Aluminum fractions in surface water from reservoirs by coagulation treatment with polyaluminum chloride (PAC): Influence of initial pH and OH-/Al3+ ratio

Five Al fractions were separated during the specific surface water treatment from reservoirs in Ji'nan using three PAC products with varying OH-/Al3+ ratios in this study to investigate the coagulation performance and residual Al separation as a function of initial pH in detail. Some extra data were enumerated in terms of residual Al ratio and proportion of Al speciation. It can be found that compared with PAC(15) and PAC(23). PAC(20) showed superior natural organic matter (NOM) and turbidity removal capacity with broader pH range (5.0-8.0) and it showed relatively lower content for any Al fraction examined in this research. PAC products showed favorable coagulation performance at conditions of 6.0 < initial pH < 7.0. Additionally, residual Al content (specially dissolved monomeric Al) was relatively low when initial pH was between 7.0 and 8.0. Majority of total Al existed in form of dissolved Al, especially at initial pH < 7.0. Most of dissolved Al was strongly bound or polymeric colloidal. Meanwhile, dissolved inorganically monomeric Al was almost the only component in dissolved monomeric Al. Residual Al ratio of PAC products varied in the following order: PAC(15) > PAC(23) > PAC(20) and residual Al ratio can be controlled when solution initial pH was between 7.0 and 8.0. (C) 2011 Elsevier B.V. All rights reserved.