Effect of oil on clarifier

[zeta2]

A thin layer of oil has appeared on the surface of the mixing zone and sedimentation zone of our clarifier. I'm wondering what effect this might have on the clarifier bed (sludge). Could it cause the bed to be less dense and increase the sludge level? We suspect the oil is coming from the scraper/recirculator drives (hot weather may be melting some of the grease). The water is treated with alum and sodium aluminate and we use inert polymer for flocculation.

 

[bimr]

Would not suspect that small amount of oil to cause any problems.