| 摘要 |
PURPOSE:To reduce the COD value of waste water, which contains soluble oils used for cold rolling, at a low cost under a stable operation, by effectively flocking and separating biological metabolism-intercepting substances from the oil-containing waste water at a weak alkali, and subjecting to the treated water to a biological disposal using settled bacteria films. CONSTITUTION:Waste water containing soluble oils used for cold rolling is mixed with an acidic metal salt, and adjusted at a weak alkali level, i.e. pH 8-10, by addition of slaked lime, to facilitate a flocking operation. By this pretreatment, such biological metabilism-intercepting substances as mineral oils, fats, surfactants, etc. contained in the waste water are deposited stably with metal hydroxide flocks. The deposited flocks are separated from the waste water by a flocking and compression floating method preferably involving the addition of a high molecular flocculant. The treated waste water is then subjected to a biological disposal as a higher treatment, because it contains substances decomposable with bacteria such as lower aliphatic acids, alcohols, glycol ethers, etc,. As for the biological disposal, a stationary process involving two stages in series is adopted. Ca<2+> ions are converted to calcium carbonate by carbonic acid gas generated in the process for example, while the disposed water maintaines its pH value near 7-8 and shows a buffering effect due to generated NH3-N. Consequently, it is not necessary to neutralize the disposed water again. |
