Water pollution is endemic to human activities, ranging from urban industrial and municipal point source discharges to non-point source discharges from agriculture, logging, and mining. Until recently, only point sources have been subject to serious water quality regulation, which mandates cleanup to levels that are not expected to harm the environment. Regulation for non-point source pollution has been limited by the vast scale of the pollution and an appreciation for the economic ramifications of this scale when ordering cleanup. Ecological engineering, with its emphasis on sustainable energy sources and acceleration of pollution amelioration using natural treatment systems, offers a relatively low cost alternative for large-scale treatment of non-point source pollution in particular, but also that of point sources. The flagship of ecological engineering is phytoremediation using constructed wetlands. Terrestrial phytoremediation plays a similar role in brownfield cleanup.