Water resources are an important factor for economic development and sustainable social development, and the urban sewage treatment rate has become an important indicator of the civilization of a region. Sewage treatment has evolved from primitive natural treatment and simple primary treatment to the use of various advanced technologies, advanced treatment of sewage, and reuse. The treatment process has also developed from the traditional activated sludge process and oxidation ditch process to the present multiple processes to meet different effluent requirements.
2. Sewage treatment process
The sewage treatment process is divided into processes and treatment procedures, which can be divided into pretreatment process, primary treatment process, secondary treatment process, advanced treatment process and sludge treatment process, and final sludge treatment. The purpose of grille pretreatment is to retain large pieces of material to protect the subsequent water pump pipelines and equipment from normal operation. The primary treatment process is the primary sedimentation tank, which aims to precipitate and remove the suspended solids in the sewage as much as possible. The secondary treatment process aims to use microbial metabolism to turn most of the pollutants in the sewage into carbon dioxide and water. This part is the main sewage treatment plant. The processing section has a relatively complex composition, and different processes and equipment options are not the same. The advanced treatment process is mainly to reuse the sewage for special purposes such as industry for further treatment. Usually, the treatment process includes coagulation sedimentation, filtration, dosing and chlorination, etc., and there is no outlet pumping station. The sludge treatment process and sludge treatment mainly include partial thickening, digestion, dewatering, composting or fertilizer making, agricultural landfilling, etc. The general process flow chart is as follows:
3. On-site working conditions
The sewage in the sewage collection tank is sent to the sedimentation tank through two sewage pumps. In order to prevent accidents from overflowing the sedimentation tank, the sedimentation tank is equipped with a water level detection device. When the actual water level exceeds the alarm water level, the control system automatically closes the Electric butterfly valve to prevent overflow accidents. The sewage in the sedimentation tank is then sent to the biochemical treatment tank by the biochemical water pump. The biochemical treatment tank is also equipped with a water level upper limit detection, and the water level of the biochemical treatment tank is controlled by controlling the biochemical water pump.
Fourth, frequency conversion transformation
The rapid flow when the submersible pump is started and the water cone phenomenon when it is suddenly stopped are often easy to cause the pipeline to loose or rupture, which may cause serious damage to the motor, and the valve needs to be opened/closed to reduce the impact of the water cone when the motor starts/stops. On the one hand, the operation is very intensive and difficult to meet the needs of the process. After installing the frequency converter in the submersible pump, the motor can be soft-started/soft-stopped according to the needs of the process, so that the rapid flow and water cone phenomenon can be solved. Moreover, when the flow is not large, the pump speed can be reduced. On the one hand, it can prevent the pump from working at full load for a long time, causing premature aging of the motor, and the frequency conversion soft start greatly reduces the impact on the machine when the pump starts. , And has obvious power saving effect.
5. Advantages of Easydrive CV3100 inverter
1. After installing the easy drive CV3100 inverter, the smooth soft start mode of the motor can reduce the impact on the power grid and equipment.
2. The frequency converter has various electronic protection devices such as overcurrent, overload, overvoltage, overheating, etc., and has a wealth of fault alarm output functions, which can effectively protect the normal operation of the sewage treatment system.
3. The stepless speed regulation has changed the original electromagnetic speed regulation method, which can greatly reduce the mechanical wear of the water pump and the motor, and at the same time reduce the maintenance cost of the equipment.
4. It has a significant power-saving effect. Driven by the inverter, the motor speed is adjusted according to the flow rate. The motor speed decreases and the operating current decreases, thereby reducing equipment power consumption and saving energy.
The sewage treatment plant has not only improved the degree of automation and control accuracy, but also greatly benefited from energy saving and consumption reduction. The comprehensive power saving rate has reached 35%, and the corporate and social benefits have been greatly improved. Application of frequency converter in a sewage treatment plant in Vietnam