The upper and lower sewage water levels and upper and lower limit alarm water levels are set in the sedimentation tank. Its control process is when the water reaches the limit, the water level detector will send signals to PLC (programmable logic controller), PLC (programmable logic controller) started rising frequency converter and sends frequency signal output to the frequency converter. When the frequency converter has reached 50 hz and the water level is still at the lower limit position, PLC (programmable logic controller) signal switch of sewage pump one will switch to run the power frequency. After a delay, the frequency converter will start the sewage pump 2.
In contrast, when the water reaches limit position, the sewage pump 1 will stop, the signal frequency of PLC (programmable logic controller) drop. If there are any other reasons like the water pump, making the water level below the lower or upper limit and leading to water level alarm, the water level detector will send alarm signal to PLC (programmable logic controller), the PLC outputs start alarm circuit (alarm lamp and ring) to prompt the operator to check the reason.
Aerator and submersible water pump are the core equipment of sewage treatment. The speed of aerator blower (roots fan)and submersible water pump need to be controlled by variable frequency drives.
variable frequency drive used in sewage treatment plant
Sewage treatment aerobic partial dissolved oxygen concentration. Oxygen concentration has a great impact on the treatment results. If dissolved oxygen concentration is too low, sewage treatment can not meet the standard. If the dissolved oxygen concentration is too high, it will not only waste electric energy, but also may make the activated sludge floating up so that the effluent cannot reach the standard.
The purpose of the aerator blower and variable frequency drive is to control the dissolved oxygen concentration in CASS tank to be stable at a constant value.
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