A Granny-Trike/Rickshaw design
Google had a contest called, "Innovate or Die", and the winner filtered brackish water as they pedaled a Granny trike! http://googleblog.blogspot.com/2008/01/team-aquaduct-wins-innovate-or-die.html
So, this is what inspired me to draw this, and now I'm in the process of building a prototype!
Another option would be to use 1.5" to 2" diameter sched40 threaded aluminum conduit that is bent into an arch with a hydraulic hand pump pipe bender. (Buy one for $150 through Harbor Freight Tool Co.)