FUZZY CONTROL OF COAGULATION REACTION THROUGH STREAMING CURRENT MONITORING

A fuzzy logic controller (FLC) incorporating the streaming current det ector (SDC) was utilized in the automatic control of the coagulation r eaction. Kaolinite was used to prepare synthetic raw water, and ferric chloride was used as the coagulant. The control set point was decided at a streaming current (SC) of -0.05 and pH of 8.0 from jar tests, ze ta potential and streaming current measurements. A bench-scale water t reatment plant with rapid mix, flocculation, and sedimentation units, operated in a continuous-flow mode, was utilized to simulate the react ion. Two critical parameters affecting the coagulation reaction, i.e., pH and streaming current, were chosen as process outputs; while coagu lant dose and base dose were chosen as control process inputs. They we re on-line monitored and transduced through a FLC. with raw water of i nitial turbidity of 110 NTU, residual turbidity of lower than 10 NTU b efore filtration was obtained. Results show that this combination func tions satisfactorily For coagulation control. (C) 1997 IAWQ. Published by Elsevier Science Ltd.