Bubble plumes to reduce Microcystis
Nieuwe Meer, AMSTERDAM
Problem
Lake Nieuwe Meer, a lake near Amsterdam (area = 1,32 km2, max. depth = 30 m, Ptot > 500 mg/m3) is used as a regional recreation area. The problem was extensive growth of Microcystis. In summer a big green carpet of algae covered the water surface, and oxygen was lacking in the hypolimnion.
Bubble plumes
Pressurized air is conducted through small, flexible pipes from a land-base to the lake bottom. The water from the lower layers reaches the surface, spreads out and flows back to the ground. Microcystis is prevented from staying in the euphotic zone and hindered in its growth.
The installed compressor capacity is 85 kW, which is equivalent to an upper middle-class motor car. The installation is specifically designed for the Microcystis problem. It is based on the physical data of the algae and the plant.
Results
The mass of Microcystis is up to 20 times lower than during the years before mixing and no scum appears any more. A shift from cyanobacterial dominance (mainly Microcystis) towards flagellates, green algae and diatoms has occurred. The hypolimnion is sufficiently oxygenated.
Feasibility
Bubble plumes are an efficient, low cost and low energy solution to reduce algae growth, improve reservoirs and obtain suitable conditions for drinking-water supply. They are particularly useful as a rapid remedy for overfertilized lakes.
For a successful application, the plant must be designed specifically for the particular problem. The present level of knowledge allows us to design and dimension such installations.
