METHOD FOR PROCESSING SULFURIC ACID-CONTAINING DRAIN WATER

摘要

PROBLEM TO BE SOLVED: To prevent a membrane from clogging and breaking when insoluble substances formed by adding a calcium compd. into a sulfuric acid-contg. drain water is processed by means of membrane separation. ;SOLUTION: Ca(OH)₂ is added in the first reaction tank 1 to make pH to be 4.0-6.0, and Ca(OH)₂ is also added in the second reaction tank 2 to make pH to be 6.5-8.5, and then, MF or UF membrane separation processing is performed. In addition, by making pH to be 4.0-6.0 in the first reaction tank 1, crystalline particles with an appropriate size can be deposited under an appropriate reaction speed to prevent the membrane from being damaged. By making pH to be 6.5-8.0 in the reaction tank 2, unreacted scale component can be efficiently deposited to prevent the scale from being deposited on the membrane surface. Clogging and trouble caused by scale of the membrane are avoided to be able to keep stably the flux of the membrane for a long time. Frequency of cleaning with chemicals becomes less to decrease cost of chemicals. The life of the membrane becomes longer and the frequency of exchange of the membrane becomes less and the cost of the membrane is decreased. Operational efficiency of the apparatus is also improved.;COPYRIGHT: (C)1997,JPO