LCA analysis of different WWTP processes

Wastewater treatment plants have the main objective to treat the incoming wastewater to meet specified discharge criteria. Different process configurations requiring different amount of resources such as energy and chemicals. The selection of process configuration can also impact the amount of energy produced from digestion of the sludge to biogas. In this study we compare the environmental impact of treating wastewater to two different levels of effluent quality (total phosphorus concentration, 1 mg P/L and 0.3 mg P/L) in three different process configurations using dynamic process modelling and life cycle assessment (LCA). The different processes studied were Pre-precipitation, Simultaneous precipitation and Biological phosphorous removal. Automatic process control in the models was used to achieve similar treatment results for the different processes. Operational data in the form of direct emissions to water and air, energy consumption, chemical consumption, production of sludge and biogas were generated by dynamic process simulations. The operational data were used in the LCA to calculate the environmental impact in five different categories, where global warming potential (GWP) also known as carbon footprint, was one. The results show that pre-precipitation gives the lowest GWP per m3 of treated water for both effluent standards. Bio-P gives the highest GWP.

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