ALGAE & CYANOBACTERIA
Table 1 (continued)
PRINCIPLE – MODE OF ACTION
Nutrient control in catchments will require engagement of landholders, government
agencies, and primary producers, and commitment to a long-term strategy. Critical
for the management of cyanobacterial blooms and failure to control nutrients may
compromise the success of management options.
Aerators & Mixers
Mixing the water column stops cyanobacteria moving into optimum light conditions,
reducing their growth rate and ability to compete with other algae such as diatoms,
which depend on mixing to remain in suspension. Aeration and mixing can also
help maintain oxic conditions at the water/sediment interface thereby preventing
phosphorus release into the overlying water, which can support the growth of
cyanobacteria. Destratification is achieved by using either bubble plume aerators
Bubble Plume Aerators Work by releasing a series of fine air bubbles from a hosepipe near the bottom of
the lake. As the bubbles rise they entrain water from different depths into a plume.
When the plume reaches the surface the air dissipates and the plume plunges to a
depth of equivalent density and moves through the reservoir as an intrusion. Return
currents flow on each side of the intrusion and generate basin scale circulation.
Solar-powered water circulating pumps create near-laminar water flows by drawing
deeper water towards the surface. This provides constant, long-distance water mixing
and high-flow, long-distance circulation™ (LDC).
WEARS “Resmix Mixer” The “Resmix Mixer” is a floating propeller that gently pushes water from the surface
down to break up stratification.
Hypolimnetic oxygenation Oxygen is injected into the hypolimnion to achieve oxic conditions and prevent
phosphorus release. Used for fisheries management where fish require warm surface
and cool bottom water. Has advantage that nutrients can become limiting in the
surface water as stratification resists deep mixing and entrainment of nutrients from
deeper in the water column. Appropriate design and careful operation is required to
inject oxygen without rising air bubbles disrupting stratification.
Dilution and Flushing Can remove both cyanobacteria biomass and phosphorus that supports its growth.
Requires enough water to cover inflow.
Withdrawal of Hypolymnetic
Removes phosphorus rich water at the sediment/water interface caused by stratified
conditions. Requires enough inflow to cover withdrawal and downstream effects of
Solar Powered Mechanical
APRIL–JUNE 2012 S DRINKING WATER RESEARCH 14