Venturi aerator installed for Bega Cheese’s wastewater system

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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