Domestic wastewater from kitchens, bathrooms, and human waste, etc., used to be collected in units of several houses in underground decomposition tanks near the houses, from where it eventually percolated into the ground. (Ref. 1, 2) However, as the drinking water supply is from wells, there were concerns about groundwater becoming contaminated, and the early completion of a sewage treatment facility was sought. (Ref. 2)

As part of the 1969 Ogasawara Islands Reconstruction Plan it was decided to develop a community sewage treatment facility (with a capacity for 2,000 people), and facilities such as a sewage treatment plant, pipe culverts, and a relay pump station were constructed and put into operation from September 1973. Since then, facilities have been improved and upgraded to respond to the deterioration of the original facilities, and following expansion of the treatment plant it is currently capable of treating water for a population of 2,200 and a maximum sewage volume of 1,400 m3 per day. (Ref. 2)

On Hahajima construction of a community sewage treatment facility (with a capacity for 1,000 people) began in 1975 and like Chichijima, upon completion it entered into operation from April 1980. Subsequent improvements and upgrading have been implemented, with the result that the facility can treat water for 1,000 people and a maximum sewage volume of 500m3 per day. (Ref. 2)

Ref. 1: Nanpo Doho Engokai, Ogasawara no genkyo: Fu Ogasawara henkan no kiroku (Current Situation of Ogasawara: Record of the Reversion of Ogasawara), 1969, p. 27.

Ref. 2: Tokyo Metropolitan Ogasawara Branch Office, Kannai Gaiyo (Overview of the Jurisdiction), 2019 ed., pp.223-225.