Geospatial analysis and method for integrating nature-based solutions while planning sewage treatment in cities.

Nature-based solutions such as Constructed Wetlands (CW) and waste stabilization ponds used for cleaning wastewater are regarded as Natural Treatment Systems (NTS). NTS have relatively larger land requirements as compared to mechanized treatment technologies; however, they are favourable from a life cycle perspective due to lower energy usage. The diverse climatic conditions across the world make it difficult to generalize the land requirement for NTS, which depends on geospatial factors such as temperature, solar radiation, and elevation. The present research considers the land required to treat wastewater as an intrinsic function of the location, introduces the concept of 'treatment potential' of sewage treatment technologies and develops a novel decision support to determine the same using open-source global datasets. For any selected study region, the geospatial decision support provides results in the form of graphs, raster statistics, 3D surface plots and a land requirement map for visualization. The estimated land requirements can be integrated with site-specific constraint of land availability, to determine the treatment potential of a particular treatment technology at the given location. Application of this methodology to a land parcel in an Indian city yielded a treatment potential of 128 KLD for 0.9 m deep CW with 75% treatment efficiency. Further, application to residential building yielded land requirement of 88 m2 for CW while an existing installation using 100 m2, validates that the decision support could be used for assessing preliminary NTS feasibility. The developed decision support is a novel application of geospatial studies for planning NTS in cities.