ABSTRACT
The degradation of microcystin by adsorbed bacteria on GAC (granular active carbon) filter from a water treatment facility was investigated. Dominant bacteria isolated from GAC were indigenous microorganisms, Psuedomonas sp. and Flavobacterium sp. The direct exposure of dominant GAC bacteria to microcystins resulted in a significant reduction of microcystin levels in both shaking and static conditions (t-test; p < 0.01). In bacteria-treatments, the half-life of microcystin was 2.6-3.5 days in both conditions. Based on this result, approximately 9-10 days would be estimated for 90% or up to 18-21 days of 99% of toxin to be degraded. This biological degradation by the GAC bacteria in combination with existing purification systems has potential to increase the efficiency of water purification.
Subject(s)
Adsorption , Carbon , Filtration/instrumentation , Flavobacterium/metabolism , Half-Life , Microcystins/metabolism , Pseudomonas/metabolismABSTRACT
Cyanobacterial blooms and associated microcystins in hypertrophic stagnant West-Nakdong River were investigated at weekly intervals from April to August, 1999. Microcystis spp. accounted for over 85% of the numeric abundance of total phytoplankton. Microcystins were present in the blooms sampled between May and August. The peak of total microcystin (microcystin-LR + -RR) levels (maximum level; 612 microg g(-1)) was detected in the initial stage of the bloom (mid May), at the same time as high N/P ratio and high Microcystis biomass. This study indicated that total microcystins of this regulated river was positively correlated to Microcystis biomass, absolute nutrient concentration and TN/TP ratio.