• emission reduction;
  • environmental load;
  • industrial ecology;
  • input-output model;
  • sewage sludge;
  • waste incineration


This article proposes a linear programming model that is based on the wastewater treatment input-output model (W2IO) to identify the lowest-emission choice among alternative feasible options for wastewater treatment; this model can be considered as an application of the waste input-output linear programming model (WIO-LP) to wastewater issues. Using the data of the Tokyo metropolitan W2IO table, I apply this model to obtain the optimal wastewater treatment options under alternative scenarios. The Pareto frontiers of environmental loads are derived to show the trade-off relationships among various types of environmental load and the effect of the introduction of high-temperature incineration of dewatered sludge on the generation of environmental loads. The main conclusion of the study is that when all three types of environmental load (landfill level, global warming potential, and chemical oxygen demand) are considered, the introduction of high-temperature incineration causes the widening of the Pareto frontier of environmental loads and also causes it to move closer to the origin.