Which Hot lime softener is better an Upflow or a Downflow?

[ConsultUS]

I am visiting an old plant with no engineering records, this plant has several hot lime softeners of diferent types and dimentions,
Some are upflow , where the new water goes down a central pipe and up trought a mud bed
.
Other softeners are of the down flow type where new water goes at the top from a distribution cone, and sludge goes to the bottom.
Which one is better , what is the operation procedures for one or the other, every body in the plant has different opinions.
Thanks

 

[DeltaCascade]

We have upflow sludge blanket softener, where influent stream enters below the sludge bed and rise thorugh it, and upflow sludge recirculation softener where the downcomer entry is above the sludge bed. Both units typically have sludge recirculation (typically about 20%, versus about 3% for downflow).

Upflow units are typically best for silica removal (precipitation or adsorption onto MgO / Mg(OH)2 particles). The upflow design also lends itself to use of internal compartments for filter backwash storage and condensate or treated water deaeration.