Special Issue for the 13th IWA International Specialist Conference

Scenario analysis for reduction of pollutant load discharged from a watershedby recycling of treated water for irrigation

Eisaku Shiratani , Yoshiyuki Munakata , Ikuo Yoshinaga , Tomijiro Kubota , Koji Hamada , Tadayoshi Hitomi


Received October 25, 2009,Revised January 04, 2010, Accepted , Available online

Volume 22,2010,Pages 878-884

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A model in which a river model was layered on a distributed model (double-layered model) was developed to analyse the transport of water and pollutants (nitrogen, phosphorus, and BOD as organic matter) in watersheds and rivers. The model was applied to the watershed of Abragafuchi Lake, Japan, where serious water pollution has occurred over three decades, and the applicability of the model was demonstrated. Scenarios of recycling of sewage treated-water into agriculture to reduce pollutant load discharged into the lake were analysed. The results showed that irrigating paddy fields with the sewage-treated water could contribute to conserving water and reducing pollutant load, with reduction rate in BOD, nitrogen, and phosphorus ranging from 6%–36%, 16%–46%, and 18%–51%, respectively. Particularly, the results indicated that, irrigating paddy fields with the treated water during non-cropping periods and the accompanying reduction in withdrawn water from the river were more e ective in reducing pollutant loads discharged into the lake. Further study is required on the e ect of recycled water on crop cultivation and soil conditions for safe implementation.

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