Reverse osmosis secondary scaling

A problem occurs after only ten days of operation. You need to search carefully to determine whether the raw water analysis and recovery rate selection of this system are reasonable. What is the entire grading process and design of your system? Is the pretreatment condition good? I wonder which anti-scaling product you are using. If it doesn’t work, just click on it and there is no scaling. You can open it and take a look.

The amount of antiscalant added is not enough or not added. Take another look at the design of the RO system. Are there any problems?

This is definitely not the reason for insufficient scale inhibitor. If it is insufficient, the pressure difference between the middle section and the concentrated water should become smaller. Your reason is probably microbial contamination, mainly at the second section of the import. ——What is your raw water? What treatment process is used? It is recommended that you sterilize the raw water.

I think it is unlikely to be a problem of microbial contamination, because a significant feature of microbial contamination is that the pressure difference in the first section increases significantly. Based on the poster's description, I think it may be caused by scaling. I suggest checking the inhibitor dosing system and conducting water quality analysis.

Is there any change in the water production? The pressure difference appears abnormal after only ten days of operation. I think it cannot be a scaling problem. Is there a cationic activator or other solid matter that blocks the water production channel and causes the pressure difference to increase.

It shouldn't be a problem with the anti-scaling agent. Personally, I don't think this will happen even if I don't add the anti-scaling agent for 10 days.； According to the data provided by the poster, the recovery rate is a bit high, and whether there is a problem with the system design. It is best to disassemble the membrane and check it, so that it is easier to find the cause.

What is the basis for why this situation will not occur even if no antiscalant is added for ten days? What is the fundamental reason for the increase in pressure difference caused by high recovery rate? Haha, I also hope that the author will announce the analysis and diagnosis results as soon as possible.  

Is there any problem with the meter? After 10 days of operation, the pressure difference reached 0.7, which is too high. What was the pressure difference when it started running? If the pressure difference in the second stage is too large, there is a possibility of scaling. Does the antiscalant match the water quality?

I agree with the fifth floor, it is unlikely to be biological pollution. And if it gets clogged so quickly, the problem is quite serious. Usually, without adding anti-scaling agent, it is unlikely that the pure water will get clogged. You can first check the water quality report to see if the design is reasonable. ； Then check the operation status and equipment status. You can also disassemble the membrane casing to see the status of pollutants.

The pressure of 0.7MPa is the limit for a section of membrane element. You'd better check the model of the antiscalant and the actual amount added.； Re-analyze the quality of your raw water to determine whether the antiscalant is used correctly. ； Estimate the consumption of antiscalant and determine the actual amount of antiscalant added.

The preprocessing is not done well. Consider whether the preprocessing is reasonable?

A problem occurred within ten days and backwashing was required. It was probably because the pretreatment was not well designed. It is recommended that LZ provide water quality and process flow. Let’s help you analyze

water quality: Cl-:191.27mg/l, Ca2+211.62mg/l Mg2+34.99mg/l PH=7.34 The process is: Raw water, sand filter, security filter, RO, mixed bed, produced water

Groundwater, right? Is the system still running intermittently? It's the kind that starts for a few hours and then stops for a few hours. It doesn't run 24 hours a day! It is recommended to open the port of the second-stage membrane to check. Personally, I still think that the possibility of microorganisms is very high. Because if it is a problem with the antiscalant, that is, after scaling occurs, it is equivalent to closing the concentrated water valve. At this time, the overall pressure should increase and the pressure difference between the second stage should decrease. ； If it is a pretreatment problem, it should be blocked at the inlet end of the membrane. At this time, the pressure difference in the first stage should rise significantly, and the pressure difference in the second stage may also rise, but the amplitude should be less than the pressure difference in the first stage. ； If it is microorganisms, because the flow rate on the water inlet side is very fast, microorganisms cannot grow on the RO membrane. By the second stage, the flow rate is relatively small, and after the anaerobic process of the first stage membrane, the number of microorganisms has also increased, so it is easy to breed microorganisms. ； If the system design is a bit unreasonable, such as 3: 2 arrangement, etc. At this time, the flow rate of the second section is much smaller than that of the first section, so it is easier for microorganisms to breed. ——It is recommended that you check it yourself. After all, what others say is based on other people’s experience, and your own first-hand information is more accurate! ! !

The increase in pressure difference between the two stages is basically caused by scaling. The most important thing for reverse osmosis is to perform corresponding operation and maintenance. Use regular reverse osmosis agents, control the pH value of the incoming water below 7.5, and control the residual chlorine below 0.1 mg per liter. It is not normal for problems to occur within ten days.

Scaling may account for more than 90% of the cases. Judging from the water quality indicators given, the ion concentration is high, which is likely to cause scaling. Check the amount and type of antiscalant added and whether it is added according to the manufacturer's requirements. In addition, check whether the quality of the raw water fluctuates too much and whether backwashing has been performed. Generally, if the frequency of use is high, backwashing is required every 2-3 days, which will cause * * Reduces the likelihood of scaling. Check the COD of the raw water to see if it is due to organic pollution.

Personally, I suggest checking the following contents one by one. A large pressure difference between the second stage is most likely due to scaling. You can remove the water outlet cover of the second stage to verify. For scaling, please refer to 1 below. The hardness and pH of the incoming water cannot be measured at one time point. It is recommended to observe it for several days to exclude a stream of water with a very high pH or a high hardness in a certain period of time2. Has the liquid level of the medicine dropped normally? The dosage has been recalculated. It has just been put into operation. Is the medicine mismatched? 3. Is the equipment operation recovery rate normal? 75% recycled concentrated water is 4 times that of concentrated water. The recovery rate is too high and even chemicals can’t hold it

Personally, I suggest checking the following contents one by one. A large pressure difference between the second stage is most likely due to scaling. You can remove the water outlet cover of the second stage to verify. For scaling, please refer to 1 below. The hardness and pH of the incoming water cannot be measured at one time point. It is recommended to observe it for several days to exclude a stream of water with a very high pH or a high hardness in a certain period of time2. Has the liquid level of the medicine dropped normally? The dosage has been recalculated. It has just been put into operation. Is the medicine mismatched? 3. Is the equipment operation recovery rate normal? 75% recycled concentrated water is 4 times that of concentrated water. The recovery rate is too high and even chemicals can’t hold it

The original poster posted this post in 2009. I don’t know if I’ve seen any replies now. The parameter conditions given by the poster himself are somewhat sparse, and the upstairs also gives several possibilities based on experience. If the poster sees it, he will also answer your questions and finally diagnose the system.