TREATMENT OF WASTE WATER FROM WASTE GAS DESULFURIZATION PROCESS

摘要

PURPOSE:To treat dithionic acid and fluorine in waste water by adding hydrochloric acid to the waste water from a gypsum separation process and, after decomposing a COD causing component under heating, adding a calcium compound to the treated water to neutralize the same. CONSTITUTION:The supernatant water 24 containing hardly decomposable dithionic acid from a gypsum separation process 4 is sent to an acid decomposition process 6 and hydrochloric acid is added to said water in an amount of 0.2-20%. Subsequently, the supernatant water 24 is supplied to a steam mixer 13 to be heated to 95-130 deg.C and sent to a decomposition tank 14 to decompose dithionic acid in the supernatant water 24. The treated water 26 is guided to a rough neutralizing process 7 and the pH thereof is adjusted to 2-4 by slaked lime 38 to preliminarily precipitate gypsum and slaked lime 38 is further added in a pH control process 8 to adjust the pH of waste water to 7-9 and fluorine in waste water is precipitated and removed as calcium fluoride. By this method, dithionic acid and fluorine are removed and a sludge amount is reduced.