Abstract
In order to clarify the purification mechanism of eutrophicated lake water, correlation between aquatic environmental factors and micro-animals appeared on the biofilm in a biological treatment reactor was examined. The reactor packed with non-adsorbing carrier, honeycomb tube was continuously run feeding lake water of Lake Kasumigaura as a water source at 2 hydraulic retention time during 5 years from 1990 to 1995. The maximum removal parameter was total Mn with the removal ratio of 78.2% for 2 hours, and the removal of other important parameters; total Fe, turbidity, 2-methylisoborneol (2-MIB), chlorophylla and COD in the eutrophic waters were 75.3%, 71.9%, 67.4%, 62.1% and 28.4%, respectively. As for the aquatic environmental factors influencing to the treatment potential, there was a favorable correlation between the composition of micro-animals on the biofilm and algal removal ratio in the raw water. It was clarified that the higher numbers of filter-feeder and filamentous feeder like Trithigmostoma, Stentor and Stylonychia were correlated with the efficient reduction of filamentous algae, such as the genera of Phormidium and Oscillatoria. High appearence of filamentous feeder, Trithigmostoma and Nassula fed on 2-MIB producer, P. tenue highly corresponded to the removal of 2-MIB.
