AWWA ACE61855

Microcystins (MC) are hepatotoxins containing cyclic heptapeptides and Microcystin- LR(MC-LR) has been strongly linked to liver tumors. MC are chemically stable in water and can't be effectively removed by conventional water treatment processes. This study investigated the removal rates and paths of MC by several water treatment processes. The ELISA and HPLC were used for detection of MC. The concentration of microcystins in Lake Taihu, China is higher than the guide one suggested by the World Health Organization (WHO). It became a potential threat to human health. The distributions of microcystins in Lake Taihu were different in different seasons and sites. The microcystins concentration had significant correlation with the water temperature, TP, Chl-a, CODMn, pH, cyanobacteria biomass and total algae biomass. The investigation showed that the prechlorination of eutrophic lake water led to the release of intracellular toxins to water phase. The extracellular MC had no change in the coagulation-sedimentation process. 17.2%-40.4% of extracellular MC and 19.0%-36.6% of total MC were removed by filtration. 30%- 45.3% of extracellular MC and 30%-51.7% of total MC were removed by chlorination. The cascade biological contact oxidation reactor was more effective and stable for the treatment of eutrophic water than a one-step reactor. Within 2 hours, the removal rates of extracellular MC, MC-RR and MC-LR reached over 85%, 81.7% and 86.7%, respectively, and the removal rates of total MC, MC-RR and MC-LR reached over 84%, 80.5% and 71.5%, respectively. In the biological pretreatment procedure for eutrophic water, MC were degraded by special bacteria and assimilated by heterotrophic microorganisms. The biological activated carbon (BAC) process was used for the advanced treatment for drinking water containing MC. 60.6% of MC-RR, 63.3% of MC-YR and 68.8% of MC-LR were removed within 1.5 hours. In this process MC were removed by two paths, one was MC degraded directly by microorganisms and the other was MC degraded by microorganisms after adsorbed by activated carbon. Includes 13 references, tables, figures.