An Approach to Dewatering Optimization Using UV/Visible Spectroscopy by Monitoring Polymer Concentration in Centrate

This study presents a method for in-line and real-time measurement of polymer concentration in water and centrate samples that is based on UV-vis spectrophotometry. The method is quick, simple and accurate, and can detect as low as 0.05 mg/L polymer. Absorbance spectra of two polymers were established in the wavelength range of 191.5-750 nm in three concentration ranges (0.1 to 1 mg/L, 1 to 10 mg/L, and 10 to 20 mg/L). Highest absorbance values were recorded at 191.5 nm for all polymers. UV absorbance of the polymers gradually decreased between 191.5-240 nm and there was no significant absorbance beyond 240 nm. Incremental increases in polymer concentrations resulted in incremental increases in absorbance values, and a strong linear relationship (R2 > 0.97) between concentration and absorbance held at 191.5, 200 and 210 nm for the polymers. Detection limits were established in distilled water and centrate samples collected from a wastewater treatment plant. In distilled water samples, the lowest detection limit measured was 0.05 mg/L. In centrate samples, the lowest detection limit measured was 0.25 mg/L.