Dewatering optimization with in-line and real-time measurement of polymer: results from full-scale treatment plants.

Full-scale testing was carried out at two wastewater treatment plants to determine whether residual polymer concentration, measured by filtrate and centrate absorbance at 191 nm, can be used to identify the optimum polymer dose and achieve in-line and real-time dewatering optimization. The first plant uses high speed centrifuges and the second plant uses belt filter presses for dewatering. During the testing, the polymer dose incrementally increased to cover the under-dose, optimum dose and over-dose polymer ranges, and the centrate/filtrate absorbance at 191 nm, turbidity and cake solids were measured. The results showed that absorbance measurements at 191 nm exhibited a parabolic shaped curve with increasing polymer dose, where the minimum absorbance corresponded to the optimum polymer dose. The method can directly measure the residual polymer concentration and determine the optimum polymer dose accordingly, and is planned to be used in the development of a dewatering automation system in the future.