There is a misunderstanding above. I didn't say that the US military does not have a team for water purification. I'm just saying that I don't KNOW personally - who in our military covers that sort of thing (who's got the equipment, which base, etc.). I'm sure the gear and training exists somewhere.

The suggestion to use Navy ships is still an excellent idea.

We're apparently doing a lot of the right thing in Puerto Rico right now. What I'm reading tells me that the Navy, Marine Corps and the American Red Cross are leading the efforts.

The MEU is unique in that its air and ground combat elements are combined with a logistics combat element under one commander; other services do not unite the command of air and ground forces until much higher command levels.
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This air-ground task force concept is designed to thoroughly exploit the combat power inherent in air and ground assets by closely integrating them into a single force. The MEU brings all the supplies and logistical support it needs to sustain itself for quick mission accomplishment or to pave the way for any follow-up forces. This self-sustainment allows more flexibility in disposition and operations of forces, and allows the MEU to initiate operations sooner and let support catch up later, without having to wait for external logistical support to begin a mission. Deployments on U.S. Navy amphibious assault ships allows MEUs to seabase around the globe, ready for deployment at short notice.
A typical MEU has approximately 2,200 Marines and sailors.