How to use reverse osmosis antiscalant?

The correct use of reverse osmosis antiscalants requires controlling the dosage, location, and frequency of addition. Reverse osmosis antiscalants can effectively prevent calcium and magnesium ion scaling in reverse osmosis systems, ensuring efficient operation of the system. In industrial water treatment scenarios, if not used correctly, scaling can cause a decrease in the performance of reverse osmosis membranes, affecting the quality and efficiency of water production. Reasonable use can extend the lifespan of the membrane and reduce maintenance costs. Next, we will explain in detail how to do it.

 

1. Preparation before use

      （1） Understand the system condition

      Before using reverse osmosis antiscalants, it is necessary to have a detailed understanding of the water quality and membrane material type of the system. Different water qualities contain different types and concentrations of hardness ions such as calcium and magnesium, as well as other substances that may scale. Different membrane materials (such as CA membranes, TFC membranes, nanofiltration membranes, and ultrafiltration membranes) also have different requirements for scale inhibitors. For example, certain membrane materials may be more sensitive to specific chemicals and require the selection of compatible reverse osmosis antiscalants. Determine the appropriate type of scale inhibitor through water quality analysis report and technical parameters of membrane materials.

 

 

      （2） Choose the appropriate scale inhibitor

      There are various types of reverse osmosis antiscalants on the market, each with different compositions and properties. Select scale inhibitors with corresponding functions based on the specific requirements of the system, such as water quality characteristics, membrane type, operating parameters (such as recovery rate, pressure, temperature), etc. For example, for high hardness water quality, scale inhibitors that can effectively control scaling such as calcium carbonate and calcium sulfate should be selected; For water containing metal ions such as iron and aluminum, it is necessary to choose scale inhibitors that have good chelating and stabilizing effects on the metal ions. At the same time, compatibility between scale inhibitors and other water treatment chemicals (such as fungicides, pH regulators, etc.) should be considered to avoid adverse reactions.

      （3） Prepare dissolution equipment and solution

      When dissolving reverse osmosis antiscalants, pure water should be used and water sources containing a large amount of impurities should be avoided to avoid affecting the effectiveness of the scale inhibitors. Prepare a clean dissolution container, such as a plastic bucket or specialized dissolution tank, and equip it with a stirring device to ensure that the scale inhibitor can dissolve evenly. Accurately weigh the required amount of scale inhibitor according to the ratio in the product manual, slowly add it to purified water, and turn on the stirring device to continue stirring for a period of time until the scale inhibitor is completely dissolved, forming a uniformly concentrated solution.

 

2. Add operation steps

      （1） Determine the investment point

      Reverse osmosis antiscalants are usually uniformly added to the inlet water of the reverse osmosis system through a metering pump. The injection point is usually located after the security filter and before the reverse osmosis membrane module. This dosing position ensures that the scale inhibitor can be fully mixed with the incoming water, exerting the best scale inhibition effect before entering the membrane module. If the injection point is too early, the scale inhibitor may be consumed or react with other substances during the pretreatment stage; If the injection point is too late, it may not be able to prevent fouling on the membrane surface in a timely manner.

      （2） Set the parameters of the metering pump

      Set the stroke and frequency of the metering pump based on the specific conditions of the system, such as inlet flow rate, concentration of scale inhibitor, and required dosage. The stroke of the metering pump determines the volume of liquid pumped each time, while the frequency determines the number of times pumped per unit time. By adjusting these two parameters, the dosage of scale inhibitor can be precisely controlled. For example, if the inflow rate is 100m ³/h and according to the instructions for using the scale inhibitor, 3mg of scale inhibitor needs to be added per cubic meter of water, then the parameters of the metering pump can be calculated and set to add 300mg of scale inhibitor per hour.

      （3） Start the dosing system

      After confirming that the parameters of the metering pump are set correctly, start the metering pump and evenly add the dissolved reverse osmosis antiscalant solution to the system. At the same time, it is necessary to closely observe the operation of the system to ensure that the scale inhibitor can be added stably and accurately. During the initial operation of the system, the water quality of the incoming and outgoing water can be regularly monitored, especially the concentration changes of hardness ions such as calcium and magnesium, to verify the effectiveness of the scale inhibitor.

 

3. Monitoring and adjustment during use

      （1） Regularly monitor water quality

      During the use of reverse osmosis antiscalants, it is necessary to regularly monitor changes in the water quality of the system. In addition to detecting the concentration of hardness ions, other indicators that may affect membrane performance, such as pH value, turbidity, residual chlorine, etc., should also be considered. If signs of water quality deterioration or membrane fouling are found, such as a decrease in water production, a decrease in desalination rate, an increase in pressure difference, etc., the cause should be analyzed in a timely manner, and the dosage of scale inhibitor should be adjusted or the type of scale inhibitor should be replaced.

      （2） Check the dosing equipment

      Regularly check the working status of the metering pump and dosing system to ensure accurate dosing of the metering pump and no leakage in the dosing pipeline. Check if the stroke and frequency of the metering pump are consistent with the set values, and if the liquid level in the dosing tank is normal. If a malfunction is found in the metering pump or the dosage is inaccurate, timely maintenance or calibration should be carried out to ensure that the scale inhibitor can be added to the system according to the required dosage.

      （3） Adjust the dosage according to the operating parameters

      The operating parameters of reverse osmosis systems, such as recovery rate, pressure, and temperature, may be adjusted over time. The changes in these parameters will affect the concentration of scaling substances in water and the tendency of scaling on the membrane surface, so it is necessary to adjust the dosage of scale inhibitors in a timely manner according to the actual situation. For example, when the recovery rate of the system increases, the concentration of scaling substances in the influent will increase. At this time, the dosage of scale inhibitor should be appropriately increased to prevent membrane fouling.

 

4. Combined use with other chemicals

      In reverse osmosis systems, in addition to using reverse osmosis antiscalants, other chemicals such as fungicides and pH regulators may also be used. When using these chemicals, it is important to ensure good compatibility with reverse osmosis antiscalants. Avoid chemical reactions between different chemicals, which can result in precipitation or reduce their performance. For example, certain fungicides may react with the components in the scale inhibitor, affecting the scale inhibition effect or causing membrane fouling. Before use, a small-scale experiment should be conducted to verify the compatibility between different chemicals, and the operation of the system should be closely observed during actual operation.
      Proper use of reverse osmosis antiscalants requires preparation before use, strictly following the dosing operation steps, strengthening monitoring and adjustment during use, and paying attention to the coordination with other chemicals. Only in this way can the role of reverse osmosis antiscalants be fully utilized, ensuring the stable operation of the reverse osmosis system, improving the water production and quality of the system, and extending the service life of the membrane.

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