To add on to Don's accurate assessment, remember when the sludge does not settle and massive surface accumulation occurs, you will lose some to carryover from the secondary clarifier, most likely why you have a drop in MLSS concentration. Physical removal of accumulating surface scum or temporary high pressure jetting tends to speed up the recovery, by breaking the surface scum you will encourage re-settling that will be aided by the addition of the floc. In the event that filamentous bacteria tend to dominate colonisation, you may want to consider applying chlorine - be aware you run the risk of complete process failure if your chlorination is too high as you will destroy too many, or all of your biomass.
Published by Gary Brown, Water Practitioner at Dikubu Water
To add on to Don's accurate assessment, remember when the sludge does not settle and massive surface accumulation occurs, you will lose some to carryover from the secondary clarifier, most likely why you have a drop in MLSS concentration.
Physical removal of accumulating surface scum or temporary high pressure jetting tends to speed up the recovery, by breaking the surface scum you will encourage re-settling that will be aided by the addition of the floc.
In the event that filamentous bacteria tend to dominate colonisation, you may want to consider applying chlorine - be aware you run the risk of complete process failure if your chlorination is too high as you will destroy too many, or all of your biomass.