On facebook there are a lot of interesting group about environment, wetlands and so on. I'm member of the group Homesteading/Survivalism https://www.facebook.com/homesteading where last march was published this beautiful and meaningful picture with this caption: "An excellent example of the role plants play in keeping our soil intact and even clean of impurities".
Well, up to date this image have 18904 Like, 534 comments, 12638 shares.... I think this is fantastic.
These three bottles show the important role of the plants to absorbe and trap nutrients, suspended solids etc. The same stuation you can obtain with treatment wetlands!