Traditionally, Water Authorities and many Industrial Enterprises in Australia have adopted surface aerators for the aeration of earthen lagoon based wastewater treatment plants (WWTP), be they municipal or industrial. A large percentage of these WWTPs are based on earthen lagoons and aeration is the main energy consumer associated with the treatment processes associated with them.
These surface aerators could be high or low speed “splasher” types, or could use draft tubes, be “brush and blade”, or be paddle wheel aerators. All have reasonable oxygen transfer efficiencies of around 1.5 kg.O2 / kWh. No matter which one or how efficient the choice, all sit or float on the surface of the water, requiring operators to “boat” to them for maintenance. As an added “issue”, some units that require pontoons are at risk of capsizing in strong winds.
A different approach is to use a Venturi Aeration unit in conjunction with a self-priming pump. The self-priming pump draws water from the lagoon [or tank], accelerates it through the Venturi aerator, and pumps highly oxygenated water back into the lagoon. The aerator uses the “venturi” effect to draw upwards of 2.2 times more air than the volume of liquid pumped, before intensely mixing the air and water in the unit’s “oxidising zone”.
Although capable of delivering up to 1.86kg of O2/kWh, the major benefit is in the greatly reduced WHS issues. Because all monitoring and maintenance is done on the bank of the lagoon or side of the tank the risks associated with “boating” to units or the risks associated with the use of overhead cranes to access them is eliminated.
Another advantage with the system is the installation simplicity. Some aeration upgrades to lagoons can take weeks or months to complete, along with the risks associated with working over [polluted] water. The Venturi aeration system with pump only requires a slab at the side of the lagoon.