank before filling the resin. During the filling process, the water collector should be shaken from time to time to adjust its position and install the cover.
6. After filling the resin and connecting the filter pipe, open the vent hole at the top of the filter tank first, slowly pour in water until the vent hole overflows and no more bubbles are produced, and then close the vent hole to start making water.
Purified water equipment is widely used in industries such as pharmaceuticals, cosmetics, and food. Currently, the main processes used are two-stage reverse osmosis technology or two-stage reverse osmosis + EDI technology. The parts that come into contact with water use SUS304 or SUS316 materials. Combined with a composite process, they control the ion content and microbial count in the water quality. In order to ensure stable operation of the equipment and consistent water quality at the end of use, it is necessary to strengthen the maintenance and upkeep of the equipment in daily management.
1. Regularly replace filter cartridges and consumables, strictly follow the equipment operation manual to replace related consumables;
2. Regularly verify the operating conditions of the equipment manually, such as triggering the pre-treatment cleaning program manually, and checking the protection functions such as under-voltage, overload, water quality exceeding standards and liquid level;
3. Take samples at each node at regular intervals to ensure the performance of each part;
4. Strictly follow the operating procedures to inspect the operating conditions of the equipment and record relevant technical operating parameters;
5. Regularly control the proliferation of microorganisms in the equipment and transmission pipelines effectively.
Purified water equipment generally uses reverse osmosis treatment technology to remove impurities, salts, and heat sources from water bodies, and is widely used in industries such as medicine, hospitals, and biochemical chemical industry.
The core technology of purified water equipment uses new processes such as reverse osmosis and EDI to design a complete set of purified water treatment processes with targeted features. So, how should purified water equipment be maintained and maintained on a daily basis? The following tips may be helpful:
Sand filters and carbon filters should be cleaned at least every 2-3 days. Clean the sand filter first and then the carbon filter. Perform backwashing before forward washing. Quartz sand consumables should be replaced after 3 years, and activated carbon consumables should be replaced after 18 months.
The precision filter only needs to be drained once a week. The PP filter element inside the precision filter should be cleaned once a month. The filter can be disassembled and removed from the shell, rinsed with water, and then reassembled. It is recommended to replace it after about 3 months.
The quartz sand or activated carbon inside the sand filter or carbon filter should be cleaned and replaced every 12 months.
If the equipment is not used for a long time, it is recommended to run at least 2 hours every 2 days. If the equipment is shut down at night, the quartz sand filter and activated carbon filter can be backwashed using tap water as the raw water.
If the gradual reduction of water production by 15% or the gradual decline in water quality exceeds the standard is not caused by temperature and pressure, it means that the reverse osmosis membrane needs to be chemically cleaned.
During operation, various malfunctions may occur due to various reasons. After a problem occurs, check the operation record in detail and analyze the cause of the fault.
Features of purified water equipment:
Simple, reliable, and easy-to-install structure design.
The entire purified water treatment equipment is made of high-quality stainless steel material, which is smooth, without dead angles, and easy to clean. It is resistant to corrosion and rust prevention.
Directly using tap water to produce sterile purified water can completely replace distilled water and double-distilled water.
The core components (reverse osmosis membrane, EDI module, etc.) are imported.
The full automatic operation system (PLC + human-machine interface) can perform efficient automatic washing.
Imported instruments can accurately, continuously analyze, and display water quality.
Reverse osmosis membrane is an important processing unit of reverse osmosis pure water equipment. The purification and separation of the water rely on the membrane unit to complete. Correct installation of the membrane element is essential to ensure normal operation of the reverse osmosis equipment and stable water quality.
Installation Method of Reverse Osmosis Membrane for Pure Water Equipment:
1. Firstly, confirm the specification, model, and quantity of the reverse osmosis membrane element.
2. Install the O-ring on the connecting fitting. When installing, lubricating oil such as Vaseline can be applied on the O-ring as needed to prevent damage to O-ring.
3. Remove the end plates at both ends of the pressure vessel. Rinse the opened pressure vessel with clean water and clean the inner wall.
4. According to the assembly guide of the pressure vessel, install the stopper plate and end plate on the concentrated water side of the pressure vessel.
5. Install the RO reverse osmosis membrane element. Insert the end of the membrane element without the saltwater sealing ring parallel into the water supply side (upstream) of the pressure vessel, and slowly push 2/3 of the element inside.
6. During installation, push the reverse osmosis membrane shell from the inlet end to the concentrated water end. If it is installed in reverse, it will cause damage to the concentrated water seal and membrane element.
7. Install the connecting plug. After placing the entire membrane element into the pressure vessel, insert the connection joint between the elements into the center pipe of the element's water production, and as needed, apply silicone-based lubricant on the O-ring of the joint before installation.
8. After filling with all the reverse osmosis membrane elements, install the connecting pipeline.
The above is the installation method of reverse osmosis membrane for pure water equipment. If you encounter any problems during installation, please feel free to contact us.
The mechanical filter is mainly used for reducing the turbidity of the raw water. The raw water is sent into the mechanical filter filled with various grades of matched quartz sand. By utilizing the pollutant interception ability of the quartz sand, larger suspended particles and colloids in the water can be effectively removed, and the turbidity of the effluent will be less than 1mg/L, ensuring the normal operation of subsequent treatment processes.
Coagulants are added to the pipeline of the raw water. The coagulant undergoes ion hydrolysis and polymerization in the water. The different products from hydrolysis and aggregation are strongly adsorbed by the colloid particles in the water, reducing the particle surface charge and diffusion thickness simultaneously. The particle repulsion ability decreases, they will get closer and coalesce. The polymer produced by hydrolysis will be adsorbed by two or more colloids to produce bridging connections between particles, gradually forming larger flocs. When the raw water passes through the mechanical filter, they will be retained by the sand filter material.
The adsorption of the mechanical filter is a physical adsorption process, which can be roughly divided into a loose area (coarse sand) and a dense area (fine sand) according to the filling method of the filter material. Suspension substances mainly form contact coagulation in the loose area by flowing contact, so this area can intercept larger particles. In the dense area, the interception mainly depends on the inertia collision and absorption between suspended particles, so this area can intercept smaller particles.
When the mechanical filter is affected by excessive mechanical impurities, it can be cleaned by backwashing. Reverse inflow of water and compressed air mixture is used to flush and scrub the sand filter layer in the filter. The trapped substances adhering to the surface of the quartz sand can be removed and carried away by the backwash water flow, which helps to remove sediment and suspended substances in the filter layer and prevent filter material blockage. The filter material will restore its pollutant interception capacity fully, achieving the goal of cleaning. The backwash is controlled by the inlet and outlet pressure difference parameters or timed cleaning, and the specific cleaning time depends on the turbidity of the raw water.
In the process of producing pure water, some of the early processes used ion exchange for treatment, using a cation bed, an anion bed, and a mixed bed processing technology. Ion exchange is a special solid absorption process that can absorb a certain cation or anion from water, exchange it with an equal amount of another ion with the same charge, and release it into the water. This is called ion exchange. According to the types of ions exchanged, ion exchange agents can be divided into cation exchange agents and anion exchange agents.
The characteristics of organic contamination of anion resins in pure water equipment are:
1. After the resin is contaminated, the color becomes darker, changing from light yellow to dark brown and then black.
2. The working exchange capacity of the resin is reduced, and the period production capacity of the anion bed is significantly decreased.
3. Organic acids leak into the effluent, increasing the conductivity of the effluent.
4. The pH value of the effluent decreases. Under normal operating conditions, the pH value of the effluent from the anion bed is generally between 7-8 (due to NaOH leakage). After the resin is contaminated, the pH value of the effluent may decrease to between 5.4-5.7 due to the leakage of organic acids.
5. The SiO2 content increases. The dissociation constant of organic acids (fulvic acid and humic acid) in water is greater than that of H2SiO3. Therefore, organic matter attached to the resin can inhibit the exchange of H2SiO3 by the resin, or displace H2SiO3 that has already been adsorbed, resulting in premature leakage of SiO2 from the anion bed.
6. The amount of washing water increases. Because organic matter adsorbed on the resin contains a large number of -COOH functional groups, the resin is converted to -COONa during regeneration. During the cleaning process, these Na+ ions are continuously displaced by mineral acid in the influent water, which increases the cleaning time and water usage for the anion bed.
Reverse osmosis membrane products are widely used in the fields of surface water, reclaimed water, wastewater treatment, seawater desalination, pure water, and ultra-pure water manufacturing. Engineers who use these products know that aromatic polyamide reverse osmosis membranes are susceptible to oxidation by oxidizing agents. Therefore, when using oxidation processes in pre-treatment, corresponding reducing agents must be used. Continuously improving the anti-oxidation ability of reverse osmosis membranes has become an important measure for membrane suppliers to improve technology and performance.
Oxidation can cause a significant and irreversible reduction in the performance of reverse osmosis membrane components, mainly manifested as a decrease in desalination rate and an increase in water production. To ensure the desalination rate of the system, membrane components usually need to be replaced. However, what are the common causes of oxidation?
(I) Common oxidation phenomena and their causes
1. Chlorine attack: Chloride-containing drugs are added to the system's inflow, and if not fully consumed during pretreatment, residual chlorine will enter the reverse osmosis membrane system.
2. Trace residual chlorine and heavy metal ions such as Cu2+, Fe2+, and Al3+ in the influent water cause catalytic oxidative reactions in the polyamide desalination layer.
3. Other oxidizing agents are used during water treatment, such as chlorine dioxide, potassium permanganate, ozone, hydrogen peroxide, etc. Residual oxidants enter the reverse osmosis system and cause oxidation damage to the reverse osmosis membrane.
(II) How to prevent oxidation?
1. Ensure that the reverse osmosis membrane inflow does not contain residual chlorine:
a. Install online oxidation-reduction potential instruments or residual chlorine detection instruments in the reverse osmosis inflow pipeline, and use reducing agents such as sodium bisulfite to detect residual chlorine in real-time.
b. For water sources that discharge wastewater to meet standards and systems that use ultrafiltration as pre-treatment, adding chlorine is generally used to control ultrafiltration microbial contamination. In this operating condition, online instruments and periodic offline testing should be combined to detect residual chlorine and ORP in water.
2. The reverse osmosis membrane cleaning system should be separated from the ultrafiltration cleaning system to avoid residual chlorine leakage from the ultrafiltration system to the reverse osmosis system.
The resistance value is a critical indicator for measuring the quality of pure water. Nowadays, most water purification systems in the market come with a conductivity meter, which reflects the overall ion content in the water to help us ensure the accuracy of the measurement results. An external conductivity meter is used to measure water quality and perform measurement, comparison and other tasks. However, external measurement results often exhibit significant deviations from the values displayed by the machine. So, what is the problem? We need to start with the 18.2MΩ.c m resistance value.
18.2MΩ.cm is an essential indicator for water quality testing, which reflects the concentration of cations and anions in the water. When the ion concentration in the water is lower, the resistance value detected is higher, and vice versa. Therefore, there is an inverse relationship between resistance value and ion concentration.
A. Why is the upper limit of ultra-pure water resistance value 18.2 MΩ.cm?
When the ion concentration in the water approaches zero, why is the resistance value not infinitely large? To understand the reasons, let's discuss the inverse of resistance value - conductivity:
① Conductivity is used to indicate the conduction capacity of ions in pure water. Its value is linearly proportional to the ion concentration.
② The unit of conductivity is usually expressed in μS/cm.
③ In pure water (representing ion concentration), the conductivity value of zero does not exist practically because we cannot remove all ions from water, especially considering the dissociation equilibrium of water as follows:
From the above dissociation equilibrium, H+ and OH- can never be removed. When there are no ions in the water except for [H+] and [OH-], the low value of conductivity is 0.055 μS/cm (this value is calculated based on the ion concentration, the ion mobility, and other factors, based on [H+] = [OH-] = 1.0x10-7). Therefore, theoretically, it is impossible to produce pure water with a conductivity value lower than 0.055μS/cm. Moreover, 0.055 μS/cm is the reciprocal of 18.2M0.cm that we are familiar with, 1/18.2=0.055.
Therefore, at a temperature of 25°C, there is no pure water with a conductivity lower than 0.055μS/cm. In other words, it is impossible to produce pure water with a resistance value higher than 18.2 MΩ/cm.
B. Why does the water purifier display 18.2 MΩ.cm, but it is challenging to achieve the measured result on our own?
Ultra-pure water has a low ion content, and the requirements for the environment, operating methods, and measuring instruments are very high. Any improper operation may affect the measurement results. Common operational errors in measuring the resistance value of ultra-pure water in a laboratory include:
① Offline monitoring: Take out the ultra-pure water and place it in a beaker or other container for testing.
② Inconsistent battery constants: A conductivity meter with a battery constant of 0.1cm-1 cannot be used to measure the conductivity of ultra-pure water.
③ Lack of Temperature Compensation: The 18.2 MΩ.cm resistance value in ultra-pure water generally refers to the result under a temperature of 25°C. Since the water temperature during measurement is different from this temperature, we need to compensate it back to 25°C before making comparisons.
C. What should we pay attention to when measuring the resistance value of ultra-pure water using an external conductivity meter?
Referring to the content of the resistance detection section in the GB/T33087-2016 "Specifications and Test Methods for High Purity Water for Instrumental Analysis," the following matters should be noted when measuring the resistance value of ultra-pure water using an external conductivity meter:
① Equipment requirements: an online conductivity meter with temperature compensation function, a conductivity cell electrode constant of 0.01 cm-1, and a temperature measurement accuracy of 0.1°C.
② Operating steps: Connect the conductivity cell of the conductivity meter to the water purification system during measurement, flush the water and remove air bubbles, adjust the water flow rate to a constant level, and record the water temperature and resistance value of the instrument when the resistance reading is stable.
The equipment requirements and operating steps mentioned above must be strictly followed to ensure the accuracy of our measurement results.
Mixed bed is short for mixed ion exchange column, which is a device designed for ion exchange technology and used to produce high-purity water (resistance greater than 10 megaohms), generally used behind reverse osmosis or Yang bed Yin bed. The so-called mixed bed means that a certain proportion of cation and anion exchange resins are mixed and packed in the same exchange device to exchange and remove ions in the fluid.
The ratio of cation and anion resin packing is generally 1:2. The mixed bed is also divided into in-situ synchronous regeneration mixed bed and ex-situ regeneration mixed bed. In-situ synchronous regeneration mixed bed is carried out in the mixed bed during operation and the entire regeneration process, and the resin is not moved out of the equipment. Moreover, the cation and anion resins are regenerated simultaneously, so the required auxiliary equipment is less and the operation is simple.
Features of mixed bed equipment:
1. The water quality is excellent, and the pH value of the effluent is close to neutral.
2. The water quality is stable, and the short-term changes in operation conditions (such as inlet water quality or components, operating flow rate, etc.) have little effect on the effluent quality of the mixed bed.
3. Intermittent operation has a small impact on the effluent quality, and the time required to recover to the pre-shutdown water quality is relatively short.
4. The water recovery rate reaches 100%.
Cleaning and operation steps of mixed bed equipment:
1. Operation
There are two ways to enter water: by product water inlet of the Yang bed Yin bed or by initial desalination (reverse osmosis treated water) inlet. When operating, open the inlet valve and the product water valve, and close all other valves.
2. Backwash
Close the inlet valve and the product water valve; open the backwash inlet valve and the backwash discharge valve, backwash at 10m/h for 15min. Then, close the backwash inlet valve and the backwash discharge valve. Let it settle for 5-10min. Open the exhaust valve and the middle drain valve, and partially drain the water to about 10cm above the resin layer surface. Close the exhaust valve and the middle drain valve.
3. Regeneration
Open the inlet valve, the acid pump, the acid inlet valve, and the middle drain valve. Regenerate the cation resin at 5m/s and 200L/h, use reverse osmosis product water to clean the anion resin, and maintain the liquid level in the column at the surface of the resin layer. After regenerating the cation resin for 30min, close the inlet valve, the acid pump, and the acid inlet valve, and open the backwash inlet valve, the alkali pump, and the alkali inlet valve. Regenerate the anion resin at 5m/s and 200L/h, use reverse osmosis product water to clean the cation resin, and maintain the liquid level in the column at the surface of the resin layer. Regenerate for 30min.
4. Replacement, mix resin, and flushing
Close the alkali pump and the alkali inlet valve, and open the inlet valve. Replace and clean the resin by simultaneously introducing water from the top and bottom. After 30min, close the inlet valve, the backwash inlet valve, and the middle drain valve. Open the backwash discharge valve, the air inlet valve, and the exhaust valve, with a pressure of 0.1~0.15MPa and a gas volume of 2~3m3/(m2·min), mix the resin for 0.5~5min. Close the backwash discharge valve and the air inlet valve, let it settle for 1~2min. Open the inlet valve and the forward wash discharge valve, adjust the exhaust valve, fill the water until there is no air in the column, and flush the resin. When the conductivity reaches the requirements,open the water production valve, close the flushing discharge valve, and start producing water.
If after a period of operation, the solid salt particles in the brine tank of the softener have not decreased and the produced water quality is not up to standard, it is likely that the softener cannot automatically absorb salt, and the reasons mainly include the following:
1. First, check whether the incoming water pressure is qualified. If the incoming water pressure is not sufficient (less than 1.5kg), a negative pressure will not be formed, which will cause the softener to not absorb salt;
2. Check and determine whether the salt absorption pipe is blocked. If it is blocked, it will not absorb salt;
3. Check whether the drainage is unblocked. When the drainage resistance is too high due to excessive debris in the pipeline's filter material, a negative pressure will not be formed, which will cause the softener to not absorb salt.
If the above three points have been eliminated, then it is necessary to consider whether the salt absorption pipe is leaking, causing air to enter and the internal pressure to be too high to absorb salt. The mismatch between the drainage flow restrictor and the jet, leakage in the valve body, and excessive gas accumulation causing high pressure are also factors affecting the softener's failure to absorb salt.