| 摘要 |
<p>PURPOSE:To suppress the foaming in an aeration tank and to prevent the decrease in the pH of the mixed liquid in the tank by aerating oxygen-contg. gas of 30-70% oxygen concn. in sewage at 50-85% efficiency for dissolving oxygen and treating the sewage biologically. CONSTITUTION:Raw water (night soil), return sludge of 2.5 times of the raw water, and the mixed liquid. contg. nitric acid from a nitrification tank are circulated in the amt. of 22 times of the raw water to a denitrification tank so as to be subjected to about 90% denitrification by anaerobic mixing and stirring. The water is then conducted into a nitrification tank where the water is subjected to the nitrification. The nitrification is accomplished by providing a circulation ipe for removing the mixed liquid from the upper part of the tank and returning the same to the bottom part of the tank and circulating the mixed liquid with said pipe. Gas of 30% oxygen concn. is supplied to the circulation pipe, and the mixed liquid is treated at 52.0% efficiency for dissolving oxygen by controlling the circulation flow of the sewage. As a result, the flow rate of the waste gas is 68.2 Nm<3> and 1kg NaOH is used with 1kl night soil in order to regulate the mixed soln. to 7.0pH.</p> |
