A wastewater treatment plant located in Central Pennsylvania went
through an extensive upgrade to resolve problems associated with fats, oils and
grease products. 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. The dissolved oxygen content in this effluent was
almost negligible due to the de-chlorination process.
To comply with the revised requirements, the engineer selected a Venturi
Aerator (VA) to add the required oxygen to the effluent. The selection of the
venturi aerator was based mainly on its simple design as well as the fact that
the engineer could utilise an existing pump on the site.
The VA 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.
The aspirated water is pumped into an additional 5000-litre aeration
chamber, the mixing action and pressure in the VA transferring oxygen from the
ambient air into the water.
The outcomes have been very positive: In winter months, the WWTP is able
to maintain DO levels of >10.0mg/L while in summer months they can
consistently exceed 7.0mg/L.
Venturi aerators are often used with Gorman-Rupp self priming
centrifugal pumps, allowing all equipment to be mounted on lake or basin banks,
and making them easily accessible for monitoring and maintenance.
The full case study of the Pennsylvania WWTP can be accessed at this link.