Home > Venturi aerator installed for Bega Cheese’s wastewater system

Venturi aerator installed for Bega Cheese’s wastewater system

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article image Ripples from the aerator ‘radiate’ to all parts of the lagoon, ensuring a good level of mixing.
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Hydro Innovations was engaged by Bega Cheese to install a venturi aerator for the wastewater system at their Strathmerton plant in Victoria.

In 2018, Bega Cheese Environmental Manager – Northern Victoria, Sean Trebley was tasked with the upgrade of their Strathmerton plant’s wastewater aeration system. The wastewater system consisted of a DAF unit, which flowed into an aerated lagoon, with the effluent subsequently stored in two non-aerated lagoons during winter, before irrigation in summer.

Aerators are needed to keep the COD down and reduce odours in the aerated as well as non-aerated lagoons downstream. Their existing equipment consisted of ageing surface aerators in the aerated lagoon, comprising of two 22kW units and six 8kW units; generally only one or two of these units were operated at any time.

Over a number of years these surface aerators had progressively failed because of age and repairing them meant deploying cranes and/or boats to access them. This process was expensive and had resulted in damage to the dam liner. Eventually it became uneconomical to keep repairing the aerators. It was, therefore, decided to look for a solution that was safer for operators and easier to maintain.

Trebley contacted Hydro Innovations to discuss the use of their ‘bank-mounted’ Venturi-Aeration systems. Mounted on the banks of lagoons, these systems use a self-priming pump to draw water from the lagoon. The pump discharges it under pressure through the Venturi-Aerator. The unit draws in atmospheric air using the venturi effect, mixes it with the water being pumped, and discharges it back into the lagoon, charged with dissolved oxygen.

The Bega Cheese team liked the idea of a bank-mounted system because it gave operators easy access to equipment for monitoring and/or repair, making it much safer and more cost-effective to maintain. Their only concern was whether the units were as efficient as the surface mounted technologies.

Hydro Innovations informed Trebley’s team that with the use of the right pump, oxygen transfer efficiency (OTE) for Venturi-Aeration units can be as high or higher than 1.86kgO2/kWh, making them at least as efficient as the surface (floating) technologies.

The aerated lagoon contained 45ML of effluent with in-flows of 80-120ML per year. This required a 150mm Venturi-Aeration unit paired with a Gorman-Rupp V6A60-B self priming pump featuring a hydraulic efficiency of 70 per cent.

Bega Cheese installed the Venturi-Aerator early in 2019. Since the installation, operators have seen a continued increase in the dissolved oxygen (DO) level, and COD fall by 50 per cent even though the higher level of mixing was re-suspending settled solids, which became more ‘bioavailable’ to the CFUs.

The Bega Cheese crew is happy with the ever increasing levels of DO, the reduction in COD, and their odour-free lagoon. The Wastewater & Maintenance Teams are also pleased that monitoring and maintenance can be done safely, without the use of cranes, boats or winches.

More information about Venturi-Aerators or Gorman-Rupp pumps can be obtained from info@hydroinnovations.com.au.

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