Abstract
The toxicity of 7 polyacrylamide flocculants (AG) was tested on fish. The 48-h LC50 of A and B (nonionic) to carp (Cyprinus carpio), goldfish (Carassius auratus) and Japanese killifish (Oryzias latipes) were high, and those of C, E and G (anionic) were low to some extent, but the range of the values was between 150 and 530 mg·L-1. Nevertheless, 48-h LC50 of C to nibblers (Girella punctata) in sea water was 840 mg·L-1.
Safe concentrations and application factors of the flocculants to fish were estimated through the long-term toxicity tests. These values of C, D and E were small to carp and goldfish, that is, safe concentration of C was less than 8 mg·L-1, those of D and E were 210 mg·L-1, and application factors of these flocculants were 0.010.03. No effect was observed on nibblers in sea water with 84 mg·L-1 of C during 14 weeks.
Reduced specific viscosity of the flocculants was measured, dissolving them into the fresh water used in toxicity tests. Moreover, the viscosity of C was measured in sea water. It was lower than in fresh water. There are the tendencies that 48-h LC50 and safe concentration of anionic and nonionic flocculants decrease as the viscosity.
