Ecological engineering or ecotechnology, the exciting mixture of applied ecology, environmental engineering, biotechnology, systems control and complexity sciences has been matured recently into a well-established discipline with its own methodology. Its application fields range from natural habitat preservation and restoration, sustainable resource management to treatment of waste streams of high variety.

While the basis of ecoengineering is the ecological design – i.e. the principle which mimics efficient natural processes – the “reactor,” the construction and the technology show a wide variety. The solutions vary from the simplest natural lakes with minimal engineering (e.g. controlled inflow, outflow, water level) to highly engineered artificial reactor systems placed on the surface or built under the surface combined with greenhouses and/or fisheries. The most common solutions use for surface and subsurface waste streams treatment (i) in situ placed operations such as aeration, or water recycling, (ii) artificially constructed wetlands with deep and shallow pools, marshes, various water flows and vegetation, or (iii) reactive subsurface constructions.

This chapter gives an overview of ecoengineering tools and technologies, covering passive systems, conventional reactor-based solutions and new developments in the field of advanced artificial ecosystems along with their main performance figures and characteristic application areas.