Prakash Floating Plastic balls on the surface of storage tank help to prevent air entrainment to a large extent. I have read some articles on "World Oil" earlier issues on the effect of air prevention using plastic balls on the surface of storage tanks. Off hand - i do not remember the issue and volume number. You could try some older issues from 1999 - 2002 in "World Oil" and "Oil & Gas". You would get some published articles. On oil skimming effect, i am not sure if this will have effective way to prevent oil skimming. Oil skimming may not be effective in WW system as it is internal process related and depends on the flocculant added and the flocculant chemical additive efficiency. Trust this helps you C.V.Srinivasan Nishi Engineers Pvt Ltd India March 22, 2007 E-mail: nishi@vsnl.com >In Dolphin's Gas processing plant, waste water is being >treated and stored in Equalization Tank 17.5 m dia x 16 m >high. Flocculant is added to WW before it enters the tank. >WW is pumped thru' the Multi-media and Polishing filters >before re-injecting in the Disposal wells. The Equalization >tank has a floating type skimmer to extract traces of oil >that could be present in the WW. The Flocculant added helps >to aglomerize small (less than 1 micron) FeS particles and >get settled in the Tank or get strained in the filters. We >also have a three blade mixer running at 423 rpm -- tip to >tip blade diameter of 570 mm to aid the flocculation process > >In order to avoid WW contact with air in the Tank, it is >proposed to add two layers of plastic balls of 100 mm dia >(estimated number = 56,000) that will float on the WW >surface cutting off the air. The questions are: >--- with the plastic ball floating in the tank can we >achieve oil skimming? >--- does anybody has experience of such plastic balls to >avoid air contact -- is it effective?