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After wastewater is treated through the secondary clarifier, it is clean enough to discharge from the plant, except for very small viruses and bacteria. To eliminate these biological contaminants, disinfection processes are employed.
There are several acceptable methods to disinfect wastewater. Chlorination is widely used. Chlorine gas is pumped into the waste stream after it leaves the secondary clarifiers. The chlorine is given 30 or more minutes to kill all remaining biological agents in the water. A serpentine channel is employed to provide the processing time required.
With the chlorine disinfection technique, sulfur dioxide (SO2) must be applied to the water after the disinfection step to remove all chlorine before dis-charge of water from the treatment plant.
An alternate, and increasingly popular technique for disinfection is UV radiation. The water effluent is exposed to a UV lamp in the tank. Adequate exposure to the UV radiation will kill all organisms.
Both techniques require monitoring of flow rate using ultrasonic open channel flow control .
The chlorinator and sulfinator equipment require pressure and vacuum monitoring and control.
At the plant effluent gate, the discharge rate is monitored by an ultrasonic open channel flow meter. Gate position may be monitored with a cable displacement transducer.
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Effluent Water Disinfection
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