Thursday, March 21, 2013

Standby Decanter

The purpose of Continuous Improvement Project (CIP) is to install temporary floating decanter for SBR plant. There are a few types of decanter were currently equipped at SBR plant. SBR have faced a lot of cases of decanter breakdown especially for arm type decanter. Unlike wastewater pump, installation of decanter at SBR plant never provide standby thus when a unit of decanter breakdown, STP operators have to mitigate the situation in order to keep process sustainability at required level. Failure to have proper action and meeting regulatory compliance will escalate operator into authorities action.

The temporary floating decanter will be installed according to depth of decant about 0.8m to 1.2m from top water level. The pump must be provided with a horizontal base baffle plate and attached to the bottom pump cage to minimize direct suction of settle suspended solid inside SBR tank. The temporary decanter outlet pipe must be higher than water level to prevent siphon condition.

Power source of existing decanter will be diverted to the temporary floating decanter, however some modification required especially on the contactor and overload according to power requirement by the pump. The pump should receive operation signal from PLC or main programming in order to replace function as decanter.
In order installation meets objective, some modification on PLC is required to disable certain interlock such as upper and bottom limit switch of existing decanter. The pump will start when the SBR system has completed the ‘settling’ stage. In some cases, timer counter for SBR programming system is required for the pump to limit its operation just after settling stage and before aeration stage.

Float switch installation may also important to cut off pump operating whenever water at lower pumping level.

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