| 摘要 |
PURPOSE:To efficiently remove calcium at a low cost and to inhibit adhesion of scale by adding part of acid fermentation liquid containing an organic acid produced in an acid fermentation stage to waste water and separating calcium contained in water as the insoluble compound of the organic acid and calcium and thereafter performing anaerobic treatment for waste water. CONSTITUTION:Waste water 5 is introduced into a mixing tank 1. Part of acid fermentation liquid 7 containing an organic acid is supplied to the mixing tank 1 from an acid fermentation tank 3. The organic acid is allowed to react with calcium contained in waste water to produce the insoluble compound of the organic acid and calcium. Separation liquid 12 separated in a liquid-solid separation tank 2 is supplied to the acid fermentation tank 3. Organic substance contained such as a saccharide is decomposed into an organic acid such as acetic acid, propionic acid, butyric acid and lactic acid by acid producing bacteria. Part of acid fermentation liquid 7 is returned to the mixing tank 1 and the residual is supplied to a methane fermentation tank and methane fermentation is performed therefor by methane producing bacteria. Thereby calcium is efficiently removed at a low cost and anaerobic treatment can be performed. |
