NF system
1、 NF startup operation 1. Low flow exhaust: Open the NF inlet electric slow opening valve, concentrated water quick flushing valve, and fresh water unqualified discharge valve (this valve can be ignored in NF automatic state), then start the NF feed pump and exhaust at low flow for 3 minutes. At the same time, slightly open the exhaust valve of the security filter to exhaust the security filter. Wait until there is no gas in the exhaust of the security filter, and then close the exhaust valve of the security filter. 2. High flow flushing: After the low flow exhaust is completed, start the high-pressure pump. Start the scale inhibitor and rinse with high flow rate for 3 minutes. 3. After the high flow flushing is completed, close the NF concentrated water quick flushing valve and NF fresh water unqualified discharge valve (NF outlet valve is normally open and cannot be closed under normal circumstances), and NF will enter the operating state. At present, the inlet flow rate of NF is controlled at around 10T/H, the fresh water flow rate is around 6.5T/H, and the concentrated water flow rate is around 3.5T/H. The inlet pressure is 0.25Mpa, and the concentrated water pressure is 0.15 Mpa. 4. Explanation of several indicators for NF inlet water: ⑴ Temperature: The upper limit of NF inlet water temperature can reach 45 ℃, but this temperature is only the performance test temperature of the membrane and cannot be used as a reference temperature for NF operation. Generally, the inlet water temperature of NF should be controlled between 20 ℃ and 28 ℃. Excessively high or low inlet water temperature either affects the long-term operation performance of the membrane or the high inlet water pressure of NF affects freshwater production. ⑵ PH value: According to the actual situation on site, the pH value of NF inlet water should be controlled between 5.5 and 6.5, otherwise it will easily cause metal oxide and hydroxide fouling and blockage SDI value: It is best to check the SDI value after running for half an hour at startup. When testing, pay attention to flushing the SDI pipeline for a few minutes first, then exhaust and tighten the diaphragm compression cover, and adjust the pressure to 0.21Mpa. During the initial operation of the system, the SDI value may be high due to the presence of a large amount of particulate pollutants in the pipeline. Formula: (1-t0/t15)/15 × 100t0- the time required for the first 500mL of water connection. T15- The time required to receive 500mL of water after 15 minutes Residual chlorine: The residual chlorine in NF inlet water must be strictly controlled below 0.1mg/L. If the residual chlorine is greater than this value, please add sodium bisulfite. Sodium bisulfite must be treated with food grade chemicals, and the specific dosage should be adjusted according to the ORP of the NF influent. Stop adding sodium bisulfite when the inlet ORP is less than 400mv (PH7). 2、 During NF operation, if NF runs continuously for 1 hour, a large flow flushing is required. Open the NF concentrated water quick flushing valve, and NF will enter a high flow flushing state for about 3 minutes. After flushing, close the NF concentrated water quick flush valve. ② After half an hour of system operation, start recording operational data. Including the temperature and current of the water pump. The data shall be based on the instrument display on site Check if the dosing of the metering pump is normal, if the outlet pressure of the metering pump and the flow of the medicine at the inlet of the metering pump are normal. If there is no medicine or very little, please check. In practical engineering, many users only know how to turn on the metering pump and ignore the actual dosing situation of the metering pump, resulting in inaccurate dosing and system failures. Therefore, it is necessary to pay attention to the occurrence of such situations. Attention should be paid during the inspection process. The dosage of scale inhibitor should follow the dosage of the chemical manufacturer. The current dosage of scale inhibitor is 10ppm. ④ When the inlet pressure of the NF high-pressure pump is too low, less than 0.05MPa, the corresponding high-pressure pump will immediately stop working.
3、 NF shutdown: ⑴ High flow flushing; Open the NF concentrated water quick release valve and NF unqualified water discharge valve. Stop the scale inhibitor and adjust the pH of the acid metering pump. Rinse with high flow rate for 2 minutes Stop the pump: After the high flow flushing is completed, stop the 2 # high-pressure pump, and then stop the NF feedwater pump. Close the NF inlet electric slow opening valve Freshwater flushing: Open the NF inlet flushing water valve and the inlet and outlet valves of the flushing water pump. Start the flushing water pump and flush for 3 minutes. After flushing, stop the flushing pump, close the NF inlet flushing water valve, NF concentrated water quick flushing valve, and NF unqualified water discharge valve. RO system 1. RO startup operation ⑴ Low flow exhaust: Open the RO inlet electric slow opening valve, concentrated water quick flushing valve, and fresh water unqualified discharge valve. Restart the RO feedwater pump and perform low flow exhaust for 3 minutes. At the same time, slightly open the exhaust valve of the security filter to exhaust the security filter. Wait until there is no gas in the exhaust of the security filter, and then close the exhaust valve of the security filter Large flow flushing: After the small flow exhaust is completed, start the high-pressure pump and the scale inhibitor metering pump. Rinse with high flow rate for 3 minutes After the high flow flushing is completed, close the RO concentrated water quick flushing valve and the RO fresh water unqualified discharge valve (the RO outlet valve is normally open and cannot be closed under normal circumstances), and the RO will enter the operating state. At present, the inlet flow rate of RO is controlled at around 10T/H, the fresh water flow rate is around 6.5T/H, the concentrated water flow rate is around 3.5T/H, and the concentrated water return flow rate is around 3T/H Explanation of several indicators for RO inlet water: I. Temperature: The upper limit of RO inlet water temperature can reach 45 ℃, but this temperature is only the performance test temperature of the membrane and cannot be used as a reference temperature for RO operation. Generally, the inlet water temperature of RO should be controlled between 20 ℃ and 28 ℃. Excessively high or low inlet water temperature either affects the long-term operation performance of the membrane or the high inlet water pressure of RO affects freshwater production. II PH value: Generally speaking, the desalination rate of RO membrane is optimal between pH 6.0 and 8.0. Based on the characteristics of the on-site leachate, it is recommended to control the pH value between 6.0 and 7.0, with a value of 6.5 being more suitable. A higher pH value is more likely to form metal oxide colloid pollution in the front section of the RO membrane or hydroxide colloid and sulfate scaling pollution on the concentrated water side in the end section. SDI value: It is best to check the SDI value after running for half an hour after startup. When testing, pay attention to flushing the SDI pipeline for a few minutes first, then exhaust and tighten the diaphragm compression cover, and adjust the pressure to 0.21Mpa. During the initial operation of the system, the SDI value may be high due to the presence of a large amount of particulate pollutants in the pipeline. Formula: (1-t0/t15)/15 × 100t0- the time required for the first 500mL of water connection. T15- The time required to receive 500mL of water after 15 minutes. IV. Residual chlorine: The residual chlorine in the RO inlet water must be strictly controlled below 0.1mg/L. If the residual chlorine is greater than this value, please add sodium bisulfite. Sodium bisulfite must use food grade chemicals, and the specific dosage should be adjusted according to the ORP of the RO inlet water. Stop adding sodium bisulfite when the inlet ORP is less than 400mv (PH7).
2、 During the operation of RO, if the RO runs continuously for less than 1 hour, a large flow flushing is required. Open the RO concentrated water quick flushing valve, and the RO will enter a high flow flushing state for about 3 minutes. After flushing, close the RO concentrated water quick flushing valve. ② After half an hour of system operation, start recording operational data. Including the temperature and current of the water pump. The data shall be based on the instrument display on site Check if the dosing of the metering pump is normal, if the outlet pressure of the metering pump and the flow of the medicine at the inlet of the metering pump are normal. If there is no medicine or very little, please check. In practical engineering, many users only know how to turn on the metering pump and ignore the actual dosing situation of the metering pump, resulting in inaccurate dosing and system failures. Therefore, it is necessary to pay attention to the occurrence of such situations. Attention should be paid during the inspection process. The dosage of scale inhibitor should follow the dosage of the chemical manufacturer. The current dosage of scale inhibitor is 10-16ppm. The pH of the RO inlet water is between 6.2 and 6.7. Due to the high salt content in the RO inlet water, strict inspection of the scale inhibitor is necessary to ensure the safe operation of the RO. When preparing scale inhibitors, it is advisable to consider the daily operating time of RO and control it within 3-4 hours. Medications that exceed the above number of days must be disposed of and re prepared. (During inspection, pay attention to observing whether there are any precipitated inorganic salts in the RO concentrated water discharge flowmeter. If there are a few, immediate measures should be taken to check the addition of scale inhibitors and pH acid. At the same time, it is also necessary to check and control the pH value of the concentrated water to not exceed 7.8, otherwise the RO inlet pH value needs to be reduced accordingly.) ④ When the inlet pressure of the RO high-pressure pump is too low, the corresponding high-pressure pump will immediately stop working. 3、 Shutdown of RO: ⑴ High flow flushing; Open the RO concentrated water quick discharge valve and the RO unqualified water discharge valve. Stop the scale inhibitor. Rinse with high flow rate for 2 minutes Stop the pump: After the high flow flushing is completed, stop the high-pressure pump first. Then stop the RO feedwater pump. Close the RO inlet electric slow opening valve Freshwater flushing: Open the RO inlet flushing water valve and the inlet and outlet valves of the flushing water pump. Start the flushing water pump and flush for 3 minutes. After flushing, stop the flushing pump, close the RO inlet flushing water valve, RO concentrated water quick flushing valve, and RO unqualified water discharge valve. The chemical cleaning of NF and RO should first be explained that the cleaning agents, judgment, and cleaning methods of RO and NF are completely consistent. Therefore, only the cleaning of NF will be described here, and the cleaning of RO can be carried out according to NF cleaning. Secondly, before cleaning NF, it is necessary to determine the chemical cleaning conditions of NF, and then determine the pollutants before conducting chemical cleaning. (Please refer to the Dow film product manual for specific content.) ⑴ The chemical cleaning conditions for NF are determined based on initial operating data or operating data after the previous effective cleaning. There can only be one benchmark for comparison.
Conditions for NF cleaning: ① Decrease the water flow rate by 10-15%. ② The salt tolerance rate has increased by 10-15% The pressure difference has increased by 10-15% The water supply pressure has increased by 10-15%. When making judgments above this level, attention should be paid to the changes in various factors to avoid interference from certain factors, such as temperature interference in determining water production flow rate, interference in determining salt permeability, judgment of operating pressure and pressure difference, etc. Sometimes it is also important to note that the outlet pressure of the security filter has an impact on the operating pressure of NF and the inlet flow rate. A higher outlet pressure leads to a corresponding increase in NF inlet pressure and flow rate. Of course, it's not as obvious as temperature. But it is also a disruptive factor. So the running record data should be complete and the judgment should be meticulous. So after adjusting the flow of the outlet flow control valve, concentrated water discharge valve, and concentrated water return valve of the high-pressure pump, they cannot be moved arbitrarily. Otherwise, it will have a significant impact on the collection of initial running data for NF, and the comparison of cleaning conditions in the future will not be possible. Of course, it is also necessary to exclude data changes caused by mechanical failures of membrane components and systems. Do not simply handle it as a membrane that needs to be cleaned. If there is no significant change in all data after running the system for 5-6 months, maintenance cleaning should also be carried out, mainly to clean biological pollution and sterilization. Because bacterial and biological pollution typically increase exponentially over time, this cannot be ignored and is often implicit, difficult to detect and distinguish. So the situation where reverse osmosis is not cleaned for a year or several years and all data is normal does not exist, and this understanding is also worth discussing. At the same time, it should be noted that sometimes membrane pollution is not a single type of pollution, but often two or more types of pollution. Therefore, there are two types of pollution: primary pollution and secondary pollution. The general cleaning principle is to clean the primary pollution first, and then the secondary pollution. As for the cleaning of acid before alkali or alkali before acid, most of them follow this principle Identification of pollutants: It is more convenient to determine what type of pollution it is based on pressure and pressure difference. Generally speaking, when the pressure difference increases, the water production flow rate decreases and the conductivity increases, it is mainly due to metal colloid pollution or organic matter substances and colloids. Sometimes, due to the excessive pressure difference of the security filter and the failure to replace the filter element in time, the filter element may break and leak some larger particulate matter and filter fiber. The overall pressure increases, the water production flow rate decreases, and the effluent conductivity increases, mainly due to inorganic salt scaling pollution. The reason for this is that the concentrated water side causes insoluble salts to precipitate beyond their solubility product. If the overall pressure increases, the water flow rate decreases, and the effluent conductivity does not change significantly, then it is mainly due to biological pollution. In addition, a more cautious method is to dismantle one end plate of the membrane shell, take a sample of the pollutant, and send it to the laboratory for analysis and judgment. Finally, experimental cleaning can also be used to verify whether the judgment is correct Selection of cleaning formula: Please refer to the medication formula in the membrane product manual. Different pollutants correspond to different drug formulations Preparation of chemical cleaning tank: First, place the tank at a suitable water level, and then add the chemicals. The water used for dispensing must be fresh NF water. Then circulate the medicine to ensure thorough mixing. The medicine circulation valve of the medicine box can be opened, and the inlet valve of the cleaning security filter should not be opened for now. Every time the dressing is changed, clean water should be used to rinse the medicine box, and the waste liquid can be discharged from the drainage valve of the medicine box. When adding medicine to the medicine box, do not pour the entire bag of medicine into the suction port of the chemical cleaning pump. The concentration and pH value of the medication must strictly follow the formula requirements Cleaning steps: The NF system is a single-stage system, and cleaning is relatively simple. NF cleaning: Use cleaning solution to remove the water present in the NF membrane. Open the NF fresh water side liquid reflux valve, NF concentrated water quick discharge valve, and NF cleaning solution inlet valve. Close the NF concentrated water discharge valve, NF concentrated water reflux valve, and NF outlet valve. Then open the inlet valve of the cleaning security filter. Restart the chemical cleaning pump and adjust the flow rate of the cleaning solution to around 14m3/h. Replace the water present in NF with low flow rate and low flow rate until the cleaning solution is discharged from the outlet of the NF concentrated water quick flushing valve, preferably for another 5 minutes. When there is very little medication available at this time, it is recommended to refill the medication and not use a small amount of medication to circulate and clean NF. Such cleaning will be time-consuming and ineffective, resulting in twice the effort and half the result.
⑸ High speed cycle cleaning: Open the NF cleaning solution reflux valve, NF fresh water side liquid reflux valve, and close the NF concentrated water quick flushing valve. Gradually increase the circulating flow rate from 14m3/h to 48m3/h. When cycling, pay attention to checking the effective usage amount and color turbidity of the cleaning solution. If it is too little or turbid, it is necessary to re prepare the cleaning solution. Generally, membranes contaminated by organic organisms or with severe pollution require a longer cycle time. Usually, the NF cycle of general pollution lasts about 2 hours. During the circulation process, add medication in a timely manner according to changes in the pH value of the medication to replenish drug consumption. During the circulation process, the cleaning principle of "high flow rate, low pressure" should be followed. Therefore, the pressure of the NF cleaning solution should be as low as possible, but the flow rate should be as high as possible. Generally, the cleaning pressure should not exceed 0.3Mpa, because excessive cleaning pressure will make it difficult to separate pollutants from the membrane. So the previous cleaning flow rate value is only a rough reference value, and there is no need to be limited to this flow rate value. The following cleaning traffic data is also the same. It is mainly determined by adjusting the empirical cleaning pressure appropriately Soaking: The soaking time of NF membrane is also determined by the degree of contamination of NF membrane. When soaking, pay attention to whether the concentration of the medicine solution reaches the initial concentration and whether the pH value is appropriate. Stop the cleaning pump during soaking, close the NF reflux valve and NF cleaning solution inlet valve. Soak for about 4 hours for general pollution Recirculation: After soaking, open the NF liquid reflux valve and NF cleaning solution inlet valve, then turn on the cleaning pump and circulate again for about 2 hours at a flow rate of 24m3/h. During the circulation process, it is also necessary to observe the turbidity of the medicine and add the medication in a timely manner. After the cycle is completed, the reaction and consumption of the liquid medicine can be observed, and a decision can be made whether to discharge the liquid medicine or continue cleaning. But sometimes the above methods are limited to the discrimination of inorganic salts, and cannot make such simple treatments for organic or biological pollution. For such pollution, it takes longer cleaning and soaking time to be effective. After the cycle is completed again, you can proceed to the next step of water cleaning and close the NF cleaning reflux valve Water cleaning: In practical operation, it is recommended to first rinse with fresh water and then rinse NF with NF water. Close the NF cleaning solution inlet valve, NF cleaning solution reflux valve, and fresh water side reflux valve. Open the NF unqualified water discharge valve, NF concentrated water quick flushing valve, NF inlet flushing water valve, flushing pump outlet valve, start the flushing pump so that the flushing inlet pressure is not greater than 0.3Mpa, and after flushing for 10 minutes, stop the flushing pump. After stopping the flushing pump, close the NF inlet flushing water valve and flushing pump outlet valve. Open the NF inlet electric slow opening valve and start the NF feed pump to flush NF. The disadvantage of this method is that the water volume is relatively small and the flushing time is long. The advantage is that it consumes less fresh water from reverse osmosis and increases the output rate of reverse osmosis. The flushing process ends when the conductivity of the incoming water is not significantly different from the pH of the concentrated water outlet. Attention: ① When NF requires two or more agents to be cleaned separately, the previous agent should be washed clean from the cleaning box, security filter, pipeline, and NF membrane before proceeding to the next agent cleaning. Water can be poured into the medicine box, and two to three boxes of NF can be rinsed with water from the cleaning pump to clean the medicine box, the security filter, and its cleaning pipeline During cleaning, various cleaning data should be recorded, including the type, concentration, flow rate, pressure, circulation time, soaking time, etc. of the chemical solution. After each cleaning, an evaluation of the cleaning effect must be conducted to determine whether the cleaning is effective or ineffective. Analyze the reasons, summarize the experience, and provide a foundation for the next successful cleaning. Precautions for daily operation of NF and RO systems
1. Strictly keep operation records of the equipment. Complete records of various operating pressure, flow rate, and other data of the equipment should be kept, especially the initial operating data and the operating data after each cleaning. These data have great reference for measuring the performance status and cleaning success of the NF membrane. Require the system to record operational data every 2 hours. Generally, operational data is recorded half an hour after the system is turned on. 2. Each shift should check and inspect the start, sound, and temperature of the pump, as well as whether the pneumatic and electric valves are open and closed normally, to prevent damage to the system pipeline caused by valve reasons. 3. The measurement of SDI value should be done once a day. 4. When NF is not running for a short period of one week, it should be run for at least one hour every day. When running, use ultrafiltration to produce fresh water to NF, and do not use stagnant water stored in the water tank to protect NF during operation. So during the period when the system is not running, do not discharge water from the water tank. Drain water during system maintenance operation. For shutdowns of more than a week, medication is needed to protect NF, usually by chemically cleaning the NF before sealing the NF system with protective solution. Please refer to the detailed introduction in the Dow film product manual for the specific formula of the protective liquid. 5. The medicine in the dosing box is highly susceptible to bacterial and microbial contamination due to its dilute concentration. Furthermore, its medicinal properties will degrade over time. So please keep the typical usage days within 4 days. For extremely dilute solutions of 2-3%, it can only last for 2 days. Please pay attention to this, especially in summer. In some users, there are often cases where the medicine prepared two or three months before the system shutdown has turned black and discolored, and is still being added to the system. 6. The on-site instruments -0RP meter and PH meter - need to be calibrated every two to three months. Other instruments can undergo maintenance checks and calibrations every six months. Please pay attention to the calibration of the instrument. Only accurate calibration of the instrument can grasp the performance of the equipment, and thus ensure the safe operation of the equipment. 7. The on-site water pump should be regularly inspected for its operation. Calibrate the water pump coupling, tighten the water pump base bolts, and add cooling lubricating oil, etc. Please refer to the manuals of various water pumps for specific maintenance measures.
