1、 MBR membrane fouling judgment

      On line maintenance and cleaning: it has nothing to do with the pressure difference. Stop filtering regularly (about once a week) and drive the low concentration (300 ~ 500mg / L) solution into the membrane for cleaning.   

      Online enhanced washing: monitor and manage the suction negative pressure of membrane module, and the suction negative pressure shall not exceed the set value. (this value is the initial value of suction pressure + 15kpa). When the set value is exceeded, the solution shall be cleaned immediately to restore the membrane performance.   

      When operating according to the standard flow, the initial pressure difference between membranes caused by the suction of membrane module during operation is P1, which is called the initial pressure difference). However, the display value of differential pressure gauge will be different due to the different erection method of piping and the position of instruments. Please note.    

      When using the membrane module (during filtration operation), record the initial differential pressure P1. During the long-term filtration of activated sludge, the adsorption of organic substances such as protein on the membrane surface, and the pressure difference between membranes rises slowly.   

      Off line cleaning: if the on-line enhanced cleaning cannot effectively restore the membrane performance, the membrane module can be directly immersed in the drug solution for off-line cleaning.

2、 MBR membrane cleaning method   

      MBR membrane module cleaning methods mainly include online maintenance cleaning, online enhanced cleaning and offline cleaning.   

1. On line maintenance cleaning    

      Maintenance cleaning regularly removes the pollutants on the membrane surface to inhibit the thickening of the polluted layer and the rise of transmembrane differential pressure, so as to achieve the purpose of stable operation. Stop aeration during maintenance cleaning.   

      The frequency of maintenance cleaning is usually once a week. NaClO with effective chlorine concentration of 300mg / L ~ 500mg / L is quantitatively injected into the membrane module from the water production side. The injection time of the agent is 30min. After the injection of the agent, it is soaked for 30min. The dosage per unit membrane area is 2 ~ 2.5l/m2, and the total dosage shall be calculated according to the capacity of the transmission pipeline.   

2. Online enhanced washing   

      The on-line enhanced washing is carried out every 1-3 months or when the suction pressure exceeds the set value (= when the pressure difference between membranes rises), which aims to remove the pollutants on the membrane surface and restore the membrane performance to a state close to the initial state.   Stop aeration, quantitatively inject cleaning solution from the water production side with NaOCl solution with effective chlorine concentration of 2000-3000mg / L for 30 min, and stand for 90 min after injection. The dosage per unit membrane area is 2 ~ 2.5l/m2, and the total dosage shall be calculated according to the capacity of the transmission pipeline.  

      After NaOCl cleaning, if the transmembrane pressure difference is still high, online pickling (1-2% oxalic acid, 1-2% citric acid, 0.1 ~ 0.2% hydrochloric acid) can be carried out to remove inorganic scale. During acid cleaning, the NaOCl in the pipeline and pump shall be cleaned first to avoid the generation of toxic gas.   Note: when cleaning with acid, if you have any questions, please contact the technician of our company.

3. Offline cleaning   

      When the two current cleaning methods cannot restore the membrane performance, it is necessary to carry out off-line cleaning, lift the membrane module out and immerse it in a special cleaning tank, remove pollutants, and restore the membrane performance to a state close to the initial value. Generally, immersion cleaning can significantly restore the membrane performance.

      During off-line cleaning, immerse the whole membrane module or single membrane into alkaline cleaning agent (NaClO solution with effective chlorine concentration of 2000-3000 mg / L and pH 10-11) or acidic cleaning agent (1-2% oxalic acid or citric acid, 0.1-0.5% sulfuric acid or hydrochloric acid). The soaking time is 6 ~ 24 h for NaClO and 2 h for acid.   

      Before the membrane module is immersed in the cleaning tank, the sludge attached to the membrane surface shall be cleaned with water, which can reduce the use of cleaning agent and improve the cleaning effect. During immersion cleaning, intermittent aeration can be used to fully mix the agents and maintain the concentration of agents on the membrane surface. If necessary, agents such as NaClO can be added intermittently to maintain the concentration of cleaning solution.

3、 Cleaning method of membrane module in MBR membrane treatment station   

      1. Stop the inlet water pump, outlet suction pump and aeration fan. After the liquid in the MBR tank settles for 4 hours, drain the supernatant with the submersible sewage pump, expose the aeration pipe and outlet pipe, unscrew the union, and transfer the membrane tank from the MBR tank as a whole (there are two methods: one is to use a crane to transfer it out, and the other is to install I-beam and hoist on the MBR tank).

      2. Clean the inside and outside of the membrane tank with tap water and remove the activated sludge attached inside the membrane; At this time, pay attention not to let the sludge on the unloaded suction pipe pollute the interior of the suction pipe and do not directly wash with more membrane wires.   

      3. The original car washing device in the warehouse is used as the cleaning tank, and the membrane module is completely immersed in the cleaning tank filled with the specified liquid medicine. Let it stand for 6-24 hours. Consider whether the liquid medicine needs to be heated according to the actual situation.

      4. After the immersion time, take out the membrane module from the immersion cleaning tank, wash it fully with water, and remove the drug solution attached to the membrane module.

      5. Install the membrane module into the membrane tank and hang it on the two ears of the membrane tank with nylon belt or rope. Be careful not to slip. When lifting the membrane tank with hoist, put it into the membrane tank at the correct position, align the outlet pipe and aeration pipe, and there shall be no air leakage after the pipeline is connected; Start the blower for aeration for more than 30 minutes; Then start the water outlet pump and control the water output at 1.0m ³/ Min, run for more than 30 minutes, and then put into normal operation.   

      6. Before discarding the liquid medicine, sodium hypochlorite is reduced with sodium thiosesulfate (Na2S2O3 nH2O), and then sodium hydroxide is neutralized with hydrochloric acid. If it is neutralized with hydrochloric acid first, it is easy to cause danger.