Environmental sustainability assessment of captive conventional sewage treatment plant designs

Although several designs of sewage treatment plants (STP) are being employed, their performances are measured in terms of the water quality parameters of STP outlets. Life cycle assessment (LCA) approach employed in the present study is confined to the gate-to-gate approach in order to identify the hotspots in every link of the supply chain, from the collection of sewage to the disposal/usage of treated water. The study being carried out involves the assessment of two conventional STP's sustainability performance through inventory analysis, followed by a water footprint assessment. Based on the study, Fluidized Bed Bio Reactor (FBBR) is found to be a better option as per life cycle impact assessment (LCIA) compared to sequential bio-reactors (SBR). However, both are at the same level of water footprint requirement. All the dominant impacts observed in the study, especially global warming, human (non) carcinogenic toxicity, land use and fossil resource scarcity, are damage-inducing and are primarily short term by nature. Sludge processing is found to be one of the significant environmental hotspots (as indicated by both impact analysis and water footprint assessment), which needs to be addressed to make these systems truly eco-friendly using suitable process modifications and protective measures.