It is absolutely normal and necessary!

They are part of the foodweb living in the sludges with bacteria, amoebae, ciliates, nematodes, etc ... Their number increases with the age of sludge.

Dear Mehta,

They are the predators of the wastewater environment. They are usually fed with bacteria and small protozoa specimens. They show that the oxygen level is good. A few of them in the field of view indicate that the activated sludge environment is stable and healthy. But if you see dozens of rotifers in the field of view, this indicates that the active sludge is getting older.

Good luck.

Dear Priyanka

Rotifers are the most abundant macro invertebrates in an activated sludge system. In the activated sludge system, rotifers have shown to be helpful in reducing bulking by preying on the filamentous bacteria “Microthrix” which is associated with bulking in wastewater systems. They are mostly found in very stable activated sludge systems. They are excellent indicators of the health of the sludge and suggest whether the sludge is of good quality, is stable, and has plenty of oxygen or not. In general, presence of rotifers in the wastewater effluent could be a useful indicator for treatment system monitoring.

Regards,

Ata

Sharing link:

https://books.google.es/books?id=AEFgBXjOj-YC&pg=PA218&lpg=PA218&dq=What+do+we+conclude+when+rotifers+are+seen+in+wwtp?&source=bl&ots=eH6TrBE1w2&sig=wzJUEoEEdwBGqdDi4tkAANPs_f4&hl=ca&sa=X&ved=2ahUKEwijqpmR-9nZAhWFWRQKHU96CsIQ6AEwBXoECAYQAQ

Regards!