Cost Savings in the Ozone Treatment of Paper Mill Effluents Achieved by a Closed-Loop Ozone Control System

摘要

Control strategies were created to reduce the operating costs of ozone stages of effluent treatment plants in paper mills as well as to improve the quality of the effluent. Biologically treated effluents from five mills were subjected to laboratory and pilot tests. All COD target values could be reached and maintained with SAC-based control strategies. Disturbing events were compensated with a deviation of only 2 % within maximum 3.1 volume exchanges, depending on the kind of event. The SAC (spectral absorption coefficient) was found to be highly suitable for controlling the ozone dosage. In a SME paper mill, 20 % of the operating costs of an ozone plant can be saved. The return on investment for such a system is thus about eight months.