This turbine done from 3 parts: turbine itself, that was used with some changes from thing http://www.thingiverse.com/thing:13188 and case that consists from bottom part with motor holder and top part that covers turbine. Even with small 12V DC Motor it works perfect and powerfull enough.
Print turbine (file "Turbine 2.STL") with high quality and cover parts (files "Turbine Cover (Top).STL" and "Turbine Cover (Bottom).STL") with wall thickness 0.8 mm and normal or high quality. In top part of cover you'll need to remove thin wall inside that needed only to form flat surface on top without using support structures (you can easy see it, as it is 0.4 mm thin). You can cut it using usual paper knife for example. Assemble cover together using M3x9 (or M3x12) bolts and nuts. Turbine designed to be connected to motor adapter with single M4x30 bolt. I used 25-32 mm tension band to handle the motor inside bottom part of cover.
I also attached adapter for motor that I have in file "Motor Gear Connector (Sliced) - 2.STL". Print two parts and connect together with two M3x16 bolts and nuts, put inside single M4 nut to be used for turbine connection.
Turbine top cover has end that fit just fine 30 mm pipe adapter designed here: http://www.thingiverse.com/thing:39745 and was done to be used together with it (take some time to see how and where it can be used together with this adapter).
Note: In some .STL files you'll need to flip Y-Z planes to place details correct on printing table.
Use free for your needs! ;)