Abstract
The author has conducted a water quality research targeting to measure the pollution caused by coliform bacillus in Kiyotake River and the entire river that flows into it starting from the source of the river flow until to the Kiyotake Town and it was found that while pollution at the upstream pass the environment standard, the middle and the lower stream highly exceeded it. Particularly, the pollution level of Oka River that flows to Kiyotake River was reported to be very high. This is caused by inflow of domestic wastewater to Oka River through municipal sewerage system, and is suspected to be the reason of the high pollution rate.
In this research, focus was being put at municipal sewerage system drainage; the pollution rate, water quality and coliform bacillus concentration of domestic wastewater that flows into it and it was found that:
1) Although the level of coliform bacillus of the treated wastewater flowing out from private or shared septic tank passes the environmental standard, it is still a cause of water pollution in municipal sewerage drainage. 2) It was proven that the daily life drainage of the each home, which is being discharged to the river by going through the municipal sewerage drainage, was the cause of coliform group pollution of the Oka River. 3) For private septic tank which is receiving annual legal inspection, it was proven that coliform group number of 103-106MPN/100mL order is being discharged when water is used at most. 4) It is found that the concentration of coliform group, Phosphoric acid, TOC, and SS in domestic wastewater (gray water) is very high and it is very important to strengthen the conversion from single type private sewage to combined type private sewage or to impose an appropriate maintenance system to every private sewage unit.
