As part of an upgrade to a rural WWTP plant, a revised permit required them to maintain a >6.0 mg/L level of dissolved oxygen [DO] in the effluent discharged, because it flowed into an adjacent stream. This effluent contained almost no DO due to the dechlorination process. To comply, the engineer selected a Venturi Aerator [VA] to add the required oxygen.
A Venturi-Aerator is a device used used in conjunction with a self-priming pump to mix and aerate tanks, ponds and lagoons. The pump draws water from the source and pumps it into the Venturi Aerator.
The Venturi Aerator was selected because of its simple design, and because it could be utilised with an existing pump on the site. The aerator adds DO to the water by drawing in atmospheric air via the Venturi process, using pressure and velocity from the pump. Water exiting the Venturi nozzle expands into large macro droplets that are surrounded by 2.2 volumes of air that is aspirated.
An additional 5000 litre aeration chamber was used to pump the aspirated water into. The mixing action and pressure in the Venturi Aerator, transfers oxygen from the ambient air into the water.
The results were very positive, where in winter months, the WWTP is able to maintain DO levels of >10.0mg/L, and in the summer months they can consistently exceed 7.0mg/L.
Venturi Aerators are often used with Gorman-Rupp self priming centrifugal pumps so that all equipment can be mounted on lake or basin banks, making them easily accessible for monitoring and maintenance, eliminating the need for cranes and additional safety precautions.