Secondary Clarifiers after ICEAS process?

[sjohns4]

I just started working on a project to replace a failing UV system at a local WWTP and take a look at the aeration system which, according to the operators, seems to be oversized.

The plant was upgraded not long ago to an ICEAS (Intermittent Cycle Extended Aeration System) process. The existing primary clarifiers as well as the existing secondaries were re-used, but the primaries were re-piped so all are secondaries now. There are no primaires present.

From my limited knowledge of an SBR process this does not make a lot of sence. I thought one of the advantages of an SBR was primary and secondary sludge settling was acomplished in the same tank as aeration? There is no phosporous removal or limits.

The blowers in the plant are multistage centrifiguals, which also doesn't make sence b/c of the wild swing in air flows due to the varying water levels. This seems like a straight forward fix of installing correctly sized PD's or possibly turbos to deliver a more constant and controllable air flow. Comments welcomed here too.

Maybe this will start some good discussion....


Thanks,

Mike

 

[bimr]

If you already have the clarifiers, why would you not continue to use the clarifiers?

The discharge rate through the existing clarifiers may be higher than the discharge rate out of a ICEAS batch tank.

You probably would make a different evaluation if you proposing to install all new equipment,

 

[sjohns4]

Additional equipment to maintain, cost to replace drives, cost to power pumps, etc.

Here's another catch. The ICEAS batch tanks can decant upto an instantanous flow rate of 18 MGD. They decant to a gravity outfall leading to the UV system. One of the manholes is really a wet well sump with pumps designed for a total flow of 4 MGD to be sent to the clarifiers. Flow above 4 MGD flows on to the UV. The clarifier effluent is reintroduced to the effluent outfall just upstream of the UV unit.

Not sure what's going on here...

 

[QualityTime]

To me it is not clear. Do you have SBR tanks followed by secondary clarifiers?