Planned Reuse of Domestic Wastewater in Rural Area

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Firstly, the review of the research was conducted. Secondly, in order to define the actual status of the reuse of the treated wastewater from rural sewerage for agriculture, representative 18 rural sewerage and 4 public sewerage were investigated. Main findings are : 1) The main purpose was the prevention of the water shortage. Fertilizer effect of the treated wastewater and the water purification function of the farmland were not considered. 2) The treated wastewater was mainly utilized for paddy fields. 3) In many cases, the reuse were practiced throughout the irrigation season every year. 4) The sending systems of the treated wastewater for the farmland were very diverse. 5) The planning conditions of treated wastewater were determined without the consideration for the reuse. 6) A wide variety of treatment systems was employed. The problems for these conditions of the reuse were also defined. Thirdly, investigations of the "O area" in Ehime prefecture were conducted, where the treated wastewater reuse for paddy fields was actually practiced. In the area, the treated wastewater was diluted in the irrigation pond or by river water. Main findings are : 1) The reuse resulted in the ordinary harvest of rice plants under the general conditions of the fertilization and the utilization of agricultural chemicals. 2) The number of coliform groups and heterotrophes in treated wastewater were smaller than the natural water in this area : e.g. river water. 3) The purification function of paddy fields were effective for NOx-N.4) The sending of the treated wastewater to the pond resulted in the increase of the volume of over flow water. This condition led to the reduction of labor for management of the water gate of the pond. 5) The treated wastewater sent to the pond were tended to be not completely mixed and to be remained in the depth of 1-2m in the summer season. The reason of the retention was also clarified.