| 摘要 |
PURPOSE:To appropriately control the amt. of slaked lime to be added to raw water and prevent the occurrence of an excessive sludge by a method wherein hydrochloric acid is added to the sampled raw water contg. phosphorus in a small amt. at a time and a test tank is provided to automatically detect the inflection point of the pH change taking place relative to the amt. of hydrochloric acid added. CONSTITUTION:Raw water 8 is partially introduced for sampling from a first raw water tank 18 into a test tank 19, to which hydrochloric acid is added in a small amt. at a time. By a computing element 27 and a pH meter 28 provided in the test tank 19, a change in the pH value of the raw water 8 taking place relative to the amt. of the hydrochloric added is automatically measured so as to automatically detect its inflection point. When the inflection point characteristic of the raw water 8 contg. the phosphorus of a high concn. is detected, the pH at the inflection point on the most acidic side is automatically set by the computing element 27 as a pH for the next pH adjusting tank 20. The pH adjusting tank 20 has a pH meter 29 and the hydrochloric acid is automatically added to the raw water 8 until the pH set by the test tank 19 is reached. When a specific inflection point is not detected, the raw water 8 is automatically adjusted until it is neutral. |
