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Lift Stations Septage Receiving Sludge Transfer & Recirculation

4. Clarifier Scum 5. Sludge Lagoons

Introduction Vaughan ‘Chopper’ Pumps can be applied into any municipal application that involves pumping solids-laden slurries and fits hydraulically into the available performance characteristics. More specifically, Vaughan pumps in the following applications provide a cost effective method of eliminating plugging problems and optimizing system performance. Submittals are increasingly required on municipal pump installations.

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WASTEWATER TREATMENT PROCESSES 4) CLARIFIER SCUM The inherent recirculation around the inlet to a chopper pump usually causes enough mixing to keep air binding from occurring in scum pits that have short retention times. If a scum pit has a long retention time, then the scum tends to concentrate and form a blanket on the top. As the pit level is pumped down, this blanket can block the pump suction. In this case, the optional recirculation nozzle (for vertical wet well and submersible pumps) should be included to premix the scum pit prior to pump out. Also, since chopper pumps have heavy duty oil bath lubricated bearing and seal systems, the scum pits can be pumped completely down to the pump inlet without damage to the pump bearings or seal due to loss of coolant or lubricant. This allows full removal of the scum during each pump-down. CH2M Hill Engineering recently published an internal report recommending Vaughan Chopper Pumps with recirculation nozzles on all scum pumping applications. With the addition of a motor low current monitoring system in the pump controls, the ‘Off’ function can be based on low motor current draw rather than ‘Off’ mercury float switch. Once the liquid level drops to the point where air enters the pump inlet, the current draw will drop off and the low current relay shuts the pump off.

Application Details  Vertical wet well and submersible pumps are best for pumping scum pits, as the pump inlet is then located in the scum, and optional recirculation nozzles are available and should be considered.  Horizontal and pedestal pumps in this application are susceptible to air binding. Recommend recirculation nozzle.  Large scum pits usually require recirculation prior to pump out.  An optional automatic valve actuator can also be provided.  Performance is always based on discharge conditions, not Performance in the recirculation mode.  Disintegrator tools are not recommended.  Generally, use high efficiency chemical duty motors.  Recommend motor low current monitoring system for pump "OFF" except on 3600 RPM pumps.