Nature-inspired ecotechnological approaches toward recycling and recovery of resources from wastewater

Wastewater is degraded and discarded water inevitably and ubiquitously generated from human facilities and anthropogenic activities, and discharged into the environment. It is a cocktail of countless chemicals, both beneficial and harmful ones ranging from organic matter to toxic metals, nutrients to persistent organic pollutants and pathogens, and is therefore, rightly regarded as a blessing in disguise. United Nations Sustainable Development Goals (SDG) 6.3 urges humanity reducing pollution, discharge of hazardous contaminants mixed in wastewaters into the waterbodies, halving the proportion of untreated wastewater and substantially increasing safe reuse, recycling and resource recovery globally by 2030. It calls for a paradigm shift in the approach of wastewater treatment and its reclamation from capital and energy intensive conventional technology to low-cost, environment friendly, sustainable ecotechnology. Ecotechnology is the design of sustainable systems in sync with natural systems following ecological principles, which integrate human society with its natural environment for mutual benefits. It uses Nature as model, measure, and mentor, attempts to design with Nature, and follows the ecological principles of reliance on solar energy, species cooperation, and material cycling and regeneration. The basic idea is that our treatment system can be modeled on natural ecosystems. The working and architecture of natural systems offer a blueprint for such technological design. The design philosophy, in essence, takes advantage of the wealth of information available from Mother Nature's living library—its biodiversity. The present book chapter attempts to present a comprehensive picture of nature-inspired ecological treatment, regenerative reclamation and valorization of wastewater through closing the loop. It shows how ecosystem mimics portray structural diversity yet functional unity in different ecotechnologies such as living machines, floating treatment wetlands, waste stabilization ponds train, constructed wetlands, hydroponics, and wastewater-fed aquaculture, all employing a range of functional organisms from Mother Nature's living library, comprising microbes, macrophytes, mollusks, fish, and other species, as a collaborative enterprise.