Preliminary evaluation of the performance of new pre-polymerised inorganic coagulants for lowland surface water treatment

This paper is concerned with the performance of relatively new kinds of pre-polymerised inorganic coagulants, poly-alumino-iron-sulphate (PAFS) and polyferric sulphate (PFS). Laboratory experiments were undertaken to evaluate the PAFS and PFS, in comparison with conventional coagulants such as ferric sulphate (FS) and aluminium sulphate (AS), for the coagulation of algal-type model waters and a lowland surface water containing algae and natural organic matter (NOM). Experimental results demonstrated that under the conditions studied, the performance of pre-polymerised coagulants were consistently superior to conventional coagulants (i.e., FS and AS). This is attributed to the presence of a range of pre-formed polymerised species. The coagulation mechanism of PAFS and PFS has been discussed in the paper. (C) 1998 IAWQ. Published by Elsevier Science Ltd.