Wastewater treatment in the urban environment

Constructed wetlands are a valid option for wastewater treatment even in urban areas. In the city, they can be implemented in roof tops, abandoned industrial areas, vertical surfaces of buildings, backyards, porches and public parks. In the suburbs, greywater can be treated in private gardens and reused for irrigation. The performance and control restraints often found disappointing in nature-based systems have been overcome in the past two decades: current systems achieve effluent qualities similar to conventional sewage treatment plants. With area requirements expected to come down to 2.0 m(2) per p.e. they would need only two or three times more space. To the core task of treating wastewater they add valuable ecosystem services like micro-climate regulation, rainwater retention, production of renewable energy and/or food, air filtering, noise reduction and recreational values as biotopes with flora and fauna. They represent a new philosophy of dealing with wastes: recycling of nutrients from a valuable resource instead of mere disposal. The new concepts of closing loops call for a more integrated approach represented by the ecological engineer. With its expertise in landscape design and plant usage, horticulture is a key science to promote ecological engineering.