The Design And Implementation Of BAF Backwash Control System

In recent years, because of the growing population and rapid economic development,there are more and more humAn consumptions of water resources. In addition, humAnirrational behavior, deforestation and unreasonable grazing also cause the obviousdeterioration of water on the earth. Global freshwater resources decrease significantly, and thesharpening contradictions between the supply and demAnd intensify. Sewage treatment isgetting attention widely.Biological aerated filter (BAF) is a new sewage treatment technology developed in the20th century, which has been widely used. In the process of biological aerated filter running,the microbial membrane on the surface of filter mAterial layer will thickening gradually, andat the beginning of the thickening, the impurity removal rate will be increased, but with thethickening of biological membrane, the activity of the biofilm will reduce, accompanied by acertain degree of loss. Appropriate backwash is the guarantee of the normAl work of theaeration tank, the effect of backwash is cleaning packing, restoring the activity of the biofilm,and at the same time ruling the suspended solids of filter mAterial retention and aged biofilmoutside of the filter. Referencing pertinent literature, the backwash way, the strength ofbackwash, backwash time and backwash cycle time are important factors affecting backwashrunning efficiency. Air and water backwash process is a combination of a variety of actionssuch as air shear and friction, water flow shear and friction, and the friction between the filtermAterial particles, so the recoil effect is best; Reasonable backwash intensity, backwash timeand backwash cycle time can be very good to clean the filter mAterial, and the biologicalmembrane can also get a larger degree of recovery.Researching status at home and abroad, water backwash operations generally stay inmAnual operation, and due to humAn factors, recoil time and recoil strength can’tbe guaranteed greatly, the recoil effect is not obvious, which is not only a waste of mAnpower,but also an increase of energy consumption. In addition, the quality situation of wastewatercan not be real-time monitored. Combining the status quo at home and abroad, this systemdesigns a set of automAtic control scheme and the backwash models include water model, gasmodel, water and gas model, liquid level model, water quality model, and water level and quality model. The first three modes are automAtic modes, which can set up the strength ofbackwash, backwash time and backwash cycle. Last three ones are intelligent modes,combining expert experience to get expert knowledge base, they provide appropriatebackwash intensity and duration of backwash according to the water quality conditions insidethe aeration tank detected by height sensor and turbidity meter. To reduce energy consumption,inverter output is used as the output mode beside electromAgnetic valve output.The system selects STM32F107single-chip microcomputer based on ARM Cortex-M3kernel as the core processor, to complete intelligent backwash control of the aeration tank.MAn-mAchine interface chooses TFT color screen which is integrated with highperformAnce, low power consumption and easy use. In the end, the trial operation of aerationtank intelligent backwash control instrument in sewage plant is successful, and backwasheffect is obvious, at the same time avoiding the deficiencies of back wash process in thesewage factory before. The system greatly meets the aeration tank backwash control with itsreasonable structure design, low cost and strong practicability.