During the operation of multi-media filtration equipment, backwashing is the key link to maintain its filtration performance. Reasonable control conditions and optimization strategies can effectively improve the operation efficiency and service life of multi-media filtration equipment. The core goal of backwashing is to remove impurities such as suspended matter and colloids trapped in the filter layer and restore the filtration capacity of the filter media. The setting of control conditions needs to comprehensively consider factors such as filter media characteristics, inlet water quality, and operation cycle.
The start of backwashing is usually based on two main conditions: one is that the filtration pressure difference reaches the set threshold. When the impurities trapped in the filter layer gradually increase, the resistance of water flowing through the filter layer increases, and the value monitored by the pressure difference sensor exceeds the preset value, the backwashing program is triggered; the second is that the operation time reaches the set cycle. Even if the pressure difference does not reach the threshold, backwashing is required regularly to avoid excessive accumulation of impurities in the filter layer. These two conditions complement each other to ensure that the filter layer is always in a reasonable working state.
Water flow control during backwashing is a key link. The backwashing water flow must have sufficient strength to loosen the filter media particles so that impurities can be separated from the filter media surface and discharged with the water flow. However, the water flow intensity should not be too large, otherwise it may cause excessive tumbling and wear of the filter material, or even cause confusion in the filter material grading, affecting the filtering effect. In actual operation, it is necessary to determine the optimal backwash flow rate and flow rate through debugging according to the type, particle size and bulk density of the filter material, so that the filter material is suspended and there is no serious material leakage.
The timing control of backwashing should not be ignored. The typical backwashing process usually includes water flushing, air-water mixed flushing, and re-water flushing. The water flushing in the initial stage is mainly used to loosen the filter material and initially flush impurities. Subsequently, air is introduced for air-water mixed flushing. The rupture and disturbance of bubbles are used to further peel off the pollutants on the surface of the filter material. Finally, the remaining impurities are completely removed by water flushing. The time allocation of each stage needs to be adjusted according to the degree of pollution of the filter layer. When the pollution is heavy, the time of air-water mixed flushing can be appropriately extended to enhance the cleaning effect.
Optimizing the backwashing strategy needs to start from multiple dimensions. On the one hand, the online monitoring of the multi-media filtration equipment can obtain the filter layer pressure difference, effluent water quality and other data in real time, dynamically adjust the start-up conditions and operating parameters of the backwashing, and achieve precise control. For example, when the inlet water quality suddenly deteriorates and the filter layer pollution speed is accelerated, the backwashing cycle is automatically shortened or the backwashing intensity is increased to avoid the filtration effect affected by excessive accumulation of impurities. On the other hand, it is also very important to reasonably select the backwashing water source. Using treated clean water or recycled water as the backwashing water source can reduce the new impurities introduced during the backwashing process and improve the flushing efficiency.
The performance maintenance of the filter material is an important basis for backwashing optimization. After long-term operation, the filter material may become hardened, fail or change in particle size due to adsorption of impurities, chemical reactions and other reasons, affecting the backwashing effect and filtration performance. Therefore, the filter material needs to be inspected and regenerated regularly. For inorganic filter materials such as quartz sand and manganese sand, the adsorbed metal oxides, colloids and other impurities can be removed by acid washing, alkali washing and other methods; for organic filter materials such as activated carbon, heating regeneration and chemical regeneration can be used to restore its adsorption capacity to ensure that the filter material always maintains a good working condition.
In addition, energy saving and consumption reduction are also important goals of backwash optimization. The traditional backwash process often consumes a lot of water and energy. By using frequency conversion technology to adjust the speed of the backwash water pump and dynamically adjusting the backwash flow and pressure according to actual needs, unnecessary energy consumption can be reduced. At the same time, recycling the available resources in the backwash drainage, such as collecting the initial cleaner backwash water for pretreatment, or treating the backwash wastewater through sedimentation, filtration, etc., can further reduce the waste of water resources and improve the overall economy and environmental benefits of multi-media filtration equipment. By comprehensively considering control conditions, water flow and timing management, filter material maintenance and energy-saving measures, etc., a scientific and reasonable backwash optimization strategy can be formed to ensure the stable and efficient operation of multi-media filtration equipment.
