Dear Saifeldin,

I am a PhD student too and I know how difficult it is to choose a topic for the research. I would suggest you to take a problem related with waste water or water reservoir near by your place. If possible, take a current environmental problem in your area as a topic for your research. It will have great impact and will help people in your vicinity as well.

Good luck!

Dear Saifeldin,

You might choose " Water and Wastewater Treatment Engineering".

Engineering approaches to protecting water quality . Theory and conceptual design of systems for treating municipal and industrial wastewater and drinking water.

Hoping this will be helpful,

Rafik 

thank you dear brother that is a good suggestion 

At which institute are you studying ? Does the education program not have a list of possible subjects ready ?

thank you Mr Meers 

I did not decide  at which institute I will do it , further more my basic study was food engineering technology in addition to that I am not a resident of my home, that why I am  asking support   

 Dear Saifeldin,

I am a PhD student too and I know how difficult it is to choose a topic for the research. I would suggest you to take a problem related with waste water or water reservoir near by your place. If possible, take a current environmental problem in your area as a topic for your research. It will have great impact and will help people in your vicinity as well.

Good luck!

A more specific topic within watewater treatment would be the relative feasibility of diferent AOPs, preferably in a concrete local problem, as suggested by Amit.