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.