Quantitative evaluation of effects of the soft interventions or cleaner production in households and the hard interventions: A Social Experiment Programme in a large river basin in Japan

Efforts have been made to reduce municipal wastewater pollutant discharge and improve river water quality in the Yamato-gawa River basin since 2005, as part of a Social Experiment Programme. The Programme was the first one in Japan to disseminate soft interventions in households, measurements to reduce pollutant discharge, in a large river basin with more than two million population. The soft interventions in households are similar to cleaner production in industrial sector because they are not the wastewater treatment and changing of lifestyles. This paper presents several methods for quantification of the pollutant discharge reduction. Two hypothetical soft intervention combinations were defined, the effects of 16 soft interventions were estimated using their proliferation rates, and estimated pollutant discharge reduction was compared with changes in river water quality during the Programme events. For the first method, environmental accounting housekeeping (EAH) books were applied to estimate a 38-53% reduction in biological oxygen demand (BOD), 26-40% reduction in total nitrogen (TN), and 21-32% reduction in total phosphorus (TP). These estimation results were comparable with the field survey results of approximately 100 person population, which were conducted in the late 1980s. Soft interventions were found to be several times more cost effective than hard interventions, such as development of municipal wastewater treatment and river water purification systems. The BOD discharge reduction effects of soft interventions initiated during Programme events increased from 0.3-2.3% in 2005-2007 to 2.4-4.7% in 2007-2009. The questionnaire surveys found that participants in the Programme events in average newly implemented three or four soft interventions in addition to those already implemented at normal times.

The left graph shows the effects of soft and hard interventions on BOD discharge/load reduction in the main channel of the Yamato-gawa River, which were estimated based on BOD discharge/load in 2005. The soft interventions' effects were found to be comparable to those of hard interventions, i.e. development of municipal wastewater treatment systems and river water purification facilities, in 2007-2009. The right graph shows that the soft interventions were found to be significantly cost effective in reducing pollutant discharge/load in the river basin.Highlights► Effects of the soft and hard interventions were quantitatively evaluated. ► Soft interventions can reduce pollutant discharges of BOD (38-53%), TN (26-40%), and TP (21-32%). ► Soft interventions' effects on water quality were estimated using their proliferation rates. ► Soft interventions were more cost-effective than hard interventions by several orders (214 kg-BOD day−1 per JPY 1 million). ► Newly implemented soft interventions reduced BOD discharge by 2.4-4.7% in 2008-2010.