Residual aluminum control for source water with high risk of overproof coagulant residue: A novel application of principal component analysis

Abstract

This study first applied the principle component analysis (PCA) and multivariate linear regression analysis (MLRA) to estimate the level of aluminum residue in two full-scale clarifiers, i.e. Densadeg and mechanical clarifier, potentially providing a predictive approach for aluminum residue and operation cost control. For Densadeg, effective relationships were established between aluminum residue and factors including FeCl3 dose, water temperature and turbidity (R2=0.802 and 0.774 for total and soluble Al, respectively). These three factors facilitated the control of aluminum residue, and FeCl3 dose was the most important. More factors were needed to effectively evaluate the residual total aluminum in mechanical clarifier, including the dose of FeCl3 and polyaluminum chloride (PACl), turbidity and tryptophan-like protein similarly contributing to the presumption result (R2=0.817). And water temperature also showed important impact on soluble aluminum besides the four factors aforementioned (R2=0.793). FeCl3 dosage and turbidity enhanced aluminum removal for both clarifiers, while water temperature showed distinct effects: negative for Densadeg but positive for mechanical clarifier. Tryptophan-like protein was associated with an undesirable increase in aluminum residue, as showed by the evaluation of aluminum residue in mechanical clarifier. Aluminum residue in Densadeg was less vulnerable to the fluctuation of PACl dose and organic matters.