ベトナム国ハノイ市郊外集落における排水・廃棄物管理とその影響 : 窒素・リンフロー分析

Hanoi, the capital of Vietnam, is facing rapid modernization, leading to the improper management of waste and wastewater. The purpose of this study was to evaluate the impacts of waste and wastewater management on water environment, in terms of nitrogen and phosphorus flows. Trai hamlet, located in the south part of Hanoi, was selected as a research community. A waste and wastewater stream survey was implemented by a door-to-door interview for 100 households. A material flow model of nitrogen and phosphorus was developed with focus on sub-urban waste and wastewater management. Then, the model was applied for the study area. The results showed that the component receiving the largest amount of nutrients was paddy field, 435.1 kg-N/ha/year and 89.8 kg-P/ha/year, in which 40% of N and 65% of P were derived from chemical fertilizer. Although waste and wastewater recycling is widely implemented, the management of pig liquid waste is a serious problem in this area since most of them were discharged directly to the water bodies. The total nutrient loads to the water bodies in 2010 was 187.3 kg-N/ha/year and 13.4 kg-P/ha/year, of which paddy field accounted for 70% of nitrogen and fish pond did for 60% of phosphorus.