The ro reverse osmosis membrane on the industrial pure water equipment needs to be cleaned after a period of use. If it does not affect the water yield and conductivity of the produced water, thus affecting the water quality, it is necessary to check whether the conductivity displayed on the electric cabinet has decreased after the equipment has been used for a period of time. If it has decreased or the water yield has decreased, the ro reverse osmosis needs to be cleaned. The methods for cleaning the ro membrane of industrial pure water equipment are as follows:
When using reverse osmosis, if the installed water yield decreases by 10%, if the salt penetration rate doubles, or the differential pressure drop doubles, it indicates that the reverse osmosis needs to be cleaned (but it should be noted that the drop in temperature will also cause the water yield to decrease, which is a normal phenomenon. In addition to periodic cleaning, it is better to run at low pressure for several minutes each time you start up to remove the concentrated water in the reverse osmosis device and drain it, instead of entering the next level unit.
1. Physical cleaning method
The simplest physical cleaning method is to wash the Dow membrane with water at low pressure and high flow rate for 30 minutes, which can restore the water permeability of the membrane to a certain extent, but the water permeability still decreases after a long time. The membrane surface can also be washed with water and air mixed fluid at low pressure for 15 minutes. This method is effective for cleaning the membrane polluted by organic substances at the initial stage.
2. Chemical cleaning method
① Citric acid solution: under high pressure or low pressure, use 1% - 2% citric acid aqueous solution to wash the membrane continuously or circularly. This method has a good cleaning effect on Fe (OH) 3 pollution.
② Ammonium citrate solution: add ammonia water into the solution of citric acid or prepare a solution with different PH values. You can also add HCL into the solution of ammonium citrate and adjust the PH value to 2-2.5. For example, in 190L deionized water, 277g of ammonium citrate is dissolved and the PH value of the solution is adjusted to 2.5 with HCL. This solution can be circularly cleaned in the membrane system for 6 hours. If the solution is heated to 35-40 ℃, the cleaning effect is better, The solution has good cleaning effect on inorganic pollution, but the cleaning time is long.
③ Enzymatic detergent is used to treat the membrane, which is particularly effective for organic pollution, especially for protein, oil and other organic pollutants. If the cleaning effect is better at 50 ℃ - 60 ℃, generally after 10 days or half a month of operation, 1% enzyme added detergent is used to clean the membrane at low pressure. Because the concentration of enzyme added detergent is low, the immersion time is required to be longer.
④ Concentrated salt water, it is effective to clean the membrane that severely punishes the limb pollution with concentrated salt water. This is because the high concentration salt water can weaken the interaction between colloids and promote the formation of micelles.
⑤ Water soluble emulsion, which is very effective for cleaning the membrane polluted by oil and iron oxide, generally cleaning for 30-6 minutes.
⑥ Hydrogen peroxide solution, for example, dilute 0.5L and 30% H2O2 with 12L deionized water, and then clean the membrane surface. This method is particularly effective for organic pollution.
⑦ For sodium hypochlorite and formaldehyde solution, different treatment measures should be taken according to different membranes for bacterial pollution. Aromatic polyamide membranes can be cleaned with 1% (weight) formaldehyde solution. At the same time, it is necessary to regularly analyze the residual chlorine in reverse osmosis concentrated water to keep 0.2-0.5mg/l to prevent bacterial proliferation.
⑧ Oxalic acid and EDTA solution. For the metal oxide precipitation on the membrane, it is better to clean it with oxalic acid and EDTA solution.
Industrial water equipment - RO membrane cleaning method.
2022 10/17