Aerating your dam is one of the best things you can do for the health of your aquatic ecosystem, however, not all dam aeration systems are created equal. Lets dive into the factors to consider when selecting the right system for your specific needs.
Wastewater dams need aeration for a number of reasons. Some need aeration to reduce BOD, COD, or ammonia/nitrogen [TKN]. Some just need a reduction in odours, and some may have blue-green algae issues. Some aeration systems help with some of these, but not others, some are efficient, yet difficult and/or expensive to maintain, some are excellent at all aspects, and others just don’t suit the aeration of dams at all. Diffused air systems, while excellent and very efficient when used in concrete basins, are not ideal for dam aeration, because they do not provide a mixing function, and would be very difficult/expensive to maintain. They also provide no treatment for blue/green algae.
Submersible or jet aerators are compact and can achieve high oxygen transfer rates, and are excellent for tank aeration, but they do have some drawbacks for dam aeration. Firstly, they produce their best oxygen transfer at deep levels [up to 7 metres]. Next, they require lifting devices [cranes], which makes repairs expensive and difficult, and renders monitoring or preventative maintenance, non-existent.
Low-speed surface [or splasher] aerators are also used for dam aeration. They are available in a large range of sizes [from just 1kW, up to in excess of 100kW] and offer excellent oxygen transfer. They do have some downsides though. They can only be accessed by crane or boat, making them expensive and/or dangerous to maintain or monitor. Replacing gearbox oil is also not a cheap operation. On top of this, they naturally create aerosols [because of the nature of their operation], which may cause health issues for operators and the general public, particularly in windy locations].
Draft Tube aerators are also used in dam aeration. They float on pontoons and can be placed around a dam for the best effect. They can transfer oxygen at a reasonable rate, but they do have a few drawbacks. Their propellers can get caught up in wastewater debris, they can only be accessed by crane, boat or tethers, and they can capsize in high winds
An option that does tick all of the boxes, is the EchoStorm venturi aeration system from Gorman-Rupp. The system utilises a self-priming pump to draw water from the dam, then at pressure, forces it through a static venturi unit to draw in atmospheric air, mix and condition it with the water, and “re-inject” the water back into the dam, saturated with dissolved oxygen.
This is a bank-mounted system, so operators can safely access the pump and EchoStorm without the need for a crane or boat or infrastructure like floating walkways. This delivers the opportunity for regular monitoring and the implementation of inexpensive preventative maintenance programs, improving reliability, extending equipment service life, and minimizing the incidence of annoying breakdowns.
Smaller systems can deliver Oxygen Transfer rates of up to 1.5 kgO2/hour, with the largest system able to deliver 16 kgO2/hour. For larger needs, the system is highly scalable by using multiple aerators, even driving multiple units from one pump.
The introduced oxygen helps with the reduction of BOD, COD and TKN, while the velocity from the nozzles aids mixing. If the treatment of blue/green alga is a goal, the mixing zone within the EchoStorm bursts the vacuoles within algae cells to sink them and prevent the photosynthesis cycle, steadily reducing it.
