Application of SINOVO Frequency Inverter in Sewage Treatment Plant

The urban sewage treatment process can be divided into pretreatment process, primary treatment process, secondary treatment process, advanced treatment process, sludge treatment process, and final sludge treatment according to the process and treatment procedures.

The purpose of pretreatment is to retain bulk materials to protect the subsequent pump pipelines and equipment from normal operation.

The primary treatment process is the main primary sedimentation tank, which aims to precipitate and remove the suspended solids in the sewage as much as possible.

The purpose of the secondary treatment process is to use microbial metabolism to convert most of the pollutants in the sewage into carbon dioxide and water. This part is the main part of the sewage treatment plant.

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 and sedimentation, filtration, dosing and chlorination, etc., and there is no pumping station. Sludge treatment process and sludge treatment mainly include partial concentration, digestion, dehydration, composting or fertilizer making, and agricultural landfill of sludge in water plants. The general process flow chart is as follows:

II. Application of frequency inverter in sewage treatment

Fans and water pumps are mainly used in sewage treatment equipment systems.

From the above process flow, it can be seen that aerators and submersible pumps are the core equipment of sewage treatment.

1) The application of the frequency converter on the blower The blower sends the compressed air into the aeration tank through the pipeline, so that the oxygen in the air is dissolved in the sewage to supply the microorganisms in the activated sludge. When the blower is started under the power frequency state, the current impact is large, which is easy to cause grid voltage fluctuation. However, the blower has a certain wind pressure, and the air volume can only be adjusted by the number of work units and the air outlet valve. In actual production operation, it is often controlled by adjusting the air outlet valve. , that increases the resistance of the tube, and thus a lot of energy is wasted on the valve.

With the wide use of variable frequency speed regulation, SD600 series inverters are applied to the blower by taking advantage of the wide speed regulation range and hard mechanical characteristics of the frequency converter. Because the soft start of the inverter greatly reduces the impact on the power grid when the motor starts, and during normal operation, the outlet valve is opened to the maximum, and the speed of the motor is properly adjusted according to the requirements of the process and parameters to adjust the air volume of the pipeline. , so as to adjust the oxygen content in the sewage.

Moreover, the closed-loop automatic control can be easily realized according to the feedback signal (4~20ma) of the dissolved oxygen sensor. A lot of cumbersome manual operations are avoided, and it has obvious power saving effect.

2) The application of the frequency inverter on the submersible pump The current impact when the submersible pump starts and the way of adjusting the pressure/flow is similar to that of the blower. The rapid flow when the submersible pump is started and the water cone phenomenon when the submersible pump is suddenly stopped are often easy to cause the pipeline to become loose or ruptured, which may cause serious damage to the motor, and the valve needs to be opened/closed when the motor starts/stops to reduce the impact of the water cone. On the one hand, the operation has high work intensity, and it is difficult to meet the needs of the process. After the submersible pump is installed with a variable frequency governor, 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 rate is not large, the speed of the pump can be reduced. On the one hand, it can prevent the pump from working at full load for a long time, resulting in premature aging of the motor, and the soft start of the variable frequency greatly reduces the impact on the machine when the pump starts. , and has obvious power saving effect.

III. Application effect

The use of SD600 series inverters for blowers and submersible pumps in sewage treatment plants not only eliminates many troublesome manual operations and unsafe hidden dangers, but also keeps the system running in an energy-saving state, extending the equipment life.

The service life can better meet the production needs. The rich control functions of SD600 series inverter can easily realize closed-loop automatic control with other control systems, and SD600 adopts the standard MODBUS communication protocol, and it is also easy to realize centralized control in DCS system. Therefore, the use of frequency converters in sewage treatment systems has a very good promotion value.