| 摘要 |
PURPOSE:To attain to reduce treatment cost, by a method wherein the concn. of chromic acid in the hot drain in the outlet side of a heat exchanger for heating a chromic acid solution is measured at a proper time and said drain is introduced into a general drain treatment system in a usual state such that said concn. is equal to or less than a tolerant value while introduced into a waste chromic acid solution treatment system when equal to or more than the tolerant value. CONSTITUTION:Hot drain in the outlet side of a chromic acid solution heating heat exchanger 4 using steam or hot water as a heating medium arranged in a chromic acid solution storage tank 1 is stored in a drain storage tank 9. The concn. of chromic acid in this hot drain is measured by a electric conductivity meter 10. In a usual state such that the concn. of chromic acid is equal to or less than a tolerant value, the hot drain is introduced into a general drain treatment trough 13. When the concn. of chromic acid exceeding the tolerant value is detected, said drain is introduced into a chromic acid drain tank 16 and treated separately.
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