• Separating water from what?
• Filtration?
• Cyclonic separation?
• Evaporation?
• Ion exchange?
• Reverse osmosis?
• Electrodialysis?
• At what temperature, pressure and flowrate?
• What size and weight?
• What make of light transport aircraft?
• What do the original aircraft manufacturers have to say?

Aren't all aircraft transport? What do you mean by "modified"?

I mean we are modifiying it according to some missions defined by the contract for Navy. We are integrating some systems.

I thought this problem had long been solved as far as fuel tanks are concerned from what I know. Typically since water is heavier it goes to the bottom of the tank, and you just drain the water out of the tank prior to starting up the engine. Possibly we need some more detailed information about your "light aircraft". I am not aware of any particular need for any complicated system for removing water since it separates naturally from fuel due to its different weight.

We have installed two equipment (Fixed Frequency Converter- FFC) inside the top fairing of the A/C (CASA CN-235) and to cool down them we need outside air. We have to prevent water get into equipments.