Why is there foam in the MBR membrane separation tank for wastewater treatment? What should I do?

In the process of processing, there is still a headache, that is, too much foam. What should I do with these bubbles? In fact, it is enough to hand over the MBR membrane pool defoamer.

Seeing this, some sewage treatment manufacturers may have opinions, not that I don't know that I can use a tool like a defoamer, but I am worried that this type of defoamer will harm biological bacteria, have an impact on the MBR system, or damage the diafiltration membrane, which will then lead to clogging of the ultrafiltration membrane. Some manufacturers are worried that the amount of defoamer will be too much, which will affect the progress of water treatment or overflow, and affect the activated mud and bacteria. We have also learned about these problems when communicating with other experts.

Manufacturers' worries are not unreasonable, but in fact, as long as you understand the function of the defoamer, I believe that everyone will reduce their doubts.

MBR membrane pool sewage treatment defoamer is a defoamer specially designed for various biological water treatment systems, which has no adverse effect on various fungi of water species, will not damage the membrane, and will not cause pollution. It has good alkali and acid resistance, fast defoaming speed, and lasts for a long time, which can reach the processing time of the entire water treatment process.

Add a defoamer, or the most practical way to do it, is to add a few drops of oil (cooking oil is fine).

The reason for this is the large amount of aeration and the fact that the wastewater contains surfactants. It can be controlled by spraying a defoamer.

Influencing factors of contamination of MBR membranes:

1. Characteristics of sludge mixture:

2. Operating conditions: cross-flow and turbulent flow, pressure

3. Membrane module: membrane material, membrane pore size, membrane structure

Solution to the contamination of MBR membranes

1. Change the characteristics of the suspension: MBR membrane pollutants mainly come from the activated sludge mixture, and the pretreatment of the membrane and the change of its filtration characteristics can effectively reduce and slow down the membrane pollution. A small amount of flocculant can be added to the bioreactor to flocculate and coagulate fine particles and reduce their deposition on the membrane surface.

2. Shedding and removal of pollutants on the membrane: set an aeration device to increase the aeration volume, produce a water flow shear effect on the surface of the membrane, cause the vibration of the membrane filament near the MBR membrane module, and accelerate the shedding of the deposited pollutants on the membrane surface; When the membrane pollution reaches a certain level, the membrane module should be cleaned to ensure the normal operation of the system, and the commonly used cleaning methods include hydraulic cleaning, chemical cleaning, and ultrasonic cleaning.

3. Reduce the concentration of activated sludge mixture into the membrane: the specific method can add filler to the bioreactor to make the suspended microorganisms adhere to the filler, which can not only accelerate the decomposition rate of pollutants by microorganisms, but also effectively reduce the concentration of activated sludge mixture into the membrane, or control the working flux of the membrane to be lower than the critical flux, delay the deposition rate of pollutants on the membrane, prolong the life of the MBR membrane, and control membrane pollution.

4. Optimize and improve the membrane module: The optimal design of the MBR membrane module should fully consider the placement of the membrane module, the water quality, and the pipe diameter and length of the hollow fiber membrane. Tests have shown that

When there is no aeration, the transverse placement of the membrane filament is better than the axial direction, and the axial placement effect is better when there is aeration. The test results of membrane diameter show that in the cross-flow system, the thin membrane filament is better than the coarse membrane filament, regardless of whether it is aerated or not. Through the model calculation, it is found that when the length of the membrane filament is and the appropriate inner diameter of the membrane is long, the piston flow can effectively increase the membrane flux.

MBR membrane cleaning method

Maintenance cleaning regularly removes contaminants from the membrane surface to inhibit the thickening of the fouling layer and the rise of the cross-membrane pressure difference to achieve the purpose of stable operation. During maintenance cleaning, stop aeration.

The frequency of maintenance cleaning is usually 1 time for 1 week, using Naclo with an effective chlorine concentration of 300mg L and 500mg L, which is quantitatively injected into the membrane module from the permeable side, the agent injection time is 30 minutes, and the agent is soaked for 30 minutes after the injection is completed. The dose per unit membrane area is 2, and the total amount of medicine prepared should be calculated as the capacity of the transportation pipeline.

**Intensive washing is carried out every 1-3 months or when the suction pressure exceeds the set value (when the pressure difference between the membranes rises), the purpose of which is to remove contaminants from the membrane surface and restore the membrane performance to a state close to the initial state. The aeration was stopped, and the Naocl solution with an effective chlorine concentration of 2000-3,000 mg L was injected quantitatively from the permeate side for 30 min, and after the injection was completed, it was allowed to stand for 90 min. The dosage per unit membrane area is 2, and the total amount of reagent preparation should be calculated as the capacity of the conveying pipeline.

After NaOCL cleaning, if the transmembrane pressure difference is still high, ** pickling (1-2% oxalic acid, 1-2% citric acid, hydrochloric acid) can be carried out to remove inorganic scale. When performing acid cleaning, the NaOCL in the pipeline and pump should be cleaned first to avoid the formation of chlorine (toxic gas).

3. Offline cleaning

When the membrane performance cannot be restored by the first two cleaning methods, offline cleaning should be carried out, and the membrane module should be hoisted out and immersed in a special cleaning tank to remove pollutants and restore the membrane performance to a state close to the initial value. Immersion cleaning generally restores membrane properties significantly. For off-line cleaning, the entire module or individual diaphragms are immersed in an alkaline cleaning agent (Naclo solution with a chlorine concentration of 2000-3,000 mg L, pH 10 11) or an acidic cleaning agent (1-2% oxalic or citric acid, sulfuric acid, or hydrochloric acid).

The soaking time is 6 for 24 h and 2 h for acid. The membrane is a single-channel tubular ceramic membrane, the channel support is a porous ceramic material, the inorganic membrane (Al2O3) is plated on the inner surface of the channel, and the membrane filtration adopts a cross-flow process, that is, the main body of the activated sludge mixture flows through the membrane surface along the axial direction, and the filtered water passes through the membrane surface along the radial direction.

How to clean MBR membrane after use?

Clause. 1. Strengthen pretreatment.

Pretreatment is particularly important for the MBR process. Sewage contains a lot of impurities, fibers and suspended solids, which will block the surface of the membrane, thereby reducing the permeable area of the membrane and causing membrane pollution.

Install a fine screen of less than 1 mm. Install a fine sieve on the flow measurement of the biotank. Install a fine sieve in the membrane tank.

Clause. 2. Physical cleaning.

Clause. 3. Chemical cleaning.

The membrane is soaked and cleaned with chemicals.

**Cleaning: In order to prolong the cleaning cycle of MBR membrane, you can consider adding quantitative Naclo and HC1 to the backwash at an interval of 3-6 days for **chemical backwashing, each backwash for 3-5 minutes, and wait for the agent to backwash into the diaphragm, and then put it for 20-30 minutes before putting in normal water, and continue to aerrate during the cleaning process.

Offline cleaning: When the operating negative pressure is exceeded, the MBR diaphragm needs to be cleaned offline in time. The cleaning method is to remove the MBR diaphragm from the membrane frame, rinse the surface of the diaphragm with clean water, and remove the activated sludge attached to the surface of the diaphragm.

It was then soaked with quantitative Naclo and quantitative NaOH solution respectively to kill the bacteria attached to the membrane surface and remove the organic matter and colloidal substances attached to the membrane surface. Then rinse the surface of the diaphragm with clean water, and backwash the diaphragm for 2-3 minutes after loading the membrane cell, and the MBR diaphragm flux can be restored.

Nalco Water can be considered for membrane synergists, which can effectively inhibit the fouling of the MBR stack, extend the cleaning cycle of the MBR stack, reduce membrane filament damage, and extend the service life of the module. The cleaning cycle of the module can be extended from 1-2 months before the application of the synergist to 5-7 months (the specific situation is determined according to the working conditions). At the same time, the synergist does not have any negative impact on the sewage treatment system, which can reduce the formation of foam in the system to a certain extent.

For details, please refer to "Application of MBR Membrane Synergist in Membrane Bioreactor", which was jointly published by Nalco Water and CNOOC.

Brief description of the process flow:

The regulating tank collects sewage, balances the water quality and quantity, and adjusts the pH; Ensure the stable operation of the system;

Anaerobic pond anaerobic pond generally refers to the biochemical system in which dissolved oxygen is controlled in between. It mainly decomposes macromolecular organic matter into small molecular organic matter, which is convenient for subsequent process treatment, removes part of COD, and plays a role in phosphorus removal.

Anoxic pondAnoxic pond is relatively anaerobic and aerobic, and generally refers to the biochemical system between dissolved oxygen. It mainly removes nitrogen-containing wastewater such as ammonia nitrogen.

Under the condition of aeration and oxygenation, the degraded organic matter in the aerobic pond is further degraded into carbon dioxide and water by the aerobic microorganisms in the pool, which completely decomposes the organic matter, and at the same time, the phosphorus-releasing microorganisms absorb excess phosphorus to remove phosphorus.

MBR membrane pools.

After biochemical treatment, the sewage enters the membrane pool and is separated by MBR membrane to further improve the effluent quality.

The effluent of the MBR membrane pool of the clear water tank enters the clear water pool, or is reused, or directly discharged.

How about this? I found it from **.

Equipment operation procedures, process unit operation procedures, and abnormal emergency procedures.

Treatment system for MBR membrane process.

The MBR sewage treatment system usually consists of three parts: a regulating tank, a biological aeration tank and a clean water tank.

The sewage removes large particles of impurities through the grid, enters the regulating tank, and enters the aerobic reaction pool by the sewage lifting pump to remove ammonia oxygen (when the ammonia content in the sewage is high, it is recommended to use the facultative oxygen reaction tank), and then enters the membrane biological aeration tank, in the membrane bioreactor, the organic pollutants in the sewage are degraded by microorganisms to generate water that meets the COD standard, and then the water treated by the separation membrane with a large number of micropores on the surface is separated from the microorganisms in the pool.

In addition to being reused, the reclaimed water in the reclaimed water pool is also used for the backwashing of membrane modules, in order to prevent the growth of algae and bacteria, a small amount of chemicals should be put into the reclaimed water pool regularly.

This Dongdong, the manufacturer will provide you with one, find the manufacturer!

1. Strengthen the pretreatment before the MBR membrane, control the water inlet of the MBR membrane pool, and prevent suspended solids and hard objects above microns from entering the membrane pool, which is very damaging to the membrane filament.

2. What kind of chemical materials are used in the sewage pretreatment section? To avoid the use of chemicals that are harmful to the membrane, reduce the amount of PAM, and prevent adhesion to the membrane, you can consult the membrane supplier and select the appropriate chemical material through the material of the membrane.

3. Reduce the use of surfactants and prevent oil from entering the membrane pool.

4. Control the aeration volume of the membrane to achieve the design air volume, the air volume is too small, and the backflush frequency is low, which will cause sludge to accumulate on the membrane surface.

The control measures are basically these, it is recommended that you contact the first business to solve the problem, the specific situation and the installation method of the membrane, the aeration method, are related to the occurrence of pollution, to determine the scene.

There is no way to solve the problem of contamination of MBR membranes, and it can only be cleaned regularly.