I'd suggest to plate your Scenedesmus on solid agar medium (just add 10g/L of agar to your current medium). Most ciliates should die straight away. If required, you can also dilute and streak your alga to pick clean cells and remove the eukaryotic contaminants.

Thanks Dr Gachon . But we started algae treatment and it is better that we remove ciliphora from culture without damaging to algae do you know another way to this work. 

Similar problem was discussed here some while ago:

https://www.researchgate.net/post/Are_there_any_control_measures_for_amoeba_growing_in_microalgae_cultures

Adding KMNO4 dilute solution will help

see this link

http://www.scielo.cl/pdf/lajar/v40nSpecIssue/art05.pdf