Drifter why are you such a twat. You are the one who misidentified a wetland easement as a constructed wetland. They are two entirely different things. A constructed wetland is simply another approach to sewage treatment or storm water treatment. A sewage pipe running through a wetland easement that isn't a constructed wetland.
I am talking about a non-government waste treatment system which actually has a cleaner effluent than the traditional septic tank system and arguably a cleaner effluent than municipal sewage treatment. I contend that a constructed wetland is better for self sufficiency and I get it you disagree. I doubt you have read anything in detail about constructed wetlands and are basing your opinions on how you assume it works. You are not alone in this misunderstanding. It is a significant problem in obtaining permits and getting around zoning restrictions.
Old septic tank breeches have allowed for raw sewage to seep into ground water. And these breeches are often sighted as a reason for expanding government sewage treatment. Often these advocates are unaware that cracks in sewage pipes allow for raw sewage to seep into ground water or when pumping stations are overwhelmed by storm water influx but that is another long discussion. There are increased maintenance issues with septic tanks such as sludge removal. Trust me this isn't a fun process and will be even more horrible and toxic if there is no sludge pumping equipment available. Maintenance of Anaerobic bacteria due to die off. Many of the maintenance issues with septic systems are virtually eliminated with constructed wetlands.
Personally, I chose to buy a home that was part of a municipal system mostly because I did not want to deal with a septic tank. Now, if I was seriously contemplating a self-sufficient agricultural project and building it from scratch, I would invest in a gravity fed constructed wetland.
Overview of benefits
http://www.flemingc.on.ca/CAWT/index.cfm?page=benefitsIf you are starting from scratch the costs are nearly the same to set up. The difference shows up in the maintenance cost over the life of the system. The other huge benefit is that this type of system makes it possible to build on land which is not suitable for a traditional system. And that land tends to be far less expensive than land which perks and can handle a traditional septic system.