With the rapid advancement of water treatment technologies, control systems have become increasingly complex. This complexity brings about more challenges in managing large-scale ultrafiltration sewage treatment systems. Ensuring efficient, stable, and safe operation has become a critical research focus for the future development of such systems. This paper presents a case study on the 600,000 tons/day ultrafiltration system at Beijing Xiaohongmen Wastewater Treatment Plant. It addresses key issues such as corridor competition during backwashing and air scrubbing, which not only protects the ultrafiltration membranes but also improves system reliability.
To tackle the fluctuating inflow volume, an adaptive step water intake control method is implemented, enabling “on-demand control†by adjusting the system’s processing capacity based on the actual inflow. This ensures continuous and stable operation of the entire ultrafiltration system. Additionally, the problem of water hammer, a long-standing challenge in large-scale ultrafiltration systems, is effectively mitigated using variable frequency S-curve pump shutdown and PWM valve control techniques. To further enhance system stability, a queue scheduling algorithm is employed to manage corridor competition, while dual ring network technology (large ring + small ring) is introduced to ensure overall system stability.
The ultrafiltration sewage treatment system operates on the principle of membrane filtration, where pressure drives the separation of contaminants from water. The system uses large-scale ultrafiltration membranes to purify and screen large volumes of wastewater. The control system, based on Rockwell Automation PLC, manages the pneumatic valves through a remote I/O system connected via a “main ring + sub-ring†network. The system comprises three main stations and 48 sub-stations, each with Ethernet communication capabilities, forming a large ring network.
In terms of inlet control, the system must balance the inflow with the ultrafiltration capacity to avoid overloading or underutilizing the membrane. A step-based adaptive control strategy is used to adjust the water intake according to the inflow pattern, which varies throughout the day due to human activity. By analyzing historical data, a parameter table was developed to guide the system’s response to different inflow conditions, ensuring optimal performance without frequent adjustments that could destabilize the system.
For filtration and cleaning operations, the system cycles through four stages: water production, backwashing, air scrubbing, and emptying. To prevent conflicts during these stages, a queuing mechanism is implemented, following a first-in-first-out (FIFO) logic. This ensures fair and timely access to shared equipment, reducing the risk of operational delays and membrane damage.
Water hammer, caused by sudden changes in flow velocity, is addressed through optimized pump shutdown and valve control. Variable frequency drives are used to implement S-curve stop functions, while PWM control allows for slow closure of pneumatic valves, significantly reducing pressure surges. These measures enhance the safety and longevity of the system's infrastructure.
Overall, the implementation of adaptive control strategies, queue scheduling, and advanced valve management has ensured the reliable and efficient operation of the ultrafiltration system at Xiaohongmen Wastewater Treatment Plant. The results demonstrate the feasibility of applying these techniques to other large-scale ultrafiltration systems, offering a model for future developments in water treatment technology.
Description
-Contact Resistance:≤50mΩ
-Insulation Resistance:≥100mΩ
-Dielectric Strength:1,500V,
-1min Electronic Life:10,000 cycles
-Operating temperature:T120
-Rating current/voltage:6A 250V AC
Features
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â—† Micro contact gap,High speed operation,High sensitirity,Micro operatizon travel.
â—† Long life & high reliability
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