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Sewage treatment plant pump equipment selection, installation and operation and maintenance
**I. Introduction**
Qingdao's sewage treatment plant has undergone several phases of development. The first phase, with a capacity of 50,000 tons per day, was completed in 2002. The second phase, also with a capacity of 50,000 tons per day, was finished in 2008. A major upgrade was carried out in 2011, which included the renovation of both phases. The facility is equipped with a total of 85 different types of pumps, with an overall power capacity of 1038 kW. This paper explores and analyzes the selection, installation, operation, and maintenance of pump equipment, providing practical insights and guidance for similar projects.
**II. Pump Selection**
In a wastewater treatment plant, pumps play a critical role in lifting raw sewage, returning activated sludge, and discharging excess sludge. To handle these tasks effectively, specialized sewage pumps such as submersible sewage pumps and screw pumps are commonly used. When selecting pumps, the following principles should be followed:
1. The pump must meet the required head and flow rate, with the operating point located within the high-efficiency range.
2. Over long-term operation, the pump should maintain high efficiency, low energy consumption, and minimal maintenance costs.
3. The operating point of the pump must be determined by the intersection of the pump characteristic curve (HQ) and the pipeline characteristic curve (He-Qe), ensuring stable and efficient performance.
4. The net positive suction head available (NPSHa) must be greater than the net positive suction head required (NPSHr) to avoid cavitation.
5. Pump selection should be based on actual test data from the manufacturer and empirical calculations for pipeline resistance.
**III. Installation of Pumps**
Proper installation is crucial for the long-term performance of pumps. Before installation, detailed plans, construction drawings, and technical specifications must be reviewed. The foundation must be prepared and inspected to ensure it meets design requirements. The pump base should be adjusted carefully, with anchor bolts placed correctly. The motor must be aligned precisely with the pump shaft to ensure smooth operation. After installation, grouting and welding are performed to secure the structure.
**IV. Operation and Maintenance of Pumps**
Pump management involves regular inspection, maintenance, and troubleshooting. Submersible pumps can be operated using variable frequency drives to save energy. However, not all pumps may be equipped with this technology. Proper control strategies must be implemented to balance efficiency and cost. For screw pumps, maintaining the correct speed and protecting against dry running are essential. Regular checks of the stator temperature, mechanical seals, and impeller wear are necessary to prevent failures.
**V. Case Study: Pump Failure Analysis and Solutions**
Impeller corrosion and wear due to the presence of abrasive particles and corrosive substances in wastewater can significantly reduce pump efficiency. Repair methods such as shot peening, thermal spraying, or polymer coating can restore performance. Another common issue is valve blockage in dosing pumps, often caused by hardened chemicals. A liquid storage device was designed to prevent this, allowing the pump to operate smoothly without frequent clogging.
**VI. Conclusion**
Effective pump management is essential for the successful operation of a wastewater treatment plant. From selection to installation and maintenance, each step requires careful planning and execution. By learning from past experiences and continuously improving practices, the plant can ensure reliable and efficient operations, contributing to environmental protection and sustainable development.