There are several reasons why your grease trap cleaning may leave an.
If an odor lingers for a short while right after a trap service has been completed, this is typically due to the water flowing back into the trap and the odor will soon dissipate as the trap fills up.
Odors coming from the floor drains could be due to a backup in the line leading to the trap. Pouring very hot water down the drains will often help alleviate the odor. If the odor persists after pouring water down the drains, you may need to contact a plumber to snake the lines.
Grease trap odors can also escape through a worn or corroded gasket around your manhole cover allowing gases to escape.