I think biological treatment options make the most sense, especially with reagrd to stormwater, another topic I'm glad you brought up. With the proper undertatdning one can "manipulate" ecosystems to do what they would do naturally. I am unfamiliar with treetop gardens, so unless you want to expound I'll stay clear.

The other ideas that you mentioned, specifically wetlands, are a great idea. I think the only real problem with personal wetlands for treatment is the time required to get to safe levels (and education level.awareness of the person running it). For example some of the reactions carried out by bacteria are concetration dependent, so as they further reduce down a pollutant, let's say...phenol...the longer it may take to get to "safe" levels. Wetlands are also, typically quiescent bodies. If I remember corretly, I think there horizontal velocity (the rate at which water travels through, parellel to the ground) is something like 3m/day. That's slow. Kadlec and Knight (1998?) have a GREAT reference book for wetlands. It's mad comprehensive. It not only gives design parameters, but case studeis, cost estimates, and the types of plants that can be used in those facilities. Wetlands are where my heart is, if you can't tell. Oh I guess maybe we shoudl defien wetlands.

Wetlands (commonly called swamps, bogs, marshes, etc.) are watery ecosystems in which water covers a confinign layer of soil for the majority of the year. They are usually marked by a shallow dpeth of water with woody plants and tress that can pump oxygen throught tissue in its roots from beneath the water surface (ex. the beautiful cyprus trees in Charleston). Many scientists refer to wetlands as the "kidneys of the landscape," for that is their function. The serve to "filter" out organic material as well as nutrients before the water reaches either another surface water body or an aquifer. Wetlands can be both fresh water and saltwater.

Constructed wetlands are those specifically constructed and designed for the treatment of some water. It could be muncipal waste (after some treatment) or it could be a storm water facility (i.e. to treat rainwater or runoff). The same caveat that i made in teh "I don't buy the vegetarian thing" Post goes for constructed wetlands also. That is when designing them the engineering team needs to consider the suitability if that option for that particualr area. Specifically, is the soil a confingn soil like clay or silt so that you may prevent aquifer recharge (stormwater seeping into the groundwater) should it not be desried. If you want to have floating plants, make sure they are indigenous and noninvasive. Etc.