SCENARIO-BASED ANALYSIS OF REDUCTION EFFECTS OF IMPROVING SEWAGE TREATMENT RATE ON ECOLOGICAL RISK: A CASE STUDY OF GUNMA PREFECTURE

Abstract

 We developed the method for evaluating reduction effects on ecological risk according to improvement of sewage treatment rate by using AIST-SHANEL Ver. 3.0, and applied it to Gunma prefecture’s sewage treatment plan. LAS and AE, chemicals used for detergent, are targeted for and we prepared SSD (species sensitivity distribution) functions to estimate the values of PAF (potentially affected fraction of species). We set a present scenario and three future scenarios: Present scenario stands for baseline scenario where prefecture-wide sewage treatment rate is 72.2% in FY2015; Scenario A reachs to 76.1% in FY2030 by improving connection rate of sewage line; Scenario B reachs to 89.2% in FY2030 by replacement of private wastewater treatment tank; and Scenario D reachs to 100% in FY2040. River concentrations of LAS and AE were estimated in each scenario and reduction effects on PAF were cleared through comparison between scenarios.