Automated Chemical Feed Strategies for Process Water Clarification, 1995 Recycling Symposium Proceedings

Dominic S. Rende

Jeffrey R. Cantrall

Ann M. Capozzi

Nalco Chemical Company

The management of specialty chemicals for process water reuse is critical to efficient operations in pulp and paper manufacturing. The manual testing of water quality and the manual calibration of chemical feed systems are no longer acceptable practices that guarantee process water quality for subsequent reuse. Significant advances in sensor technology and microprocessor-based control have lead to fully automated process water and effluent water clarification systems that consistently meet mill and regulatory requirements.

This paper describes a chemical feed system that over-comes the limitations inherent in manual adjustment and simple proportionate control strategies. To provide efficient control, accurate measurement of process parameters that directly affect process water reuse is required. These process parameters include pH, total suspended solids, dissolved solids, colour, and the like. Various feed strategies are compared. Commercial installations are described.