Generally coagulation is a good method for removing oils from water (for example http://dx.doi.org/10.1016/j.clay.2011.05.014). Also electrocoagulation with aluminium or iron anodes, can have great results, but I suppose this is a little bit more extreme.

Thanks Dear Nikos for the response. Pl. send me a link for the full paper text for my research need.

Thanks

Best Regards

Jha

Liquid liquid separation if small amount?

Recently we have shown that alumina nano particles functionalized with petroleum vacuum residue is an effective adsorbent for oil removal from oil in fresh water. Details can be found in this recent publications: Journal of Colloid and Interface Science 425 (2014) 168–177.

You can use adosbant-polymere, or surfactant

Yes! You can use a modified form of an API oil-water separator. There are a lot of internet resources available to design it.

you can use air flotation units to remove oil and grease from gry water 

Thanks Mr. Waleed, do you mean aeration can work well?, I had tried aeration but could not succeed much., 

I think you can use API or DAF if there is large size of oil droplets but for dissolved oil and greases you can followed Combined treatment of adsorption and oxidation process.

I hope This help

Thanks Dear Younis for a good answer.

Jha