According to the characteristics of membrane materials and membrane separation, all links from MBR design, process flow to equipment operation are considered to reduce concentration polarization and membrane fouling to a low level and also make MBR run efficiently while extending its service life, reducing filtration cost. The following methods to extend the service life of MBR are for your reference:
1. Effective Pretreatment of Material Liquid
Take effective pretreatment of the feed liquid(raw material) to improve the water quality of the membrane module inlet water. To adopt methods such as pre-flocculation, pre-filtration or changing the pH of the solution to remove some solutes that can interact with the membrane. To make the sludge concentration of the influent water less than 10000mg/l, maintain the pH value between 5-9 and the temperature of the influent water between 5-45 degree Celsius, so that to extend the service life of MBR.
2. Improvement of Membrane Materials and Optimization of MBR Membrane Modules
Membrane material, pore size and hydrophobicity of the membrane surface all affect the rate of membrane fouling to a certain extent. Membrane materials commonly used in MBR are polypropylene resin, polyvinylidene fluoride, polyolefin, etc. The study also fund that the characteristics of membrane modules, such as the tightness, length and diameter of the membrane filaments, also have an impact on the filtration performance of the membrane. Therefore, the optimized design of membranes is also an effective way to extend the service life of MBR.
3. Control to Operate Under Critical Membrane Flux
Critical flux refers to the existence of a critical value in constant flux filtration under certain operating conditions. When the membrane flux is greater than this value, the transmembrane pressure rises rapidly and membrane fouling develops rapidly. When the membrane flux is less than this value, membrane fouling develops very slowly. Critical membrane flux is related to hydraulic operating conditions, membrane separation operation mode, feed liquid properties and inherent membrane properties. The concept of critical membrane flux is getting more and more attention.
4. Intermittent Operation
In the submerged MBR Membrane Modules, the operation mode of intermittent suction is designed to stop the membrane filtration regularly, so that the net flow rate from the liquid to the membrane surface is zero. Then the sludge deposited on the membrane surface is relaxed under the action of aeration bubbling and then falls off the membrane surface, so that partially restore the filtration performance of the membrane. The longer the suction process, the more contaminants will accumulate on the membrane surface. The longer the suction is stopped, the more reversible contaminants on the membrane surface will fall off, and the better the recovery of membrane filtration performance will be.
5. Enhanced Aeration and Backwash
Enhanced aeration can reduce the organisms deposited on the membrane surface(that is reverse pollution). And for blockage caused by soluble substances entering the membrane pores and irreversible pollution of the gel layer on the membrane surface, backwashing can effectively control membrane pollution, extend the use time of MBR, thereby reducing the cost of filtration.
6. Place Membrane Modules Reasonably
The placement of the membrane module should consider the distance between the membrane module and the wall of the aeration tank, the distance between the membrane module and the air diffuser, and the distance between the membrane module and the liquid level of reactor, the air diffuser and the bottom of the aeration tank, and to ensure that the water flows vertically upward from the bottom of the pool, the surface of the membrane and the water flow are evenly contacted, so that the downward water flow can be evenly distributed around the membrane unit to minimize the concentration polarization. It is beneficial to slow down the formation of mud cake and promote the shedding of the mud cake layer to achieve the purpose of delaying membrane pollution.