| Summary: | 碩士 === 國立聯合大學 === 環境與安全衛生工程學系碩士班 === 94 === An automatic pH-ORP (oxidation-reduction potential) titration device was developed in this study to be applied to dynamically control the doses of wastewater chlorination and dechlorination. The peaks or valleys on the pH and ORP profiles in the titration/back-titration could indicate the influent concentrations of chlorine-consumed materials (mainly ammonia nitrogen for chlorination) and residual chlorines (for dechlorination). The required dose for chlorination can be determined and optimized by multiplying the identified ammonia concentration to the optimal chlorine to nitrogen weight ratio (Cl/N). The required dechlorination dose was also found to be correlating to the residual chlorine concentration with linear relationship. These experimental results make an innovative and dynamic feed-forward dose control for wastewater chlorination and dechlorination. Two control factors, CFC and CFD, were proposed to regulate the chlorination and dechlorination doses to meet the requirements of total coliform counts and residual chlorination concentrations for different proposes of wastewater reclamation. The pH-ORP titration/back-titration can precisely predict the required doses for wastewater chlorination and dechlorination. In addition, a Back Propagation Neural Network (BPN) was also used to build the control model, which was successfully used to predict the required doses, effluent total coliform count, and effluent chlorine residuals. A series of continuous wastewater chlorination and dechlorination experiments were conducted in a continuous laboratory-scale reactor to evaluate the proposed control strategy. The results of the continuous control experiments have shown that both of the chlorination and dechlorination were effectively controlled, appropriate disinfection efficiencies and remaining chlorine residuals in effluent were controlled simultaneously for different treated targets. Additionally, the potential benefit on chemical saving was also achieved.
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