THE EFFECT OF FERRIC-CHLORIDE FLOCCULATION ON CYANOBACTERIAL CELLS

Taste, odour and cyanobacterial toxins are not generally removed durin g conventional water treatment and can sometimes be increased during t he treatment process due to cell lysis. Some reasons for this have bee n documented in the literature, but there appears to be contradictory evidence regarding the effect of flocculation. In an earlier study, al uminium sulphate did not appear to cause lysis of cells of cultured Mi crocystis aeruginosa or Anabaena circinalis, nor increase the amount o f microcystin-LR or geosmin in the water. In this study the effect of ferric chloride an cultured cells of M. aeruginosa and A. circinalis w as evaluated at concentrations that would occur in a water treatment p lant. The results showed that ferric chloride did not appear to cause cell lysis of cultured M. aeruginosa and A. circinalis. However, ferri c chloride seemed to stimulate growth of both M. aeruginosa and A. cir cinalis in the experiments with South Para Reservoir Water. (C) 1998 E lsevier Science Ltd. All rights reserved.