How much better is flat membrane than hollow membrane? Can I change the flat membrane after using the hollow membrane?

Comparison of advantages between flat membrane and hollow membrane

(1) has better anti-pollution performance.

Compared with hollow fiber membrane bioreactor, flat membrane bioreactor can maintain the stable operation of Qualcomm (flux, i.e. membrane water yield) at higher activated sludge concentration, and has lower pretreatment requirements. In the actual use process, although there will be grilles, depilators and other equipment in the pretreatment facilities, it is inevitable that some objects such as hair will enter the aeration tank. When the hollow fiber membrane bioreactor is running, the membrane filaments are always in a shaking state under aeration, so these hairs are easily entangled with the membrane filaments. When the sludge concentration reaches a certain level, there will be mud lumps, which will entangle more and more membrane filaments, greatly reducing the effective membrane area of hollow fiber filaments and causing a sharp decline in membrane flux. Moreover, such problems are difficult to fix and usually can only be replaced.

The suitable activated sludge concentration (MLSS) of flat membrane bioreactor is 6000- 10000mg/L, which is much higher than that of hollow fiber membrane bioreactor. The structure of flat membrane module is composed of a plurality of membrane elements arranged and assembled, which realizes the controllable gap between membranes, is convenient for gas-liquid mixed flow to clean the membrane surface online, and has excellent anti-pollution performance.

In addition, the flat membrane bioreactor can well remove the attachments on the membrane surface by adjusting the aeration intensity at the bottom of the module and the scouring effect of gas-water mixture on the membrane surface. Even if the membrane surface is silted in a short time due to factors such as excessive sludge viscosity, the whole membrane can be taken out, washed with a low-pressure water gun and reassembled into a membrane module, so that the membrane can run effectively for a long time, but hollow fibers cannot be cleaned in this way.

(2) Good mechanical stability and no broken wires.

In the actual use process, the hollow fiber membrane module will inevitably break wires, and the reasons include two aspects:

First, the uneven wall thickness caused by defects in the spinning process, of course, this situation is relatively rare and can be further avoided by purchasing high-quality products;

The second is the root fracture caused by the fatigue of spinning materials.

The hollow fiber yarn needs to be sealed with epoxy resin at the place where the two ends connect the parts. Because of the capillary phenomenon of the filament itself, the root will definitely suck a short section. Due to inflation, hollow fiber will always be in a large vibration phenomenon under working condition, which will cause material fatigue at the root for a long time, and epoxy resin itself is a brittle material. Once the wire breakage caused by fatigue of this material occurs, it is often large-scale and fatal to the membrane bioreactor, which will not only seriously affect the effluent quality, but also lead to the scrapping of the whole module.

Different from this, the flat membrane has non-woven fabric as the guiding layer and 3 mm ~ 5 mm ABS board as the supporting layer, so the strength is much higher than that of hollow fiber, and similar phenomena will not occur at all, which can completely ensure high-quality effluent quality.

(3) The cleaning mode is more convenient and the cleaning cycle is longer.

Cleaning of membrane components can be divided into online cleaning and offline cleaning.

On-line cleaning of hollow fiber membranes is frequent and the cleaning process is complicated. It is necessary to pump the prepared chemicals into the membrane filament under pressure through a metering pump to complete the cleaning. On the one hand, the online cleaning of flat membrane is realized by aeration in operation, on the other hand, it is realized by online chemical cleaning.

By controlling the aeration rate of the aeration system at the bottom of the module, the flat membrane bioreactor can effectively wash the membrane surface, prevent excessive deposition of sludge on the membrane surface during pumping and control the pollution of the membrane surface during operation. Chemical cleaning (on-line cleaning) of flat membrane components is also simpler. Just pour the prepared medicine back into the membrane from the suction port and soak it for a period of time.

For off-line cleaning of hollow fiber membranes, the whole membrane module must be hoisted, put in a cleaning pool and soaked with chemicals. The cleaning of flat membrane can not only lift out the membrane components for cleaning, but also pull out the membrane elements for cleaning. The diversity of off-line cleaning methods of flat membrane also solves the problem that the narrow engineering site is not suitable for hoisting.

At the same time, compared with hollow fiber-membrane bioreactor, the cleaning cycle of flat membrane bioreactor is longer, which can reach more than 3 months. If the working pressure is always in a relatively low state, it may not even be cleaned. The flat membrane module can also recover membrane flux by physical cleaning methods such as low-pressure water gun washing, which is almost impossible for hollow fiber membranes.

(4) Long service life and low operating cost.

According to incomplete statistics, the average service life of hollow fiber membrane in the market at present is about 4 years in domestic sewage, municipal sewage and similar domestic sewage treatment projects, about 2 years in industrial wastewater, pharmaceutical wastewater and other projects, and it can hardly be used in landfill leachate, electroplating wastewater and refractory organic wastewater.

In the market, the average life of flat membrane is about 5 years in the treatment projects of domestic sewage, urban sewage and similar domestic sewage, and about 3 years in the projects of industrial wastewater and pharmaceutical wastewater. It can be used in landfill leachate, electroplating wastewater, refractory organic wastewater and other projects.

The replacement period of flat membrane is longer than that of hollow fiber membrane, which greatly reduces the operation cost and ensures good operation conditions. At the same time, the flat membrane can be replaced by a single piece, and the replacement cost is relatively low.

(5) The diaphragm replacement process is simple.

Due to the unique design of the flat membrane module, in the process of membrane damage and replacement, the membranes can be replaced one by one without replacing the bracket. However, if the intermediate fiber membrane filaments break to a certain number, the whole module will be scrapped, and if the whole membrane module needs to be replaced, the cost will be greatly increased.