Plate membrane separation technology, as an efficient and low-pollution purification technology that integrates separation and concentration, has the characteristics of simple operation, convenient maintenance, low energy consumption, and strong adaptability. It has gradually been widely recognized and applied by environmental protection workers and environmentalists in related industries' sewage treatment.
Comparison of advantages between flat membrane and hollow membrane
(1) Better anti pollution performance.
Compared to hollow fiber membrane bioreactors, flat membrane bioreactors can maintain stable operation of high throughput (i.e. membrane water production) at higher activated sludge concentrations, with lower requirements for pre-treatment.
In actual use, although there may be equipment such as grilles and hair removal machines in the pre-treatment facilities, it is still difficult to avoid entering objects such as hair in the aeration tank.
During the operation of a hollow fiber membrane bioreactor, the membrane filaments are always in a shaking state under aeration, making it easy for these hairs to entangle the membrane filaments. When the sludge concentration reaches a certain level, mud lumps will appear, causing more and more membrane filaments to entangle together, greatly reducing the effective membrane area of the hollow fiber filaments and causing a sharp decrease in membrane flux. Moreover, such problems are difficult to repair and usually can only be replaced.
The applicable activated sludge concentration (MLSS) range of the flat membrane bioreactor is 6000-10000mg/L, which is much higher than that of the hollow fiber membrane bioreactor. The structure of the flat membrane module is composed of multiple membrane elements arranged and assembled, achieving controllable gaps between the membranes, facilitating online cleaning of the membrane surface by gas-liquid mixed flow, and superior pollution resistance performance.
In addition, the flat membrane bioreactor can effectively remove attachments on the membrane surface by adjusting the aeration intensity at the bottom of the module and the flushing effect of the air water mixture on the membrane surface. Even if sedimentation occurs on the membrane surface due to factors such as excessive sludge viscosity in the short term, the membrane can be removed as a single piece and assembled back into the membrane module through low-pressure water gun flushing, enabling the membrane to operate effectively for a long time, Hollow fibers cannot be cleaned through this method.
(2) Good mechanical stability, without wire breakage.
In actual use, hollow fiber membrane components inevitably experience wire breakage, which includes two reasons:
One is the uneven wall thickness caused by defects in the spinning process, which is rare and can be further avoided by purchasing high-quality products;
The second is root fracture caused by fatigue of spinning materials.
Hollow fiber strands need to be sealed with epoxy resin at the connection points of the components at both ends. Due to the capillary phenomenon of the fiber strands themselves, a small segment will definitely be sucked up at the root. Due to aeration, hollow fibers are always subjected to significant vibration during operation, which can cause material fatigue at the root. Epoxy resin itself is a brittle material, and the breakage caused by material fatigue often occurs on a large scale. For membrane bioreactors, the damage is fatal, and it not only seriously affects the water quality of the effluent, It can also lead to the scrapping of the entire component.
Unlike this, the inner part of the flat membrane has non-woven fabric as the guide layer and 3mm~5mm ABS board as the support layer, resulting in much higher strength than hollow fibers and no similar phenomenon, fully ensuring high-quality effluent quality.
(3) The cleaning method is more convenient and the cleaning cycle is longer.
The cleaning of membrane components can be divided into online cleaning and offline cleaning.
The online cleaning of hollow fiber membranes is relatively frequent, and the cleaning process is complex. The prepared chemical agents need to be pressurized and injected into the membrane fibers through a dosage pump to complete the cleaning. The online cleaning of flat membrane is achieved through both aeration during operation and online chemical cleaning.
The flat membrane bioreactor can effectively hydraulic flush the membrane surface by controlling the aeration rate of the aeration system at the bottom of the component, preventing excessive sludge accumulation on the membrane surface during the suction process, and controlling the pollution on the membrane surface during operation. The chemical cleaning (online cleaning) of flat membrane components is also simpler, simply pour the prepared agent back into the membrane from the suction port and soak it for a period of time.
The offline cleaning of hollow fiber membranes must lift out the entire membrane component, place it in a cleaning pool, and soak it with chemical agents. The cleaning of flat membrane can either lift out the membrane components for cleaning or extract individual membrane components for cleaning. The diversity of offline cleaning methods for flat membrane also solves the problem of small engineering sites that are not suitable for lifting.
Meanwhile, compared to hollow fiber membrane bioreactors, flat membrane bioreactors have a longer cleaning cycle, with a cleaning cycle of over 3 months. Moreover, if the working pressure remains relatively low, they may not even be cleaned. The flat membrane module can also be physically cleaned using methods such as low-pressure water gun flushing to restore membrane flux, which is almost impossible for hollow fiber membranes.
Plate membrane separation technology, as an efficient and low-pollution purification technology that integrates separation and concentration, has the characteristics of simple operation, convenient maintenance, low energy consumption, and strong adaptability. It has gradually been widely recognized and applied by environmental protection workers and environmentalists in related industries' sewage treatment.
(4) Long service life and low operating costs
According to incomplete statistics, the average lifespan of hollow fiber membranes on the market is about 4 years in domestic sewage, municipal wastewater, and similar domestic sewage treatment projects, and about 2 years in industrial wastewater, pharmaceutical wastewater, and other projects. They are almost unusable in projects such as landfill leachate, electroplating wastewater, and refractory organic wastewater.
The average lifespan of flat membrane in domestic wastewater, municipal wastewater, and similar domestic wastewater treatment projects on the market is about 5 years, and in industrial wastewater, pharmaceutical wastewater, and other projects, the average lifespan is about 3 years. It can be applied to projects such as landfill leachate, electroplating wastewater, and refractory organic wastewater.
The replacement cycle of flat membrane is longer than that of hollow fiber membrane, which greatly reduces operating costs and ensures good operating conditions. At the same time, the flat film can achieve single sheet replacement, and the replacement cost is relatively lower.
(5) The membrane replacement process is simple
Due to the unique design of flat membrane components, the membrane can be replaced individually during the process of membrane damage replacement, without the need to replace the bracket. If the number of broken fibers in the intermediate fiber membrane reaches a certain level, the entire component will be scrapped and the entire membrane component needs to be replaced, which will greatly increase the cost.
(Source | New Horizon of Water Treatment)
