Coagulation control plays a significant role in the final yield of sludge volume during water and wastewater treatment. The precise control of coagulant dosage, floc formation and aggregation behaviour becomes the important target for the coagulation process both in water and wastewater treatment. A critical review is presented first in this paper on the recent advances in coagulation control. In particular, the development of an in-situ image detecting system (IDS) based on characterization of floc properties, involving average diameter, fractal dimension and apparent strength is discussed. The results show that the data obtained from the IDS are generally in accordance with the outcome of common coagulation experiment, and have sensitivity for the slow stirring rate, raw water turbidity and coagulant dosage, in different degrees. The combination of IDS and ANN model is also discussed. This provides a possibility for applying the proposed IDS to control the coagulation process in water and wastewater treatment.
Keywords: coagulation, floc, fractal dimension, image detecting system, neural network