MECHANICAL REMOVAL OF HEAVY CYANOBACTERIAL BLOOM IN THE HYPER-EUTROPHIC LAKE DIANCHI

In eutrophic lakes dense concentration of the outbreak of cyanobacterial bloom could reach up to 108-9cells/l in the water. By using several techniques as gravitational shaking, rotating shaking and centrifuging, the surface water was cleaned out in turn of condensing, dehydrating to harvest the algal mud; and then drying to powder or not according to the further requirement for processing. During April 2001 to November 2002 the technology was applied in lake Dianchi for 351 days. The total amount of treating surface water in lake Dianchi was 42648m 3,amounted to 460.83tons in dry weight of algal powder. In accordance with the composition determination of total nitrogen, total phosphors, total potassium, crude organic matters and heavy metals in algal powder, the removed algal biomass corresponded to taking out of 37.33t(N), 2.71t(P), 2.49t(K), and 200.32t(crude organic matters), as well as the heavy metals of 2.289kg(Pb), 2.23kg(As), 2.3kg(Hg), 0.51kg(Cd) respectively from the lake. The results indicated that the mechanical removing is a feasible and helpful way in the hyper-eutrophic water bodies to control the out-breaking of cyanobacterial bloom and to reduce the inner nutrient load.