Floating sludge

Hello, I was hoping to get some help from some experts here on a floating sludge issue I'm having. We are an electroplating facility and the WWT system is a continuous flow hydroxide precipitation system with one clarifier in use at any time. I've started seeing a thick layer of sludge floating on top of my clarifier in the sections between the lamella plate channels (the area that is open to the bottom of the clarifiers and between the plate packs). I first thought it was cause by excess polymer, but it doesn't feel like polymer. I've brought some in the lab and tried a few different things to get it to settle but nothing really seems to work. Nitric breaks it up and causes it to go back into solution but that's not going to help fix whatever is causing it. The pH of this sludge is about 9.9 where my effluent is around 9.4.
Does anyone have any thoughts or any thoughts I can try to figure out why it's happening and how to stop it? My effluent is still clear, but I'd like to get this to settle and stop happening.

Thanks for any help and time.