With the continuous development of water treatment technology, membrane technology has been widely applied. However, membrane fouling is a complex process in the application of membrane components, involving many factors, and the relationship between these factors is complex.
As a new type of water treatment technology, membrane bioreactors (MBRs) combine membrane separation units with biological treatment units. As the MBR flat sheet membrane process combines membrane separation technology with traditional wastewater biological treatment technology, it greatly improves solid-liquid separation efficiency and eliminates the need for secondary sedimentation tanks. By reducing the F/M ratio and reducing the residual sludge production, the MBR process has advantages compared to traditional activated sludge processes such as high pollutant intercept efficiency, excellent and stable water quality, high volume load, small footprint, low residual sludge volume, complete separation of hydraulic and sludge retention time, flexible operation control, and high automation.
Membrane fouling in the MBR flat sheet membrane refers to the adsorption and sedimentation of sludge flocs, colloidal particles, dissolved organic matter or inorganic salts in the mixed liquor on the membrane surface or adsorption causing the pore size of the membrane to decrease or block, increasing the resistance of water through the membrane, reducing filtration and resulting in a decrease in membrane flux or an increase in transmembrane pressure.
MBR membrane fouling reduces membrane permeability and causes high energy consumption as the transmembrane pressure increases. As the level of membrane fouling increases, the membrane treatment capacity gradually decreases. In order to maintain water production flux, effective cleaning and maintenance are required to restore and maintain flux. To achieve this, we need to analyze its influencing factors, identify the key factors affecting MBR flat sheet membrane flux recovery and achieve the goal of effective recovery and delaying the membrane fouling rate, thereby prolonging the service life of the membrane.
The commonly used treatment methods for dyeing and printing wastewater mainly include physical and chemical methods, biochemical methods, membrane technology and other combined processes. It is difficult to achieve deep treatment and reuse goals solely by a single treatment process. Multiple processes must be integrated and combined to achieve the goal of reuse.
Currently, traditional biological methods for effluent treatment cannot meet discharge standards, and the combination of MBR membrane technology and biological treatment technology has become a way to meet the requirements of processing dyeing and printing wastewater.
In the treatment of dyeing and printing wastewater, the MBR membrane bioreactor is divided into three phases: primary filtration, secondary filtration, and denitrification. Primary filtration mainly filters out large particle solids such as sediment in wastewater to pretreat wastewater. Secondary filtration is performed in the anaerobic zone, where organic matter reacts with activated sludge to further filter wastewater. Denitrification is performed in the aerobic and anoxic zone to remove nitrogen from wastewater, followed by the use of MBR membrane technology.