To obtain a high rice yield and quality for animal feed without synthetic fertilizers, an experiment with bench-scale apparatus was conducted by applying continuous irrigation with treated municipal wastewater (TWW). Uniform rice seedlings of a high-yield variety (Oryza sativa L., cv. Bekoaoba) were transplanted in five treatments to examine different TWW irrigation directions (“bottom-to-top” and “top-to-top” irrigation) and fertilization practices (with and without P-synthetic fertilizers) as well as one control that simulated the irrigation and fertilization management of normal paddy fields. The highest rice yield (14.1 t ha⁻¹), shoot dry mass (12.9 t ha⁻¹), and protein content in brown rice (14.6%) were achieved using bottom-to-top irrigation, although synthetic fertilizers were not applied. In addition, this subsurface irrigation system could contribute to environmental protection by removing 85–90% of nitrogen from TWW more effectively than the top-to-top irrigation, which showed a removal efficiency of approximately 63%. No accumulation of heavy metals (Fe, Mn, Cu, Zn, Cd, Ni, Pb, Cr, and As) in the paddy soils was observed after TWW irrigation for five months, and the contents of these metals in the harvested brown rice were lower than the permissible limits recommended by international standards. A microbial fuel cell system (MFC) was installed in the cultivation system using graphite-felt electrodes to test the capacity of electricity generation; however, the electricity output was much lower than that reported in normal paddy fields. Bottom-to-top irrigation with TWW can be considered a potential practice to meet both water and nutrient demand for rice cultivation in order to achieve a very high yield and nutritional quality of cultivated rice without necessitating the application of synthetic fertilizers.

開発途上国の今後の水道整備の在り方を検討するため，利害関係者の評価や改善要望を定量的に把握する必要がある．本研究では，ベトナムの大学生による水道の利用実態と水道水に対する評価について，地域によるそれらの差異を明らかにするためにアンケート調査を実施し，136件の回答を用いてクロス集計およびFisherの正確確率検定，平均値の差の検定を行った．その結果，都市と農村において水道整備状況や水道水の利用実態が異なるにもかかわらず，両地域において水道水に対する評価が良く，改善要望が高かった．水道整備によって水汲み労働からの解放や健康リスクの減少が実現されたため，満足度が高い一方で，給水される水の水量や水圧の不足，雨季の水質悪化などの新たな問題が生じるため，改善要望が高いことが示唆された．