Hybrid input–output analysis of wastewater treatment and environmental impacts: A case study for the Tokyo Metropolis

This paper proposes a new hybrid input–output model designed to analyze both the generation and treatment of wastewater. This model, named wastewater treatment input–output model (WWIO), can be regarded as an extension of the waste input–output model (WIO) (Nakamura, S. and Kondo, Y., 2002. Input–output analysis of waste management. Journal of Industry Ecology, 6(1): 39–63.). As an application, I compiled the Tokyo Metropolitan WWIO table for 2000, which comprises 482 economic sectors, 11 wastewater treatment sectors, 12 types of wastewater-related waste and 6 types of environmental load. The model was applied to different scenarios to compare alternative wastewater treatment systems. The results indicate that replacing the simple treatment with the high-class treatment improves the quality of treated water while increasing CO2-equivalent emissions. Meanwhile, when the dewatered sludge is incinerated instead of landfilling, both CO2-equivalent emissions and landfill volume decrease.