For this Kalk reactor I used whatever I had on hand (my basement is mini junk yard) and only expenses were for 6 inch acrylic tube and 2 1/2 inch flange with a cap.
Cost to me:~35CND and 1 hour of cheap labor.
Peristaltic pump is not included in the cost since you can run it with different setups but that is my weapon of choice.
Acrylic tube that holds water is 6 inches diameter 18 inches tall.
When I built this thing I had no intentions to post it anywhere so I have no details of building it step by step, but if there is enough interest I can get some more details on what I used and how.
Here are some pics of THE THING:

Driving force.

Doing what it is made for.

BTW: It works great.