The US Environmental Protection Agency (EPA) also works on wetland systems. This link drive you to the EPA wetlands programs http://water.epa.gov/type/wetlands/index.cfm where you can find a lot of information on the "wetland's world", from natural to treatment weltand, from why they are valuable to how EPA protect them..
Here below the links to the complete publications list
a) the useful Manual of CW treatment of municipal wastewaters:
b) and the link to the North American Database (NADBVersion2): http://firehole.humboldt.edu/wetland/twdb.html
2) another link to publications: http://water.epa.gov/type/wetlands/wetpubs.cfm
This list include general information as " HANDBOOK OF CONSTRUCTED WETLANDS FOR AGRICULTURE, DOMESTIC, COAL MINES ETC" and other following useful texts.